PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT INTERCHANGE_FORMAT = ASCII PUBLICATION_DATE = 2000-05-31 NOTE = "N/A" END_OBJECT = TEXT END 820-013 Deep Space Mission System (DSMS) External Interface Specification JPL D-16765 TRK-2-23 Media Calibration Interface Original Release: June 1, 1985 Change 02: May 31, 2000 Document Owner: Approved by: ______________________________ ________ T. Runge Date Troposphere Calibration Software CDE Document Owner: ______________________________ ________ A. Kwok Date System Services Development Engineer Tracking and Navigation Services Approved by: Approved by: ______________________________ ________ W. Tai Date Manager, TMOD Systems Engineering and Standards Office Approved by: ______________________________ ________ L. Cangahuala Date System Services Manager Tracking and Navigation Services Approved by: ______________________________ ________ J. Stipanuk Date Interface Engineer and Release Authority Prepared By: Approved by: ______________________________ ________ T. Runge Date Troposphere Calibration Software CDE Reviewed By: Approved by: ______________________________ ________ A. Kwok Date TMOD System Engineer ______________________________ ________ V.I. Altunin Date Telecommunications and Mission Services Manager Approved by: ______________________________ ________ A. I. Beers Date Telecommunications and Mission Services Manager ______________________________ ________ R.D. Benson Date Telecommunications and Mission Services Manager Approved by: ______________________________ ________ A.L. Berman Date Telecommunications and Mission Services Manager _________________________ ________ P.E. Beyer Date Telecommunications and Mission Services Manager Approved by: ______________________________ ________ A.F. Chang Date Telecommunications and Mission Services Manager ______________________________ ________ R.L. Gillette Date Telecommunications and Mission Services Manager Approved by: ______________________________ ________ D.P. Holmes Date Telecommunications and Mission Services Manager ______________________________ ________ E.B. Luers Date Telecommunications and Mission Services Manager Approved by: ______________________________ ________ J.C. McKinney Date Telecommunications and Mission Services Manager ______________________________ ________ P.T. Poon Date Telecommunications and Mission Services Manager Approved by: ______________________________ ________ B.G. Yetter Date Telecommunications and Mission Services Manager ______________________________ ________ M. Connally Date System Services Development Engineer DSN Science Services ______________________________ ________ D. Linick Date Manager, Deep Space Mission System Operations Office Approved by: ______________________________ ________ J. Wackley Date Operations Change Log Revision Date Pages/Sections Change Summary New issue 05/01/1983 All Change 1 02/15/1999 C..1 Clarification of 2-digit year. Change 2 05/31/2000 All Update troposphere and solar Plasma calibration specifications and reformat. Contents 1 Introduction 1.1 Purpose and Scope 1.1.1 Applicability of This Release 1.2 Revision and Control 1.3 Applicable Documents 1.4 Notation and Conventions 1.5 Abbreviations 2 Functional Overview 3 Detailed Interface Description 3.1 CSP Command Language 3.1.1 Command Verbs 3.1.2 Data Types 3.1.3 Frequency Band 3.1.4 Transmission Media 3.1.5 Time Spans 3.1.6 Network Complex or Station 3.1.7 Data Source 3.1.8 Computation Specifiers 3.1.9 Sign of Calibration 3.1.10 Number Formats 3.1.11 Comments 3.2 Media Calibrations 3.2.1 Ionospheric Calibrations 3.2.2 Tropospheric Calibrations 3.2.3 Solar Plasma Calibrations 3.3 File Naming Conventions 3.4 Protocols and Configuration 3.5 Dependencies Figures Figure Page Figure 3-1: Example Ionospheric Calibration Figure 3-2: Seasonal Tropospheric Models for DSCC 10 Figure 3-3: Example Tropospheric Calibrations Figure 3-4: Example Solar Plasma Calibration Tables Table Page Table 3-1: CSP Elements Used in Media Calibrations 1 Introduction Section 1 Introduction 1.1 Purpose and Scope This module specifies the format and content of the media calibration data that are provided by the Media Modeling (MEDIA) Subsystem to the Orbit and Trajectory (NAV) Subsystem, for use by project navigation and radio science teams, multi- mission spacecraft navigation, and other investigators. These calibrations improve the accuracy of spacecraft orbit determination and radio science investigations by compensating for the media transmission effects of the Earth's troposphere and ionosphere and the interplanetary solar plasma on the propagation of radio metric signals. 1.1.1 Applicability of This Release This module is change number 2. It reflects the current usage of real time corrections to the seasonal troposphere models, and describes a new implementation of solar plasma calibrations, which have not been used recently. Table 3-1 has been modified to: improve clarity; add data type DOPRNG, which applies to both DOPPLER and RANGE and is now the most commonly-used data type in media calibrations; delete the data type specifiers F1, F2, F3, F3C, and PLOP and the frequency band specifier BAND, which were used only in the obsolete solar plasma calibrations; and add the frequency band specifier DOWNLINK, which is used in the new solar plasma calibrations. 1.2 Revision and Control Revisions or changes to the information herein presented may be initiated according to the procedure specified in the Introduction to Document 820-013 (reference [2]). 1.3 Applicable Documents 1. 820-062, DSMS Terms and Abbreviations, DSMS Requirements and Design. 2. 820-013, D-16765, DSMS External Interface Specification, OPS-6-3 and OPS-6-21. 3. http://eis.jpl.nasa.gov/nav/doc/documentation.html, Navigation and Mission Design Section Software, DPTRAJ-ODP. 4. Journal of Geophysical Research, Vol, 101, No. B2, 1996, Global Mapping Functions for the Atmospheric Delay at Radio Wavelengths, A.E. Niell. 5. DSN Progress Report, Vol XIV, April 15, 1973, A New Method to Predict Wet Zenith Range Correction from Surface Measurements, C.C. Chao. 1.4 Notation and Conventions Calibration time span limiters provide only two digits for the year field. Year values 69 through 99 are to be interpreted as years 1969 through 1999. Year values 00 through 68 are to be interpreted as years 2000 through 2068. 1.5 Abbreviations Abbreviations used in this document are defined with the first textual use of the term. Abbreviations and acronyms approved for use are listed in Document 820-062 (reference [1]). Abbreviations appearing in this module, but not documented in 820-062 are: ASCII American Standard Code for Information Interchange CSP Control Statement Processor (of the Orbit Determination Program) GPS Global Positioning Satellite Functional Overview Section 2 Functional Overview Media calibrations are provided in the form of American Standard Code for Information Interchange (ASCII) text files. They are created and delivered by the Tracking Systems Analytic Calibration (TSAC) Operations Unit in response to user requests. Delivery is accomplished via File Transfer Protocol (FTP) by "pushing" files of calibrations over the JPLnet institutional network to the user's computer or a central NAV repository, at intervals that are determined by the user's accuracy and timeliness requirements and negotiated with the TSAC operations unit. The location of the NAV repository is subject to change and should be obtained from TSAC Operations. A separate calibration file is provided for each medium (ionosphere, troposphere, or solar plasma) desired. Ionosphere and solar plasma calibration files provide one calibration per tracking pass, or other time period of interest, at each Deep Space Communications Complex (DSCC) or Deep Space Station (DSS). Troposphere calibration files provide two calibrations for each pass: a "dry" delay calibration and a "wet" delay calibration. Each calibration occupies approximately 160 to 320 bytes of storage. Detailed Interface Description Section 3 Detailed Interface Description Media calibrations conform to the Control Statement Processor (CSP) language used by the Orbit Determination Program (ODP) to adjust or delete data points. The CSP language is described in detail in reference [3] under DPTRAJ-ODP, Programs - By Model (Volume 1), Model Descriptions, Data Editing. Section 3.1 below identifies the CSP command elements that may be used in media calibrations. Section 3.2 provides further information and examples specific to ionospheric, tropospheric, and solar plasma calibrations. Section 3.3 describes the naming conventions used for the media calibration files. Interface dependencies are described in section 3.4. 3.1 CSP Command Language A CSP command consists of a command verb followed by optional scope limiters and computation specifiers, terminated by a period. Spaces are not significant. Most commands extend over multiple lines of text. The CSP language elements that may be used in media calibrations are listed in Table 3-1 and described in the following subsections. Table 3-1: CSP Elements Used in Media Calibrations Type of Element Elements Used Command Verbs ADJUST DELETE Data Types DOPPLER RANGE DOPRNG VLBI DVLBI Frequency Band DOWNLINK Computation Specifier BY NRMPOW BY CONST BY TRIG BY DNRMPOW BY DCONST BY DTRIG Transmission Medium MODEL(DRY NUPART) MODEL(CHPART) MODEL(WET NUPART) MODEL(DRVID) Time Span FROM TO AT BEFORE AFTER Network Complex DSN(C10) DSN(C40) DSN(C60) or Station DSN(dss) for a specific DSS number Source SCID QUASAR Comments # 3.1.1 Command Verbs The media calibrations use two CSP command verbs: ADJUST and DELETE. The calibrations themselves are expressed by ADJUST commands, which specify corrections to one or more radio metric data types; e.g., ADJUST(DOPRNG). DELETE commands may be used to instruct the ODP not to process certain data that could not be calibrated. 3.1.2 Data Types Data type limiters indicate the specific radio metric data type(s) to be adjusted or deleted; e.g., ADJUST(DOPRNG). The data type limiters used in the media calibrations are: DOPPLER (Doppler data), RANGE (range data), DOPRNG (Doppler and range data), VLBI (VLBI data), and DVLBI (Delta-VLBI data). Most media calibrations refer to data type DOPRNG since Doppler/Range tracking is by far the most common. 3.1.3 Frequency Band The applicable downlink frequency band is specified for solar plasma calibrations in the form DOWNLINK(x) where x is either S, X, L, C, or K. 3.1.4 Transmission Media Media calibrations refer to one of four media: ionospheric charged particles (media model MODEL(CHPART)), tropospheric wet delay (MODEL(WET NUPART)), tropospheric dry delay (MODEL(DRY NUPART)), and solar plasma (MODEL(DRVID)). Only wet and dry tropospheric delay calibrations are typically mixed together in a single calibration file. 3.1.5 Time Spans The time span limiters that may be used in media calibrations are FROM, TO, AT, BEFORE, and AFTER. FROM and TO are always used together while AT, BEFORE and AFTER are used alone. Each time span limiter is followed by a parenthesized date and time in the format YY/MM/DD,HH:MM:SS; e.g., 00/02/15,14:45:00. All times refer to Universal Time Coordinated (UTC). The year, month, day, hour, and minute values are two-digit integers; the seconds value is floating point. Years 69 through 99 are to be interpreted as 1969 through 1999 and years 00 through 68 are to be interpreted as 2000 through 2068. Up to three of the right-most time fields may be omitted, in which case their values are taken to be zeros. Each calibration applies only during the time span specified. If the limiter is AT, the time span is from one millisecond before the given time to one millisecond after. 3.1.6 Network Complex or Station The applicable tracking sites for media calibrations may be specified by DSCC number or by DSS number. DSCC specifications have the form DSN(Cnn) where nn is the complex number; e.g., DSN(C10). These are the more common, since the media effects are essentially the same for all stations at a given complex. Individual stations are specified in the form DSN(nn) where nn is the DSS number; e.g., DSN(15). See module OPS-6-3 of 820-13 [2] for the DSS identifiers. 3.1.7 Data Source Applicable data sources for media calibrations are specified by spacecraft or quasar number. Spacecraft are identified in the form SCID(nn) where nn is the decimal spacecraft number given in module OPS-6-21A, Table 3-4 of 820-13 [2]. Quasar sources of VLBI data are identified in the form QUASAR(nn) where nn is the quasar number. If no data source is specified, the calibration is applicable to any data source. Tropospheric calibrations may omit a source specification, since they do not refer to a specific spacecraft line-of-sight. 3.1.8 Computation Specifiers Computation specifiers indicate how the data corrections are expressed in ADJUST commands. Media calibrations may be expressed by a constant (computation specifier BY CONST), by a normalized power series (BY NRMPOW), or by a Fourier series (BY TRIG). If the constant or the coefficients are expressed in double precision, the computation specifier is preceded by the letter "D" (e.g., BY DNRMPOW). The computation specifier is followed by a parenthesized, comma-separated list of numerical coefficients. Up to 24 single-precision or 12 double-precision coefficients are allowed in one series. Their interpretation is described below for each type of computation that may be used. In these descriptions S and E refer to the start and end of the applicable time span, which are generally specified by the FROM and TO time span limiters. A constant correction of size C is expressed in the form BY CONST(C). A normalized power series is expressed in the form BY NRMPOW(CO, C1, ... ,CN). The calibration at time T is computed as CO + C1 * X + C2 * X2 + ... + CN * XN, where T is replaced by the normalized, dimensionless argument X = 2 * ( (T - S) / (E - S) ) - 1, which is -1 at T = S and +1 at T = E. A Fourier series is expressed in the form BY TRIG (P, AO, Al, B1, A2, B2, ..., AN, BN). The calibration at time T is A0 + AlcosX + B1sinX + A2cos2X + B2sin2X +...+ ANcosNX + BNsinNX, where X = 2p * (T - S) / P and P is the period of the fundamental mode, in seconds. 3.1.9 Sign of Calibration Positive ionospheric and tropospheric calibrations indicate positive range delays. Positive solar plasma calibrations indicate an increase in the range delay due to solar plasma. Media calibrations are (effectively) subtracted from ODP range observables. ODP Doppler observables are corrected by (effectively) subtracting troposphere calibrations while adding ionosphere and solar plasma calibrations, since the charged particle effect advances the Doppler phase. 3.1.10 Number Formats The formats for single- and double-precision floating-point numbers are generally the same as the standard FORTRAN G format. However, the sign of the exponent of a floating-point number may replace the letter D or E; for example, 1.234E-3 may be written 1.234-3. 3.1.11 Comments Additional commentary may appear in a CSP command if it is preceded by a number sign (#). All characters from a number sign to the end of the text line are ignored by the ODP. 3.2 Media Calibrations 3.2.1 Ionospheric Calibrations The distribution of charged particles in the ionosphere is highly inhomogeneous. The magnitude of the ionospheric range delay at a given site depends on the spacecraft line-of-sight and on the observing frequency, time of day, season, and time since start of the current solar cycle. At S-band, the zenith ionospheric delay ranges from less than 1 meter to more than 8 meters, and the delay at 0 degrees elevation is about 3.5 times as large. Ionospheric calibrations are given by a normalized power series for each spacecraft tracking pass at each tracking complex or station. An example is shown in Figure 3-1. Except in special circumstances, the time span of each calibration is from spacecraft rise (0 degrees) to set (0 degrees) at the receiving station or complex. The calibration represents the one-way line-of- sight ionospheric range delay to the spacecraft, in meters at a nominal S-band frequency of 2295 Mhz. The ODP adjusts the calibration to the actual radio metric tracking frequency used. Figure 3-1: Example Ionospheric Calibration ADJUST(DOPRNG)BY NRMPOW(2.9261,-1.6357,3.5563,0.0388,2.1934) MODEL(CHPART) FROM(99/12/01,03:31)TO(99/12/01,15:32)DSN(C40)SCID(82).#S60 ADJ 991207 14:17 Ionospheric calibration files typically contain calibration predictions for all future tracking passes in the same calendar month. These are replaced by calibrations as those become available. They provide a fallback in case a calibration cannot be created for any given tracking pass. 3.2.2 Tropospheric Calibrations The tropospheric delay is comprised of a wet delay, caused by the permanent dipole in atmospheric water vapor, and a hydrostatic or dry delay, caused by induced dipoles in all atmospheric gasses. The zenith dry delay ranges from about 2 to 2.2 meters at the DSN sites. DSN zenith wet delays are smaller and more variable, ranging from a few centimeters to 25 centimeters or more. The slant-range factor is approximately 1 / sinX, which is about 10 at 6 degrees elevation. To a large degree, the troposphere is azimuthally symmetric. Therefore, tropospheric calibrations represent the zenith wet and dry delays and the ODP uses mapping functions [4] to perform the slant-range correction to the spacecraft elevation. Thus, tropospheric calibrations are not necessarily specific to a particular spacecraft. They may be produced for specific spacecraft tracks and include corresponding spacecraft identifiers, or they may simply "cover the clock" at a given DSCC and apply to all spacecraft by omitting a spacecraft scope limiter. First order calibration of the tropospheric delays is accomplished with seasonal models [5] which do not depend on real time data and need only be delivered once. These models represent the one-way zenith wet and dry delays, in meters, as Fourier series calibrations as shown in Figure 3-2. They are routinely used in all ODP runs. More accurate tropospheric calibrations are derived from real time weather and GPS data. These calibrations are expressed as normalized power series corrections, in meters, to the one-way seasonal model delays, in order to avoid double-calibrating. Examples are shown in Figure 3-3. The zenith dry delay decreases about 0.25 mm for each additional meter of altitude. Dry delay calibrations refer to the altitude of the intersection of axes of the 70m antenna at each DSCC. The seasonal models include adjustments for the altitudes of each of the other DSN antennas. Figure 3-2: Seasonal Tropospheric Models for DSCC 10 ADJUST(DOPRNG)BY TRIG(31557600., 0.0870, -0.0360, -0.0336, 0.0002, 0.0200, 0.0008, -0.0021, -0.0036, -0.0002) MODEL (WET NUPART)FROM(72/01/01,00:00)TO(48/01/01,00:00)DSN(C10). #ADJ 920121 02:23 ADJUST(DOPRNG)BY TRIG(31557600., 2.0521, 0.0082, -0.0005, -0.0004, 0.0033, -0.0015, 0.0005, -0.0011, 0.0036) MODEL (DRY NUPART)FROM(72/01/01,00:00)TO(48/01/01,00:00)DSN(C10). #ADJ 920121 02:23 Figure 3-3: Example Tropospheric Calibrations ADJUST(DOPRNG)BY NRMPOW(-0.0352, -0.0319, 0.0316, 0.0214) MODEL (WET NUPART)FROM(99/11/12,04:24)TO(99/11/12,16:35:00)DSN(C40)SCID(82). ADJUST(DOPRNG)BY NRMPOW( -0.0141, -0.0015, -0.0023) MODEL (DRY NUPART)FROM(99/11/12,04:24)TO(99/11/12,16:35:00)DSN(C40)SCID(82). 3.2.3 Solar Plasma Calibrations The distribution of solar plasma is highly irregular in regions of space near the sun. Solar plasma calibrations are usually required only when a spacecraft is near superior conjunction. The calibrations represent the change in round- trip range delay due to solar plasma that has accumulated since the beginning of the track, in meters, as normalized power series. They are identified with the receiving DSCC and the down-link frequency band. The calibration time span is the actual time span of the 2-way or 3-way ranging data. If the transmitting station changes during a track, the calibration will end and a new one for the same receiving DSCC will be started. The ionospheric portion of the round-trip charged particle delay is removed so that only the solar plasma contribution remains. An example solar plasma calibration is shown in Figure 3-4. Figure 3-4: Example Solar Plasma Calibration ADJUST(DOPRNG)DOWNLINK(X)BY NRMPOW( 2.0465, 2.1997, 0.0358, -0.7583, 0.2619) MODEL(DRVID)FROM(03/03/13,14:20)TO(03/03/13,18:18)DSN(C10)SCID(82). 3.3 File Naming Conventions Media calibration file names are constructed to indicate the applicable transmission medium, spacecraft, dates, and tracking data type(s). The specific naming conventions are subject to change and should be confirmed with TSAC Operations. The following describes the conventions that are used currently. Media calibration file names have the form medum_sc_datespan_datatype.CSP; e.g., TROPCAL_82_0002_DOPRNG.CSP. medium is either IONCAL, TROPCAL, or PLSMCAL; sc is the spacecraft id number; datespan indicates the range of UTC dates covered by the calibrations; and datatype is one of the data type limiters listed in section 3.1.2, usually DOPRNG. datespan refers to the start dates of the calibrations. It takes one of three forms: 1. yymmdd_MMDD is used for TROPCAL and PLSMCAL files that contain less than a full calendar month of calibrations; e.g., 000201_0214 for the first two weeks of February, 2000. These files are typically created for daily-to-weekly deliveries and are replaced by files of type 2 below shortly after the end of the month. 2. yymm is used for files that contain one full calendar month of calibrations; e.g., 0002 for February of 2000. These files are typically created shortly after the end of the month. The same form is used for daily-to-weekly delivery IONCAL files, which contain calibrations for the first part of the month and predictions for the rest of it. 3. yymm_YYMM is used for IONCAL files that contain calibrations and predictions for month yymm plus predictions for the next month YYMM. These files are typically created for the last scheduled delivery of month yymm. 3.4 Protocols and Configuration The protocols required for file transfer include Internet Protocol (IP), Transmission Control Protocol (TCP), and File Transfer Protocol (FTP). See 820- 019, DFL-1-3 for the well-known port number for FTP. The FTP file transfers are in ASCII mode. The file structure is a string of bytes. Stream mode is used to send the data. There is no encryption. 3.5 Dependencies The creation and delivery of media calibrations depend on the user making prior arrangements with the TSAC Operations Unit for the desired calibrations and delivery schedule. The creation of spacecraft line-of-sight ionospheric calibrations depends on the user providing TSAC Operations with a spacecraft trajectory P-file (see reference [3], ODP-DPTRAJ, File Formats, Output File Format Descriptions, Spacecraft Ephemeris) or state vector that gives the spacecraft position as a function of time. This is normally done via e-mail or FTP per a verbal arrangement with TSAC Operations, as often as necessary to maintain adequate knowledge of the spacecraft position. The creation of media calibrations for VLBI or delta-VLBI tracking data depends on the user providing TSAC Operations with the quasar number(s) and the spacecraft and quasar observing schedules. The creation of solar plasma calibrations depends on the user configuring the ranging parameters appropriately to acquire useful DRVID (Differenced Range vs. Integrated Doppler) data.