Stanford Center for Radar Astronomy Magellan Project Software Interface Specification SU-MGN-SCVDR Surface Characteristics Vector Data Record prepared by Richard A. Simpson Joseph D. Twicken Michael J. Maurer Center for Radar Astronomy Stanford University Stanford, CA 94305-4055 415-423-3525 Version 1.0 1 October 1992 CONTENTS 1. General Description ............................................. 1 1.1. Overview ................................................ 1 1.2. Scope ................................................... 1 1.3. Applicable Documents .................................... 1 1.4. System Siting ........................................... 2 1.4.1. Interface Location and Medium ................... 2 1.4.2. Data Sources, Transfer Methods, and Destina- tions ........................................... 2 1.4.3. Generation Method and Frequency ................. 3 1.5. Assumptions and Constraints ............................. 3 1.5.1. Usage Constraints ............................... 3 1.5.2. Priority Phasing Constraints .................... 3 1.5.3. Explicit and Derived Constraints ................ 3 1.5.4. Documentation Conventions ....................... 3 1.6. Acknowledgement ......................................... 4 2. INTERFACE CHARACTERISTICS ....................................... 5 2.1. Hardware Characteristics and Limitations ................ 5 2.1.1. Special Equipment and Device Interfaces ......... 5 2.1.2. Special Setup Requirements ...................... 5 2.2. Volume and Size ......................................... 5 2.3. Labeling and Identification ............................. 5 2.3.1. Magnetic Label .................................. 5 2.3.2. External Tape Label ............................. 5 2.4. Interface Medium Characteristics ........................ 6 2.5. Failure Protection, Detection, and Recovery Procedures .. 6 2.6. End-of-File Conventions ................................. 6 2.7. End-of-Volume Conventions ............................... 6 3. ACCESS .......................................................... 7 3.1. Programs Using the Interface ............................ 7 3.2. Synchronization Considerations .......................... 7 3.2.1. Timing and Sequencing Considerations ............ 7 3.2.2. Effective Duration .............................. 7 3.2.3. Priority Interrupts ............................. 7 3.3. Input/Output Protocols, Calling Sequences ............... 7 4. Detailed Interface Specifications ............................... 8 4.1. Structure and Organization Overview ..................... 8 4.2. Substructure Definition and Format ...................... 8 4.2.1. SFDU Labels and Headers ......................... 9 4.2.2. Data Physical Blocking .......................... 9 4.2.3. Block Length .................................... 9 5. SCVDR Data Block Format Descriptions ............................ 10 5.1. SFDU Label Structures ................................... 10 5.1.1. Data File Nomenclature .......................... 10 SU-MGN-SCVDR v 1.0 Page i 5.1.2. Generic Data File Structure ..................... 11 5.1.3. Generic Catalog Keyword Labels .................. 12 5.2. Volume Header File ...................................... 15 5.3. Orbit Header File ....................................... 17 5.4. Altimetry Inversion File ................................ 22 5.4.1. Altimetry Inversion Header Record ............... 24 5.4.2. Altimetry Inversion Data Record ................. 29 5.5. Inversion Fit File ...................................... 39 5.6. Image Data Files ........................................ 48 5.7. Emissivity Data File .................................... 59 5.8. G-Matrix File ........................................... 72 5.9. Volume Trailer File ..................................... 79 A. BINARY DATA FORMAT .............................................. 81 A. VAX Integer Fields .............................................. 81 B. VAX Floating-Point Fields ....................................... 81 C. IEEE Integer Fields ............................................. 82 D. IEEE Floating-Point Fields ...................................... 83 SU-MGN-SCVDR v 1.0 Page ii FIGURES Figure 5-1. Sample Varying-Length File Structure ....................... 12 Figure 5-2. Sample SCVDR Catalog/Keyword Label ......................... 13 Figure 5-3. Stanford Volume Header File (VHF) Format .................. 16 Figure 5-4. Stanford Orbit Header File (OHF) - Block Format ............ 17 Figure 5-5. Stanford Altimetry Inversion File (ANF) - Block Format ..... 23 Figure 5-6. Stanford Inversion Fit File (NFF) - Block Format ........... 40 Figure 5-7. Stanford Image Data File (SIF and OIF) - Block Format ...... 49 Figure 5-8. Stanford Emissivity Data File (EDF) - Block Format ......... 59 Figure 5-9. Stanford G-Matrix File (GMF) - Block Format ................ 72 Figure 5-10. Stanford Volume Trailer File (VTF) Format .................. 79 TABLES Table 5-1. Data File Nomenclature ...................................... 10 Table 5-2. Stanford Orbit Header Record SFDU (hr_rec) .................. 19 Table 5-3. Stanford Altimetry Inversion Header Record SFDU (nh_rec) .. 24 Table 5-4. Stanford Altimetry Inversion Data Record SFDU (nr_rec) ...... 30 Table 5-5a. Stanford Altimetry Inversion Record Flag Values (nr_flags) .. 35 Table 5-5b. Stanford Altimetry Inversion Thermal Noise Estimates (thn_t) ..................................................... 35 Table 5-5c. Stanford Altimetry Inversion Calibration Details (calib_t) .. 37 Table 5-5d. Stanford Altimetry Inversion SAB Header (sab_hdr_t) ......... 39 Table 5-6. Stanford Inversion Fit Header Record (fh_rec) ............... 42 Table 5-7. Stanford Inversion Fit Data Record SFDU (fr_rec) ............ 45 Table 5-8. Stanford Inversion Fit Record Flag Values (fr_flags) ........ 46 Table 5-9. Stanford Scattering Function Definitions .................... 47 Table 5-10. Stanford Image Header Record SFDU (ih_rec) .................. 50 Table 5-11. Stanford Image Data Record SFDU (ir_rec) .................... 53 Table 5-12. Stanford Image Statistics Data Structure (bin_t) ............ 58 Table 5-13. Stanford Image Data Record Flag Values (ir_flags) ........... 58 Table 5-14. Stanford Emissivity Header Record SFDU (eh_rec) ............. 62 Table 5-15. Stanford Emissivity Data Record SFDU (er_rec) ............... 67 Table 5-16. Stanford Emissivity Data Record Flag Values (er_flags) ...... 72 Table 5-17. Stanford G-Matrix Header Record SFDU (gh_rec) ............... 74 Table 5-18. Stanford G-Matrix Data Record SFDU (gr_rec) ................. 76 SU-MGN-SCVDR v 1.0 Page iii DOCUMENT CHANGE LOG +----------+------------+----------+----------------------------------------+ | REVISION | REVISION | SECTION | REMARKS | | NUMBER | DATE | AFFECTED | | +----------+------------+----------+----------------------------------------+ | 0.8 | 26 June 92 | All | Major upgrade of details following | | | | | review by Project and interested | | | | | scientists; overall logical structure | | | | | not affected appreciably. ANSI labeled | | | | | tapes become tar tapes. | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | Distrib- | Add Joyner, Anderson, Saunders, Hinnen | | | | ution. | update addresses; improve layout/ | | | | | alignments. | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | Table of | add page numbers | | | | Contents | | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | 1.3 | Consolidate descriptions of Stanford | | | | | software into a single (as yet | | | | | unwritten) document; renumber other | | | | | Applicable Documents (and references | | | | | to them in subsequent sections). | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | 1.4.1 | Add DEC DS3100 to list of workstations | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | 2.3.2 | Substitute semicolon between "last" | | | | | and "version" | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | 5.1.3 | Substitute "even-numbered" for "even" | | | | | in footnote | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | 5.1.3 | Remove extraneous "f" at end of lines | | | | | for NAV_UNIQUE_ID and PROCESS_TIME | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | 5.3 | Substitute real ADIDs assigned by JPL | | | | 5.4 | SFDU Control Authority | | | | 5.5 | | | | | 5.6 | | | | | 5.7 | | | | | 5.8 | | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | 5.4.1 | Add nh_maxB and nh_maxN | | | | 5.6 | Add ih_maxB and ih_maxI | | | | 5.7 | Add eh_meth_syst, eh_meth_geom, | | | | | eh_meth_telem, eh_pad er_ss_prev[10], | | | | | er_Sprime, er_Tsen, and er_pad3 | | | | 5.8 | Add gh_maxB, gh_maxR, gh_maxF, | | | | | gh_maxBR, and eh_maxBF | +----------+------------+----------+----------------------------------------+ SU-MGN-SCVDR v 1.0 Page iv +----------+------------+----------+----------------------------------------+ | REVISION | REVISION | SECTION | REMARKS | | NUMBER | DATE | AFFECTED | | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | 5.4.1 | Add explanation for "insensitive" | | | | 5.5 | version numbers under definitions | | | | | for nh_ver, fh_ver | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | 5.4.2 | Correct definition for nr_burst | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | Table 5-9| Add description of method used to | | | | | obtain rms slope from Muhleman | | | | | function | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 |Table 5-12| Substitute 90 for 75 | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | 5.6 | Move bin_t description from footnote | | | | | to become new Table 5-12; renumber | | | | | following tables | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | 5 | Adopt consistent use of uchar | | | | | (unsigned 8-bit integer) and char | | | | | (character text) | +----------+------------+----------+----------------------------------------+ | 1.0 | 29 Sept 92 | All | Minor editorial corrections/ | | | | | improvements | +----------+------------+----------+----------------------------------------+ SU-MGN-SCVDR v 1.0 Page v ITEMS TO BE DETERMINED +----------+----------+-------------------------------------+------------+ | REVISION | SECTION | ITEM | RESOLUTION | | NUMBER | AFFECTED | DESCRIPTION | | +----------+----------+-------------------------------------+------------+ | 0.5 | Contents | Fill in page numbers | done | +----------+----------+-------------------------------------+------------+ | 0.5 | 1.3 | Flesh out and reorder Applicable | done | | | | Documents section | | +----------+----------+-------------------------------------+------------+ | 0.5 | Several | Need JPL Control Authority | done | | | | designation for: | | | | | Orbit Header Record | | | | | Altimetry Inversion Record | | | | | Inversion Fit Record | | | | | Image Data Record | | | | | Emissivity Data Record | | | | | Stanford G-Matrix Record | | | | | Altimetry Inversion Aggregation | | | | | Inversion Fit Aggregation | | | | | Image Data Aggregation | | | | | Emissivity Data Aggregation | | | | | G-Matrix Aggregation | | | | | Altimetry Inversion Header | | | | | Inversion Fit Header | | | | | Image Header | | | | | Emissivity Header | | | | | G-Matrix Header | | +----------+----------+-------------------------------------+------------+ | 0.5 | Table 5-9| Definition for Muhleman function | done | | | | rms; is present expression for so? | | +----------+----------+-------------------------------------+------------+ | 0.8 | 1.3 | Write summary document(s) on | | | | | processing which precedes the | | | | | SCVDR step, Applicable Doc 9 | | +----------+----------+-------------------------------------+------------+ | 0.8 | 4.2.1 | Include reference to | not done | | | | SFOC-5-SYS-*DU-NJPL and/or TPS-113? | | +----------+----------+-------------------------------------+------------+ | 0.8 | Table 5-7| Revise to show each solution result | not done | | | | as a separate substructure | | +----------+----------+-------------------------------------+------------+ | 0.8 | Footnote | Move bin_t definition from footnote | done | | | | to a table of its own | | +----------+----------+-------------------------------------+------------+ | 0.8 | all | Types char and uchar are not | made | | | | consistently used throughout the | consistent | | | | document | | +----------+----------+-------------------------------------+------------+ SU-MGN-SCVDR v 1.0 Page vi DISTRIBUTION MIT G. Pettengill 37-641 P. Ford 37-601 Stanford R. Simpson Durand 232 L. Tyler Durand 232 M. Maurer Durand 232 E. Holmann Durand 232 J. Twicken Durand 232 Cornell University D. Campbell NAIC Washington University R. Arvidson Earth and Planetary Sci. U.S. Geological Survey L. Soderblom Branch of Astrogeology JPL/MGN C. Leff 230-225 J. Miller 230-216 T. Thompson 230-225 S. Wall 230-225 J. Plaut 230-225 R.S. Saunders 230-225 JPL/PDS G. Woodward 525/3610 R. Joyner 525/3610 T. Anderson 525/3610 JPL/SFDU Control Authority R. Hinnen 301-280 SU-MGN-SCVDR v 1.0 Page vii ACRONYMS AND ABBREVIATIONS ALT Altimeter ALT-EDR Altimetry Experiment Data Record (tape) ALTINV Stanford Altimetry Inversion (program) ANF Altimetry Inversion File of the SCVDR ANSI American National Standards Institute ARCDR Altimetry and Radiometry Composite Data Record ASCII American Standard Code for Information Interchange C-BIDR Compressed Basic Image Data Record (tape) CCSDS Consultative Committee for Space Data Systems CCT Computer Compatible Tape COMP Stanford amplitude and timing compensation (program) dB Decibel DMAT Data Management and Archive Team EDF Emissivity Data File of the SCVDR EDR Experiment Data Record ENGEX Engineering data extraction and conditioning (program) FIR Finite Impulse Response GIPS MIT General Image Processing System (program) GMF G-Matrix File of the SCVDR GMX Stanford G-Matrix calculation (program) GVDR Global Vector Data Record IEEE Institute of Electrical and Electronic Engineering IAU International Astronomical Union ID identifier, identification JPL Jet Propulsion Laboratory J2000 IAU Official Time Epoch K Degrees Kelvin km Kilometers MGN Magellan MIT Massachusetts Institute of Technology MLOAD Stanford Magnetic Tape Loading (program) NAIF Navigation and Ancillary Information Facility NAV Navigation Subsystem/Team ODL Object Definition Language (PDS) OHF Orbit Header File of the SCVDR OHR Orbit Header Record OIF Oblique Sinusoidal Equal Area Image Data File ONU Output Network Unit PDS Planetary Data System RADI Stanford emissivity processing (program) RADP Processing Parameters consolidation for radiometry (program) RATM Atmospheric radiative transfer calculation (program) RCOMP Radiometry compensation (program) RMAP Stanford compressed image reduction (program) SAB SAR/Altimeter Burst SABEX SAB header extraction (program) SAR Synthetic Aperture Radar SCET Space Craft Event Time SCLK Spacecraft Clock (time) SCVDR Surface Characteristics Vector Data Record SFDU Standard Formatted Data Unit SFOC Space Flight Operations Center SU-MGN-SCVDR v 1.0 Page viii SIF Sinusoidal Equal Area Image Data File SIS Software Interface Specification SPARC Sun Scalable Processor Architecture SPK Spacecraft and Planet Kernel Format, from NAIF SSLFIT Stanford Synthetic Scattering Law Fit (program) UTC Coordinated Universal Time tar (UNIX) tape archiver utility TBD To Be Determined TDB Temps Dynamique Barycentrique-IAU Standard Ephemeris Time UNIX operating system VBF85 Venus Body Fixed Coordinates, adopted by the IAU in 1985 VHF Volume Header File of the SCVDR VTF Volume Trailer File of the SCVDR SU-MGN-SCVDR v 1.0 Page ix SU-MGN-SCVDR v 1.0 Page x CHAPTER 1 General Description 1.1. Overview This Software Interface Specification (SIS) contains the description of the Surface Characteristics Vector Data Record (SCVDR) tapes produced for the Magellan (MGN) Project. The Magellan Project is managed by the Jet Propulsion Laboratory (JPL); SCVDR tapes are created at Stanford University. SCVDR tapes contain results of processing Magellan altimetry, SAR image, and emissivity[1] data to obtain electrical and physical properties of Venus' surface [1]. 1.2. Scope The format and content specifications in this SIS apply to all phases of the Magellan Project for which the SCVDR is produced. 1.3. Applicable Documents (1) Tyler, G.L., R.A. Simpson, M.J. Maurer, and E. Holmann, "Scattering pro- perties of the Venusian surface: preliminary results from Magellan," J. Geophys. Res., 97, 13115-13139, 1992. (2) MGN 630-79, Rev. D, "Magellan Planetary Constants and Models", D.T. Lyons, Magellan Mission Design, JPL, January 9, 1991. (3) MIT-MGN-ARCDR, Software Interface Specification, Altimetry and Radiometry Composite Data Record, MIT Center for Space Research, 12 September 1991. (4) ANSI X3.27-1978, American National Standards Institute, Magnetic Tape Labels for Information Exchange, Appendix X, Label and Volume Organiza- tion, April 18, 1977. (5) JJPL-0006-01-00, JPL SFDU Description and Usage. Issue 5, March 7 1988. (6) D-7669, Planetary Data System - Data Preparation Workbook, Version 2.0, Jet Propulsion Laboratory, 3 May 1991. (7) SFOC-2-DPS-CDB-Ephemeris, NAIF Ephemeris File, JPL Navigation Ancillary Information Facility, July 15, 1988. (8) SDPS-101, Full-Resolution Basic Image Data Record, Revision D, Jet Pro- pulsion Laboratory, 6 March 1992. ____________________ [1] Throughout this document, we will often refer to passive measurement of thermal radiation from Venus as emissivity measurements; the SCVDR records and files that contain data from those measurements will be called emis- sivity records and emissivity files. Our MIT colleagues use the same spacecraft data and have generated records and files which they call ra- diometry results [8] that share many of the same attributes. We make the distinction in wording solely to emphasize that the Stanford and MIT data sets, although in many ways comparable, are in fact different. SU-MGN-SCVDR v 1.0 Page 1 (9) Simpson, R.A., M.J. Maurer, and E. Holmann, Stanford Magellan Data Pro- cessing System, TBD. (10) MGN-IDPS-102, Magellan Software Interface Specification, Compressed- resolution Basic Image Data, JPL, February 14, 1990. (11) HS513-5029, Magellan Radar Sensor Compensation Report, ed. C. Cuevas, Hughes Aircraft Corporation, 18 August 1989. (12) D-4613, Magellan Mission Operations System-Radar Interface Requirements Document (630-204), Hughes Aircraft Corporation, May 1987. (13) SFOC-1-CDB-MGN-SCLKvSCET, Magellan SCLK/SCET Coefficients File, Final, 2 November 1989. 1.4. System Siting 1.4.1. Interface Location and Medium SCVDR tapes are created by the Stanford Magellan processing system, which con- sists of DEC DS3100, DEC DS5000, Sun 4/110, and Sun SPARC-2 workstations; a DECsystem 5400 file server; and associated peripherals. 1.4.2. Data Sources, Transfer Methods, and Destinations SCVDR tapes contain files created by the Stanford Magellan processing system. Input to the SCVDR is provided by programs [1,9]: MLOAD loads original data from tape to disk, and removes SFDU headers ALT carries out pulse compression and Fourier analysis on data from ALT-EDR tapes; results from this step are saved as range-Doppler arrays GMX computes matrices, dependent on geometrical factors, which are required by the altimetry inversion program ALTINV ALTINV converts altimetry range-Doppler arrays to estimates of the surface scattering function near nadir SSLFIT fits analytic scattering functions to the scattering function solutions provided by ALTINV RMAP reduces compressed image data (from C-BIDR tapes) to estimates of the surface scattering function at oblique angles and pixel histograms RADI converts measurements of Venus' microwave thermal emission to estimates of surface brightness and emissivity COMP computes radiometric compensation for altimetry system RADP converts Processing Parameters files associated with sinusoidal and oblique image data into a single file for use by RADI ENGEX extracts and conditions specified channels from telemetry stream, using DECOM/DECAL and ENGINEERING files (and MIT decommutation module) SABEX extracts SAB headers from SAB_HEADER file and saves for input to RADI RCOMP performs radiometric and timing compensation for RADI; uses HAC algo- rithms and atmospheric model results from RATM SU-MGN-SCVDR v 1.0 Page 2 RATM computes atmospheric brightness and attenuation based on Magellan- adopted standard model and refinements SCVDRs are written on 8 mm cartridge tapes using the UNIX tar utility. Pro- duct tapes are provided to the MGN Data Management and Archive Team (DMAT), which forwards the tapes to Magellan users. 1.4.3. Generation Method and Frequency SCVDR tapes are generated by reformatting and manipulating output files from Stanford programs MLOAD, ALTINV, SSLFIT, RMAP, RADI, and GMX. Each SCVDR con- tains data from up to 100 sequential orbits. SCVDRs are generated when the data for the appropriate orbits become available. 1.5. Assumptions and Constraints 1.5.1. Usage Constraints None. 1.5.2. Priority Phasing Constraints None. 1.5.3. Explicit and Derived Constraints None. 1.5.4. Documentation Conventions 1.5.4.1. Data Format Descriptions The reference data unit is the byte. In the SCVDR, data are stored in fields with various sizes and formats, viz. one-, two-, and four-byte binary integers, four- and eight-byte binary floating-point numbers, and strings of characters. Data are identified throughout this document as char 8 bits character short 16 bits integer long 32 bits integer float 32 bits floating point (sign, exponent, and mantissa) double 64 bits floating point (sign, exponent, and mantissa) u (prefix) unsigned (as with ulong for unsigned 32-bit integer, uchar is an unsigned 8-bit integer) other special data structures such as sfdu, calib_t, etc. which are described within this document The detailed formats of the numeric fields of the product tapes are defined in Appendix A. If a field is described as containing n bytes of ASCII character string data, this implies that the leftmost (lowest numbered) byte contains the first char- acter, the next lowest byte contains the second character, and so forth. Char- acter strings are written to tape with lower numbered bytes preceding higher numbered bytes. An array of n elements is written as array[n]; the first element is array[0], and the last is array[n-1]. Array[n][m] describes an n m element array, with SU-MGN-SCVDR v 1.0 Page 3 first element array[0][0], second element array[0][1], and so forth-according to C language conventions, not FORTRAN conventions. 1.5.4.2. Time Standards The SCVDR uses the January 1.5, 2000 epoch as the standard time for Spacecraft Event Time (SCET). Within the data files, all times are reported in Spacecraft Event Time, expressed as a binary double precision data field representing the number of elapsed seconds of Ephemeris Time (TDB) since noon, January 1, 2000 [2]. The SCVDR uses a string of 23 ASCII characters when a local time, such as the time that a certain processing activity began, is required. The format is `YYYY-MM-DDThh:mm:ss.fff', where `-', `T', `:', and `.' are fixed delimiters; `YYYY' is the year `19nn' or `20nn'; `MM' is a two-digit month of year; `DD' is a two-digit day of month; `T' separates the date and time segments of the string; `hh' is hour of day; `mm' is the minutes of hour (00-59); `ss' is the seconds of hour (00-59); and `fff' is in milliseconds. "Local" times are given in Coordinated Universal Time (UTC). 1.5.4.3. Coordinate Systems The SCVDR uses two coordinate systems-the J2000 coordinate system and the VBF85 coordinate system [2]. 1.5.4.4. Limits of This Document This document applies only to the SCVDR product. 1.5.4.5. Typographic Conventions To make Section 5 of this document more readable, the following combinations of fonts and typefaces are used for special purposes: Boldface for symbolic names of SFDU components, e.g. length field. Typewriter for label keywords and all other ASCII character string values (for example, 'CCSD1Z000001', always enclosed in quotation marks), decimal values (for example, 1990, with no quotes), and hexadecimal values (for example, 0xff, with leading 0x). 1.6. Acknowledgement This document, and the product it defines, have been deliberately modeled after the Magellan ARCDR product from the MIT Center for Space Research [3]. The ARCDR has been well tested in the Magellan environment, and it is intended that the SCVDR be designed in such a way as to maximize the inheritance avail- able. The contributions of Peter Ford of MIT, both toward formatting the SCVDR and in preparing this document, are particularly appreciated. Readers may recognize large blocks of text that have been adapted here from the ARCDR SIS with little change. In those sections and elsewhere, however, any errors in the description of the SCVDR product should be attributed solely to this document's Stanford authors. SU-MGN-SCVDR v 1.0 Page 4 CHAPTER 2 INTERFACE CHARACTERISTICS 2.1. Hardware Characteristics and Limitations 2.1.1. Special Equipment and Device Interfaces The SCVDR data are stored on 8 mm cartridge tapes using the UNIX tar (tape archiver) utility. Original SCVDR products are written in IEEE or VAX binary format using a workstation at Stanford. SCVDR product tapes delivered to DMAT are copies of the original tape(s), with formats as selected by eventual end users (see Dis- tribution page to this document). If additional copies of the SCVDR are requested from Stanford, they will be generated from these original copies. 2.1.2. Special Setup Requirements None. 2.2. Volume and Size The SCVDR data for each orbit consist of a set of six files, as detailed in Section 4. The altimetry, image, and emissivity files vary in length according to the characteristics of the spacecraft orbit at the time of data acquisition and with spacecraft system functions and telemetry quality. A typical set of six files from an early orbit in the Magellan Mission comprises 10 MBytes. Each SCVDR product tape contains data from a maximum of 100 orbits. 2.3. Labeling and Identification 2.3.1. Magnetic Label N/A 2.3.2. External Tape Label Each volume has an external label defining its contents. The label includes the following structure as the unique product identifier: SCVDR.first-last;version PROCESS_TIME=YYYY-MM-DDThh:mm:ss.fff DATA_FORMAT_TYPE=cccc where `first' and `last' are 5-digit decimal numbers denoting, respectively, the Project assigned orbit numbers of the first and last orbit contributing data to the product tape. `Version' is a decimal version number which is ini- tialized at `1' for each product tape and incremented by 1 for each subsequent iteration of that product tape. For test tapes, `version' consists of the single character `T' followed by a decimal number which is initialized at `1' for each test tape and incremented by 1 for each subsequent iteration of that test tape. SU-MGN-SCVDR v 1.0 Page 5 The external label also shows the product creation time (PROCESS_TIME in Sec- tion 5.2; see also Section 1.5.4.2) and the binary format (DATA_FORMAT_TYPE in Section 5.2; see also Section 2.1.1). 2.4. Interface Medium Characteristics SCVDR products are contained on 8 mm cartridge magnetic tapes. 2.5. Failure Protection, Detection, and Recovery Procedures None. 2.6. End-of-File Conventions End of file labeling complies with SFDU standards (see Section 4). 2.7. End-of-Volume Conventions End of volume labeling complies with SFDU standards (see Section 4). SU-MGN-SCVDR v 1.0 Page 6 CHAPTER 3 ACCESS 3.1. Programs Using the Interface Data contained on an SCVDR tape will be accessed by programs at the home institutions of Magellan and other investigators. Those programs cannot be identified here. It is anticipated that the SCVDR will be a primary input to the creation of the Global Vector Data Record (GVDR) product at Stanford. The GVDR creation process has not yet been defined. 3.2. Synchronization Considerations 3.2.1. Timing and Sequencing Considerations Data in the altimetry, image, and emissivity files are arranged by "footprint" number, starting from 1. Footprint spacing is a function of altitude and Doppler resolution, but increasing footprint numbers always indicate increas- ing SCET measurement times. 3.2.2. Effective Duration Except for test versions, SCVDR product tapes delivered to DMAT are the final versions. That does not preclude reissuance of an SCVDR if subsequent correc- tions and/or updates justify such action. 3.2.3. Priority Interrupts None. 3.3. Input/Output Protocols, Calling Sequences None. SU-MGN-SCVDR v 1.0 Page 7 CHAPTER 4 Detailed Interface Specifications 4.1. Structure and Organization Overview The SCVDR consists of a series of UNIX tar files on 8 mm cartridge tape. The first tar file contains the SCVDR Volume Header File. The next-to-last and last tar files contain, respectively, the SCVDR G-Matrix File and the SCVDR Volume Trailer File. Between the first and next-to-last tar files are tar files (one per Magellan orbit for up to 100 orbits) which contain results of Stanford analyses of Magellan data. In the following diagram the numbers on the left refer to the parts of Section 5 that describe the detailed format of these files. +-----+--------------------------+------------+ | 5.2 | Volume Header File | Orbits n-m | +-----+--------------------------+------------+ Repeating tape files for orbits n through m (up to six data files per tape file) +-----+--------------------------+------------+ | 5.3 | Orbit Header File | Orbit i | +-----+--------------------------+------------+ | 5.4 | Altimetry Inversion File | Orbit i | +-----+--------------------------+------------+ | 5.5 | Inversion Fit File | Orbit i | +-----+--------------------------+------------+ | 5.6 | SIN Image Data File | Orbit i | +-----+--------------------------+------------+ | 5.6 | OBL Image Data File | Orbit i | +-----+--------------------------+------------+ | 5.7 | Emissivity Data File | Orbit i | +-----+--------------------------+------------+ +-----+--------------------------+------------+ | 5.8 | G-Matrix File | Orbits n-m | +-----+--------------------------+------------+ | 5.9 | Volume Trailer File | Orbits n-m | +-----+--------------------------+------------- If neither ALT-EDR nor C-BIDR is available for a particular orbit, the entire set of orbit files are omitted from the SCVDR tape. The omission will be noted in the Catalog/Keyword Label of the Volume Header File. If either the ALT-EDR or C-BIDR (but not both) is missing or unusable, the corresponding data file(s) is recorded, but the SFDU header label is followed by zero logical data records. 4.2. Substructure Definition and Format Section 5 of this document details the use of Standard Formatted Data Unit (SFDU) labels and headers and provides a description of the data files on the tape. The G-Matrix File is described in Section 5.8; the Volume Header and Trailer Files are detailed in Sections 5.2 and 5.9, respectively. SU-MGN-SCVDR v 1.0 Page 8 4.2.1. SFDU Labels and Headers SFDU labels [5] are used to identify and characterize each file on the product tapes. To conform with the convention adopted for other Magellan data pro- ducts, all length fields in SFDU labels are recorded as 8-byte ASCII values. 4.2.2. Data Physical Blocking SCVDR tapes are constructed using the UNIX tar utility. The first tar opera- tion writes the Volume Header File to tape. Subsequent tar operations write data for specific orbits to tape. Data for the ith orbit will be in a later file than data from the j'th orbit if i>j. The next to last tar operation writes the G Matrix File to tape. The final tar operation writes the Volume Trailer File to tape. If there are k orbits of data in the SCVDR, the tape will contain k+3 tar files. Only default settings are used for the tar operations. The tar operation writes one tar header block to tape, one or more blocks containing file data, and two blocks filled with zeros. Blocks contain 512 bytes each and are typi- cally handled in groups of 20. System default conventions for padding unused space in blocks are used. Within the tar files, logical records span blocks. Each logical record begins with an SFDU header label. Therefore, file blocks, except the first following the tar header block, do not necessarily begin with SFDU headers. 4.2.3. Block Length Default block length of 512 bytes is used. SU-MGN-SCVDR v 1.0 Page 9 CHAPTER 5 SCVDR Data Block Format Descriptions 5.1. SFDU Label Structures Each data file contains a series of Standard Formatted Data Units (SFDU's). Each SFDU begins with a 12-byte type header, followed by an 8-byte length indicator, and a varying-length value field. The SCVDR uses several SFDU types: Primary Label A string beginning `CCSD1Z', identifying the data as obeying the conven- tions of the CCSDS authority. Catalog/Keyword Label A string beginning `NJPL1K' that further identifies each data file by a series of `KEYWORD=VALUE' definitions. Data Aggregate A string beginning `NJPL1I' that begins a fixed-length block of data. Aggregation Marker A pair of strings beginning `CCSD1R' that sandwiches collections of data with length that is otherwise undefined. 5.1.1. Data File Nomenclature Names and abbreviations for data files are shown in Table 5-1. +-------------------------------------------------------------------+ | Table 5-1. Data File Nomenclature | +--------------------------+---------+------------------------------+ | SCVDR Product | Abbrev- | Data Object or Product Type | | File Name | iation | SFDU Keyword Value | +--------------------------+---------+------------------------------+ | Volume Header File | VHF | | +--------------------------+---------+------------------------------+ | Orbit Header File | OHF | 'ORBIT HEADER FILE' | +--------------------------+---------+------------------------------+ | Altimetry Inversion File | ANF | 'INVERSION FILE' | +--------------------------+---------+------------------------------+ | Inversion Fit File | NNF | 'INV FIT FILE' | +--------------------------+---------+------------------------------+ | SIN Image File | SIF | 'SIN IMAGE FILE' | +--------------------------+---------+------------------------------+ | OBL Image File | OIF | 'OBL IMAGE FILE' | +--------------------------+---------+------------------------------+ | Emissivity Data File | EDF | 'EMISSIVITY FILE' | +--------------------------+---------+------------------------------+ | G-Matrix File | GMF | 'G MATRIX FILE' | +--------------------------+---------+------------------------------+ | Volume Trailer File | VTF | | +--------------------------+---------+------------------------------+ SU-MGN-SCVDR v 1.0 Page 10 5.1.2. Generic Data File Structure The generic structure of data files is shown in Figure 5-1. It begins with a 12-byte `CCSD1Z000001' type field and an 8-byte length field. These are fol- lowed by a keyword and value SFDU, a header data SFDU, and a collection of data SFDUs. +------------------------------------------------------------------+ | Figure 5-1. Sample Varying-Length File Structure | +---+---+---------------------------------+--------------+---------+ | T | | CCSD1Z000001 | CCSDS | CCSDS | | | | | label | | +---+---+---------------------------------+--------------+ | | L | | 00000xxx | Length Field | Header | +---+---+---------------------------------+--------------+---------+ | V | T | NJPL1K00KL00 | K-Label | | +---+---+---------------------------------+--------------+ Keyword | | | L | 00000xxx | Length Field | and | +---+---+---------------------------------+--------------+ Value | | | | | Keywords | SFDU | | | V | Catalog and Keyword Information | and | | | | | | Values | | +---+---+---------------------------------+--------------+---------+ | | T | NJPL1I00TBDH | I-Label | | +---+---+---------------------------------+--------------+ | | | L | 00000xxx | Length Field | Header | +---+---+---------------------------------+--------------+ SFDU | | | | | Header | | | | V | Data Fields for Header Record | Record | | | | | | Data | | +---+---+---------------------------------+--------------+---------+ | | T | CCSD1R000003 | Start Label | | +---+---+---------------------------------+--------------+ | | | L | 00000xxx | Length Field | Aggr | +---+---+---------------------------------+--------------+ Start | | | | DELIMITER=SMARKER | | Marker | | | V | PRODUCT_NAME=cccccccc | Start Value | | | | | TYPE=NJPL1I00TBDD | | | +---+---+---------------------------------+--------------+---------+ | | T | NJPL1I00TBDd | I-Label | | +---+---+---------------------------------+--------------+ | | | L | 00000xxx | Length Field | | +---+---+---------------------------------+--------------+ | | | | | | | | | V | Data Fields for Data Records | Data | | | | | | | | +---+---+---------------------------------+--------------+ | | | T | NJPL1I00TBDd | I-Label | Data | +---+---+---------------------------------+--------------+ SFDUs | | | L | 00000xxx | Length Field | (Many) | +---+---+---------------------------------+--------------+ | | | | | | | | | V | Data Fields for Data Records | Data | | | | | | | | +---+---+---------------------------------+--------------+ | | |...| ... | | | +---+---+---------------------------------+--------------+---------+ | (continued on next page) | +------------------------------------------------------------------+ SU-MGN-SCVDR v 1.0 Page 11 +------------------------------------------------------------------+ | Figure 5-1 (contd). Sample Varying-Length File Structure | +---+---+---------------------------------+--------------+---------+ | | T | CCSD1R000003 | End Label | | +---+---+---------------------------------+--------------+ Aggr | | | L | 000000xx | Length Field | End | +---+---+---------------------------------+--------------+ Marker | | | V | DELIMITER=EMARKER | End Value | | | | | PRODUCT_NAME=cccccccc | | | +---+---+---------------------------------+--------------+---------+ When the collection of data SFDUs has variable length (for example, the altimetry, image, emissivity, and G-matrix files), the collection of data SFDU's is bounded by a pair of SFDU "R" labels that identify the start and end of that collection. These labels start with the string `CCSD1R000003', as shown in Figure 5-1. The keywords `DELIMITER' and `PRODUCT_NAME' have the values shown in the following figures. When the bounded data contain more than a single registered SFDU aggregate, the additional "R" label keyword `TYPE' must be used to describe the data format. If "R" labels bound varying length data, the length recorded in the primary `CCSD1Z' label is the length of the catalog/keyword SFDU, plus the length of the header data SFDU, plus the length of the first "R" label SFDU. Otherwise, the length recorded in the primary label is that of the remainder of the file, i.e. 20 less than the total number of bytes in the data file. Sections 5.2 through 5.9 describe specific data file and record structures in detail. Section 5.1.3 describes the generic keyword and label SFDU. 5.1.3. Generic Catalog Keyword Labels The SFDU catalog keyword label is made up of a set of fields that completely identify each file according to its type, content, origin, and version. In addition, the label contains time tags identifying the time and date on which the data were created. The value of the catalog keyword label is an ASCII string comprising several keyword/value pairs. Alphanumeric characters are always in UPPERCASE. Under- score characters (0x5f) are used between words-no "white spaces" such as null (0x0), space[1] (0x20), or tab (0x9) are permitted. All numeric fields are of fixed length, and unused leading digit positions are filled with ASCII zero (`0') characters. The "keyword=value" syntax used in SCVDR keyword labels is a subset of the "Object Definition Language" (ODL) used by the Planetary Data System [6]. Each keyword/value pair is separated by an equals sign and is terminated by a car- riage return (0xd) followed by a line feed (0xa), which are not shown in the following figures. Figure 5-2 identifies some of the parameters that will appear in SCVDR keyword fields. ____________________ [1] Catalog keyword headers must contain an even number of bytes. To accom- plish this, an ASCII blank (0x20) may be added before the last carriage return and line feed. Subsequent data then line up on even-numbered boun- daries. SU-MGN-SCVDR v 1.0 Page 12 +---------------------------------------------------------+ | Figure 5-2. Sample SCVDR Catalog/Keyword Label | +---+--------------------------------------+--------------+ | T | NJPL1K00KL00 | K-Label | +---+--------------------------------------+--------------+ | L | 00000xxx | Length Field | +---+--------------------------------------+--------------+ | V | DATE_SET_NAME=SCVDR.nnnnn-nnnnn.v | | | | DATA_OBJECT_TYPE=SCVDR | | | | PRODUCT_SEQUENCE_NUMBER=nnnnn | | | | PRODUCT_FILE_NAME=cccccccc | | | | PRODUCT_TYPE=cccccccc | | | | MISSION_ID=4 | | | | MISSION_NAME=MAGELLAN | Keywords | | | SPACECRAFT_ID=18 | and | | | SPACECRAFT_NAME=MAGELLAN | Values | | | ORBIT_NUMBER=nnnnn | | | | UPLOAD_ID=ccccc | | | | NAV_UNIQUE_ID=cccccc | | | | HARDWARE_VERSION_ID=nnn | | | | MAJOR_SOFTWARE_VERSION_ID=nnn | | | | MINOR_SOFTWARE_VERSION_ID=nnn | | | | PROCESS_TIME=YYYY-MM-DDThh:mm:ss.fff | | | | DATA_FORMAT_TYPE=cccc | | +---+--------------------------------------+--------------+ K-Label `NJPL1K00KL00', the SFDU Catalog/Keyword label, where `1' indicates that an ASCII length field follows. The `KL00' sub-field indicates that the keywords follow ODL syntax. Length Field Eight bytes, ASCII, with leading zeroes manda- tory; the length of the value field, including two bytes per keyword/value pair for the (unil- lustrated) carriage return and line feed, and a possible trailing blank if required to make this length an even number. Keywords and Values DATA_SET_NAME= The unique product identifier from the external label (Section 2.3.2) in the format `SCVDR.first-last.version'. This keyword appears only in the Volume Header File. DATA_OBJECT_TYPE= Always `SCVDR'. The intention is that the value of the keyword `DATA_SET_NAME=' should be unique within all instances of the `DATA_OBJECT_TYPE='. This keyword only appears in the Volume Header File. PRODUCT_SEQUENCE_NUMBER= A 5-character numeric string, with leading zeroes, that is incremented by 1 for each SCVDR product. The first will be numbered `00001'. SCVDR products with identical sequence numbers can be assumed to be identical. This keyword appears only in the Volume Header File. SU-MGN-SCVDR v 1.0 Page 13 PRODUCT_FILE_NAME= The unique file name that identifies a data file. This keyword does not appear in the Volume Header or Trailer files. For other files the names are of the form OHFnnnnn.v ANFnnnnn.v NFFnnnnn.v SIFnnnnn.v OIFnnnnn.v EDFnnnnn.v GMFnnnnn.v where prefixes are as shown in Table 5-1, `nnnnn' indicates the orbit number (or first orbit number in the case of the G-Matrix File), and `v' denotes the version number of the file. PRODUCT_TYPE= The type of the data file, which takes on one of the values listed in the third column of Table 5-1. This keyword does not appear in the Volume Header or Trailer Files. MISSION_ID= The single character `4'. MISSION_NAME= The character string `MAGELLAN'. SPACECRAFT_ID= For real data, the two-digit number `18'. For simulated data, the number `28'. SPACECRAFT_NAME= The character string `MAGELLAN'. ORBIT_NUMBER= A five-digit integer with leading zeroes, iden- tifying the orbit from which this data set was generated. Multiple orbit numbers are used only in the Volume Header File label, where they are separated by commas and enclosed in parentheses, i.e. `(nnnnn,nnnnn,...)'. The list of multiple orbit numbers denotes the order of Magellan orbit numbers of the data files contained in this product. Orbits begin at apoapsis. The numbers are the same as those used on the corresponding ALT-EDR and C-BIDR input tapes. UPLOAD_ID= Six characters `PBBBBC', where `P' is the mis- sion phase, `BBBB' is the upload number within that phase, and `C' is a revision indicator in the range A-Z NAV_UNIQUE_ID= A character string indicating the orbit solution used in the ephemeris file(s) for processing. NB: orbit solutions may be different for altimetry and image data processing; for all of Magellan Cycle 1 and much of Cycle 2, only a single NAV_UNIQUE_ID was available during con- struction of the SCVDR. HARDWARE_VERSION_ID= A 3-digit number, `nnn', identifying the hardware version number of the Stanford data SU-MGN-SCVDR v 1.0 Page 14 processing system used to create this SCVDR file or volume. MAJOR_SOFTWARE_VERSION_ID= A 3-digit number, `nnn', identifying the major software version number of the Stanford SCVDR program used to create this file or volume. MINOR_SOFTWARE_VERSION_ID= A 3-digit number, `nnn', identifying the minor software version number of the Stanford SCVDR program used to create this file or volume. PROCESS_TIME= Indicates the time (UTC) at which the product was created or substantially modified. See Sec- tion 1.5.4.2 for format. For the Volume Header File this is the time which appears on the external label (Section 2.3.2). DATA_FORMAT_TYPE= Either `VAXX' or `IEEE', depending on the format in which binary fields are represented in the data records. This is the format which appears on the external label (Section 2.3.2). 5.2. Volume Header File Each SCVDR product tape begins with a Volume Header File (VHF)-a set of SFDU volume descriptors and catalog keywords. It identifies the number and sequence of orbits on this multi-orbit product. Compared with the generic data file structure (Section 5.1.2) the Volume Header File contains only the CCSD header, the keyword and value SFDU, and the aggregation start marker. The corresponding aggregation end marker is contained in the Volume Trailer File. +----------------------------------------------------------------------+ | Figure 5-3. Stanford Volume Header File (VHF) Format | +---+---+--------------------------------------+--------------+--------+ | T | | CCSD1Z000001 | CCSDS Label | CCSDS | +---+---+--------------------------------------+--------------+ Header | | L | | 00000xxx | Length Field | | +---+---+--------------------------------------+--------------+--------+ | V | T | NJPL1K00KL00 | K-Label | | | +---+--------------------------------------+--------------+ | | | L | 00000xxx | Length Field | | | +---+--------------------------------------+--------------+ | | | V | DATA_SET_NAME=SCVDR.nnnnn-nnnnn.v | | | | | | DATA_OBJECT_TYPE=SCVDR | | | | | | PRODUCT_SEQUENCE_NUMBER=nnnnn | | | | | | MISSION_ID=4 | |Keyword | | | | MISSION_NAME=MAGELLAN | Keywords | and | | | | SPACECRAFT_ID=18 | and | Value | | | | SPACECRAFT_NAME=MAGELLAN | Values | SFDU | | | | ORBIT_NUMBER=(nnnnn[,nnnnn,...]) | | | | | | HARDWARE_VERSION_ID=nnn | | | | | | MAJOR_SOFTWARE_VERSION_ID=nnn | | | | | | MINOR_SOFTWARE_VERSION_ID=nnn | | | | | | PROCESS_TIME=YYYY-MM-DDThh:mm:ss.fff | | | | | | DATA_FORMAT_TYPE=cccc | | | +---+---+--------------------------------------+--------------+--------+ | (Continued on next page) | +----------------------------------------------------------------------+ SU-MGN-SCVDR v 1.0 Page 15 +----------------------------------------------------------------------+ | Figure 5-3 (contd). Stanford Volume Header File (VHF) Format | +---+---+--------------------------------------+--------------+--------+ | | T | CCSD1R000003 | Start Label | | | +---+--------------------------------------+--------------+ Aggr | | | L | 00000xxx | Length Field | Start | | +---+--------------------------------------+--------------+ Marker | | | V | DELIMITER=SMARKER | Start | | | | | PRODUCT_NAME=SCVDR | Value | | +---+---+--------------------------------------+--------------+--------+ CCSDS Label `CCSD1Z000001', the CCSDS primary SFDU label. Length Field Eight bytes, ASCII, with leading zeroes manda- tory; the length of the remainder of the Volume Header File. Keyword and Value SFDU See Section 5.1.3. Aggregation Start Marker Start Label `CCSD1R000003', the SFDU Aggregation Marker label, indicating the start of a data aggrega- tion of unspecified length. This aggregation consists of the remainder of the product, and is matched by an ending marker in the Volume Trailer File. Length Field Eight bytes, ASCII, with leading zeroes manda- tory; the length of the remainder of the aggre- gation marker SFDU. Start Value DELIMITER= The character string `SMARKER', indicating that this is the start of a data aggregation. PRODUCT_NAME= The character string `SCVDR'. SU-MGN-SCVDR v 1.0 Page 16 5.3. Orbit Header File Each Orbit Header File (OHF) identifies the orbit number, time frame, and orbital geometry for one Magellan orbit. The file format is illustrated in Figure 5-4. Compared with the generic data file structure (Section 5.1.2) the OHF contains only the CCSD header, the keyword and value SFDU, and the header record SFDU. The OHF header record block is depicted in Table 5-2 and has a fixed length of 280 bytes. +----------------------------------------------------------------------+ | Figure 5-4. Stanford Orbit Header File (OHF) - Block Format | +---+---+--------------------------------------+--------------+--------+ | T | | CCSD1Z000001 | CCSDS Label | CCSDS | +---+---+--------------------------------------+--------------+ Header | | L | | 00000xxx | Length Field | | +---+---+--------------------------------------+--------------+--------+ | V | T | NJPL1K00KL00 | K-Label | | | +---+--------------------------------------+--------------+ | | | L | 00000xxx | Length Field | | | +---+--------------------------------------+--------------+ | | | V | PRODUCT_FILE_NAME=OHFnnnnn.v | | | | | | PRODUCT_TYPE=ORBIT_HEADER_FILE | |Keyword | | | | MISSION_ID=4 | | and | | | | MISSION_NAME=MAGELLAN | | Value | | | | SPACECRAFT_ID=18 | Keywords | SFDU | | | | SPACECRAFT_NAME=MAGELLAN | and | | | | | ORBIT_NUMBER=nnnnn | Values | | | | | UPLOAD_ID=cccccc | | | | | | HARDWARE_VERSION_ID=nnn | | | | | | MAJOR_SOFTWARE_VERSION_ID=nnn | | | | | | MINOR_SOFTWARE_VERSION_ID=nnn | | | | | | PROCESS_TIME=YYYY-MM-DDThh:mm:ss.fff | | | | | | DATA_FORMAT_TYPE=cccc | | | | +---+--------------------------------------+--------------+--------+ | | T | NJPL1I000004 | I-Label | Orbit | | +---+--------------------------------------+--------------+ Header | | | L | 00000260 | Length Field | Record | | +---+--------------------------------------+--------------+ (Table | | | V | Data Fields for Orbit Header Record | | 5-2) | +---+---+--------------------------------------+--------------+--------+ CCSDS Label `CCSD1Z000001', the CCSDS primary SFDU label. Length Field Eight bytes, ASCII, with leading zeroes manda- tory; the length of the remainder of the Orbit Header File. Keyword and Value SFDU See Section 5.1.3. Orbit Header Record See Table 5-2 and the definitions following it. ____________________ [2] Data element definitions use the conventions of the C programming language. Refer to appendix A for a bit-level description of field types. SU-MGN-SCVDR v 1.0 Page 17 +----------------------------------------------------------------------------+ | Table 5-2. Stanford Orbit Header Record SFDU (hr_rec) | +---+-----+--------+---------------+-----------------------------------------+ |Off| Len | Type | Name | Description (see footnote 2) | +---+-----+--------+---------------+-----------------------------------------+ | +0| 20 | sfdu | hr_sfdu | SFDU label and length | +---+-----+--------+---------------+-----------------------------------------+ | 20| 4 | ulong | hr_orb | Orbit number | +---+-----+--------+---------------+-----------------------------------------+ | 24| 4 | ulong | hr_ninv | Number of Altimetry Inversion Records | +---+-----+--------+---------------+-----------------------------------------+ | 28| 4 | ulong | hr_nfit | Number of Inversion Fit Records | +---+-----+--------+---------------+-----------------------------------------+ | 32| 4 | ulong | hr_nismg | Number of SIN Image Data Records | +---+-----+--------+---------------+-----------------------------------------+ | 36| 4 | ulong | hr_niomg | Number of OBL Image Data Records | +---+-----+--------+---------------+-----------------------------------------+ | 40| 4 | ulong | hr_nems | Number of Emissivity Data Records | +---+-----+--------+---------------+-----------------------------------------+ | 44| 4 | uchar | hr_pad1[4] | spares | +---+-----+--------+---------------+-----------------------------------------+ | 48| 8 | double | hr_inv_start | First Inversion Fpt Time (SCET,TDB | +---+-----+--------+---------------+-----------------------------------------+ | 56| 8 | double | hr_inv_end | Last Inversion Fpt Time (SCET,TDB) | +---+-----+--------+---------------+-----------------------------------------+ | 64| 8 | double | hr_fit_start | First Fit Fpt Time (SCET,TDB) | +---+-----+--------+---------------+-----------------------------------------+ | 72| 8 | double | hr_fit_end | Last Fit Fpt Time (SCET,TDB) | +---+-----+--------+---------------+-----------------------------------------+ | 80| 8 | double | hr_simg_start | First SIN Image Fpt Time (SCET,TDB) | +---+-----+--------+---------------+-----------------------------------------+ | 88| 8 | double | hr_simg_end | Last SIN Image Fpt Time (SCET, | +---+-----+--------+---------------+-----------------------------------------+ | 96| 8 | double | hr_oimg_start | First OBL Image Fpt Time (SCET, | +---+-----+--------+---------------+-----------------------------------------+ |104| 8 | double | hr_oimg_end | Last OBL Image Fpt Time (SCET, | +---+-----+--------+---------------+-----------------------------------------+ |112| 8 | double | hr_ems_start | First Emissivity Fpt Time (SCET, | +---+-----+--------+---------------+-----------------------------------------+ |120| 8 | double | hr_ems_end | Last Emissivity Fpt Time (SCET, | +---+-----+--------+---------------+-----------------------------------------+ |128| 15 | sclk | hr_avg_sclk | Predict Periapsis Time (SCLK fmt [13]) | +---+-----+--------+---------------+-----------------------------------------+ |143| 23 | char | hr_avg_sma | Average Semi-Major Axis (km) | +---+-----+--------+---------------+-----------------------------------------+ |166| 23 | char | hr_avg_ecc | Average Eccentricity | +---+-----+--------+---------------+-----------------------------------------+ |189| 23 | char | hr_avg_incl | Average Inclination (deg) | +---+-----+--------+---------------+-----------------------------------------+ |212| 23 | char | hr_avg_lon | Avg Longitude of Ascending Node (deg) | +---+-----+--------+---------------+-----------------------------------------+ |235| 23 | char | hr_avg_arg | Average Argument of Periapsis (deg) | +---+-----+--------+---------------+-----------------------------------------+ |258| 6 | uchar | hr_pad2[6] | spares | +---+-----+--------+---------------+-----------------------------------------+ |264| 16 | uchar | hr_spare[16] | spares | +---+-----+--------+---------------+-----------------------------------------+ |280| | +---+------------------------------------------------------------------------+ SU-MGN-SCVDR v 1.0 Page 18 Element Name Type Length Description hr_sfdu sfdu 20 SFDU Label and Length: `NJPL1I00000400000260'. The designator `0004' is registered with the NJPL SFDU authority as the "Orbit Header Record". hr_orb ulong 4 The Magellan Orbit Number corresponding to the following five files (altimetry inversion, inversion fit, sinusoidal im- age, oblique sinusoidal image, and emis- sivity). An orbit begins at apoapsis, and the number corresponds to the input data from the corresponding ALT-EDR and/or C-BIDR tape(s). hr_ninv ulong 4 Number of Altimetry Inversion Records- the number of nr_rec SFDU's in this orbit's Altimetry Inversion File. hr_nfit ulong 4 Number of Inversion Fit Records-the number of fr_rec SFDU's in this orbit's Inversion Fit File. fr_nrec and nr_nrec should be the same. hr_nsimg ulong 4 Number of Sinusoidal Equal Area Image Data Records-the number of ir_rec SFDU's in this orbit's Sinusoidal Image Data File. hr_noimg ulong 4 Number of Oblique Sinusoidal Equal Area Image Data Records-the number of ir_rec SFDU's in this orbit's Oblique Image Data File. hr_nems ulong 4 Number of Emissivity Data Records-the number of er_rec SFDU's in this orbit's Emissivity Data File. hr_pad1[4] uchar 4 spares hr_inv_start double 8 First Inversion Footprint Time (SCET)- the S/C ephemeris time (seconds of TDB since J2000. see Section 1.5.4.2) that represents the first altimeter inversion footprint of this orbit. It is equal to the nr_scet value in the first nr_rec record of this orbit's Altimetry Inver- sion File. hr_inv_end double 8 Last Inversion Footprint Time (SCET)-the S/C ephemeris time (seconds of TDB since J2000. see Section 1.5.4.2) that represents the last altimeter inversion footprint of this orbit. It is equal to the nr_scet value in the last nr_rec record of this orbit's Altimetry Inver- sion File. SU-MGN-SCVDR v 1.0 Page 19 hr_fit_start double 8 First Inversion Fit Footprint Time (SCET)-the S/C ephemeris time (seconds of TDB since J2000. see Section 1.5.4.2) that represents the first inversion fit footprint of this orbit. It is equal to the nr_scet value in the first nr_rec record of this orbit's Altimetry Inver- sion File. hr_fit_end double 8 Last Inversion Fit Footprint Time (SCET)-the S/C ephemeris time (seconds of TDB since J2000. see Section 1.5.4.2) that represents the last inversion fit footprint of this orbit. It is equal to the nr_scet value in the last nr_rec record of this orbit's Altimetry Inver- sion File. hr_simg_start double 8 First SIN Image Footprint Time (SCET)- the S/C ephemeris time (seconds of TDB since J2000. see Section 1.5.4.2) that represents the first sinusoidal image footprint of this orbit. It is equal to the ir_scet value in the first ir_rec record of this orbit's sinusoidal image data file. hr_simg_end double 8 Last SIN Image Footprint Time (SCET)-the S/C ephemeris time (seconds of TDB since J2000. see Section 1.5.4.2) that represents the last sinusoidal image footprint of this orbit. It is equal to the ir_scet value in the last ir_rec record of this orbit's sinusoidal image data file. hr_oimg_start double 8 First OBL Image Footprint Time (SCET)- the S/C ephemeris time (seconds of TDB since J2000. see Section 1.5.4.2) that represents the first oblique image foot- print of this orbit. It is equal to the ir_scet value in the first ir_rec record of this orbit's oblique image data file. hr_oimg_end double 8 Last OBL Image Footprint Time (SCET)-the S/C ephemeris time (seconds of TDB since J2000. see Section 1.5.4.2) that represents the last oblique image foot- print of this orbit. It is equal to the ir_scet value in the last ir_rec record of this orbit's oblique image data file. hr_ems_start double 8 First Emissivity Footprint Time (SCET)- the S/C ephemeris time (seconds of TDB since J2000. see Section 1.5.4.2) of the first emissivity measurement of this or- bit. It is equal to the er_scet value in the first er_rec record of this orbit's emissivity data file. SU-MGN-SCVDR v 1.0 Page 20 hr_ems_end double 8 Last Emissivity Footprint Time (SCET)- the S/C ephemeris time (seconds of TDB since J2000. see Section 1.5.4.2) of the last emissivity measurement of this or- bit. It is equal to the er_scet value in the last er_rec record of this orbit's emissivity data file. hr_avg_sclk sclk 15 Predicted Periapsis Time (SCLK)-the periapsis time of the predicted orbit in spacecraft clock units (see [13] for de- tails on SCLK format). hr_avg_sma char 23 Semi-Major Axis (km)-the semi-major axis of the predicted orbit[3]. hr_avg_ecc char 23 Eccentricity-the eccentricity of the predicted orbit[3]. hr_avg_incl char 23 Inclination (degrees)-the inclination of the predicted orbit[3] with respect to the xy-plane of the J2000 coordinate system. hr_avg_lon char 23 Longitude of Ascending Node (degrees)- the angle in the xy-plane of the J2000 coordinate system to the ascending node of the predicted orbit[3]. hr_avg_arg char 23 Argument of Periapsis (degrees)-the an- gle in the plane of the predicted or- bit[3] from the ascending node in the xy-plane of the J2000 coordinate system to the periapsis. hr_pad2[6] uchar 6 spares hr_spare[16] uchar 16 spares ____________________ [3] The "predicted" orbit is based on the elements used to generate the uplink commands for the current mapping pass. It represents an average over the entire orbit, and is not the result of post-orbit navigation solutions. The elements should be used for comparison purposes only, since they may involve large errors. The predicted orbit elements are copied from the orbit header file of the ALT-EDR tape, or, if unavailable, from the orbit header of the C-BIDR. SU-MGN-SCVDR v 1.0 Page 21 5.4. Altimetry Inversion File CCSDS Label `CCSD1Z000001', the CCSDS primary SFDU label. Length Field Eight bytes, ASCII, with leading zeroes manda- tory; the length of the remainder of the Altimetry Inversion File header. Keyword and Value SFDU See Section 5.1.3. Inversion Header Record See Table 5-3. Aggregation Start Marker Start Label `CCSD1R000003', the SFDU Aggregation Marker label, indicating the start of a data aggrega- tion of unspecified length. This aggregation consists of a varying number of Altimetry Inver- sion Record SFDU's (nr_rec), as shown in Table 5-4. Length Field Eight bytes, ASCII, with leading zeroes manda- tory; the length of the remainder of the aggre- gation marker SFDU. Start Value DELIMITER= The character string `SMARKER', indicating that this is the start of a data aggregation. PRODUCT_NAME= The character string `ALTIMETRY_INVERSION'. TYPE= The character string `NJPL1I000025', where `0025' indicates that the data between the SMARKER and EMARKER labels comprise a registered SFDU aggregation (the Altimetry Inversion Aggre- gate), composed of a set of registered NJPL aggregates. Altimetry Inversion Record See Table 5-4. Aggregation End Marker End Label `CCSD1R000003', the SFDU Aggregation Marker label, indicating the end of a data aggregation of unspecified length. This matches the above "Start Marker". Length Field Eight bytes, ASCII, with leading zeroes manda- tory; the length of the remainder of the aggre- gation marker SFDU. End Value DELIMITER= The character string `EMARKER', indicating that this is the end of a data aggregation. PRODUCT_NAME= The character string `ALTIMETRY_INVERSION'. SU-MGN-SCVDR v 1.0 Page 22 +----------------------------------------------------------------------+ | Figure 5-5. Stanford Altimetry Inversion File (ANF) - Block Format | +---+---+--------------------------------------+--------------+--------+ | T | | CCSD1Z000001 | CCSDS Label | CCSDS | +---+---+--------------------------------------+--------------+ Header | | L | | 00000xxx | Length Field | | +---+---+--------------------------------------+--------------+--------+ | V | T | NJPL1K00KL00 | K-Label | | +---+---+--------------------------------------+--------------+ | | | L | 00000xxx | Length Field | | | +---+--------------------------------------+--------------+ | | | V | PRODUCT_FILE_NAME=ANFnnnnn.v | | | | | | PRODUCT_TYPE=INVERSION_FILE | | Keyword| | | | MISSION_ID=4 | | and | | | | MISSION_NAME=MAGELLAN | | Value | | | | SPACECRAFT_ID=18 | Keywords | SFDU | | | | SPACECRAFT_NAME=MAGELLAN | and | | | | | ORBIT_NUMBER=nnnnn | Values | | | | | UPLOAD_ID=cccccc | | | | | | NAV_UNIQUE_ID=cccccc | | | | | | HARDWARE_VERSION_ID=nnn | | | | | | MAJOR_SOFTWARE_VERSION_ID=nnn | | | | | | MINOR_SOFTWARE_VERSION_ID=nnn | | | | | | PROCESS_TIME=YYYY-MM-DDThh:mm:ss.fff | | | | | | DATA_FORMAT_TYPE=cccc | | | | +---+--------------------------------------+--------------+--------+ | | T | NJPL1I000005 | I-Label | ALT | | +---+--------------------------------------+--------------+ Inver | | | L | 00000xxx | Length Field | Header | | +---+--------------------------------------+--------------+ SFDU | | | V | Data Fields for Altimetry Inversion | | (Table | | | | Header Record | | 5-3) | | +---+--------------------------------------+--------------+--------+ | | T | CCSD1R000003 | Start Label | | | +---+--------------------------------------+--------------+ | | | L | 000000xx | Length Field | Aggr | | +---+--------------------------------------+--------------+ Start | | | V | DELIMITER=SMARKER | | Marker | | | | PRODUCT_NAME=ALTIMETRY_INVERSION | Start Value | | | | | TYPE=NJPL1I000025 | | | | +---+--------------------------------------+--------------+--------+ | | T | NJPL1I000006 | I-Label | ALT | | +---+--------------------------------------+--------------+ Inver | | | L | 00000xxx | Length Field | Record | | +---+--------------------------------------+--------------+ (Table | | | V | Altimetry Inversion Data Records | Data | 5-4) | | +---+--------------------------------------+--------------+--------+ | | T | CCSD1R000003 | End Label | | | +---+--------------------------------------+--------------+ Aggr | | | L | 000000xx | Length Field | End | | +---+--------------------------------------+--------------+ Marker | | | V | DELIMITER=EMARKER | End Value | | | | | PRODUCT_NAME=ALTIMETRY_INVERSION | | | +---+---+--------------------------------------+--------------+--------+ SU-MGN-SCVDR v 1.0 Page 23 5.4.1. Altimetry Inversion Header Record +-------------------------------------------------------------------------+ | Table 5-3. Stanford Altimetry Inversion Header Record SFDU (nh_rec) | +---+-----+-------+-----------------+-------------------------------------+ |Off| Len | Type | Name | Description | +---+-----+-------+-----------------+-------------------------------------+ | +0| 20 | sfdu | nh_sfdu | SFDU label and length | +---+-----+-------+-----------------+-------------------------------------+ | 20| 4 | long | nh_orb | Orbit number | +---+-----+-------+-----------------+-------------------------------------+ | 24| 4 | long | nh_ver | Orbit version | +---+-----+-------+-----------------+-------------------------------------+ | 28| 2 | short | nh_altinv_major | Program ALTINV major version number | +---+-----+-------+-----------------+-------------------------------------+ | 30| 2 | short | nh_altinv_minor | Program ALTINV minor version number | +---+-----+-------+-----------------+-------------------------------------+ | 32| 2 | short | nh_alt_major | Program ALT major version number | +---+-----+-------+-----------------+-------------------------------------+ | 34| 2 | short | nh_alt_minor | Program ALT minor version number | +---+-----+-------+-----------------+-------------------------------------+ | 36| 1 | uchar | nh_cvmf | Covariance matrix flag | +---+-----+-------+-----------------+-------------------------------------+ | 37| 1 | uchar | nh_meth_inv | Inversion method ID | +---+-----+-------+-----------------+-------------------------------------+ | 38| 1 | uchar | nh_meth_sig | Variance estimation method ID | +---+-----+-------+-----------------+-------------------------------------+ | 39| 1 | uchar | nh_meth_Gamsig | Constraint variance method ID | +---+-----+-------+-----------------+-------------------------------------+ | 40| 1 | uchar | nh_meth_thermal | Thermal noise method ID | +---+-----+-------+-----------------+-------------------------------------+ | 41| 1 | uchar | nh_specf | Non-delta spectral filter flag | +---+-----+-------+-----------------+-------------------------------------+ | 42| 1 | uchar | nh_meth_frot | Doppler rotation method ID | +---+-----+-------+-----------------+-------------------------------------+ | 43| 1 | uchar | nh_pad | spare | +---+-----+-------+-----------------+-------------------------------------+ | 44| 4 | long | nh_nrec | Number of data records | +---+-----+-------+-----------------+-------------------------------------+ | 48| 1 | uchar | nh_meth_echo | Range echo processing ID | +---+-----+-------+-----------------+-------------------------------------+ | 49| 1 | uchar | nh_meth_bmax | Maximum angle method ID | +---+-----+-------+-----------------+-------------------------------------+ | 50| 2 | short | nh_hid | Pulse compression ID | +---+-----+-------+-----------------+-------------------------------------+ | 52| 2 | short | nh_comp_major | Comp major version ID | +---+-----+-------+-----------------+-------------------------------------+ | 54| 2 | short | nh_comp_minor | Comp minor version ID | +---+-----+-------+-----------------+-------------------------------------+ | 56| 2 | short | nh_maxB | Maximum size of scattering function | +---+-----+-------+-----------------+-------------------------------------+ | 58| 2 | short | nh_maxN | Maximum size of covariance matrix | +---+-----+-------+-----------------+-------------------------------------+ | 60| 12 | uchar | nh_spare[12] | spares | +---+-----+-------+-----------------+-------------------------------------+ |+72| | +---+---------------------------------------------------------------------+ SU-MGN-SCVDR v 1.0 Page 24 Element Name Type Length Description nh_orb long 4 Orbit Number-the Magellan orbit number for the data represented in these data records. nh_ver long 4 Orbit version number-the version of the altimetry data file used for these results. Obtained from the VERSION_ID keyword of the corresponding ALT-EDR Or- bit Header File (NB: This turns out not to be a good indicator of the version of the data file; the Orbit Header File it- self is rarely updated). nh_altinv_major short 2 Program ALTINV Major Version Number-the major software version number of the Stanford program ALTINV used to obtain the scattering function solution. nh_altinv_minor short 2 Program ALTINV Minor Version Number-the minor software version number of the Stanford program ALTINV used to obtain the scattering function solution. nh_alt_major short 2 Program ALT Major Version Number-the ma- jor software version number of the Stan- ford program ALT used to compute the range-Doppler array from the raw al- timetry data. nh_alt_minor short 2 Program ALT Minor Version Number-the minor software version number of the Stanford program ALT used to compute the range-Doppler array from the raw al- timetry data. nh_cvmf uchar 1 Covariance Matrix Flag-if set (1) the upper triangular portion (in row-major order) of the covariance matrix is saved in nr_cvm; if not set (0), only the di- agonal is saved. nh_meth_inv uchar 1 Inversion Method ID-code number for the specific method of overdetermined least squares used to compute the inversions. Possible values are: 0 Singular Value Decomposition (pre- ferred) 1 QR Decomposition SU-MGN-SCVDR v 1.0 Page 25 nh_meth_sig uchar 1 Variance Estimation Method ID-code number for the method used to estimate the statistical uncertainty in the input data. The resulting variance is used in a weighted least squares fit and pro- pagated to form an estimate of the in- verted uncertainty in the solution. Possible values are: 0 Use Doppler spectrum and range echo after averaging bursts and summing across range and Doppler. 1 Use full range-Doppler map before averaging and summing (preferred). 2 Use the sample variance of the data itself, rather than a priori assumptions about the observation error distribu- tions. 3 Do not estimate the variance: weight each observation equally. nh_meth_Gamsig uchar 1 Constraint Variance Method ID-code number for the method used to assign weight to the smoothing constraint that controls the shape of the inversion. Determines the scale of smoothing param- eter nr_gamma. Possible values are: 0 Use the mean of the observed data. 1 Use the value 1. 2 Use a value that causes the smoothing matrix and model matrix to contribute equally to the error criterion when nr_gamma is 1, and in proportion to nr_gamma otherwise. This depends on the variance of the observations (pre- ferred). nh_meth_thermal uchar 1 Thermal Noise Method ID-code number for the method used to account for the ef- fects of thermal noise on the observa- tions. Possible values are: 0 Ignore effects of thermal noise. 1 Before the inversion, subtract an es- timate of the thermal noise from the ob- servations. 2 Solve for the thermal noise in the inversion itself (preferred). nh_specf uchar 1 Non-Delta Spectral Filter Flag-if set (1), the Doppler spectrum has been con- volved with an FIR filter before the inversion process. The nominal filter is [0.25 0.50 0.25] but is not saved in the SCVDR. If not set (0), no filter has been used (preferred). SU-MGN-SCVDR v 1.0 Page 26 nh_meth_frot uchar 1 Doppler Rotation Method ID-code number for the method used to account for unex- pected Doppler shifts in the observed echo spectrum. Possible values are: 0 Ignore any shift. 1 Compute three inversions, with the Doppler spectrum rotated by -1, 0, and +1 bins of 935 Hz, and choose the rota- tion that gives the smallest residual error. 2 Compute the centroid of the Doppler spectrum, compute two inversions with the spectrum rotated an integer number of bins just less than and just greater than the centroid, and choose the rota- tion that gives the smaller residual er- ror (preferred). nh_pad uchar 1 spare nh_nrec long 4 Number of Data Records-the number of al- timetry inversion records that follow this header. See Table 5-4. nh_meth_echo uchar 1 Range Echo Processing ID-code number for the method used to process the range echo before the inversion. Possible values are: 0 Do not change range echo (preferred). 1 Filter the range echo with an FIR filter, nominally [0.25 0.5 0.25]. nh_meth_bmax uchar 1 Maximum Angle Method ID-code number for the method used to determine the maximum solution angle in the inversion. Possi- ble values are: 0 Use an empirically derived table in- dexed by true anomaly (preferred). 1 Choose the largest angle that avoids the effects of range aliasing for the given geometry. nh_hid short 2 Pulse Compression ID-code number for the correlation kernel used in the radar pulse compression stage, before the range-Doppler array is computed. Possi- ble values are: 0 Use the "optimal" code ([11], pages 109-110) (preferred). 1 Use the transmitted range code ([11], page 108). SU-MGN-SCVDR v 1.0 Page 27 nh_comp_major short 2 COMP major version ID-major version number of the Stanford calibration software COMP [9] used to compensate the input data for amplitude and timing ef- fects. nh_comp_minor short 2 COMP minor version ID-minor version number of the Stanford calibration software COMP [9] used to compensate the input data for amplitude and timing ef- fects. nh_maxB short 2 Maximum size of scattering function-the largest number of elements that will ap- pear in any scattering function (nr_sig0) in this orbit, equal to the largest value of nr_blen. The maximum size in bytes is thus 4*nh_maxB. nh_maxN short 2 Maximum size of covariance matrix-the largest number of elements that will ap- pear in any covariance matrix (nr_cvm) in this orbit, equal to the largest value of nr_ncvm. The maximum size in bytes is thus 4*nh_maxN. nh_spare[12] uchar 12 spares SU-MGN-SCVDR v 1.0 Page 28 5.4.2. Altimetry Inversion Data Record The Altimetry Inversion Data Record SFDU is specified in Table 5-4. +----------------------------------------------------------------------------+ | Table 5-4. Stanford Altimetry Inversion Data Record SFDU (nr_rec) | +-----+-----+---------+--------------+---------------------------------------+ | Off | Len | Type | Name | Description | +-----+-----+---------+--------------+---------------------------------------+ | +0 | 20 | sfdu | nr_sfdu | SFDU label and length | +-----+-----+---------+--------------+---------------------------------------+ | 20 | 4 | ulong | nr_nfoot | Footprint number | +-----+-----+---------+--------------+---------------------------------------+ | 24 | 4 | ulong | nr_burst | Burst number for associated ALT burst | +-----+-----+---------+--------------+---------------------------------------+ | 28 | 4 | ulong | nr_flags | Flag fields (see Table 5-5a) | +-----+-----+---------+--------------+---------------------------------------+ | 32 | 8 | double | nr_scet | Footprint time (SCET, TDB) | +-----+-----+---------+--------------+---------------------------------------+ | 40 | 8 | double | nr_gdopp | Gross (radial) Doppler shift (Hz) | +-----+-----+---------+--------------+---------------------------------------+ | 48 | 3*8 | double | nr_scpos[3] | Spacecraft position (km, J2000) | +-----+-----+---------+--------------+---------------------------------------+ | 72 | 3*8 | double | nr_scvel[3] | Spacecraft velocity (km/sec, J2000) | +-----+-----+---------+--------------+---------------------------------------+ | 96 | 3*8 | double | nr_sspos[3] | Position of sub-spacecraft point | | | | | | (km, J2000) | +-----+-----+---------+--------------+---------------------------------------+ | 120 | 3*8 | double | nr_alta[3] | ALT antenna boresight vector (J2000) | +-----+-----+---------+--------------+---------------------------------------+ | 144 | 3*8 | double | nr_sara[3] | SAR antenna boresight vector (J2000) | +-----+-----+---------+--------------+---------------------------------------+ | 168 | 8 | double | nr_rt0 | Round-trip time for bin 0 (secs) | +-----+-----+---------+--------------+---------------------------------------+ | 176 | 8 | double | nr_rpk | Position of range peak within echo | +-----+-----+---------+--------------+---------------------------------------+ | 184 | 4 | float | nr_lat | Latitude of nadir (degrees N, VBF85) | +-----+-----+---------+--------------+---------------------------------------+ | 188 | 4 | float | nr_lon | Longitude of nadir (degrees E, VBF85) | +-----+-----+---------+--------------+---------------------------------------+ | 192 | 4 | float | nr_xfoot | Along-track footprint dimension (km) | +-----+-----+---------+--------------+---------------------------------------+ | 196 | 4 | float | nr_yfoot | Cross-track footprint dimension (km) | +-----+-----+---------+--------------+---------------------------------------+ | 200 | 4 | float | nr_pvrad | Pioneer-Venus radius at nadir (km) | +-----+-----+---------+--------------+---------------------------------------+ | 204 | 4 | ulong | nr_blo | First ALT burst used | +-----+-----+---------+--------------+---------------------------------------+ | 208 | 4 | ulong | nr_bhi | Last ALT burst used | +-----+-----+---------+--------------+---------------------------------------+ | 212 | 2 | ushort | nr_bav | Number of bursts averaged | +-----+-----+---------+--------------+---------------------------------------+ | 214 | 2 | ushort | nr_Gnum | G-matrix ID | +-----+-----+---------+--------------+---------------------------------------+ | 216 | 2 | ushort | nr_blen | Number of incidence angles in soln. | +-----+-----+---------+--------------+---------------------------------------+ | 218 | 2 | ushort | nr_ncvm | Number of elements saved in nr_cvm | +-----+-----+---------+--------------+---------------------------------------+ | (Continued on next page) | +----------------------------------------------------------------------------+ SU-MGN-SCVDR v 1.0 Page 29 +----------------------------------------------------------------------------+ | Table 5-4 (contd). Stanford Altimetry Inversion Data Record SFDU (nr_rec) | +-----+-----+---------+--------------+---------------------------------------+ | 220 | 4 | float | nr_gamma | Smoothing factor | +-----+-----+---------+--------------+---------------------------------------+ | 224 | 4 | float | nr_chisq | Chi-square residual from solution | +-----+-----+---------+--------------+---------------------------------------+ | 228 | 4 | float | nr_rmss | RMS surface slope from data (radians) | +-----+-----+---------+--------------+---------------------------------------+ | 232 | 36 | thn t | nr_thn | Thermal noise estimates | +-----+-----+---------+--------------+---------------------------------------+ | 268 | 4 | float | nr_dcent | Doppler centroid (Hz) | +-----+-----+---------+--------------+---------------------------------------+ | 272 | 4 | float | nr_dcentv | Estimated variance of nr_dcent(Hz**2) | +-----+-----+---------+--------------+---------------------------------------+ | 276 | 4 | float | nr_frot | Doppler rotation in solution (Hz) | +-----+-----+---------+--------------+---------------------------------------+ | 280 | 52 | calib_t | nr_calib | Calibration details | +-----+-----+---------+--------------+---------------------------------------+ | 332 | 54 |sab_hdr_t| nr_SAB | SAB header | +-----+-----+---------+--------------+---------------------------------------+ | 386 | 2 | uchar | nr_pad[2] | spares | +-----+-----+---------+--------------+---------------------------------------+ | 388 | 16 | uchar | nr_spare[16] | spares | +-----+-----+---------+--------------+---------------------------------------+ | 404 | p | float | nr_sig0[n] | Scattering function solution, | | | | | | n=nr_blen, p=4n | +-----+-----+---------+--------------+---------------------------------------+ |404+p| p | float | nr_ang[n] | Angle vector corresponding to | | | | | | nr_sig0, q=2p | +-----+-----+---------+--------------+---------------------------------------+ |404+q| 4*m | float | nr_cvm[m] | Covariance matrix for | | | | | | nr_sig0, m=nr_ncvm | +-----+-----+---------+--------------+---------------------------------------+ | N | N=404+q+4*m | +-----+----------------------------------------------------------------------+ Element Name Type Length Description nr_sfdu sfdu 20 SFDU Header Label and Length: `NJPL1I0000060000nnnn'. The number `0006' is registered with the NJPL SFDU authority as the "Altimetry Inversion Data Record." nr_nfoot ulong 4 Footprint Number-starting from 1, the number of the Altimetry Inversion Record by increasing Altimetry Footprint Time (nr_scet). nr_burst ulong 4 Burst Number-the logical record number from the ALT-EDR burst SFDU most closely associated with this footprint. If the number of bursts averaged (nr_bav) is odd, the middle burst; if nr_bav is even, the earlier of the two middle bursts. SU-MGN-SCVDR v 1.0 Page 30 nr_flags ulong 4 Flag fields-see Table 5-5a. nr_scet double 8 Footprint Time (SCET)-the burst start time (seconds of TDB since J2000; see Section 1.5.4.2) for the burst given by nr_burst. nr_gdopp double 8 Gross Doppler Shift (Hz)-the Doppler shift resulting from motion of the spacecraft toward nadir at nr_scet. (nr_gdopp>0 means the spacecraft alti- tude is decreasing). nr_scpos[3] double 3*8 Spacecraft Position Vector (km, J2000)- the spacecraft position at nr_scet, re- lative to the Venus center of mass, ex- pressed in inertial coordinates. nr_scvel[3] double 3*8 Spacecraft Velocity Vector (km sec-1, J2000)-the spacecraft velocity at nr_scet, relative to the Venus center of mass, expressed in inertial coordinates. nr_sspos[3] double 3*8 Sub-Spacecraft Position Vector (km, J2000)-the position of the nadir point (on a reference sphere of 6051 km ra- dius) at nr_scet, relative to the Venus center of mass, expressed in inertial coordinates. nr_alta[3] double 3*8 Altimetry Antenna Boresight Vector (J2000)-unit vector along the axis of the altimetry antenna at nr_scet, ex- pressed in inertial coordinates. nr_sara[3] double 3*8 SAR Antenna Boresight Vector (J2000)- unit vector along the axis of the high- gain (SAR) antenna at nr_scet, expressed in inertial coordinates. nr_rt0 double 8 Round-Trip Time for Bin 0 (seconds)-the round-trip light time corresponding to the first range bin (before peak detec- tion and rotation) in the averaged al- timetry echo at nr_scet. nr_rpk double 8 Incremental Round-Trip Time (seconds)- the position of the echo peak with respect to the range bin used in nr_rt0 (each range bin represents an additional 0.442 microseconds of round-trip delay beyond nr_rt0.) nr_lat float 4 Latitude of Nadir (degrees N, VBF85)-the body-fixed latitude of the nadir at nr_scet, in the range of -90 (South Pole) to +90 (North Pole); the nominal latitude of the footprint. SU-MGN-SCVDR v 1.0 Page 31 nr_lon float 4 Longitude of Nadir (degrees E, VBF85)- the body-fixed longitude of the nadir at nr_scet, in the range of 0-360. Periapsis nadir increases in longitude by about 1.48 per day (about 0.2 per or- bit); the nominal footprint longitude. nr_xfoot float 4 Along-Track Altimetry Footprint Dimen- sion (km)-the along-track dimension of the intersection of the 3-dB (two-way) altimetry antenna pattern with the sur- face when the antenna boresight is aimed at nadir (a very approximate measure of the along-track footprint dimension). nr_yfoot float 4 Cross-Track Altimetry Footprint Dimen- sion (km)-the cross-track dimension of the intersection of the 3-dB (two-way) altimetry antenna pattern with the sur- face when the antenna boresight is aimed at nadir (a very approximate measure of the across-track footprint dimension). nr_pvrad float 4 Pioneer-Venus Radius at Nadir (km)- radius of Venus at the nadir point as determined from Pioneer Venus data (pro- vided by MIT in GIPS image format). nr_blou long 4 First ALT Burst Used-the number of the first burst included in the average al- timetry echo for this record. nr_bhiu long 4 Last ALT Burst Used-the number of the last burst included in the average al- timetry echo for this record. nr_bavu short 2 Number of Bursts Averaged-the total number of altimeter bursts averaged to make this record. nr_Gnum ushort 2 G-matrix ID number-identifies the range-Doppler-angle array used to invert the range-Doppler data in this averaged echo (see Section 5.8). G-matrices are indexed from 0. nr_blen ushort 2 Number of Incidence Angles in Solution- Number of angle increments in the solu- tion for the scattering function from this average echo. nr_ncvm ushort 2 Number of Elements Saved in nr_cvm-the number of covariance values stored in nr_cvm (depends on nh_cvmf; see also nr_cvm). nh_cvmf nr_ncvm 0 nr_blen+1 1 (nr_blen +1)*(nr_blen+2)/2 SU-MGN-SCVDR v 1.0 Page 32 nr_gamma float 4 Smoothing Factor-the value of the param- eter used to minimize second differences in the scattering function solution for this average echo (see also nr_meth_Gamsig in Section 5.4.1). nr_chisq float 4 Chi-Square Residual from Solution-the residual from the weighted least-square error inversion for the scattering func- tion nr_rmss float 4 RMS Surface Tilt from Data (radians)-RMS surface tilt theta<0> calculated from the nr_blen points in the solution[4]. nr_thn thn_t 36 Thermal Noise Estimates (watts per range-Doppler bin)-estimates of thermal noise (and its variance) calculated dur- ing the solution for the scattering function (see Table 5-5b). nr_dcent float 4 Doppler Centroid (Hz)-the calculated center of the spectrum of the radar re- ceiver signal. nr_dcentv float 4 Estimated variance of nr_dcent (Hz2). nr_frot float 4 Doppler Rotation Used for Solution (Hz)-the offset of the echo from its nominal center bin position assumed to be due to surface effects (an integral multiple of 935 Hz, the width of a sin- gle frequency bin)(see also nh_meth_frot in Section 5.4.1). ____________________ [4] | nr_blen |1/2 | __ | 2 1/2 | \ 2 | = | \ tan theta * p(theta ) * sin(theta ) * Dtheta | 0 | / i i i i | | /__ | | i=1 | where p(theta) = sec(theta), and K is found from nr_blen __ \ \ p(theta ) * sin(theta ) * Dtheta = 1 / i i i /__ i=1 SU-MGN-SCVDR v 1.0 Page 33 nr_calib calib_t 52 Calibration Details-the contributing factors to nr_CALT (see Table 5-5c). nr_SAB sab_t 54 SAB Header-SAR/Altimetry Burst Header (see Table 5-5d). nr_pad[2] uchar 2 spares nr_spare[16] uchar 16 spares nr_sig0[n] float 4*n Scattering Function-the so function ob- tained by inverting the average al- timetry radar echo from bursts nr_blo through nr_bhi. The function is a vec- tor of n=nr_blen numbers for the (ef- fective) incidence angles given by nr_ang. nr_ang[n] float 4*n Solution Angles for Scattering Function (radians)-the n=nr_blen angles at which the scattering function solution has been obtained. The default angles are spaced by 0.5 degrees, starting at 0.25-that is, the solution angles are 0.25, 0.75, 1.25, 1.75, ... nr_blen*0.5-0.25 degrees; note, however, that nr_ang is given in radians. nr_cvm[m] float 4*m Covariance Matrix-matrix of estimated covariances of nr_sig0 and nr_thn[0]. The size (m=nr_ncvm) and form of the ma- trix[5] that is stored depends on the value of nh_cvmf in the Inversion Header Record (see Table 5-3). If nh_cvmf is zero, only the m=nr_blen+1 diagonal entries of the matrix above are stored. If nh_cvmf is nonzero, the upper triangular portion (including the diagonal) are stored in row-major order, for a total of m=(nr_blen+1)*(nr_blen+2)/2 entries. ____________________ [5] / |nr_thn[0]-|| |T \ E | | ||(nr_thn[0]-)(nr_sig0-)| | \ | nr_sig0- || | / where E and <> denote statistical expectation, and nr_sig0 is considered a column vector. SU-MGN-SCVDR v 1.0 Page 34 5.4.2.1. Altimetry Inversion Record Flag Values +---------------------------------------------------------------------------+ | Table 5-5a. Stanford Altimetry Inversion Record Flag Values (nr_flags) | +------------------+-------+------------------------------------------------+ | Name | Value | Description (see footnote 6) | +------------------+-------+------------------------------------------------+ | NR_FLAG_NOSIGNAL | 1 | At least one burst had no signal present, | | | | according to telemetered status of | | | | transmitter and receiver. | +------------------+-------+------------------------------------------------+ | NR_FLAG_GFAR | 2 | G-matrix was computed for a spacecraft-planet | | | | geometry too different from the actual | | | | geometry (nominally 1 degree of true anomaly. | +------------------+-------+------------------------------------------------+ | NR_FLAG_BSEP | 4 | Two consecutive bursts were separated by too | | | | much distance (nominally 10 km at nadir). | +------------------+-------+------------------------------------------------+ | NR_FLAG_BWID | 8 | The bursts used in the inversion span too much | | | | total distance (nominally 50 km at nadir). | +------------------+-------+------------------------------------------------+ | NR_FLAG_RPK | 16 | The echo peak estimate nr_rpk is suspect, | | | | and should not be used. | +------------------+-------+------------------------------------------------+ 5.4.2.2. Altimetry Inversion Record Thermal Noise Estimates +---------------------------------------------------------------------------+ | Table 5-5b. Stanford Altimetry Inversion Thermal Noise Estimates (thn_t) | +----+-----+-------+---------+----------------------------------------------+ | Off| Len | Type | Name | Description | +----+-----+-------+---------+----------------------------------------------+ | +0 | 4 | float | tn_sol | Inversion solution | +----+-----+-------+---------+----------------------------------------------+ | 4 | 4 | float | tn_solv | Estimated variance of nr_thnsol | +----+-----+-------+---------+----------------------------------------------+ | 8 | 4 | float | tn_min | Smallest range-Doppler array value | +----+-----+-------+---------+----------------------------------------------+ | 12 | 4 | float | tn_avg | Average of small range-Doppler values | +----+-----+-------+---------+----------------------------------------------+ | 16 | 4 | float | tn_r | Minimum in range echo | +----+-----+-------+---------+----------------------------------------------+ ____________________ [6] The one-bit flags are defined by the decimal number that contains that bit, To test the value of, for example, the "range peak" flag you should form the logical AND of nr_flags and 16. If the result is non-zero, the flag is "set". SU-MGN-SCVDR v 1.0 Page 35 Element Name Type Length Description tn_sol float 4 Inversion Solution (watts-per-range- Doppler-bin)-Thermal noise power esti- mate calculated as one of many variables in the chi-square solution for the sur- face scattering function nr_sig0. Like- ly to be an overestimate since there is no attempt to account for radar clutter; nr_thnsol includes contributions from Venus' surface, the radar equipment, and aliased echo signal in both time/range and frequency. tn_solv float 4 Estimated Variance of nr_thnsol (watts2-per-range-Doppler-bin)-Estimate of variance in nr_thnsol from propaga- tion of errors through solution pro- cedure. tn_min float 4 Smallest Range-Doppler Array Value (watts-per-range-Doppler-bin)-Smallest value in averaged 16 by 151 (frequency by range, respectively) array of proces- sor output power. Likely to be an un- derestimate, since statistical varia- tions will force the "minimum" below the average. tn_avg float 4 Average of Small Range-Doppler Values (watts-per-range-Doppler-bin)-the aver- age of range echo bin values from 10-20 range bins before the echo peak (divided by 16). tn_r float 4 Minimum from Range Echo (watts-per- range-Doppler-bin)-the minimum value in the range echo, divided by 16. 5.4.2.3. Altimetry Inversion Calibration Details +-------------------------------------------------------------------------+ | Table 5-5c. Stanford Altimetry Inversion Calibration Details (calib_t) | +----+-----+--------+------------+----------------------------------------+ | Off| Len | Type | Name | Description | +----+-----+--------+------------+----------------------------------------+ | +0 | 1 | uchar | cl_TXA | Transmitter A flag | +----+-----+--------+------------+----------------------------------------+ | 1 | 1 | uchar | cl_RXA | Receiver A flag | +----+-----+--------+------------+----------------------------------------+ | 2 | 2 | uchar | cl_pad1[2] | spares | +----+-----+--------+------------+----------------------------------------+ | 4 | 4 | float | cl_Cpt0 | End-to-end system correction (dB) | +----+-----+--------+------------+----------------------------------------+ | (Continued on next page) | +-------------------------------------------------------------------------+ SU-MGN-SCVDR v 1.0 Page 36 +-------------------------------------------------------------------------+ | Table 5-5c. Stanford Altimetry Inversion Calibration Details (calib_t) | +----+-----+--------+------------+----------------------------------------+ | 8 | 4 | float | cl_xstrap | Cross-strapping correction (dB) | +----+-----+--------+------------+----------------------------------------+ | 12 | 4 | float | cl_dCTX | Transmitter power correction (dB) | +----+-----+--------+------------+----------------------------------------+ | 16 | 4 | float | cl_TT1 | Transmitter Stage 1 temperature (K) | +----+-----+--------+------------+----------------------------------------+ | 20 | 4 | float | cl_TOA | ONU Altimeter temperature (K) | +----+-----+--------+------------+----------------------------------------+ | 24 | 4 | float | cl_atmos | Atmospheric attenuation (dB) | +----+-----+--------+------------+----------------------------------------+ | 28 | 4 | float | cl_ant | Antenna pattern correction (dB) | +----+-----+--------+------------+----------------------------------------+ | 32 | 4 | float | cl_TRX | Receiver temperature (K) | +----+-----+--------+------------+----------------------------------------+ | 36 | 4 | float | cl_dCT | Receiver temperature attenuation (dB) | +----+-----+--------+------------+----------------------------------------+ | 40 | 1 | uchar | cl_rac | Commandable attenuation code | +----+-----+--------+------------+----------------------------------------+ | 41 | 3 | uchar | cl_pad2[3] | spares | +----+-----+--------+------------+----------------------------------------+ | 44 | 4 | float | cl_dCA | Receiver commandable attenuation (dB) | +----+-----+--------+------------+----------------------------------------+ | 48 | 4 | float | cl_CALT | Total amplitude correction (dB) | +----+-----+--------+------------+----------------------------------------+ | 52 | | +----+--------------------------------------------------------------------+ Element Name Type Length Description cl_TXA uchar 1 Transmitter A flag-if set (1), transmitter A was used; if not set (0), transmitter B was used. cl_RXA uchar 1 Receiver A flag-if set (1), receiver A was used; if not set (0), receiver B was used. cl_pad1[2] uchar 2 spares cl_Cpt0 float 4 End-to-end system correction (dB)-the end- to-end gain of the complete altimetry radar system for a closed loop test [if the antenna were removed and the outgoing (transmitted) signal were turned directly back to the receiver-including processing at Stanford]. The value of cl_Cpt0 is the measured attenua- tion during this test. cl_xstrap float 4 Cross-strapping correction (dB)-the attenua- tion caused by using transmitter A with re- ceiver B, or vice versa. SU-MGN-SCVDR v 1.0 Page 37 cl_dCTX float 4 Transmitter power correction (dB)-an estimat- ed attenuation of the available power, rela- tive to cl_Cpt0, based on telemetered meas- urements of transmitter and output network temperatures. cl_TT1 float 4 Transmitter Stage 1 temperature (K)-the telemetered temperature of the Transmitter Stage 1 Driver temperature, used to compute the transmit power. cl_TOA float 4 ONU Altimeter temperature (K)-the telemetered temperature of the ONU Altimeter temperature, used to compute the transmit power. cl_atmos float 4 Atmospheric attenuation (dB)-the expected at- tenuation due to the atmosphere for this na- dir elevation (nr_pvrad). cl_ant float 4 Antenna pattern correction (dB)-always zero because the gain pattern of the antenna is accounted for in the G-matrix calculation. cl_TRX float 4 Receiver temperature (K)-telemetered tempera- ture of the receiver. cl_dCT float 4 Receiver temperature attenuation (dB)-the portion of receiver attenuation that is dependent on receiver temperature. cl_rac uchar 1 Commandable attenuation code-the 3-bit code specifying the amount of attenuation used in the receiver front end. (See Table 5-5d and [12] for the SAB header format.) cl_pad2[3] uchar 3 spares cl_dCA float 4 Receiver commandable attenuation (dB)-the ac- tual receiver attenuation specified by the attenuation code cl_rac. cl_CALT float 4 Total amplitude correction (dB)-the total am- plitude correction expressed as an attenua- tion and computed from the formula: cl_CALT = cl_Cpt0 + cl_xstrap + cl_dCTX + cl_atmos + cl_ant + cl_dCT + cl_dCA The raw data are then calibrated by multipli- cation (in power) by 10CALT/10. SU-MGN-SCVDR v 1.0 Page 38 5.4.2.4. Altimetry Inversion SAB Header The SAB Header is carried forward from the ALT-EDR tape. Its format is sum- marized in Table 5-5d; more detailed information is available in [12]. +------------------------------------------------------------------+ | Table 5-5d. Stanford Altimetry Inversion SAB Header (sab_hdr_t) | +-----------------+------------------------------------------------+ | Length (bits) | Description | +-----------------+------------------------------------------------+ | 32 | JPL sync code 0x03915ED3 | +-----------------+------------------------------------------------+ | 192 | BAQ threshold data (24 8-bit words) | +-----------------+------------------------------------------------+ | 20 | Spares (filled with zeroes) | +-----------------+------------------------------------------------+ | 12 | Emissivity data | +-----------------+------------------------------------------------+ | 12 | Spares (filled with zeroes) | +-----------------+------------------------------------------------+ | 52 | Spacecraft time | +-----------------+------------------------------------------------+ | 16 | Spares (filled with zeroes) | +-----------------+------------------------------------------------+ | 80 | Status field | +-----------------+------------------------------------------------+ | 16 | Buffer memory, checkout flag | +-----------------+------------------------------------------------+ 5.5. Inversion Fit File The Inversion Fit File has the general structure shown in Figure 5-6. CCSDS Label `CCSD1Z000001', the CCSDS primary SFDU label. Length Field Eight bytes, ASCII, with leading zeroes manda- tory; the length of the remainder of the Inver- sion Fit File header. Keyword and Value SFDU See Section 5.1.3. Inversion Fit Header Record See Table 5-6. Aggregation Start Marker Start Label `CCSD1R000003', the SFDU Aggregation Marker label, indicating the start of a data aggrega- tion of unspecified length. This aggregation consists of a varying number of Inversion Fit Record SFDU's (nf_rec), as shown in Table 5-7. Length Field Eight bytes, ASCII, with leading zeroes manda- tory; the length of the remainder of the aggre- gation marker SFDU. Start Value DELIMITER= The character string `SMARKER', indicating that this is the start of a data aggregation. SU-MGN-SCVDR v 1.0 Page 39 +-----------------------------------------------------------------------+ | Figure 5-6. Stanford Inversion Fit File (NFF) - Block Format | +---+---+--------------------------------------+--------------+---------+ | T | | CCSD1Z000001 | CCSDS Label | CCSDS | +---+---+--------------------------------------+--------------+ Header | | L | | 00000xxx | Length Field | | +---+---+--------------------------------------+--------------+---------+ | V | T | NJPL1K00KL00 | K-Label | | | +---+--------------------------------------+--------------+ | | | L | 00000xxx | Length Field | | | +---+--------------------------------------+--------------+ | | | V | PRODUCT_FILE_NAME=NFFnnnnn.v | | | | | | PRODUCT_TYPE=INV_FIT_FILE | | | | | | MISSION_ID=4 | | Keyword | | | | MISSION_NAME=MAGELLAN | | and | | | | SPACECRAFT_ID=18 | Keywords | Value | | | | SPACECRAFT_NAME=MAGELLAN | and | SFDU | | | | ORBIT_NUMBER=nnnnn | Values | | | | | UPLOAD_IC=cccccc | | | | | | NAV_UNIQUE_ID=cccccc | | | | | | HARDWARE_VERSION_ID=nnn | | | | | | MAJOR_SOFTWARE_VERSION_ID=nnn | | | | | | MINOR_SOFTWARE_VERSION_ID=nnn | | | | | | PROCESS_TIME=YYYY-MM-DDThh:mm:ss.fff | | | | | | DATA_FORMAT_TYPE=cccc | | | | +---+--------------------------------------+--------------+---------+ | | T | NJPL1I000007 | I-Label |Inversion+ | +---+--------------------------------------+--------------+ Fit Hdr | | | L | 00000xxx | Length Field | SFDU | | +---+--------------------------------------+--------------+ (Table | | | V | Data Fields for Inversion Fit Header | | 5-6) | | +---+--------------------------------------+--------------+---------+ | | T | CCSD1R000003 | Start Label | | | +---+--------------------------------------+--------------+ | | | L | 000000xx | Length Field | Aggr | | +---+--------------------------------------+--------------+ Start | | | V | DELIMITER=SMARKER | | Marker | | | | PRODUCT_NAME=INVERSION_FIT | Start Value | | | | | TYPE=NJPL1I000026 | | | | +---+--------------------------------------+--------------+---------+ | | T | NJPL1I000008 | I-Label |Inversion| | +---+--------------------------------------+--------------+ Fit Data| | | L | 00000xxx | Length Field | Records | | +---+--------------------------------------+--------------+ (Table | | | V | Data Fields for Inversion Fit Data | Data Records | 5-7) | | +---+--------------------------------------+--------------+---------+ | | T | CCSD1R000003 | End Label | | | +---+--------------------------------------+--------------+ Aggr | | | L | 000000xx | Length Field | end | | +---+--------------------------------------+--------------+ Marker | | | V | DELIMITER=EMARKER | End Value | | | | | PRODUCT_NAME=INVERSION_FIT | | | +---+---+--------------------------------------+--------------+---------+ SU-MGN-SCVDR v 1.0 Page 40 PRODUCT_NAME= The character string `INVERSION_FIT' TYPE= The character string `NJPL1I000026', where `0026' indicates that the data between the SMARKER and EMARKER labels comprise a registered SFDU aggregation (the Inversion Fit Aggregate), composed of a set of registered NJPL aggregates. Inversion Fit Data Record See Table 5-7. Aggregation End Marker End Label `CCSD1R000003', the SFDU Aggregation Marker label, indicating the end of a data aggregation of unspecified length. This matches the above "Start Marker". Length Field Eight bytes, ASCII, with leading zeroes manda- tory; the length of the remainder of the aggre- gation marker SFDU. End Value DELIMITER= The character string `EMARKER', indicating that this is the end of a data aggregation. PRODUCT_NAME= The character string `INVERSION_FIT'. +--------------------------------------------------------------------------+ | Table 5-6. Stanford Inversion Fit Header Record (fh_rec) | +----+-----+-------+-----------------+-------------------------------------+ |Off | Len | Type | Name | Description | +----+-----+-------+-----------------+-------------------------------------+ | +0 | 20 | sfdu | fh_sfdu | SFDU label and length | +----+-----+-------+-----------------+-------------------------------------+ | 20 | 4 | long | fh_orb | Orbit number | +----+-----+-------+-----------------+-------------------------------------+ | 24 | 4 | long | fh_ver | Orbit version | +----+-----+-------+-----------------+-------------------------------------+ | 28 | 2 | short | fh_sslfit_major | Program SSLFIT major version number | +----+-----+-------+-----------------+-------------------------------------+ | 30 | 2 | short | fh_sslfit_minor | Program SSLFIT minor version number | +----+-----+-------+-----------------+-------------------------------------+ | 32 | 2 | short | fh_altinv_major | Program ALTINV major version number | +----+-----+-------+-----------------+-------------------------------------+ | 34 | 2 | short | fh_altinv_minor | Program ALTINV minor version number | +----+-----+-------+-----------------+-------------------------------------+ | 36 | 2 | short | fh_alt_major | Program ALT major version number | +----+-----+-------+-----------------+-------------------------------------+ | 38 | 2 | short | fh_alt_minor | Program ALT minor version number | +----+-----+-------+-----------------+-------------------------------------+ | 40 | 4 | long | fh_nrec | Number of inversion fit records | +----+-----+-------+-----------------+-------------------------------------+ | 44 | 2 | short | fh_nlaw | Number of synthetic scattering laws | +----+-----+-------+-----------------+-------------------------------------+ | 46 | 1 | uchar | fh_meth_inv | Inversion method ID | +----+-----+-------+-----------------+-------------------------------------+ | (Continued on next page) | +--------------------------------------------------------------------------+ SU-MGN-SCVDR v 1.0 Page 41 +--------------------------------------------------------------------------+ | Table 5-6 (contd). Stanford Inversion Fit Header Record (fh_rec) | +----+-----+-------+-----------------+-------------------------------------+ | 47 | 1 | uchar | fh_meth_sig | Variance estimation method ID | +----+-----+-------+-----------------+-------------------------------------+ | 48 | 1 | uchar | fh_meth_Gamsig | Constraint variance method ID | +----+-----+-------+-----------------+-------------------------------------+ | 49 | 1 | uchar | fh_meth_thermal | Thermal noise method ID | +----+-----+-------+-----------------+-------------------------------------+ | 50 | 1 | uchar | fh_meth_frot | Doppler rotation method ID | +----+-----+-------+-----------------+-------------------------------------+ | 51 | 1 | uchar | fh_meth_echo | Range echo processing ID | +----+-----+-------+-----------------+-------------------------------------+ | 52 | 1 | uchar | fh_meth_bmax | Maximum angle method ID | +----+-----+-------+-----------------+-------------------------------------+ | 53 | 1 | uchar | fh_specf | Non-delta spectral filter flag | +----+-----+-------+-----------------+-------------------------------------+ | 54 | 2 | uchar | fh_pad[2] | spares | +----+-----+-------+-----------------+-------------------------------------+ | 56 | 16 | uchar | fh_spare[16] | spares | +----+-----+-------+-----------------+-------------------------------------+ | 72 | | +----+---------------------------------------------------------------------+ Element Name Type Length Description fh_sfdu sfdu 20 SFDU Label and Length: `NJPL1I0000070000nnnn'. The number `0007' is registered with the NJPL SFDU authority as the "Stanford Inversion Fit Header Record". fh_orb long 4 Orbit Number-orbit number for the data to be fit. fh_ver long 4 Orbit Version Number-version number for the altimetry data file used in this processing. Obtained from the VERSION_ID keyword of the corresponding ALT-EDR Orbit Header File (NB: This turns out not to be a good indicator of the version of the data file; the Orbit Header File itself is rarely updated). fh_sslfit_major short 2 Program SSLFIT Major Version Number-the number of the major software version of Stanford program SSLFIT used to fit these data. fh_sslfit_minor short 2 Program SSLFIT Minor Version Number-the number of the minor software version of Stanford program SSLFIT used to fit these data. SU-MGN-SCVDR v 1.0 Page 42 fh_altinv_major short 2 Program ALTINV Major Version Number-the number of the major software version of Stanford program ALTINV that produced the scattering function solutions. fh_altinv_minor short 2 Program ALTINV Minor Version Number-the number of the minor software version of Stanford program ALTINV that produced the scattering function solutions. fh_alt_major short 2 Program ALT Major Version Number-the number of the major software version of Stanford program ALT used to carry out the range-Doppler processing on these data. fh_alt_minor short 2 Program ALT Minor Version Number-the number of the minor software version of Stanford program ALT used to carry out the range-Doppler processing on these data. fh_nrec long 4 Number of Inversion Fit Records in File-the number of inversions (solutions for the surface scattering law) and, hence, the number of fitted result records in this file; equal to nh_nrec. fh_nlaw short 2 Number of Synthetic Scattering Laws-the number of synthetic scattering laws com- pared against the scattering solution; "synthetic" scattering laws can include Hagfors, exponential, Gaussian, Ray- leigh, and Muhleman (see Table 5-9). fh_meth_inv uchar 1 Inversion Method ID-Identifier for inversion method (carried forward from corresponding Altimetry Inversion Header Record; see Table 5-3). fh_meth_sig uchar 1 Variance Estimation Method ID-Identifier for variance estimation technique (car- ried forward from corresponding Al- timetry Inversion Header Record; see Table 5-3). fh_meth_Gamsig uchar 1 Constraint Variance Method ID-Identifier for variance constraint technique (car- ried forward from corresponding Al- timetry Inversion Header Record; see Table 5-3). fh_meth_thermal uchar 1 Thermal Noise Method ID-Identifier for thermal noise estimation technique (car- ried forward from corresponding Al- timetry Inversion Header Record; see Table 5-3). SU-MGN-SCVDR v 1.0 Page 43 fh_meth_frot uchar 1 Doppler Rotation Method ID-Identifier for Doppler rotation technique (carried forward from corresponding Altimetry Inversion Header Record; see Table 5-3). fh_meth_echo uchar 1 Range Echo Processing ID-Identifier for range echo processing technique (carried forward from corresponding Altimetry Inversion Header Record; see Table 5-3). fh_meth_bmax uchar 1 Maximum Angle Method ID-Identifier for technique to set maximum incidence angle in solution (carried forward from corresponding Altimetry Inversion Header Record; see Table 5-3). fh_specf uchar 1 Non-Delta Spectral Filter Flag-set if Doppler spectrum was filtered before the inversion (carried forward from corresponding Altimetry Inversion Header Record; see Table 5-3). fh_pad[2] uchar 2 spares fh_spare[16] uchar 16 spares +-----------------------------------------------------------------------+ | Table 5-7. Stanford Inversion Fit Data Record SFDU (fr_rec) | +----+-----+-------+-------------+--------------------------------------+ |Off | Len | Type | Name | Description | +----+-----+-------+-------------+--------------------------------------+ | +0 | 20 | sfdu | fr_sfdu | SFDU label and length | +----+-----+-------+-------------+--------------------------------------+ | 20 | 4 | ulong | fr_nfoot | Footprint number | +----+-----+-------+-------------+--------------------------------------+ | 24 | 4 | ulong | fr_nlaw | Number of synthetic scattering laws | +----+-----+-------+-------------+--------------------------------------+ | 28 | 4 | uchar | fr_spare[4] | Spares | +----+-----+-------+-------------+--------------------------------------+ | Repeating sets of fit results (below) for fr_nlaw scattering laws | +----+-----+-------+-------------+--------------------------------------+ | -- | 4 | uchar | fr_slaw | Scattering law ID | +----+-----+-------+-------------+--------------------------------------+ | -- | 4 | ulong | fr_flags | Flag fields (see Table 5-8) | +----+-----+-------+-------------+--------------------------------------+ | -- | 4 | float | fr_p1 | Fit parameter #1 (see Table 5-9) | +----+-----+-------+-------------+--------------------------------------+ | -- | 4 | float | fr_p1v | Fit parameter #1 variance | +----+-----+-------+-------------+--------------------------------------+ | -- | 4 | float | fr_p2 | Fit parameter #2 (see Table 5-9) | +----+-----+-------+-------------+--------------------------------------+ | -- | 4 | float | fr_p2v | Fit parameter #2 variance | +----+-----+-------+-------------+--------------------------------------+ | (Continued on next page) | +-----------------------------------------------------------------------+ SU-MGN-SCVDR v 1.0 Page 44 +-----------------------------------------------------------------------+ | Table 5-7 (contd). Stanford Inversion Fit Data Record SFDU (fr_rec) | +----+-----+-------+-------------+--------------------------------------+ | -- | 4 | float | fr_rmss | RMS slope for p1, p2 (see Table 5-9) | +----+-----+-------+-------------+--------------------------------------+ | -- | 4 | float | fr_rmsv | RMS slope variance | +----+-----+-------+-------------+--------------------------------------+ | -- | 4 | float | fr_resid | Residual error in fit | +----+-----+-------+-------------+--------------------------------------+ | N | N=32+36*fr_nlaw | +----+------------------------------------------------------------------+ Element Name Type Length Description fr_sfdu sfdu 20 SFDU Label and Length: `NJPL1I0000080000nnnn'. The number `0008' is registered with the NJPL SFDU authority as the "Inversion Fit Data Record". fr_nfoot ulong 4 The Inversion Fit Record Footprint Number-starting from 1, the number of the Inversion Fit Data Record; equal to the Footprint Number nr_nfoot in the corresponding Altimetry Inversion Data Record. fr_nlaw ulong 4 Number of Synthetic Scattering Laws-the number of synthetic scattering laws com- pared against the scattering solution; "synthetic" scattering laws can include Hagfors, exponential, Gaussian, Ray- leigh, and Muhleman. Same as fh_nlaw except for type and length. fr_spare[4] uchar 4 spares The following block of entries will be repeated fr_nlaw times fr_slaw char 4 Scattering Law ID-a 4-letter identifier for one of several analytic scattering functions which can be fitted to fr_sig0. Possible values, and the sub- sequent interpretation for fr_p1 and fr_p2, are shown in Table 5-9. fr_flags ulong 4 Flag Fields (see Table 5-8). fr_p1 float 4 Scattering law parameter #1 (see Table 5-9). fr_p1v float 4 Variance in fr_p1. fr_p2 float 4 Scattering law parameter #2 (see Table 5-9). SU-MGN-SCVDR v 1.0 Page 45 fr_p2v float 4 Variance in fr_p2. fr_rmss float 4 RMS Tilt for Fitted Function (radians)(see Table 5-9) fr_rmsv float 4 Variance of fr_rmss (radians2) fr_resid float 4 Residual Error in Fit-Residual between analytic function (Table 5-9) and scattering function from inversion of data for best choices of fr_p1 and fr_p2. End of repeated block +------------------------------------------------------------------+ | Table 5-8. Stanford Inversion Fit Record Flag Values (fr_flags) | +------------------+-------+---------------------------------------+ | Name | Value | Flag Description (see footnote 7) | +------------------+-------+---------------------------------------+ | FR_FLAGS_P1MAX | 1 | p1 fit failed: p1 too large | | FR_FLAGS_P1MIN | 2 | p1 fit failed: p1 too small | +------------------+-------+---------------------------------------+ The rms tilt for the Muhleman function is approximated by a power law fit to data obtained by numerical integration. This fit is accurate to within 1% of the numerical integration results over the range 0.0008