PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 DATA_SET_ID = "VEX-V-VRA-1/2/3-NMP-0102-V1.0" PRODUCT_ID = "SRX" PRODUCT_CREATION_TIME = 2014-02-10T10:28:12.000 OBJECT = TEXT PUBLICATION_DATE = 2009-05-25 NOTE = "Software Interface Specification for Radio Science Surface Reflection files." END_OBJECT = TEXT END Stanford Center for Radar Astronomy Software Interface Specification Surface Reflection (SRX) Files prepared by Richard A. Simpson Center for Radar Astronomy Stanford University Stanford, CA 94305-9515 650-723-3525 Version 1.4 25 May 2009 PREFACE |====================================================================| | | | DOCUMENT CHANGE LOG | | | |====================================================================| |REVISION|REVISION| SECTION | REMARKS | | NUMBER | DATE | AFFECTED | | |--------+--------+------------+-------------------------------------| | 1.0 |00/01/14| All |Adapted from RSTP V1.0 SIS | |--------+--------+------------+-------------------------------------| | 1.1 |02/04/15| various |Added SRA product | |--------+--------+------------+-------------------------------------| | 1.1 |02/04/15|Acrn & Abbrv|Added AGK, HGA, SRA, TCK | |--------+--------+------------+-------------------------------------| | 1.1 |02/04/15|Distribution|List matches product distribution | |--------+--------+------------+-------------------------------------| | 1.1 |02/04/15| 1.3 |Updated [4]; added [7] | |--------+--------+------------+-------------------------------------| | 1.2 |02/04/30| 1.4.3 |Acronym error: MHS --> MGS | |--------+--------+------------+-------------------------------------| | 1.2 |02/04/30|Distribution|Added MS for Barbara McGuffie | |--------+--------+------------+-------------------------------------| | 1.3 |02/08/27| 2.2 |Added file sizes for SRA | |--------+--------+------------+-------------------------------------| | 1.4 |09/05/25| All |Generalized from MGS to all missions.| |--------+--------+------------+-------------------------------------| | 1.4 |09/05/25| ALL |Abandoned formating, pagination for | |--------+--------+------------+-------------------------------------| | 1.4 |09/05/25|Distribution|Omitted | |====================================================================| |====================================================================| | | | ITEMS TO BE DETERMINED | | | |====================================================================| | REVISION | SECTION | ITEM DESCRIPTION | RESOLUTION | | NUMBER | AFFECTED | | | |----------+----------+------------------------+---------------------| | 1.0 | | none | . | |====================================================================| Contents Preface............................................................ Document Change Log.............................................. Items to be Determined........................................... Distribution..................................................... Contents......................................................... Acronyms and Abbreviations....................................... 1. General Description............................................ 1.1. Overview................................................... 1.2. Scope...................................................... 1.3. Applicable Documents....................................... 1.4. System Siting and File Generation.......................... 1.5. Assumptions and Constraints................................ 1.5.1. Usage Constraints...................................... 1.5.2. Priority Phasing Constraints........................... 1.5.3. Explicit and Derived Constraints....................... 1.5.4. Documentation Conventions.............................. 1.5.4.1. Data Format Descriptions........................... 1.5.4.2. Time Standards..................................... 1.5.4.3. Coordinate Systems................................. 1.5.4.4. Limits of This Document............................ 1.5.4.5. Typographic Conventions............................ 2. Interface Characteristics...................................... 2.1. Hardware Characteristics and Limitations................... 2.1.1. Special Equipment and Device Interfaces................ 2.1.2. Special Setup Requirements............................. 2.2. Volume and Size............................................ 2.3. Labeling and Identification................................ 2.4. Interface Medium Characteristics........................... 2.5. Failure Protection, Detection, and Recovery Procedures..... 2.6. End-of-File Conventions.................................... 3. Access......................................................... 3.1. Programs Using the Interface............................... 3.2. Synchronization Considerations............................. 3.2.1. Timing and Sequencing Considerations................... 3.2.2. Effective Duration..................................... 3.2.3. Priority Interrupts.................................... 3.3. Input/Output Protocols, Calling Sequences.................. 4. Detailed Interface Specifications.............................. 4.1. Structure and Organization Overview........................ 4.2. Detached PDS Label......................................... 4.2.1. Label Header........................................... 4.2.2. Label Body............................................. 4.3. Data Files................................................. Appendix A. Example Labels....................................... A.1. Example SRA Label.......................................... A.2. Example SRG Label.......................................... A.3. Example SRI Label.......................................... A.4. Example SRT Label.......................................... Figure 4-2. Example SRX Label Header................................... Acronyms and Abbreviations AGK NAIF Antenna Gimbal Kernal ASCII American Standard Code for Information Interchange DSN Deep Space Network GDF GEODYN (Goddard) final ephemeris GDN GEODYN (Goddard) quick look ephemeris HGA High-Gain Antenna IAU International Astronomical Union IEEE Institute of Electrical and Electronic Engineers IPN Inner Planet Navigation (Team) ephemeris JPL Jet Propulsion Laboratory J2000 IAU Official Time Epoch K Degrees Kelvin kB Kilobytes km Kilometers MB Megabytes MGS Mars Global Surveyor NAIF Navigation and Ancillary Information Facility NASA National Aeronautics and Space Administration NAV Navigation Subsystem/Team PDS Planetary Data System RS Radio Science RSR Radio Science Receiver RSS Radio Science Subsystem RST Radio Science Team RSTP Radio Science Temperature Pressure (profile) SIS Software Interface Specification SPK Spacecraft and Planetary Kernel (ephemeris) SRA Surface Reflection Antenna file/table SRG Surface Reflection Geometry file/table SRI Surface Reflection Image SRT Surface Reflection Table SRX Surface Reflection generic file or file type TCK NAIF Spacecraft C-Kernel UTC Coordinated Universal Time 1. General Description 1.1. Overview This Software Interface Specification (SIS) describes data files produced during a Radio Science (RS) Surface Reflection investigation, when radio signals either transmitted from or received by a spacecraft were reflected from a target (planet, satellite, or other) surface. The results of such an investigation can be used to infer dielectric constant, density, and centimeter-scale roughness of the reflecting surface [1]. Data products may include: (1) a Surface Reflection Table (SRT) summarizing observables (signal strengths, Doppler offsets, etc), (2) a Surface Reflection Image (SRI) which shows signal amplitude and frequency as a function of time, (3) a Surface Reflection Geometry (SRG) file which summarizes the geometry for an observation, and (4) a Surface Reflection Antenna (SRA) file which summarizes spacecraft antenna pointing. For simplicity, the collection of Surface Reflection files or any single file or file type may be denoted by SRX in the following description. SRX files have been designed according to standards of the National Aeronautics and Space Administration (NASA) Planetary Data System (PDS) [2-3]. SRX files were first created at Stanford University, which supported a Surface Reflection investigation carried out by the Mars Global Surveyor (MGS) Radio Science Team [4]. 1.2. Scope The format and content specifications in this SIS apply to all phases of an investigation for which SRX files are produced. 1.3. Applicable Documents [1] Simpson, R.A., Spacecraft Studies of Planetary Surfaces Using Bistatic Radar, IEEE Transactions on Geoscience and Remote Sensing, 31, 465-482, 1993. [2] Planetary Science Data Dictionary, JPL D-7116, Rev. D, 15 July 1996. [3] Planetary Data System Standards Reference, JPL D-7669, part 2, 24 July 1995. [4] Tyler, G.L., G. Balmino, D.P. Hinson, W.L. Sjogren, D.E. Smith, R.A. Simpson, S.W. Asmar, P. Priest, and J.D. Twicken, Radio Science Observations with Mars Global Surveyor: Orbit Insertion Through One Mars Year in Mapping, J. Geophys. Res., 102, 23327-23348, 2001. [5] 0159-SCIENCE, Radio Science Receiver Standard Formatted Data Unit (SFDU), 820-013 Deep Space Mission Systems (DSMS) External Interface Specification, JPL D-16765, 18 February 2001. [6] Simpson, R.A., Software Interface Specification: Radio Science Digital Map (RSDMAP) Products, Mars Global Surveyor Project Radio Science Team, 9 March 1999. 1.4. System Siting and File Generation SRX files are created at an institution supporting Surface Reflection investigations using various inputs. They are delivered as part of archival data sets using methods that are mutually acceptable to the data provider and the archive. SRI files are created from raw open-loop radio science data, such as from a Radio Science Receiver (RSR) [5]. Raw data samples are processed coherently to yield power spectra. The typical SRI is 300 consecutive 512-point power spectra stored as a two-dimensional array in Radio Science Digital Map format [6]. The image generally shows the spacecraft carrier signal and any surface echoes that may be present. Each SRT file provides quantitative information in tabular form to accompany an SRI file. Estimates of carrier power and frequency are obtained by searching each spectrum for the maximum signal. The surface echo is found using a guided search algorithm for anomalously large signals to the side of the carrier. SRG files give summaries of observing geometry around events of interest. Calculations are based on an integrated spacecraft and planetary ephemeris. Although an immediate application is to interpretation of SRI and SRT files, the SRG is not limited to that application. SRA files give summaries of spacecraft high-gain antenna (HGA) pointing around events of interest. Absolute pointing is derived from spacecraft attitude and antenna pointing files. Offsets from the Earth-spacecraft line may be found from comparison of absolute pointing with data in the SRG file. 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. Data may be 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 character strings. Data are identified throughout this document as char 8 bits character uchar 8 bits integer 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) other special data structures such as time, date, etc. which are described within this document 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 character, the next lowest byte contains the second character, and so forth. 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 x m element array, with first element array[0][0], second element array[0][1], and so forth. 1.5.4.2. Time Standards SRX calculations use the January 1.5, 2000 epoch as the standard time. Within the data files, all times are reported in Universal Coordinated Time (UTC) as strings of up to 24 ASCII characters. The time 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. The decimal point and "fff" are optional. Optional suffix "Z" explicitly indicates use of the UTC reference. The date format is "YYYY-MM-DD", where the components are defined as above. A three-digit day-of-year "DDD" may be substituted for "MM-DD" in either the time or date format. 1.5.4.3. Coordinate Systems SRX files use planetocentric J2000 inertial coordinates and planetocentric fixed body coordinate system. 1.5.4.4. Limits of This Document This document applies only to SRX products. 1.5.4.5. Typographic Conventions This document has been formatted for simple electronic file transfer and display. Line lengths are limited to 80 ASCII characters, including line delimiters. No special fonts or structures are included within the file. Constant width characters are assumed for display. 2. Interface Characteristics 2.1. Hardware Characteristics and Limitations 2.1.1. Special Equipment and Device Interfaces SRX files are created using IEEE formats and are stored in electronic form on magnetic disk and other media. 2.1.2. Special Setup Requirements None. 2.2. Volume and Size SRX products typically consist of one SRI, SRT, SRG, and SRA file for each event studied. Nominal file sizes are 300, 40, 400, and 35 kB, respectively, with associated labels requiring 5, 15, 60, and 30 kB. Total volume for a single event would be approximately 820 kB. 2.3. Labeling and Identification Each file has a name which describes its contents. The name includes the following structure which uniquely identifies it among other Radio Science products: ydddHmmC.SRx where y is the least significant digit of the year ddd is the day of year H is a one character representation of the hour on which the file begins (A = 00, B = 01, ... X = 23) mm is the minute on which the file begins (see note below for convention when two acquisition systems began at the same minute; applies only to SRI and SRT files) C is a single character denoting the version of the file (first version is "A", second is "B", etc.) "SR" identifies the file as containing a Radio Science Surface Reflection data file, "x" indicates the specific product "A" summary antenna pointing table "G" summary geometry table "I" image file "T" radio observables (table) Note: Some events may be captured by more than one ground station with recording beginning at the same time. In those cases the least significant digit of mm will be modified as follows (applies only to SRI and SRT files): Least Significant Digit of "mm" for Coincident Files First Data File Second Data File Third Data File --------------- ---------------- --------------- 0 A K 1 B L 2 C M 3 D N 4 E O 5 F P 6 G Q 7 H R 8 I S 9 J T 2.4. Interface Medium Characteristics SRX products are electronic files. When stored on physical media, they follow accepted formats for those media. 2.5. Failure Protection, Detection, and Recovery Procedures None. 2.6. End-of-File Conventions End of file labeling complies with standards for storage media. 3. Access 3.1. Programs Using the Interface Data contained in SRX files will be accessed by programs at the home institutions of other investigators. Those programs cannot be identified here. 3.2. Synchronization Considerations 3.2.1. Timing and Sequencing Considerations N/A 3.2.2. Effective Duration N/A 3.2.3. Priority Interrupts None. 3.3. Input/Output Protocols, Calling Sequences None. 4. Detailed Interface Specifications 4.1. Structure and Organization Overview The SRA, SRG, SRI, and SRT files (collectively known as SRX files) are generated by Radio Science data reduction and analysis software at the investigator's institution. Each SRX file is accompanied by a detached PDS label. 4.2. Detached PDS Label The detached PDS label has two parts -- a header and body. The header contains information about the origin of the file and its general characteristics such as record type and size. The body is a complete bit- level definition of the SRX file; it includes object definitions for each component of the SRX file. Each detached PDS label is constructed of ASCII records; each record contains exactly 80 characters. The last two characters in each record are the carriage-return (ASCII 13) and line-feed (ASCII 10) characters. 4.2.1 Label Header The structure of the label file header is illustrated in Figure 4-2. Keyword definitions are given below. Not all keywords appear in all labels, nor will they always be in the same order. Examples of complete label files are given in Appendix A. |====================================================================| | | | Figure 4-2. Example SRX Label Header | | | |====================================================================| | | | PDS_VERSION_ID = PDS3 | | RECORD_TYPE = FIXED_LENGTH | | RECORD_BYTES = 100 | | FILE_RECORDS = nnn | | ^xxxx = ("ydddHmmC.SRx",1) | | ^xxxx = ("ydddHmmC.SRx",n) | | ... | | INSTRUMENT_HOST_NAME = "MARS GLOBAL SURVEYOR" | | TARGET_NAME = "MARS" | | INSTRUMENT_NAME = "RADIO SCIENCE SUBSYSTEM" | | DATA_SET_ID = "VEX-V-VRA-1/2/3-NMP-0102-V1.0" | PRODUCT_ID = "ydddHmmC.SRx" | | ORIGINAL_PRODUCT_ID = "cccccccccc" | | PRODUCT_RELEASE_DATE = YYYY-MM-DD | | DESCRIPTION = "cccccccccccccccccc" | | START_TIME = YYYY-MM-DDThh:mm:ss | | STOP_TIME = YYYY-MM-DDThh:mm:ss | | SOFTWARE_NAME = "ccccccc;Vn.m" | | PRODUCT_CREATION_TIME = 2014-02-10T10:28:12.000 | PRODUCER_ID = "MGS RST" | | | |====================================================================| PDS_VERSION_ID = The version of the Planetary Data System for which these data have been prepared (set to PDS3) RECORD_TYPE = The type of record. Set to "FIXED_LENGTH" to indicate that all records have the same length. RECORD_BYTES = The number of bytes per (fixed-length) record. Varies among products, and may vary as the product evolves. Initially set to "80" for the SRA, "688" for the SRG, "1024" for the SRI, and "50" for the SRT. FILE_RECORDS = The number of records in the SRX file; instance dependent. ^xxxx = File name and record number at which a data object begins; repeated for each data object. The SRA contains two data objects (HGA_POINTING_HDR_TABLE and HGA_POINTING_TABLE). The SRG contains two data objects (BSR_GEOM_HDR_TABLE and BSR_GEOM_TABLE). The SRT contains two data objects (SURF_HDR_TABLE) and (SURF_TABLE). The SRI contains one data object (IMAGE); in this case, the parentheses, comma, and record number are omitted. The file naming convention is defined in Section 2.3. Record number starts at 1 and is incremented once for each RECORD_BYTES. INSTRUMENT_HOST_NAME = Name of the spacecraft; for example, "MARS GLOBAL SURVEYOR". TARGET_NAME = A character string which identifies the target body; for example, "MARS". INSTRUMENT_NAME = Name of the instrument; set to "RADIO SCIENCE SUBSYSTEM". DATA_SET_ID = "VEX-V-VRA-1/2/3-NMP-0102-V1.0" product is a member. For example, "MGS-M-RSS-5-SDP-Vn.m", where "Vn.m" indicates the version number of the data set. PRODUCT_ID = A unique identifier for the product within the data set. The naming convention is defined in Section 2.3. ORIGINAL_PRODUCT_ID = The name of the file upon which this product was primarily based. This keyword is used only for SRG products, where it specifies the source SPK file. PRODUCT_RELEASE_DATE = A largely fictitious date on which the product may be released to the archive; entered in the format "YYYY-MM-DD", where components are defined in Section 1.5.4.2. Optional. DESCRIPTION = A short description of the SRX product. START_TIME = The receive ime at which the first real (or virtual, in the case of SRG files) radio sample was acquired, expressed in the format YYYY-MM-DDThh:mm:ss where the components are defined in Section 1.5.4.2. STOP_TIME = The receive time at which the last sample was acquired, expressed in the format YYYY-MM-DDThh:mm:ss where the components are defined in Section 1.5.4.2. SOFTWARE_NAME = The name and version number of the program creating the SRX file; expressed as a character string in the format "PROGRAM_NAME;n.mm" where "PROGRAM_NAME" is the name of the software and "n.mm" is the version number. Optional. PRODUCT_CREATION_TIME = 2014-02-10T10:28:12.000 expressed in the format YYYY-MM-DDThh:mm:ss where the components are defined in Section 1.5.4.2. PRODUCER_ID = The entity responsible for creation of the SRX product; for example, "MGS RST". Optional. 4.2.2 Label Body The body of the PDS label completely defines both the format and the content of the associated SRX file. It is written as one or two OBJECT definitions -- one for the header (if any) and one for the data. Examples of complete labels are given in Appendix A. Since the format and content of the SRX files may evolve over the course of a mission, users should always refer to the accompanying label for current specifications of the SRX file. 4.3. Data Files The SRA file contains summary lines for the high-gain antenna pointing at fixed time steps (typically 1, 10, or 100 s). It comprises two PDS TABLE objects -- one containing "fingerprint" information and assumed constants for the calculation and the other containing results. The structure and content of each SRA file is defined by the accompanying detached PDS label (see Section 4.2 and Appendix A). The SRG file contains summary lines for the observational geometry at fixed time steps (typically 1, 10, or 100 s). It comprises two PDS TABLE objects -- one containing "fingerprint" information and assumed constants for the calculation and the other containing results. The structure and content of each SRG file is defined by the accompanying detached PDS label (see Section 4.2 and Appendix A). The SRI file is a two-dimensional image in RSDMAP format [6]. The structure and content of each SRI file is defined by the accompanying detached PDS label (see Section 4.2 and Appendix A). The SRT data file contains estimates of the power and frequency of the spacecraft carrier and surface echo. It comprises two PDS TABLE objects -- one containing "fingerprint" information and assumed constants for the calculations and the other containing the measurements themselves. The structure and content of each SRT file is defined by the accompanying detached PDS label (see Section 4.2 and Appendix A). Note that the format and content of SRX files may evolve over the course of a mission; users should always refer to the accompanying PDS label for current format and content specifications. A. Example Labels A.1 Example SRA Label PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 FILE_RECORDS = 602 ^HGA_POINTING_HDR_TABLE = ("9127M28A.SRA",1) ^HGA_POINTING_TABLE = ("9127M28A.SRA",3) INSTRUMENT_HOST_NAME = "MARS GLOBAL SURVEYOR" TARGET_NAME = "MARS" INSTRUMENT_NAME = "RADIO SCIENCE SUBSYSTEM" DATA_SET_ID = "VEX-V-VRA-1/2/3-NMP-0102-V1.0" PRODUCT_ID = "9127M28A.SRA" START_TIME = 1999-05-07T12:28:00 STOP_TIME = 1999-05-07T12:37:59 PRODUCT_CREATION_TIME = 2014-02-10T10:28:12.000 DESCRIPTION = "This file summarizes high-gain antenna (HGA) pointing for Mars Global Surveyor (MGS) bistatic radar (BSR) observations. For highly oblique BSR, the results may also apply to the accompanying atmospheric occultation. The file gives the HGA unit vector and offset angles from the desired pointing direction as a function of time. The file comprises two tables. The first table is a single row which identifies the calculation (fingerprints). The second table (with many rows) is the HGA summary itself. File names are of the form ydddHmmC.SRA where y is the one-digit year, ddd is the 3-digit day-of-year, H is a letter denoting the hour (A=00, B=01, ..., X=23), and mm is the 2-digit minute of the first data in the file. C indicates version of the file; C='A' is the first version, 'B' is the second version, etc. ydddHmm With regard to the file naming convention, ydddHmm in these files is intended to be SIMILAR to ydddHmm in TPS and TPH occultation file names and in SRT and SRI surface scattering file names. However, because SRA files are produced independently, this correspondence cannot be guaranteed. Further, mm in the other files can sometimes include a letter -- if data were collected simultaneously at two antennas; and the version indicators (C) may be entirely different. Reconstruction of the HGA pointing was carried out by Joe Twicken using the NAIF Toolkit and kernels. The SRA file was produced by Dick Simpson of the MGS Radio Science Team (RST) as part of his Participating Scientist investigation." OBJECT = HGA_POINTING_HDR_TABLE NAME = "HGA POINTING HEADER" INTERCHANGE_FORMAT = ASCII ROWS = 1 COLUMNS = 14 ROW_BYTES = 152 ROW_SUFFIX_BYTES = 8 DESCRIPTION = "Table contains identifying information and summary data about the HGA pointing for one BSR event. Table contains a single row of 14 columns giving date, orbit number, sense of the occultation, file names used in constructing the Earth-Mars-MGS geometry, file names used in reconstructing the HGA pointing, occultation time, and average angle offsets from the desired pointing direction. Columns are delimited by commas; total space occupied by data columns and column delimiters is 150 bytes. The row is padded with 8 ASCII blanks. An ASCII carriage-return and line-feed occupy byte positions 159 and 160." OBJECT = COLUMN COLUMN_NUMBER = 1 NAME = "DATE" DATA_TYPE = DATE START_BYTE = 1 BYTES = 10 FORMAT = "A10" DESCRIPTION = "Date on which the observations began, given in a YYYY-MM-DD format where YYYY is the 4-digit year, MM is the 2-digit month, and DD is the 2-digit day." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 2 NAME = "ORBIT NUMBER" DATA_TYPE = ASCII_INTEGER START_BYTE = 12 BYTES = 5 FORMAT = "I5" DESCRIPTION = "Orbit number during which the data were collected." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 3 NAME = "OCCULTATION SENSE" DATA_TYPE = CHARACTER START_BYTE = 19 BYTES = 1 FORMAT = "A1" DESCRIPTION = "Sense of the occultation, if any. Possible values include: E for egress, I for ingress, B for both (grazing occultation), and X for undefined (for example, data acquired when there was no occultation, such as during a specular point experiment)." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 4 NAME = "DSS" DATA_TYPE = ASCII_INTEGER START_BYTE = 22 BYTES = 2 FORMAT = "I2" DESCRIPTION = "DSN antenna through which the data were collected." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 5 NAME = "SRT FILE NAME" DATA_TYPE = CHARACTER START_BYTE = 26 BYTES = 12 FORMAT = "A12" DESCRIPTION = "Name of SRT file in which reduced surface echo data have been tabulated. Left blank if there is no associated SRT file." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 6 NAME = "SRG FILE NAME" DATA_TYPE = CHARACTER START_BYTE = 41 BYTES = 12 FORMAT = "A12" DESCRIPTION = "Name of SRG file in which geometry data for the experiment have been tabulated. The SRG file is the source of the vectors defining relative positions of Earth, Mars, and spacecraft." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 7 NAME = "SOURCE SPK1 FILE NAME" DATA_TYPE = CHARACTER START_BYTE = 56 BYTES = 12 FORMAT = "A12" DESCRIPTION = "Name of SPK file used to generate the SRG file." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 8 NAME = "SOURCE SPK2 FILE NAME" DATA_TYPE = CHARACTER START_BYTE = 71 BYTES = 12 FORMAT = "A12" DESCRIPTION = "Name of SPK file used in reconstruction of the HGA pointing." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 9 NAME = "TCK FILE NAME" DATA_TYPE = CHARACTER START_BYTE = 86 BYTES = 12 FORMAT = "A12" DESCRIPTION = "Name of TCK file used in reconstruction of the HGA pointing. TCK file defines the attitude of the spacecraft body." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 10 NAME = "AGK FILE NAME" DATA_TYPE = CHARACTER START_BYTE = 101 BYTES = 12 FORMAT = "A12" DESCRIPTION = "Name of AGK file used in reconstruction of the HGA pointing. AGK file defines the azimuth and elevation gimbal angles for the HGA." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 11 NAME = "TOCC" DATA_TYPE = ASCII_REAL START_BYTE = 115 BYTES = 12 FORMAT = "F12.6" UNIT = "SECOND" DESCRIPTION = "Time at which occultation ray was tangent to the surface of Mars. Derived from the time at which the carrier was roughly 25% of its free-space intensity, adjusted for light-time to Earth, and stored in the SRT file." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 12 NAME = "AVG ANGY" DATA_TYPE = ASCII_REAL START_BYTE = 128 BYTES = 7 FORMAT = "F7.3" UNIT = "DEGREE" DESCRIPTION = "Average value of ANGY during 20 seconds after egress or 20 seconds before ingress. See below for definition of ANGY." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 13 NAME = "AVG ANGX" DATA_TYPE = ASCII_REAL START_BYTE = 136 BYTES = 7 FORMAT = "F7.3" UNIT = "DEGREE" DESCRIPTION = "Average value of ANGX during 20 seconds after egress or 20 seconds before ingress. See below for definition of ANGX." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 14 NAME = "AVG ANGZ" DATA_TYPE = ASCII_REAL START_BYTE = 144 BYTES = 7 FORMAT = "F7.3" UNIT = "DEGREE" DESCRIPTION = "Average value of ANGZ during 20 seconds after egress or 20 seconds before ingress. See below for definition of ANGZ." END_OBJECT = COLUMN END_OBJECT = HGA_POINTING_HDR_TABLE OBJECT = HGA_POINTING_TABLE NAME = "HGA POINTING" INTERCHANGE_FORMAT = ASCII ROWS = 600 COLUMNS = 6 ROW_BYTES = 80 DESCRIPTION = "Table contains HGA unit vector and offset angles from desired HGA pointing direction versus time. The tables are constructed with Earth Receive Time (ERT, or TRX) in the first column, the corresponding transmit time (TTX) in the second column, the three-element reconstructed pointing vector (HGA) in the third column, and the offset angles (ANGY, ANGX, and ANGZ) in columns 4-6. For computing the offset angles we define a local coordinate system as follows. DSD is the SRG vector from the spacecraft at transmit to the Earth at receive. DOS is the SRG vector from the center of Mars to the spacecraft at transmit time. DOP is the SRG vector from the center of Mars to the specular point at transmit time. For a transient (occultation) echo event +Y axis is in the direction of DSD +Z axis is in the direction of +Y crossed with DOS +X axis is in the direction of +Y crossed with +Z For a specular point experiment, +Y is in the direction DOP-DOS; +X and +Z are defined as above. In either case ANGY is the angle between +Y and HGA ANGX is the projection of ANGY onto the XY plane with positive values toward +X ANGZ is the projection of ANGY onto the YZ plane with positive values toward +Z This is an ASCII table. Columns and items are delimited by commas (vectors are considered to be single columns comprising three 'items'). Data and delimiters occupy the first 78 bytes of each row; rows are delimited by an ASCII carriage-return line-feed pair in byte positions 79 and 80." OBJECT = COLUMN COLUMN_NUMBER = 1 NAME = "TRX" DATA_TYPE = ASCII_REAL START_BYTE = 1 BYTES = 10 FORMAT = "F10.3" UNIT = SECOND DESCRIPTION = "Earth received time (ERT) for which the the antenna pointing calculations were made. TRX is the time (UTC) when an Earth-based observer would see this geometry. Given in seconds from midnight. For date, see Column 1 in the HGA_POINTING_HDR_TABLE." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 2 NAME = "TTX" DATA_TYPE = ASCII_REAL START_BYTE = 12 BYTES = 10 FORMAT = "F10.3" UNIT = SECOND DESCRIPTION = "Transmit time corresponding to TRX. The one-way light time for a photon traveling directly from the spacecraft to the DSN station has been subtracted from TRX." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 3 NAME = "HGA" DATA_TYPE = ASCII_REAL START_BYTE = 23 BYTES = 29 ITEMS = 3 ITEM_BYTES = 10 ITEM_OFFSET = 11 FORMAT = "F10.6" UNIT = "N/A" DESCRIPTION = "HGA unit vector in J2000 coordinates." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 4 NAME = "ANGY" DATA_TYPE = ASCII_REAL START_BYTE = 56 BYTES = 7 FORMAT = "F7.3" UNIT = "DEGREE" DESCRIPTION = "Angle between desired direction and reconstructed HGA unit vector." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 5 NAME = "ANGX" DATA_TYPE = ASCII_REAL START_BYTE = 64 BYTES = 7 FORMAT = "F7.3" UNIT = "DEGREE" DESCRIPTION = "Component of ANGY toward the surface." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 6 NAME = "ANGZ" DATA_TYPE = ASCII_REAL START_BYTE = 72 BYTES = 7 FORMAT = "F7.3" UNIT = "DEGREE" DESCRIPTION = "Component of ANGY along the limb." END_OBJECT = COLUMN END_OBJECT = HGA_POINTING_TABLE END A.2 Example SRG Label PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 688 FILE_RECORDS = 722 ^BSR_GEOM_HDR_TABLE = ("0055A00A.SRG",1) ^BSR_GEOM_TABLE = ("0055A00A.SRG",2) INSTRUMENT_HOST_NAME = "MARS GLOBAL SURVEYOR" TARGET_NAME = "MARS" INSTRUMENT_NAME = "RADIO SCIENCE SUBSYSTEM" DATA_SET_ID = "VEX-V-VRA-1/2/3-NMP-0102-V1.0" PRODUCT_ID = "0055A00A.SRG" START_TIME = 2000-02-24T00:00:00 STOP_TIME = 2000-02-24T02:00:00 ORIGINAL_PRODUCT_ID = "0031215A.SPK" PRODUCT_CREATION_TIME = 2014-02-10T10:28:12.000 DESCRIPTION = "This file summarizes observing geometry for Mars Global Surveyor (MGS) bistatic radar (BSR) observations. The results apply to both atmospheric occultations and surface scattering, but more parameters of interest for surface studies have been included. START_TIME and STOP_TIME (above) are Earth Receive Time (ERT). The file comprises two tables. The first table is a single row which identifies the calculation (fingerprints). The second table (with many rows) is the geometry summary itself. File names are of the form ydddHmmC.SRG where y is the one-digit year, ddd is the 3-digit day-of-year, H is a letter denoting the hour (A=00, B=01, ..., X=23), and mm is the 2-digit minute of the first data in the file. C indicates version of the file; C='A' is the first version, 'B' is the second version, etc. ydddHmm in these files is intended to be SIMILAR to ydddHmm in TPS and TPH occultation file names and in SRT and SRI surface scattering file names. Because SRG files are produced independently, this correspondence cannot be guaranteed. Further, mm in the other files can sometimes include a letter -- if data were collected simultaneously at two antennas; and the version indicators (C) may be entirely different. This file was produced by Dick Simpson of the MGS Radio Science Team (RST) as part of his Participating Scientist investigation." OBJECT = BSR_GEOM_HDR_TABLE NAME = "BSR GEOMETRY HEADER" INTERCHANGE_FORMAT = ASCII ROWS = 1 COLUMNS = 7 ROW_BYTES = 77 ROW_SUFFIX_BYTES = 611 DESCRIPTION = "Table contains identifying information and constants for use with the geometry in the next table. Table contains a single row of 7 columns giving DSN antenna number, input SPK file name, assumed planet radius and speed of light, latitude and longitude of a user-specified target point, and time spacing of rows in next table. Columns are delimited by commas; total space occupied by data columns and delimiters is 75 bytes. The row is padded with 611 ASCII blanks. An ASCII carriage-return and line-feed occupy byte positions 687 and 688." OBJECT = COLUMN COLUMN_NUMBER = 1 NAME = "DSS" DATA_TYPE = ASCII_INTEGER START_BYTE = 1 BYTES = 2 FORMAT = "I2" DESCRIPTION = "Deep Space Network antenna number." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 2 NAME = "SPK FILE NAME" DATA_TYPE = CHARACTER START_BYTE = 5 BYTES = 12 DESCRIPTION = "File name of the SPK file used to generate the geometry data in the BSR GEOMETRY table. File name is of the form ydddeeeC.EXT where y is the least significant digit in the year, ddd is the start day-of-year for the SPK data, eee is end day-of-year for the SPK data, C denotes the version of the SPK file ('A' is first, 'B' is second, etc.), and EXT is one of several possible extensions: SPK standard MGS NAV Team SPK file GDN quick-look Goddard reconstruction GDF final Goddard reconstruction IPN reconstruction by JPL IPNG The ydddeeeC.EXT naming convention was adopted by the MGS RST to simplify tracking of SPK files; the ORIGINAL_PRODUCT_ID can be found in the detached label for the SPK file." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 3 NAME = "RP" DATA_TYPE = ASCII_REAL START_BYTE = 19 BYTES = 12 FORMAT = "F12.3" UNIT = "METER" DESCRIPTION = "Assumed radius for spherical planet. Note that partial derivatives with respect to Rp are given for many important quantities, so the assumption of a single radius is not as restrictive as it might first seem." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 4 NAME = "VLITE" DATA_TYPE = ASCII_REAL START_BYTE = 32 BYTES = 14 FORMAT = "F14.3" UNIT = "METER PER SECOND" DESCRIPTION = "Assumed speed of light in vacuum." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 5 NAME = "TLAT" DATA_TYPE = ASCII_REAL START_BYTE = 47 BYTES = 9 FORMAT = "F9.4" UNIT = "DEGREE" DESCRIPTION = "Planetocentric latitude of user-specified target point. This point may or may not be meaningful for a given application. It was included to facilitate planning and analysis of spotlight mode surface scattering experiments." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 6 NAME = "TLON" DATA_TYPE = ASCII_REAL START_BYTE = 57 BYTES = 9 FORMAT = "F9.4" UNIT = "DEGREE" DESCRIPTION = "Planetocentric east longitude of user-specified target point. This point may or may not be meaningful for a given application. It was included to facilitate planning and analysis of spotlight mode surface scattering experiments." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 7 NAME = "DT" DATA_TYPE = ASCII_REAL START_BYTE = 67 BYTES = 9 FORMAT = "F9.3" UNIT = "SECOND" DESCRIPTION = "Time spacing between rows in next table." END_OBJECT = COLUMN END_OBJECT = BSR_GEOM_HDR_TABLE OBJECT = BSR_GEOM_TABLE NAME = "BSR GEOMETRY" INTERCHANGE_FORMAT = ASCII ROWS = 721 COLUMNS = 34 ROW_BYTES = 688 DESCRIPTION = "Table values allow reconstruction of bistatic observing geometry. The 34 columns give Earth receive time; transmit time; Mars fixed-body x, y, and z unit vectors; positions of spacecraft, DSN receiver, and various surface points (specular point, backscatter point, closest approach of occultation ray, and a user-specified target point); incidence, scattering, and bistatic angles at these points; and sensitivities of several quantities to changes in planet radius. The user-specified target point is given in areocentric latitude and longitude. Depending on the application, it may or may not be meaningful. For MGS, one such point might be the Mars Polar Lander target site. The backscatter point is where the line connecting the DSN receiver and the spacecraft intersects the planetary surface. At the backscatter point, the bistatic angle is zero. The backscatter point is only defined when the spacecraft appears silhouetted against the planet disk when viewed from the receiver on Earth (that is, when the planet surface appears to be behind the spacecraft). The raypath closest approach point is where the line connecting the receiver and spacecraft is closest to the planetary surface. This is the same construction as for the backscatter point; but the raypath closest approach point is defined only when the spacecraft is NOT silhouetted against the disk AND when the receiver-to-spacecraft distance is greater than the distance between the planet center of mass and the receiver. The specular point is where angle of incidence equals angle of reflection and where the incidence plane and the scattering plane are the same. When the spacecraft is in occultation, the specular point is not defined. Vectors are given in inertial J2000 coordinates. Latitudes and longitudes are given in areocentric fixed body (rotating) coordinates. Values at Mars are given at transmit time; values at Earth are given at ERT. Mixed quantities (e.g., vector from spacecraft to DSN station) are combinations. Mars is assumed to be a sphere of radius (3397+3397+3375)/3 kilometers. Speed of light is assumed to be 299792458 m/s. This is an ASCII table. Columns and items are delimited by commas (vectors are considered to be single columns comprising three 'items'). Data and delimiters occupy the first 686 bytes of each row; rows are delimited by an ASCII carriage-return line-feed pair in byte positions 687 and 688." OBJECT = COLUMN COLUMN_NUMBER = 1 NAME = "TRX" DATA_TYPE = ASCII_INTEGER START_BYTE = 1 BYTES = 5 FORMAT = "I5" UNIT = SECOND DESCRIPTION = "Earth received time (UTC) for which the geometrical calculations were made." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 2 NAME = "TTX" DATA_TYPE = ASCII_REAL START_BYTE = 7 BYTES = 12 FORMAT = "F12.6" UNIT = SECOND DESCRIPTION = "Transmit time corresponding to TRX. The one-way light time for a photon traveling directly from the spacecraft to the DSN station has been subtracted from TRX." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 3 NAME = "NPOLE" DATA_TYPE = ASCII_REAL START_BYTE = 20 BYTES = 29 ITEMS = 3 ITEM_BYTES = 9 ITEM_OFFSET = 10 FORMAT = "F9.6" UNIT = "N/A" DESCRIPTION = "North Pole unit vector in J2000 coordinates." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 4 NAME = "FBODX" DATA_TYPE = ASCII_REAL START_BYTE = 50 BYTES = 29 ITEMS = 3 ITEM_BYTES = 9 ITEM_OFFSET = 10 FORMAT = "F9.6" UNIT = "N/A" DESCRIPTION = "Fixed body Mars x-axis unit vector in J2000 coordinates." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 5 NAME = "FBODY" DATA_TYPE = ASCII_REAL START_BYTE = 80 BYTES = 29 ITEMS = 3 ITEM_BYTES = 9 ITEM_OFFSET = 10 FORMAT = "F9.6" UNIT = "N/A" DESCRIPTION = "Fixed body Mars y-axis unit vector in J2000 coordinates." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 6 NAME = "DOD" DATA_TYPE = ASCII_REAL START_BYTE = 110 BYTES = 41 ITEMS = 3 ITEM_BYTES = 13 ITEM_OFFSET = 14 FORMAT = "E13.6" UNIT = "METER" DESCRIPTION = "Center of Mars to DSN vector at TRX in J2000 coordinates." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 7 NAME = "DOS" DATA_TYPE = ASCII_REAL START_BYTE = 152 BYTES = 41 ITEMS = 3 ITEM_BYTES = 13 ITEM_OFFSET = 14 FORMAT = "E13.6" UNIT = "METER" DESCRIPTION = "Center of Mars to spacecraft vector at TTX in J2000 coordinates." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 8 NAME = "DSD" DATA_TYPE = ASCII_REAL START_BYTE = 194 BYTES = 41 ITEMS = 3 ITEM_BYTES = 13 ITEM_OFFSET = 14 FORMAT = "E13.6" UNIT = "METER" DESCRIPTION = "Spacecraft (TTX) to DSN (TRX) vector in J2000 coordinates." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 9 NAME = "DOT" DATA_TYPE = ASCII_REAL START_BYTE = 236 BYTES = 41 ITEMS = 3 ITEM_BYTES = 13 ITEM_OFFSET = 14 FORMAT = "E13.6" UNIT = "METER" DESCRIPTION = "Vector from center of Mars to user-specified surface point in J2000 coordinates." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 10 NAME = "DTD" DATA_TYPE = ASCII_REAL START_BYTE = 278 BYTES = 41 ITEMS = 3 ITEM_BYTES = 13 ITEM_OFFSET = 14 FORMAT = "E13.6" UNIT = "METER" DESCRIPTION = "User-specified point (TTX) to DSN (TRX) vector in J2000 coordinates." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 11 NAME = "DTS" DATA_TYPE = ASCII_REAL START_BYTE = 320 BYTES = 41 ITEMS = 3 ITEM_BYTES = 13 ITEM_OFFSET = 14 FORMAT = "E13.6" UNIT = "METER" DESCRIPTION = "User-specified point to spacecraft vector at TTX in J2000 coordinates." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 12 NAME = "THTI" DATA_TYPE = ASCII_REAL START_BYTE = 362 BYTES = 9 FORMAT = "F9.6" UNIT = "DEGREE" DESCRIPTION = "Incidence angle at user-specified point. The angle between the local surface normal and the DTS vector. Values larger than 90 mean the spacecraft is below the horizon." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 13 NAME = "THTS" DATA_TYPE = ASCII_REAL START_BYTE = 372 BYTES = 9 FORMAT = "F9.6" UNIT = "DEGREE" DESCRIPTION = "Scattering angle at user-specified point. The angle between the local surface normal and the DTD vector. Values larger than 90 mean that the DSN receiving site below the horizon." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 14 NAME = "BETA" DATA_TYPE = ASCII_REAL START_BYTE = 382 BYTES = 9 FORMAT = "F9.6" UNIT = "DEGREE" DESCRIPTION = "Bistatic angle at user-specified point. Separation angle between DSN and the spacecraft as seen at the user-specified point. Angle between DTS and DTD." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 15 NAME = "DOB" DATA_TYPE = ASCII_REAL START_BYTE = 392 BYTES = 41 ITEMS = 3 ITEM_BYTES = 13 ITEM_OFFSET = 14 FORMAT = "E13.6" UNIT = "METER" DESCRIPTION = "Center of Mars to beta=0 (backscatter) point in J2000 coordinates. If the beta=0 point does not exist, this vector is undefined and BLAT and BLON should be set to -999.9999." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 16 NAME = "BLAT" DATA_TYPE = ASCII_REAL START_BYTE = 434 BYTES = 9 FORMAT = "F9.6" UNIT = "DEGREE" INVALID_CONSTANT = -999.9999 DESCRIPTION = "Areocentric latitude of beta=0 point. Set to -999.9999 if the point does not exist." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 17 NAME = "BLON" DATA_TYPE = ASCII_REAL START_BYTE = 444 BYTES = 9 FORMAT = "F9.6" UNIT = "DEGREE" INVALID_CONSTANT = -999.9999 DESCRIPTION = "Areocentric east longitude of beta=0 point. Set to -999.9999 if the point does not exist." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 18 NAME = "DOR" DATA_TYPE = ASCII_REAL START_BYTE = 454 BYTES = 41 ITEMS = 3 ITEM_BYTES = 13 ITEM_OFFSET = 14 FORMAT = "E13.6" UNIT = "METER" DESCRIPTION = "Center of Mars to raypath closest approach (RCA) point in J2000 coordinates. The raypath is vector DSD; the RCA point is on the surface of Mars where DSD is closest. If the RCA point does not exist, DOR is undefined and RLAT and RLON should be set to -999.9999." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 19 NAME = "RLAT" DATA_TYPE = ASCII_REAL START_BYTE = 496 BYTES = 9 FORMAT = "F9.6" UNIT = "DEGREE" INVALID_CONSTANT = -999.9999 DESCRIPTION = "Areocentric latitude of the raypath closest approach point. Set to -999.9999 if the spacecraft to DSN receiver distance is less than the DSN receiver to center of Mars distance." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 20 NAME = "RLON" DATA_TYPE = ASCII_REAL START_BYTE = 506 BYTES = 9 FORMAT = "F9.6" UNIT = "DEGREE" INVALID_CONSTANT = -999.9999 DESCRIPTION = "Areocentric east longitude of the raypath closest approach point. Set to -999.9999 if the spacecraft to DSN receiver distance is less than the DSN receiver to center of Mars distance." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 21 NAME = "DOP" DATA_TYPE = ASCII_REAL START_BYTE = 516 BYTES = 41 ITEMS = 3 ITEM_BYTES = 13 ITEM_OFFSET = 14 FORMAT = "E13.6" UNIT = "METER" DESCRIPTION = "Center of Mars to specular point vector in J2000 coordinates. If the specular point does not exist, this vector is undefined and PLAT and PLON should be set to -999.9999" END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 22 NAME = "THPI" DATA_TYPE = ASCII_REAL START_BYTE = 558 BYTES = 9 FORMAT = "F9.6" UNIT = "DEGREE" DESCRIPTION = "Incidence angle at specular point. Values are undefined when the spacecraft is in occultation." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 23 NAME = "THPS" DATA_TYPE = ASCII_REAL START_BYTE = 568 BYTES = 9 FORMAT = "F9.6" UNIT = "DEGREE" DESCRIPTION = "Reflection angle at specular point. Values are undefined when the spacecraft is in occultation." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 24 NAME = "PLAT" DATA_TYPE = ASCII_REAL START_BYTE = 578 BYTES = 9 FORMAT = "F9.6" UNIT = "DEGREE" INVALID_CONSTANT = -999.9999 DESCRIPTION = "Areocentric latitude of specular point. Set to -999.9999 if the specular point does not exist (the spacecraft is in occultation)." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 25 NAME = "PLON" DATA_TYPE = ASCII_REAL START_BYTE = 588 BYTES = 9 FORMAT = "F9.6" UNIT = "DEGREE" INVALID_CONSTANT = -999.9999 DESCRIPTION = "Areocentric east longitude of specular point. Set to -999.9999 if the specular point does not exist (the spacecraft is in occultation)." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 26 NAME = "DTHTI" DATA_TYPE = ASCII_REAL START_BYTE = 598 BYTES = 9 FORMAT = "E9.2" UNIT = "DEGREE PER METER" DESCRIPTION = "Partial derivative of THTI with respect to Rp. The change in incidence angle at the user-specified target point resulting from a +1 m change in Mars radius." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 27 NAME = "DTHTS" DATA_TYPE = ASCII_REAL START_BYTE = 608 BYTES = 9 FORMAT = "E9.2" UNIT = "DEGREE PER METER" DESCRIPTION = "Partial derivative of THTS with respect to Rp. The change in scattering angle at the user-specified target point resulting from a +1 m change in Mars radius." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 28 NAME = "DBETA" DATA_TYPE = ASCII_REAL START_BYTE = 618 BYTES = 9 FORMAT = "E9.2" UNIT = "DEGREE PER METER" DESCRIPTION = "Partial derivative of BETA with respect to Rp. The change in bistatic angle at the user-specified target point resulting from a +1 m change in Mars radius." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 29 NAME = "DBLAT" DATA_TYPE = ASCII_REAL START_BYTE = 628 BYTES = 9 FORMAT = "E9.2" UNIT = "DEGREE PER METER" INVALID_CONSTANT = -9.99E-02 DESCRIPTION = "Partial derivative of BLAT with respect to Rp. The change in latitude of the backscatter point resulting from a +1 m change in Mars radius. Set to -9.99E-02 if there is no backscatter point (line from DSN station to spacecraft does not intersect the surface)." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 30 NAME = "DBLON" DATA_TYPE = ASCII_REAL START_BYTE = 638 BYTES = 9 FORMAT = "E9.2" UNIT = "DEGREE PER METER" INVALID_CONSTANT = -9.99E-02 DESCRIPTION = "Partial derivative of BLON with respect to Rp. The change in longitude of the backscatter point resulting from a +1 m change in Mars radius. Set to -9.99E-02 if there is no backscatter point (line from DSN station to spacecraft does not intersect the surface)." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 31 NAME = "DTHPI" DATA_TYPE = ASCII_REAL START_BYTE = 648 BYTES = 9 FORMAT = "E9.2" UNIT = "DEGREE PER METER" INVALID_CONSTANT = -9.99E-02 DESCRIPTION = "Partial derivative of THPI with respect to Rp. The change in incidence angle at the specular point resulting from a +1 m change in Mars radius. Set to -9.99E-02 if there is no specular point (spacecraft is in occultation)." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 32 NAME = "DTHPS" DATA_TYPE = ASCII_REAL START_BYTE = 658 BYTES = 9 FORMAT = "E9.2" UNIT = "DEGREE PER METER" INVALID_CONSTANT = -9.99E-02 DESCRIPTION = "Partial derivative of THPS with respect to Rp. The change in reflection angle at the specular point resulting from a +1 m change in Mars radius. Set to -9.99E-02 if there is no specular point (spacecraft is in occultation)." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 33 NAME = "DPLAT" DATA_TYPE = ASCII_REAL START_BYTE = 668 BYTES = 9 FORMAT = "E9.2" UNIT = "DEGREE PER METER" INVALID_CONSTANT = -9.99E-02 DESCRIPTION = "Partial derivative of PLAT with respect to Rp. The change in latitude of the specular point resulting from a +1 m change in Mars radius. Set to -9.99E-02 if there is no specular point (spacecraft is in occultation)." END_OBJECT = COLUMN OBJECT = COLUMN COLUMN_NUMBER = 34 NAME = "DPLON" DATA_TYPE = ASCII_REAL START_BYTE = 678 BYTES = 9 FORMAT = "E9.2" UNIT = "DEGREE PER METER" INVALID_CONSTANT = -9.99E-02 DESCRIPTION = "Partial derivative of PLON with respect to Rp. The change in longitude of the specular point resulting from a +1 m change in Mars radius. Set to -9.99E-02 if there is no specular point (spacecraft is in occultation)." END_OBJECT = COLUMN END_OBJECT = BSR_GEOM_TABLE END A.3 Example SRI Label PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 1024 FILE_RECORDS = 300 ^IMAGE = "9133H43A.SRI" INSTRUMENT_HOST_NAME = "MARS GLOBAL SURVEYOR" TARGET_NAME = "MARS" INSTRUMENT_NAME = "RADIO SCIENCE SUBSYSTEM" DATA_SET_ID = "VEX-V-VRA-1/2/3-NMP-0102-V1.0" PRODUCT_ID = "9133H43A.SRI" PRODUCT_RELEASE_DATE = 2000-07-28 DESCRIPTION = "This file contains a 2-D array in image format showing power vs frequency and time around the time of a Mars Global Surveyor radio occultation. A nominal image is made from 300 512-point power spectra where the spacing between spectra is 0.2048 s and the frequency spanned is 2500 Hz (4.88 Hz resolution). Images show the spacecraft carrier emerging from occultation (egress) or disappearing as the spacecraft goes behind the limb (ingress). Near the occultation time there may be a weak surface echo racing away from the carrier to lower frequencies (egress) or coming in from higher frequencies to merge with the carrier at occultation (ingress). Keywords START_TIME and STOP_TIME give the beginning and ending of data recording for the occultation. For exact times of each spectrum see the Surface Reflection Table file that corresponds to this image (same file name except for suffix .SRT). This image was produced by R.A. Simpson of the MGS Radio Science Team." START_TIME = 1999-05-13T07:43:00 STOP_TIME = 1999-05-13T07:55:00 SOFTWARE_NAME = "SURF2PDS;1999-10-13" PRODUCT_CREATION_TIME = 2014-02-10T10:28:12.000 PRODUCER_ID = "MGS RST" OBJECT = IMAGE LINES = 300 LINE_SAMPLES = 512 SAMPLE_TYPE = MSB_INTEGER SAMPLE_BITS = 16 UNIT = "DECIBEL" OFFSET = 0.0 SCALING_FACTOR = 0.01 DESCRIPTION = "This image contains values of received signal power versus frequency and time in units of decibels relative to one one watt. Values can be obtained by multiplying the sample in the image by SCALING_FACTOR and then adding OFFSET. Each line in the image corresponds to one power spectrum. The first line in the file is the LAST spectrum. The first point in a line corresponds to the lowest frequency (0 Hz)." END_OBJECT = IMAGE END A.4 Example SRT Label PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 50 FILE_RECORDS = 305 ^SURF_HDR_TABLE = ("9133H43A.SRT",1) ^SURF_TABLE = ("9133H43A.SRT",6) INSTRUMENT_HOST_NAME = "MARS GLOBAL SURVEYOR" TARGET_NAME = "MARS" INSTRUMENT_NAME = "RADIO SCIENCE SUBSYSTEM" DATA_SET_ID = "VEX-V-VRA-1/2/3-NMP-0102-V1.0" PRODUCT_ID = "9133H43A.SRT" PRODUCT_RELEASE_DATE = 2000-07-28 DESCRIPTION = "This file contains measurements of surface echoes obtained in the course of Mars Global Surveyor radio occultation observations. The time of geometric occultation and the sense of occultation (ingress or egress) were determined from high time resolution analysis of the carrier amplitude. A search was then made on either side of the carrier; if more power was found on one side, that was assumed to be from the echo. An estimate of the thermal noise background was obtained from the other side; that, in conjunction with an estimate of system temperature was used to calibrate the measurements. The table contains estimates of the peak frequency bin and the amplitude of both the carrier and the surface echo as a function of time. For more information on bistatic radar probing of planetary surfaces, see Simpson (IEEE Transactions on Geoscience and Remote Sensing, 31, 465-482, 1993)." START_TIME = 1999-05-13T07:43:00 STOP_TIME = 1999-05-13T07:55:00 SOFTWARE_NAME = "SURF2PDS;1999-10-13" PRODUCT_CREATION_TIME = 2014-02-10T10:28:12.000 PRODUCER_ID = "MGS RST" OBJECT = SURF_HDR_TABLE ROWS = 1 COLUMNS = 24 ROW_BYTES = 222 ROW_SUFFIX_BYTES = 28 INTERCHANGE_FORMAT = ASCII DESCRIPTION = "The SURF header contains ancillary data associated surface echo power measurements. Each header includes a single row of 24 data columns (220 total bytes), 28 ASCII blank characters to pad out the record, and an ASCII carriage-return line-feed pair at the end." OBJECT = COLUMN NAME = "START TIME" COLUMN_NUMBER = 1 DATA_TYPE = TIME START_BYTE = 1 BYTES = 19 UNIT = "N/A" DESCRIPTION = "The Earth Receive Time at which the first radio occultation data sample was acquired." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "STOP TIME" COLUMN_NUMBER = 2 DATA_TYPE = TIME START_BYTE = 21 BYTES = 19 UNIT = "N/A" DESCRIPTION = "The Earth Receive Time at which the last radio occultation data sample was acquired." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "OCCULTATION TIME" COLUMN_NUMBER = 3 DATA_TYPE = ASCII_REAL START_BYTE = 41 BYTES = 12 FORMAT = "F12.6" UNIT = "SECOND" DESCRIPTION = "The Earth receive time when the geometrical ray path grazed the limb. At this point half of the Fresnel zone was presumably obscured, and received carrier power should have been one-fourth of its free space value. The time was computed using power versus time output from the POWERFIT program. Maximum and minimum minimum carrier amplitudes within 3 seconds of the occultation established the amplitude range. For egress, the last sample below the 25 percent threshold served as a temporary marker. For ingress, working in time reverse order, a similar marker was found. The final occultation time was the time of the adjacent sample in the unocculted (free space) direction, usually with higher carrier power. Formal accuracy of this quantity is estimated to be +/-12.8 msec, the POWERFIT sample spacing. However, this method does not account for effects of the atmosphere at the limb; refraction is estimated to advance the occultation time by about 2 seconds on egress and to delay it by about 2 seconds on ingress." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "ORBIT NUMBER" COLUMN_NUMBER = 4 DATA_TYPE = ASCII_INTEGER START_BYTE = 54 BYTES = 5 FORMAT = "I5" UNIT = "N/A" DESCRIPTION = "Orbit number from which the data were acquired; set to zero if not known. NB: Orbit numbers were reset to 1 at the beginning of the MGS Mapping Phase (9 March 1999)." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "DSN ANTENNA NUMBER" COLUMN_NUMBER = 5 DATA_TYPE = ASCII_INTEGER START_BYTE = 60 BYTES = 2 FORMAT = "I2" UNIT = "N/A" DESCRIPTION = "Number of the DSN antenna used to collect the data (e.g., 14, 43, 65, ...)." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "OCCULTATION SENSE" COLUMN_NUMBER = 6 DATA_TYPE = CHARACTER START_BYTE = 64 BYTES = 1 FORMAT = "A1" UNIT = "N/A" DESCRIPTION = "The sense of the occultation: set to 'I' for ingress or to 'E' for egress." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "ODR FILE NAME" COLUMN_NUMBER = 7 DATA_TYPE = CHARACTER START_BYTE = 68 BYTES = 12 FORMAT = "A12" UNIT = "N/A" DESCRIPTION = "File name of the original open-loop data." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "FILTER FILE NAME" COLUMN_NUMBER = 8 DATA_TYPE = CHARACTER START_BYTE = 83 BYTES = 12 FORMAT = "A12" UNIT = "N/A" DESCRIPTION = "File name of the equalizing filter used to smooth the output spectrum." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "CARRIER TO NOISE RATIO" COLUMN_NUMBER = 9 DATA_TYPE = ASCII_REAL START_BYTE = 97 BYTES = 6 FORMAT = "F6.2" UNIT = "DECIBEL PER HERTZ" DESCRIPTION = "Estimate of unocculted carrier power to thermal noise power. An indication of overall data quality." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "SYSTEM TEMPERATURE" COLUMN_NUMBER = 10 DATA_TYPE = ASCII_REAL START_BYTE = 104 BYTES = 6 FORMAT = "F6.2" UNIT = "KELVIN" DESCRIPTION = "System temperature assumed in calibrating data to units of watts. This quantity is obtained in real time by the NASA Deep Space Network, but values appropriate for interpreting a given observation are not always available. A value of 30K is considered nominal." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "SAMPLE SPACING" COLUMN_NUMBER = 11 DATA_TYPE = ASCII_REAL START_BYTE = 111 BYTES = 8 FORMAT = "F8.6" UNIT = "SECOND" DESCRIPTION = "Time spacing of the complex samples used as input to this analysis. Spacing is twice the spacing of the original (real) samples." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "TRANSFORM LENGTH" COLUMN_NUMBER = 12 DATA_TYPE = ASCII_INTEGER START_BYTE = 120 BYTES = 5 FORMAT = "I5" UNIT = "N/A" DESCRIPTION = "Number of points in each power spectrum. Typically a number like 512." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "TIME PER SPECTRUM" COLUMN_NUMBER = 13 DATA_TYPE = ASCII_REAL START_BYTE = 126 BYTES = 8 FORMAT = "F8.6" UNIT = "SECOND" DESCRIPTION = "Time represented by each spectrum, and spacing between spectra. The product of the previous two columns multiplied by the number of spectra averaged." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "FREQUENCY RESOLUTION" COLUMN_NUMBER = 14 DATA_TYPE = ASCII_REAL START_BYTE = 135 BYTES = 7 FORMAT = "F7.4" UNIT = "HERTZ" DESCRIPTION = "Frequency resolution in each spectrum. TIME PER SPECTRUM multiplied by FREQUENCY RESOLUTION gives the number of spectra averaged incoherently." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "LOWEST NOISE BIN" COLUMN_NUMBER = 15 DATA_TYPE = ASCII_INTEGER START_BYTE = 143 BYTES = 5 FORMAT = "I5" UNIT = "N/A" DESCRIPTION = "Lowest frequency bin included in calculation of radio thermal noise background level. Noise bins should be on opposite side of carrier from surface echo." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "HIGHEST NOISE BIN" COLUMN_NUMBER = 16 DATA_TYPE = ASCII_INTEGER START_BYTE = 149 BYTES = 5 FORMAT = "I5" UNIT = "N/A" DESCRIPTION = "Highest frequency bin included in calculation of radio thermal noise background level. Noise bins should be on opposite side of carrier from surface echo." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "NUMBER OF NOISE POINTS" COLUMN_NUMBER = 17 DATA_TYPE = ASCII_INTEGER START_BYTE = 155 BYTES = 8 FORMAT = "I8" UNIT = "N/A" DESCRIPTION = "Number of noise values used to compute radio thermal noise background level. Number of frequency bins (from Columns 14 and 15) multiplied by the number of spectra gives this total." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "NOISE MEAN" COLUMN_NUMBER = 18 DATA_TYPE = ASCII_REAL START_BYTE = 164 BYTES = 10 FORMAT = "E10.4" UNIT = "N/A" DESCRIPTION = "Average of the noise measurements within the bounds defined by Columns 14-16." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "NOISE STANDARD DEVIATION" COLUMN_NUMBER = 19 DATA_TYPE = ASCII_REAL START_BYTE = 175 BYTES = 10 FORMAT = "E10.4" UNIT = "N/A" DESCRIPTION = "Standard deviation of the noise measurements within the bounds defined by Columns 14-16. For white noise and no spectral averaging Columns 17 and 18 should be very close." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "NUMBER OF MASKED FREQUENCY BINS" COLUMN_NUMBER = 20 DATA_TYPE = ASCII_INTEGER START_BYTE = 186 BYTES = 3 FORMAT = "I3" UNIT = "N/A" DESCRIPTION = "Number of frequency bins on each side of the carrier that were masked during search for and fit to the frequency track of the echo signal. If no masking were used, splatter from the carrier would dominate the search." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "FIRST TIME BIN IN FREQUENCY FIT" COLUMN_NUMBER = 21 DATA_TYPE = ASCII_INTEGER START_BYTE = 190 BYTES = 3 FORMAT = "I3" UNIT = "N/A" DESCRIPTION = "First time bin used in search for and fit to frequency track of the surface echo. Usually 41 for egress, variable for ingress." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "LAST TIME BIN IN FREQUENCY FIT" COLUMN_NUMBER = 22 DATA_TYPE = ASCII_INTEGER START_BYTE = 194 BYTES = 3 FORMAT = "I3" UNIT = "N/A" DESCRIPTION = "Last time bin used in search for and fit to frequency track of the surface echo. Usually 259 for ingress, variable for egress." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "ECHO FITTED SLOPE" COLUMN_NUMBER = 23 DATA_TYPE = ASCII_REAL START_BYTE = 198 BYTES = 11 FORMAT = "E11.4" UNIT = "HERTZ PER SECOND" DESCRIPTION = "Slope of the linear fit to surface echo position with respect to the carrier. This is the linear coefficient a in the equation f = a*t + b where f is frequency of surface echo relative to carrier t is time from the previous even hour b is constant coefficient (Column 24)." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "ECHO FITTED INTERCEPT" COLUMN_NUMBER = 24 DATA_TYPE = ASCII_REAL START_BYTE = 210 BYTES = 11 FORMAT = "E11.4" UNIT = "HERTZ" DESCRIPTION = "Intercept of the linear fit to echo position with respect to the carrier. This is the constant term b in the equation f = a*t + b where f is frequency of surface echo relative to carrier a is linear coefficient (Column 23) t is time from the previous even hour." END_OBJECT = COLUMN END_OBJECT = SURF_HDR_TABLE OBJECT = SURF_TABLE ROWS = 300 COLUMNS = 5 ROW_BYTES = 50 INTERCHANGE_FORMAT = ASCII DESCRIPTION = "Table contains time, bin numbers, and amplitudes of carrier and surface echo. Calculations were based on power spectra; typically 300 spectra were used, each having 512 frequency bins. Data are in five columns, delimited by ASCII commas (98 bytes total); the final two positions are occupied by an ASCII carriage-return and an ASCII line-feed." OBJECT = COLUMN NAME = "TIME" COLUMN_NUMBER = 1 DATA_TYPE = ASCII_REAL START_BYTE = 1 BYTES = 12 FORMAT = "F12.6" UNIT = "SECOND" DESCRIPTION = "Time at which the spectrum was calculated, in seconds from the previous ERT midnight." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "CARRIER BIN NUMBER" COLUMN_NUMBER = 2 DATA_TYPE = ASCII_INTEGER START_BYTE = 14 BYTES = 5 FORMAT = "I5" UNIT = "N/A" DESCRIPTION = "Number of the spectral bin with maximum power. This is presumed to be the carrier signal, but could, occasionally, be strong interference from a ground source. During deep occultation, this value will be random." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "SURFACE ECHO BIN" COLUMN_NUMBER = 3 DATA_TYPE = ASCII_INTEGER START_BYTE = 20 BYTES = 5 FORMAT = "I5" UNIT = "N/A" DESCRIPTION = "Number of the spectral bin containing the presumed peak of the surface echo. After determination of occultation sense (ingress or egress) a search was made of the time-frequency space in which the surface echo should be found. Area within a few bins of the carrier was excluded. This is the location of whatever peak was found -- usually the surface echo when strong." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "CARRIER POWER" COLUMN_NUMBER = 4 DATA_TYPE = ASCII_REAL START_BYTE = 26 BYTES = 11 FORMAT = "E11.4" UNIT = "WATT" DESCRIPTION = "Carrier power in watts. Obtained by summing the power in the peak bin (CARRIER BIN NUMBER) plus three bins on either side, after removal of the noise baseline." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "SURFACE ECHO POWER" COLUMN_NUMBER = 5 DATA_TYPE = ASCII_REAL START_BYTE = 38 BYTES = 11 FORMAT = "E11.4" UNIT = "WATT" DESCRIPTION = "Power in presumed surface echo. Obtained by (1) fitting a straight line to the echo offset frequency from the carrier [Column 3 - Column 2 multiplied by Hertz per bin; best fit is given by coefficients in Columns 23 and 24 of SURF_HDR_TABLE]; (2) summing powers in approximately 7 spectral bins centered on this line. This will be a poor estimate if the fit is not good." END_OBJECT = COLUMN END_OBJECT = SURF_TABLE END