PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 FILE_RECORDS = 980 DATA_SET_ID = "MEX-M-MRS-1/2/3-EXT8-4205-V1.0" PRODUCT_ID = "OPTG_SIS" PRODUCT_CREATION_TIME = 2021-10-20T14:20:53.000 OBJECT = TEXT PUBLICATION_DATE = 1996-02-28 NOTE = "Software Interface Specification for the Orbit Propagation and Timing Geometry (OPTG) File" END_OBJECT = TEXT END Table of Contents * 1. General Description o 1.1 Purpose of Interface o 1.2 Scope o 1.3 Applicable Documents o 1.4 Functional Description + 1.4.1 Data Source, Destination, and Transfer Method + 1.4.2 Pertinent Relationships with Other Interfaces + 1.4.3 Labeling and Identification + 1.4.4 Assumptions and Constraints * 2. Environment o 2.1 Hardware Characteristics and Limitations o 2.2 Interface Medium and Characteristics o 2.3 Input/Output Protocols + 2.3.1 Device Addressing + 2.3.2 Operating System Protocols + 2.3.3 Deformatting + 2.3.4 Calling Sequence o 2.4 Failure Protection, Detection, and Recovery Features + 2.4.1 Backup Requirements + 2.4.2 Security/Integrity Measures o 2.5 End-of-File (or Medium) Conventions o 2.6 Utility Programs * 3. Data Flow Characteristics o 3.1 Operational Characteristics + 3.1.1 Generation Method and Frequency + 3.1.2 Time Span of Product o 3.2 Data Volume o 3.3 Flow Rate * 4. Detailed Data Object Definition o 4.1 Structure and Organization Overview o 4.2 Data Format and Definition + 4.2.1 SFDU Data Description + 4.2.2 Non-SFDU Data Description + 4.2.2.1 Header Records + 4.2.2.2 Data Records + 4.2.2.3 Last File Record * Appendix A. Acronyms 1. GENERAL DESCRIPTION 1.1 PURPOSE OF INTERFACE This Software Interface Specification (SIS) describes the content of the Orbit Propagation and Timing Geometry File (OPTG). It is intended that this interface will satisfy requirements for the Mars Global Surveyor (MGS) and Cassini missions. 1.2 SCOPE The format and syntax specifications in this SIS applies to all phases of the mission. 1.3 APPLICABLE DOCUMENTS 699-FSO/NAV-FRD-501 Cassini Functional Requirements and Design Document SFOC0038-01-09-01 10 Jan 94 SFOC-1-CDB-ANY-CATALOG2 SFOC0099-04-00 20 Nov 92 Data Dictionary, Rev C SFOC0038-00-08-01 26 Feb 88 SFOC-1-CDB-MGN-TIMESFILE SFOC0038-01-09-03 30 Aug 94 SFOC-2-SYS-ANY-TIMEFORMS 1 Oct 94 DPTRAJ-ODP User Reference Manual, SOM Vol. 1 and Vol. 2 1 Oct 94 DPTRAJ and ODP Interfaces and File Format Descriptions, SOM, Vol. 3 1.4 FUNCTIONAL DESCRIPTION The OPTG file contains data for many trajectory and/or geometry events relative to the spacecraft, e.g., periapsis and apoapsis passage times for an orbiter, Earth and Sun occultation times, inferior and superior conjunction times, and many other events. 1.4.1 Data Source, Destinations, and Transfer Method OPTG data shall be created by the DPTRAJ program TWIST running on the NAV computer system. The destination of this file is the Central Data Base (CDB). The transfer medium is via the MGSO network. 1.4.2 Pertinent Relationships with Other Interfaces The generation of this file is dependent upon the spacecraft ephemeris file availability spanning the time over which the OPTG file is desired. 1.4.3 Labeling and Identification Internal labeling of the OPTG file is accomplished with header records as defined in Section 4.2. 1.4.4 Assumptions and Constraints None. 2. ENVIRONMENT 2.1 HARDWARE CHARACTERISTICS AND LIMITATIONS Execution of the software to generate the OPTG file shall be on the NAV computer. 2.2 INTERFACE MEDIUM AND CHARACTERISTICS NAV computer catalogued file shall use the MGSO project LAN as the medium for transmittal to the CDB. 2.3 INPUT/OUTPUT PROTOCOLS None. 2.3.1 Device Addressing N/A 2.3.2 Operating System Protocols N/A 2.3.3 Deformatting Users of the OPTG file will be required to have software to remove the SFDU data from the CDB stored file. 2.3.4 Calling Sequence N/A 2.4 FAILURE PROTECTION, DETECTION, RECOVERY FEATURES 2.4.1 Backup Requirements The Navigation Subsystem shall keep the Orbit Propagation and Timing Geometry File in the NAV computer until it is confirmed as stored within the CDB. Backups will be maintained through normal archiving procedures of the CDB. Should the CDB malfunction or the network fail, customers of the OPTG File may obtain the file via the secondary method which is to receive the data in TBD form from the NAV Subsystem. 2.4.2 Security/Integrity Measures The CDB security/integrity measures will be in effect. 2.5 END-OF-FILE (OR MEDIUM) CONVENTIONS The end-of-file is marked with an $$EOF record. 2.6 UTILITY PROGRAMS Utility programs developed by MGSO shall be used to insert and remove SFDU labels from the OPTG file. 3. DATA FLOW CHARACTERISTICS 3.1 OPERATIONAL CHARACTERISTICS 3.1.1 Generation Method and Frequency The OPTG data shall be created by NAV DPTRAJ program TWIST. The file shall be generated at a frequency consistent with project requirements. 3.1.2 Time Span of Product The time span of the file is controlled by the span of the spacecraft ephemeris input to TWIST and by user input. 3.2 DATA VOLUME The size of the file depends on the length of the trajectory and the number of event triggers (TWIST input) encountered per orbit. 3.3 FLOW RATE Determined by the LAN traffic. 4. DETAILED DATA OBJECT DEFINITION 4.1 STRUCTURE AND ORGANIZATION OVERVIEW The OPTG file is an ASCII file which consists of the SFDU header, the OPTG headers, and the OPTG data. Each will be described in the following sections. 4.2 DATA FORMAT AND DEFINITION 4.2.1 SFDU Data Description The SFDU information and structure, for the OPTG file, is illustrated in the following example: CCSD3ZS00001AAAAAAAA NJPL3KS0L015BBBBBBBB MISSION_NAME=***; SPACECRAFT_NAME=***; DATA_SET_ID= "MEX-M-MRS-1/2/3-EXT8-4205-V1.0" FILE_NAME=optg.sff; PRODUCER_ID=NAV; APPLICABLE_START_TIME=1994-04-04T07:00:00.000; APPLICABLE_STOP_TIME=1994-04-04T15:00:00.000; PRODUCT_CREATION_TIME= 2021-10-20T14:20:53.000 CCSD3RE00000BBBBBBBB NJPL3IS0nnnnCCCCCCCC In the above *** will be MARS-GLOBAL-SURVEYOR or CASSINI depending on whether the mission is MGS or CASSINI. nnnn, the DDID, will be 0357 for MGS and 0380 for CASSINI. In the actual OPTG File, the following SFDU data is located at the end of the file, following the non-SFDU data which is described in Section 4.2.2. CCSD3RE00000CCCCCCCC CCSD3RE00000AAAAAAAA 4.2.2 Non-SFDU Data Description The non-SFDU portion of the OPTG file contains data described in Sections 4.2.2.1 and 4.2.2.2 as follows: 4.2.2.1 Header Records Header RECORD 1 - Identifies file type and version/delimits start of header. Column Content Description --------------------------------------------------------------------- 01-02 "$$" Control characters signifying major control card. 03-06 "XXXX" Key Word - identifies the mission for this file, e.g. CAS for Cassini, or MGS for Mars Global Surveyor. Left justified. 14-55 "ORBIT PROPAGATION Identifies the file AND TIMING GEOMETRY FILE" 57-60 "vnnn" Identifies the file version, eg v001. Header RECORD 2 - Identifies file name. Column Content Description ------------------------------------------------------------------ 01-01 "*" Header character 03-06 "OPTG" Key Word - identifies record type. 14-72 File name File name retrieved from the Fortran 77 execution of the INQUIRE statement. Could be, for example, OPTG_TEST.TXT Header RECORD 3 - Specifies the title of the OPTG file. Column Content Description -------------------------------------------------------------------- 01-01 "*" Header character 03-07 "TITLE" Key Word - identifies record type. 14-72 Title Any alphanumeric expression up to 59 characters, input by the user via the GIN file to NAV program TWIST that generates OPTG file. This could be used to identify the purpose of the OPTG file being generated. For example, this could be text that says, "This is a test OPTG file for the cruise phase." Header RECORD 4 - Specifies JPL local file creation time. Column Content Description ---------------------------------------------------------------------- 01-01 "*" Header character 03-10 "CREATION" Key Word - identifies date and time when OPTG file was created. 14-16 "JPL" Defines time base. 18-35 "YY-MMM-DD/hh:mm:ss" Date and time in local time format. For example, 88-DEC-18/14:32:45. Header RECORD 5 - Specifies SCE start time of file coverage. Column Content Description --------------------------------------------------------------------- 01-01 "*" Header character 03-07 "BEGIN" Key Word - identifies record type. 14-16 "SCE" Defines time base. 18-39 "YY-MMM-DD/hh:mm:ss.fff" S/C event time (ephemeris time) when the OPTG file is to begin. For example, 88-DEC-18/14:32:45.050. Header RECORD 6 - Specifies SCE cutoff time of file coverage. Column Content Description -------------------------------------------------------------------- 01-01 "*" Header character 03-08 "CUTOFF" Key Word - identifies record type. 14-16 "SCE" Defines time base. 18-39 "YY-MMM-DD/hh:mm:ss.fff" S/C event time (ephemeris time) when the OPTG file is to end. Header RECORD 7 - Specifies trajectory data base for run. Column Content Description ---------------------------------------------------------------------- 01-01 "*" Header character 03-07 "PFILE" Key Word - identifies record type. 14-16 "JPL" Defines time base. 18-35 "YY-MMM-DD/hh:mm:ss" The creation date and time of the PFILE used to make the OPTG file. For example, 88-DEC-18/14:32:45. Header RECORD 8 - Specifies program that created PFILE. Column Content Description ------------------------------------------------------------------ 01-01 "*" Header character 03-09 "PVDRIVE" Name of the program that generated or "PDRIVE" the PFILE used by TWIST to create or "SEPV" the OPTG file. 14-16 "JPL" Defines time base. 18-35 "YY-MMM-DD/hh:mm:ss" Creation date and time of the program that wrote the PFILE. Header RECORD 9 - Specifies run which produced OPTG file. Column Content Description --------------------------------------------------------------------- 01-01 "*" Header character 03-07 "TWIST" Key Word - identifies program used to generate the OPTG file. 14-16 "JPL" Defines time base. 18-35 "YY-MMM-DD/hh:mm:ss" The creation date and time of the version of the program that wrote the OPTG file. Header RECORD 10 - Specifies the phase of the mission. Column Content Description --------------------------------------------------------------------- 01-01 "*" Header character 03-17 "CRUISE", Mission phase is either cruise, orbit "ORBIT INSERTION" insertion, or mapping. or "MAPPING" Header RECORD 11 Record specifying the event signifying the start of a new orbit. Column Content Description ---------------------------------------------------------------------- 01-01 "*" Header character 03-16 "ORBIT BOUNDARY" Key Word - identifies record type. 20-25 One of the event Name of the event that will signify titles from, the the start of a new orbit, input to orbit insertion or TWIST. Valid event names for this mapping phases purpose are: "PERIAP", "AEQUAX", "DEQUAX", "APOAP",. However, once an event is chosen for the orbit boundary, it should not be changed during the entire phase. 28-33 A right justified Initial orbit number input by the integer user to TWIST. LAST Header RECORD - Delimits end of header/start of data records. Column Content Description -------------------------------------------------------------------- 01-02 "$$" Characters signifying major control card. 03-05 "EOH" Key Word - identifies end of header records. 4.2.2.2 Data Records Data records correspond to geometric events occurring during the various phases; where the first record for an event contains the event type, and subsequent records contain the event body, the epoch, the orbit number, the time from periapsis, and the SEP angle. For some of the events, additional information is included as indicated. DATA RECORD n Column Content Description -------------------------------------------------------------------- 01-06 Event title Alphanumeric expression title, (<=6 characters left justitied) describing event. Possible events for cruise, orbit insertion and mapping are: "START " Start of coverage, "CONST " Body constants, "SCONB " Begin superior conjunction, "SCONE " End superior conjunction, "ICONB " Begin inferior conjunction, "ICONE " End inferior conjunction, "SCONJ " Given Sun-Earth-probe angle during superior conjunction, "ICONJ " Given Sun-Earth-probe angle during inferior conjunction, "ICONM " Inferior conjunction minimum Sun-Earth-probe angle, "SCONM " Superior conjunction minimum Sun-Earth-probe angle, "PERIAP" Closest approach, "EOCCAB " Begin geocentric atmospheric occultation, "EOCCAE " End geocentric atmospheric occultation, "SOCCAB " Begin heliocentric atmospheric occultation, "SOCCAE " End heliocentric atmospheric occultation. "EOCCSB" Begin geocentric surface occultation, "EOCCSE" End geocentric surface occultation, "SOCCSB" Begin heliocentric surface occultation, "SOCCSE" End heliocentric surface occultation. Additional possible events for mapping and orbit insertion are: "APOAP " Apoapsis passage, "AEQUAX" Ascending equator crossing, "DEQUAX" Descending equator crossing, "DLTERM" Dark-light terminator crossing, "LDTERM" Light-dark terminator crossing, "NPOLEX" North polar minimum slant range crossing, "SPOLEX" South polar minimum slant range crossing. 07-07 "," Separator 09-14 Name Name of the body/object associated with the event named. 15-15 "," Separator 17-37 Date and time to SCE ET* time in format millisecond precision YYYY-DDDThh:mm:ss.fff. For example, 1988-352T14:32:45.981 represents December 18, 1988 at 14 hours, 32 minutes, 45.981 seconds. 38-38 "," Separator 40-63 Julian date Double precision Julian date representation of the SCE /time. 64-64 "," Separator 66-71 ET-UTC to millisecond Difference between ephemeris time precision and broadcast universal time in format ss.fff. 72-72 "," Separator 74-79 Current orbit number Integer 80-80 "," Separator * ET implies ephemeris time. In all data records ephemeris time will be used for spacecraft event time. DATA RECORD n + 1 Column Content Description -------------------------------------------------------------------- 02-20 Time from periapsis Time from periapsis in the form to millisecond + or -DDDDDThh:mm:ss.fff precision 21-21 "," Separator 23-46 Sun-Earth-probe angle Double precision Sun-Earth-probe in degrees angle. Range (0 deg [Image] SEP [Image] 180 deg). 47-47 "," Separator The following extra data records contain body constants (Event = CONST): DATA RECORD CONST Column Content Description -------------------------------------------------------------------- 02-25 Base epoch Double precision seconds past J2000.0 defining the base time, t for the rotation angle polynomials. 26-26 "," Separator DATA RECORD + 1 CONST Column Content Description -------------------------------------------------------------------- 02-25 Constant term (deg) Double precision number specifying the constant term for pole right ascension. 26-26 "," Separator 28-51 Linear term Double precision number specifying (deg/(Jul cen)) the linear term for pole right ascension. 52-52 "," Separator DATA RECORD + 2 CONST Column Content Description -------------------------------------------------------------------- 02-25 Constant term (deg) Double precision number specifying the constant term for pole declination. 26-26 "," Separator 28-51 Linear term Double precision number specifying (deg/(Jul cen)) the linear term for pole declination. 52-52 "," Separator DATA RECORD + 3 CONST Column Content Description -------------------------------------------------------------------- 02-25 Constant term (deg) Double precision number specifying the constant term for the angle W. 26-26 "," Separator 28-51 Linear term Double precision number specifying (deg/day) the linear term for the angle W. 52-52 "," Separator DATA RECORD + 4 CONST Column Content Description -------------------------------------------------------------------- 02-25 Surface radius Double precision number that (km) measures equatorial surface radius. Range 0. 26-26 "," Separator 28-51 Surface occultation Double precision number that radius (km) measures equatorial surface radius for occultations. Range 0. 52-52 "," Separator 54-77 Atmospheric radius Double precision number that (km) measures the atmospheric radius at the equator. Range 0. 78-78 "," Separator DATA RECORD + 5 CONST Column Content Description -------------------------------------------------------------------- 02-25 Flattening factor Double precision number defining the flatness. Range (0 f < 1). 26-26 "," Separator The following extra records are included at the start of coverage (EVENT = START): DATA RECORD START Column Content Description -------------------------------------------------------------------- 02-07 Body name Name of the reference body for the spacecraft state coordinates 08-08 "," Separator 10-16 Coordinate system Defines the coordinate system for the label spacecraft state coordinates: "EMO2000" means Earth mean orbit and equinox of J2000.0. 17-17 "," Separator DATA RECORD + 1 START Column Content Description -------------------------------------------------------------------- 02-25 Semimajor axis (km) Double precision number giving the semimajor axis of the spacecraft orbit. 26-26 "," Separator 28-51 Orbit eccentricity Double precision number giving the eccentricity of the spacecraft orbit. Range 0. 52-52 "," Separator DATA RECORD + 2 START Column Content Description -------------------------------------------------------------------- 02-25 Orbit inclination Double precision number giving the (deg) inclination of the spacecraft orbit. Range (0 deg i 180 deg). 26-26 "," Separator 28-51 Ascending node angle Double precision number giving the (deg) longitude of the ascending node of the spacecraft orbit. Range (0 deg < 360 deg). 52-52 "," Separator 54-77 Argument of Double precision number giving the periapsis (deg) argument of periapsis. Range (0 deg < 360 deg). 78-78 "," Separator The following extra data record is present if the event is an ascending equator crossing (Event = AEQUAX): DATA RECORD AEQUAX Column Content Description -------------------------------------------------------------------- 02-25 Longitude (deg) Double precision real number that is a measure of the longitude of the spacecraft. Range (0 deg < 360 deg). 26-26 "," Separator The following extra data record is present if the event is an descending equator crossing (Event = DEQUAX): DATA RECORD DEQUAX Column Content Description -------------------------------------------------------------------- 02-25 Longitude (deg) Double precision real number that is a measure of the longitude of the spacecraft. Range (0 deg < 360 deg). 26-26 "," Separator 28-35 Local solar time to Local mean solar time at the the second spacecraft in the form hh:mm:ss. 36-36 "," Separator The following extra data record is present if the event is an entry or exit from geocentric occultation (Event = EOCCAB, EOCCAE EOCCSB, or EOCCSE): DATA RECORD OCCULT Column Content Description -------------------------------------------------------------------- 02-25 Longitude (deg) Double precision real number that is a measure of the longitude of the spacecraft. Range (0 deg < 360 deg). 26-26 "," Separator 28-51 Latitude (deg) Double precision real number that is a measure of the latitude of the spacecraft relative to the occulting body. Range (-90 deg 90 deg). 52-52 "," Separator The following extra data records are present at all apoapsis and periapsis events (Event = APOAP or PERIAP): DATA RECORD PERIAP/APOAP Column Content Description -------------------------------------------------------------------- 02-25 Semimajor axis (km) Double precision number giving the semimajor axis of the spacecraft orbit relative to the event body centered coordinate system. 26-26 "," Separator 28-51 Orbit eccentricity Double precision number giving the eccentricity of the spacecraft orbit. Range 0. 52-52 "," Separator 54-77 True anomaly (deg) Double precision number giving the true anomaly of the spacecraft. Range (-180 deg < 180 deg). 78-78 "," Separator DATA RECORD + 1 PERIAP/APOAP Column Content Description -------------------------------------------------------------------- 02-25 Orbit inclination Double precision number giving the (deg) inclination of the spacecraft orbit relative to the event body centered EME2000* coordinate system. Range (0 deg i 180 deg). 26-26 "," Separator 28-51 Ascending node angle Double precision number giving the (deg) longitude of the ascending node of the spacecraft orbit relative to the event body centered EME2000* coordinate system. Range (0 deg < 360 deg). 52-52 "," Separator 54-77 Argument of Double precision number giving the periapsis (deg) argument of periapsis relative to the event body centered EME2000* coordinate system. Range (0 deg < 360 deg). 78-78 "," Separator *EME2000 refers to the Earth Mean Equatorial J2000 reference system. DATA RECORD + 2 PERIAP/APOAP Column Content Description -------------------------------------------------------------------- 02-25 Orbit inclination Double precision number giving the (deg) inclination of the spacecraft orbit relative to the event body centered equatorial coordinate system. Range (0 deg i 180 deg). 26-26 "," Separator 28-51 Ascending node angle Double precision number giving the (deg) longitude of the ascending node of the spacecraft orbit relative to the event body centered equatorial coordinate system. Range (0 deg < 360 deg). 52-52 "," Separator 54-77 Argument of Double precision number giving the periapsis (deg) argument of periapsis relative to the event body centered equatorial coordinate system. Range (0 deg < 360 deg). 78-78 "," Separator DATA RECORD + 3 PERIAP/APOAP Column Content Description ------------------------------------------------------------------- 02-25 Body-Earth range (km) Double precision range from the event body to the Earth. Range 0. 26-26 "," Separator 28-51 Altitude (km) Double precision spacecraft altitude relative to the event body. 52-52 "," Separator The following additional records are present in the case of a periapsis (Event = PERIAP): DATA RECORD PERIAP Column Content Description ------------------------------------------------------------------ 02-25 Sun sigma angle (deg) Double precision real number that is a measure of the angle along the spacecraft orbit plane from the periapsis direction to the body-Sun direction. Range (0 deg < 360 deg). 26-26 "," Separator 28-51 Sun beta angle (deg) Double precision real number that is a measure of the angle from the spacecraft orbit plane normal vector to the body-Sun direction vector. Range (0 deg 180 deg). 52-52 "," Separator DATA RECORD + 1 PERIAP Column Content Description ------------------------------------------------------------------ 02-25 Dynamic pressure Double precision real number that (N/m2) measures the dynamic pressure on the spacecraft. Range 0. 26-26 "," Separator 28-51 Atmospheric density Double precision real number that (kg/m3) measures the atmospheric density at the spacecraft. Range 0. 52-52 "," Separator DATA RECORD + 2 PERIAP Column Content Description ------------------------------------------------------------------ 02-25 Drag pass duration Double precision real number that (sec) measures the duration* of the current drag pass. Range 0. 26-26 "," Separator 28-51 Freestream heatflux Freestream heatflux at the (W/cm2) spacecraft. Range 0. 52-52 "," Separator * As the spacecraft is entering the atmosphere, the dynamic pressure increases. When the dynamic pressure equals or exceeds .0015 n/m**2 (>=.0015), the drag interval begins. As the spacecraft is exiting the atmosphere, the dynamic pressure decreases. When the pressure is less than .0015 n/m**2 (<.0015), the drag interval ends. The drag interval is computed from the entry and exit times and is represented in seconds. If the spacecraft is located such that the dynamic pressure is always less than .0015 n/m**2, the drag duration will be zero (0). If the dynamic pressure is always greater than or equal to .0015 n/m**2 the drag duration will be set to the orbital period. DATA RECORD + 3 PERIAP Column Content Description ------------------------------------------------------------------ 02-25 Reference altitude Double precision real number that (km) specifies the reference altitude. 26-26 "," Separator 28-51 Atmospheric density Double precision real number that (kg/m3) measures the atmospheric density at the reference altitude. Range 0. 52-52 "," Separator The following extra data record is present when the event is a north or south polar crossing (Event = NPOLEX or SPOLEX): DATA RECORD NPOLEX/SPOLEX Column Content Description ------------------------------------------------------------------- 02-25 Slant range (km) Double precision real number that gives the distance between the spacecraft and the north/south pole. Range 0. 26-26 "," Separator 4.2.2.3 Last File Record This record signifies the "end of file". Column Content Description ------------------------------------------------------------------ 1-2 "$$" Control characters signifying major control card. 3-5 "EOF" Key Word - identifies the end of a file. Appendix A. ACRONYMS ASCII American Standard Code for Information Interchange MOPS Maneuver Operations Program Set NAV Navigation SIS Software Interface Specification To OPTG SIS To Navigation Software Documentation To Navigation Software Revision date: 3 February 1997 For information about this on-line document, contact Vic Legerton For information about the file described by this document, contact John Ekelund