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