CCSD3ZF0000100000001NJPL3IF0PDS200000001 = SFDU_LABEL RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 SPACECRAFT_NAME = MAGELLAN TARGET_NAME = VENUS OBJECT = TEXT PUBLICATION_DATE = 1991-09-12 BYTES = 80 NOTE = "MIT-MGN-ARCDR v 2.3 Software Interface Specification" END_OBJECT = TEXT END M.I.T. Center for Space Research PROJECT MAGELLAN Software Interface Specification MIT-MGN-ARCDR ALTIMETRIC AND RADIOMETRIC COMPOSITE DATA RECORD prepared by Peter G. Ford Center for Space Research Massachusetts Institute of Technology Cambridge, Mass. 02139 Tel (617) 253-6485 Version 2.3 September 12, 1991 ________________________________________________________________________ 1. GENERAL DESCRIPTION 1.1. Overview This Software Interface Specification (SIS) contains the description of the Altimetry and Radiometry Composite Data Record (ARCDR) product tapes for the Magellan Project. 1.2. Scope The format and content specifications in this SIS apply to all phases of the project for which this product is required. 1.3. Applicable Documents [1] ANSI X3.27-1978, American National Standards Institute, Magnetic Tape Labels for Information Exchange, Appendix X, Label and Volume Organization, April 18, 1977. [2] JJPL-0006-00-01, JPL SFDU Description and Usage. Issue 5, March 7 1988. [3] SFOC-1-MHR-MGN-SCIEDR, Magellan Software Interface Specification, SAR and Altimeter EDR/TEDR Tapes , J. Springer and B. Wilson, JPL. November 28, 1988. [4] SFOC-2-DPS-CDB-Ephemeris, NAIF Ephemeris File, JPL Navigation Ancillary Information Facility, July 15, 1988. [5] Standards for the Preparation and Interchange of Data Sets, T.Z. Martin et al., D-4683, JPL Planetary Data System, Version 1.1, October 3, 1988. [6] MIT-MGN-SDMP, Magellan Altimetry & Radiometry Data Processing Software and Data Management Plan, MIT Center for Space Research, Revision 5, September 20, 1989. [7] MIT-MGN-SDD, Magellan Altimetry & Radiometry Software Design Document, MIT Center for Space Research, Version 2.0, September 20, 1989. [8] MIT-MGN-GxDR, Magellan Altimetry & Radiometry Global Data Products Software Interface Specification, MIT Center for Space Research, Version 2.1, January 30, 1990. [9] MGN 630-79, Rev. C, Magellan Planetary Constants and Models, D.T. Lyons, Magellan Mission Design, JPL, April 11, 1988. [10] An Introduction to SPICELIB, Volumes I and II, Navigation Ancillary Information Facility, JPL Planetary Data System, September 3, 1988. [11] MIT-MGN-ERR, Magellan Altimetry Error Analysis, MIT Center for Space Research, Version 2, September 20, 1989. [12] NESYS Update, R.E. Thurman, NAIF, JPL Interoffice Memo 314.8-ret.1, June 12, 1989. 1.4. System Siting 1.4.1. Interface Location and Medium ARCDR tapes are created by the MIT A&R data processing system, consisting of Sun/4 work stations and Fujitsu 2444AC tape drives. 1.4.2. Data Sources, Destinations, and Transfer Methods ARCDR tapes contain files created by the MIT A&R data processing system, as well as copies of ephemeris files generated by the NAIF facility at JPL. ARCDR's are written in ANSI standard format on computer compatible tape (CCT). Product tapes are provided to the MGN Data Management and Archive Team (DMAT), which forwards the tapes to users. 1.4.3. Generation Method and Frequency ARCDR tapes are generated from two sources--ALT-EDR tapes created at JPL's Space Flight Operations Center (SFOC). These tapes are first sent to the MGN DMAT, which duplicates them and sends one copy to MIT. Each source volume contains up to 8 sequential orbits of Magellan data, and will be processed as soon as received. In order to correct for systematic errors in orbit determination, the partially processed data will be "staged" until 200 orbits have accumulated. An orbit correction algorithm will be applied, and the resulting data written to ARCDR tapes. Each tape will contain data from up to 60 sequential Magellan orbits. 1.5. Assumptions and Constraints 1.5.1. Usage Constraints ARCDR tapes shall be provided, through the DMAT, to project-designated teams and investigators. 1.5.2. Priority Phasing Constraints ARCDR tapes will be generated at MIT from October 1990 through the end of the mission. 1.5.3. Explicit and Derived Constraints The production of ARCDR tapes will be given the highest job priority. The time limit for this task is driven by the availability of ALT-EDR tapes from DMAT. 1.5.4. Documentation Conventions 1.5.4.1. Data Format Descriptions The reference data unit is the byte. In the ARCDR, data is stored in fields with various sizes and formats, viz. one-, two-, and four-byte binary integers, four-byte binary floating-point numbers, and character strings. The detailed formats of the numeric fields of the product tapes sent to DMAT are defined in Appendices A and B. 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 next character, and so forth. Character strings are written to tape with lower numbered bytes preceding higher numbered bytes. 1.5.4.2. Time Standards The ARCDR shall adopt the January 1.5, 2000 epoch as the standard time for SCET. Within the data files, all times will be reported in Spacecraft Event Time, expressed as a binary double precision data field representing the number of elapsed seconds of Ephemeris Time (TDB) since noon, January 1, 2000. 1.5.4.3. Coordinate Systems The ARCDR shall adopt the J2000 coordinate system for all inertial values, i.e. those that define the motion of the spacecraft relative to celestial objects. Locations on the Venus surface shall be expressed in the VBF85 coordinate system. See Applicable Document [9] for further details. 1.5.4.4. Limits of This Document This document defines the format for ARCDR product tapes. It specifies ANSI and SFDU labeling at the volume and file levels, and extends to the logical record level for altimetry and radiometry data files. The logical record content and format of NAIF ephemeris files is defined in Associated Document [4]. ________________________________________________________________________ 2. INTERFACE CHARACTERISTICS 2.1. Hardware Characteristics and Limitations 2.1.1. Special Equipment and Device Interfaces The primary input data to the MIT A&R data processing system shall be ALT-EDR tapes supplied by the MGN DMAT. These will be read with high-density (6250 bpi) tape drives by the MGMLOG and MGMCTL programs running on Sun/4 (SPARC) hardware. The output from each ALT-EDR shall consist of up to 8 altimeter files. Altimetry and radiometry files are stored on magnetic disks until approximately 200 orbits have accumulated, at which time the orbit correction program MGMORB is run to compute a set of orbit element corrections. Finally, the program MGMGEN reads up to 60 orbits of altimetry, radiometry, and ephemeris (S-kernel), constructs orbit header files, applies the corrections, reformats all binary fields to the external (VAX) representation described in Appendix A, and writes an ARCDR tape. 2.1.2. Special Setup Requirements The MGMGEN program will be run during an unattended work shift. Two high-density tape drives must be available at this time. 2.2. Volume and Size The ARCDR data for each orbit consist of a set of 4 files, as detailed in Section 4, below. The altimetry and radiometry files vary in length according to the design characteristics of that orbit and with spacecraft system functions and telemetry quality. Each ARCDR product tape contains data for a maximum of 60 orbits. Whereas it is anticipated that ARCDR products shall each be contained on a single tape volume, this arrangement cannot be assumed to be a requirement of the system. Throughout this document, "tape" may mean a one- or two-reel volume. 2.3. Labeling and Identification 2.3.1. Magnetic Label ARCDR tapes delivered to DMAT shall have level 2 ANSI standard magnetic labels (see Applicable Document [1]), and file structures as described in Section 5 of this document. In addition, each file shall be identified by a set of Standard Formatted Data Unit (SFDU) labels, as described in Applicable Document [2] and in Section 5, below. 2.3.2. External Tape Label Each volume shall have an external label defining its contents. In addition to creation time, the label shall include the following structure designated by DMAT as the generic external product label, as the unique product identifier: ARCDR.first-last;version where 'first' and 'last' are 5-digit decimal numbers denoting, respectively, the project assigned orbit numbers of the first and last orbit contributing data to this product tape. 'Version' is a decimal version number which shall be initialized at '1' for each product tape, and incremented by 1 for each subsequent iteration of that product tape. For test tapes, 'Version' shall consist of the single character 'T' followed by a decimal number which shall be initialized at '1' for each test tape, and incremented by 1 for each subsequent iteration of that test tape. 2.4. Interface Medium Characteristics Magellan ARCDR products shall be contained on one or more 1/2 inch computer compatible magnetic tapes written with 9 tracks at 6250 bytes per inch. The length of each tape reel shall be either 2400 or 3600 foot, as necessary. 2.5. Failure Protection, Detection, and Recovery Procedures The ARCDR product tapes that are delivered to DMAT shall be written in the external (VAX) data format described in Appendix A. In addition, one copy of each ARCDR product shall be retained at MIT in IEEE binary format. If a backup is requested by DMAT, it will be generated from this copy by the MGMGEN program. 2.6. End-of-File Conventions End of file labeling shall comply with SFDU standards (see Section 4, below), and with ANSI standards for multi-file magnetic tapes (see Applicable Document [1]). 2.7. End-of-Volume Conventions End of volume labeling shall comply with SFDU standards (see Section 4, below), and with ANSI standards for multi-file and multi-volume magnetic tapes. ________________________________________________________________________ 3. ACCESS 3.1. Programs Using the Interface The ephemeris files contained in ARCDR product tapes conform to the external ASCII form of SPICE S&P Kernel (SPK) files, and may be read by any programs conforming to the NAIFLIB and SPICELIB specifications in Applicable Documents [4] and [10]. ARCDR altimetry files are generated by the MIT A&R programs MGMOUT and MGMDQE, and reformatted by program MGMGEN. Radiometry files are generated by MGMSAR are reformatted by MGMGEN. Investigators' programs that use ARCDR products cannot be identified here. 3.2. Synchronization Considerations 3.2.1. Timing and Sequencing Considerations Because of the coherent algorithm adopted for altimetry processing (similar to multi-look SAR), there is no one-to-one correspondence between altimetry records and Spacecraft Event Time (SCET). Data in the altimetry records are arranged by "footprint" number. The footprint corresponding to spacecraft nadir at periapsis is numbered zero. Footprint numbers prior to periapsis are negative. Footprint spacing is a function of altitude and doppler resolution, but increasing footprint numbers always indicate increasing SCET measurement times. The radiometry file contains one data record per pair of SAR bursts. Data in the radiometry records are placed in SCET order, using the SCLK time field in the SAB file telemetry secondary headers and in the sinusoidal imaging file headers. 3.2.2. Effective Duration Except in special circumstances, the ARCDR product tapes delivered to DMAT shall be the final versions. Subsequent corrections to S/C orbit parameters can be applied directly by the end-user without having to regenerate the ARCDR itself. The method is described in Appendix B. 3.2.3. Priority Interrupts None identified. 3.3. Input/Output Protocols, Calling Sequences None identified. ________________________________________________________________________ 4. DETAILED INTERFACE SPECIFICATIONS 4.1. Structure and Organization Overview The ARCDR shall consist of a single Volume Header File and a Single Volume Trailer File that bracket from one to sixty sets of four files. In the following table, the numbers on the left refer to the parts of Section 5, below, that describe the detailed format of these files. 5.2. Volume Header File Orbits n-m 5.3. Orbit Header Record File Orbit n 5.4. Spacecraft Ephemeris File Orbit n 5.5. Altimetry Data File Orbit n 5.6. Radiometry Data File Orbit n 5.3. Orbit Header Record File Orbit n+1 5.4. Spacecraft Ephemeris File Orbit n+1 5.5. Altimetry Data File Orbit n+1 5.6. Radiometry Data File Orbit n+1 and up to 58 additional orbits of data, n+2 through m 5.7. Volume Trailer File Orbits n-m If the ALT-EDR is not available for a particular orbit, the entire set of orbit files shall be omitted from the ARCDR tape. Its omission will be noted in the Catalog/Keyword label of the Volume Header File. 4.2. Substructure Definition and Format Section 5 of this document details the use of Standard Formatted Data Unit (SFDU) labels and headers and provides a description of the data files on the tape. The Volume Header and Trailer Files are detailed in Sections 5.2 and 5.7, respectively. 4.2.1. SFDU Labels and Headers SFDU labels are used to identify and characterize each file on the product tapes. Guidelines for the use of SFDU headers are found in Applicable Document [2]. To conform with the convention adopted by other Magellan data products, all length fields in SFDU labels will be recorded by 8-byte ASCII values. 4.2.2. Data Blocking ANSI standard data tapes contain header and trailer labels. These consist of a series of 80-byte physical records, ending in single tape marks. The format is described in Applicable Document [1]. The following discussion applies to the data portions of all ANSI files on the ARCDR tape, not to the ANSI labels. All physical records shall have a fixed length of 32,500 bytes. '^' characters (0x5d) shall fill only the remainder of the last physical record of each file. No null characters shall be required if the file contains an exact multiple of 32,500 data bytes. Logical records (see Section 5) are packed into physical records where necessary, without additional padding or length indication. If the data portion of any entire file can be contained in less than 32,500 bytes, it shall be written to tape as a single record of 32,500 bytes. Where necessary, logical records span physical records. Each logical record begins with a SFDU header label. Therefore, physical records, except the first, do not necessarily begin with SFDU headers. 4.2.3. Block Length The physical record length of each ANSI data file shall be 32,500 bytes. ________________________________________________________________________ 5. ARCDR DATA BLOCK FORMAT DESCRIPTIONS 5.1. ANSI and SFDU Label Structures The physical tape volume (which may consist of more than one physical tape reel), starts with an ANSI standard 'VOL' label, and ends with a 'EOF' label. In addition, all reels prior to the last end with a 'EOV1' label. All data files start with 'HDR1' and 'HDR2' labels, and end with 'EOF1' and 'EOF2' labels. Depending on details of the computer system that reads the tapes, these labels may be sensed as additional physical files, or may be completely hidden from the user. Refer to Applicable Document [1] for details. The ANSI labels contain ASCII character-string fields reserved for user-specific information. The following three sections define those fields that contain special ARCDR values. The remainder are defined in Applicable Document [1]. Each data file contains a series of Standard Formatted Data Units (SFDU's). Each SFDU begins with a 12-byte type header, followed by an 8-byte length indicator, and a varying-length value field. For the details and philosophy of SFDU's, consult Applicable Document [2]. The ARCDR uses several SFDU types: * Primary Label A string beginning 'CCSD1Z', identifying the data as obeying the conventions of the CCSDS authority. * Catalog/Keyword Label A string beginning 'NJPL1K' that further identifies each data file by a series of 'KEYWORD=VALUE' definitions. * Data Aggregate A string beginning 'NJPL1I' that begins a fixed-length block of data. * Aggregation Marker A pair of strings beginning 'CCSD1R' that sandwiches collections of data whose length is otherwise undefined. 5.1.1. ANSI Volume Header and Trailer +------------------------------------------------------------------+ | Table 5-1. ARCDR-specific ANSI 'VOL1' and 'EOV1' Label Fields | +--------+--------+------+-------------+---------------------------+ | Offset | Length | Type | Name | Description | +--------+--------+------+-------------+---------------------------+ | +5 | 6 | char | volume_id | Tape volume serial number | | +38 | 17 | char | owner_id | Name of volume "owner" | +--------+--------+------+-------------+---------------------------+ * volume_id The volume serial number, a unique 6-character string, 'ARnnnn' where 'nnnn' is a decimal number that shall be '0001' for the first ARCDR product tape, and shall be incremented by 1 for each subsequent ARCDR product tape. For test ARCDR tapes the volume serial number shall be 'ARTnnn' where 'nnn' is a decimal number that shall be '001' for the first ARCDR test tape, and shall be incremented by 1 for each subsequent ARCDR test tape. * owner_id Set permanently to 'MIT_MGN_A_AND_R' (with 2 trailing blanks). 5.1.2. ANSI File Header/Trailer HDR1/EOF1 Field Identifier Codes +------------------------------------------------------------------+ | Table 5-2. ARCDR-specific ANSI 'HDR1' and 'EOF1' Label Fields | +--------+--------+------+-------------+---------------------------+ | Offset | Length | Type | Name | Description | +--------+--------+------+-------------+---------------------------+ | +5 | 17 | char | file_id | Tape file identifier code | +--------+--------+------+-------------+---------------------------+ * file_id The ANSI file name, a 17-character string, padded on the right with blanks, with the values for each data file as shown in the third column of Table 5-4. 'nn' is '01' for the four files that represent the first orbit on the tape, '02' for the second, through '60' for the last. 5.1.3. ANSI Header/Trailer HDR2/EOF2 Fields +------------------------------------------------------------------+ | Table 5-3. ARCDR-specific ANSI 'HDR2' and 'EOF2' Label Fields | +--------+--------+------+-------------+---------------------------+ | Offset | Length | Type | Name | Description | +--------+--------+------+-------------+---------------------------+ | +5 | 1 | char | file_format | Tape file format code | +--------+--------+------+-------------+---------------------------+ * file_format The ANSI file format code, always 'F' to indicate that all ARCDR data files are of fixed length. +------------------------------------------------------------------------+ | Table 5-4. MIT A&R Data File Nomenclature | +-----------------+--------+-------------------+-------------------------+ | ARCDR Product | MIT | Name in ANSI | Data_Object or Product | | File Name | abbrev | Header/Trailer | Type SFDU Keyword Value | +-----------------+--------+-------------------+-------------------------+ | Volume Header | VHF | 'VOLUME-HEADER' | 'ARCDR' | | Orbit Header | OHF | 'ORBIT-HEADER-nn' | 'ORBIT_HEADER_RECORD' | | Ephemeris | EPF | 'EPHEMERIS-nn' | 'EPHEMERIS,ACTUAL' | | Altimetry Data | ADF | 'ALTIMETRY-nn' | 'ALTIMETRY_FILE' | | Radiometry Data | RDF | 'RADIOMETRY-nn' | 'RADIOMETRY_FILE' | | Volume Trailer | VTF | 'VOLUME-TRAILER' | | +-----------------+--------+-------------------+-------------------------+ 5.1.4. Catalog Keyword Labels The SFDU catalog keyword label is made up of a set of fields that completely identify each file according to its type, content, origin, and version. In addition, the label contains time tags identifying the time and date on which the data were created. The value of the catalog keyword label is an ASCII string comprising several keyword/value pairs. Alphanumeric characters are always in UPPERCASE. Underscore characters (0x5f) are used between words--no "white spaces" such as null (0x0), space (0x20), or tab (0x9) are permitted. All numeric fields are of fixed length, and unused leading digit positions must be filled with ASCII zero ('0') characters. The "keyword=value" syntax used in ARCDR keyword labels is a subset of the "Object Definition Language" (ODL) used by the Planetary Data System Project. It is discussed in more detail in Applicable Document [13]. Each keyword/value pair is separated by an equals sign, and terminated by a carriage return (0xd) followed by a line feed (0xa), which are not shown in the following figures. Figure 5-1 identifies some of the parameters that will appear in ARCDR keyword fields. +----------------------------------------------------------+ | Figure 5-1. Sample MIT Catalog/Keyword Label | +---+----------------------------------------+-------------+ | T | NJPL1K00KL00 | Type label | +---+----------------------------------------+-------------+ | L | 00000xxx | length | +---+----------------------------------------+-------------+ | . | DATA_SET_NAME=cccccccccc | | | . | DATA_OBJECT_TYPE=cccccccccc | | | . | PRODUCT_NAME=cccccccc | | | V | PRODUCT_TYPE=cccccccc | | | A | HARDWARE_VERSION_ID=nn | Keywords | | L | SOFTWARE_VERSION_ID=nn | and | | U | MISSION_ID=4 | Values | | E | MISSION_NAME=MAGELLAN | | | . | SPACECRAFT_ID=18 | | | . | SPACECRAFT_NAME=MAGELLAN | | | . | PROCESS_TIME=yyyy-mm-ddThh:mm:ss.fff | | | . | ORBIT_NUMBER=nnnnn | | +---+----------------------------------------+-------------+ * Type Label 'NJPL1K00KL00', the SFDU Catalog/Keyword label, where '1' indicates that an ASCII length field follows. The 'KL00' sub-field indicates that the keywords follow ODL syntax. * Length field Eight bytes, ASCII, with leading zeroes mandatory; the length of the value field, including two bytes per keyword/value pair for the (unillustrated) carriage return and line feed, and a possible trailing blank if required to make this length an even number. * DATA_SET_NAME= The external volume identifier of the tape product. See section 2.3.2. for details. This keyword only appears in the Volume Header File. * PRODUCT_FILE_NAME= The unique file name that identifies a data file. This keyword does not appear in the Volume Header or Trailer files. * DATA_OBJECT_TYPE= Always 'ARCDR'. The intention is that the value of the keyword 'DATA_SET_NAME=' should be unique within all instances of the 'DATA_OBJECT_TYPE='. This keyword only appears in the Volume Header File. * PRODUCT_TYPE= The type of the data file, which takes on one of the values listed in the fourth column of Table 5-4. This keyword does not appear in the Volume Header or Trailer files. * HARDWARE_VERSION_ID= A 2-digit number, 'nn', identifying the hardware version number of the MIT A&R data processing system used to create this file or volume. * SOFTWARE_VERSION_ID= A 2-digit number, 'nn', identifying the software version number of the MIT A&R data processing system used to create this file or volume. * MISSION_ID= The single character '4'. * MISSION_NAME= The character string 'MAGELLAN'. * SPACECRAFT_ID= For real data, the 2-digit number '18'. For simulated data, the number '28'. * SPACECRAFT_NAME= The character string 'MAGELLAN'. * PROCESS_TIME= Indicates the time at which the product is created or substantially modified. 'yyyy-mm-ddThh:mm:ss.fff' is an ASCII string, where 'P', '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. * ORBIT_NUMBER= A five-digit integer with leading zeroes, identifying the orbit during which this data set was generated. Multiple orbit numbers are used only in the Volume Header File label, where they are separated by commas and enclosed in parentheses, i.e. '(nnnnn,nnnnn,...)'. 5.1.5. Generic File Structure When the length of a file is variable, e.g. the ephemeris, altimetry, and radiometry files, the collection of data SFDU's is bounded by a pair of SFDU "R" labels that identify the start and end of that collection. These labels start with the string 'CCSD1R000003', as shown in Figure 5-2. The keywords 'DELIMITER' and 'PRODUCT_NAME' have the values shown in the following figures. When the bounded data contain more than a single registered SFDU aggregate, the additional RRS label keyword 'TYPE' must be used to describe the data format. If "R" labels bound varying length data, the length recorded in the primary 'CCSD1Z' label is the length of the catalog/keyword SFDU plus the length of the first "R" label SFDU. Otherwise, the length recorded in the primary label is that of the remainder of the file, i.e. 20 less than the total number of bytes in the file. +---------------------------------------------------------------+ | Figure 5-2. Sample Varying-Length File Structure | +---+--------------------------------------------+--------------+ | T | CCSD1Z000001 | CCSD label | +---+--------------------------------------------+--------------+ | L | 00000xxx | length | +---+---+----------------------------------------+--------------+ | . | T | NJPL1K00KL00 | Keywd label | +---+---+----------------------------------------+--------------+ | . | L | 00000xxx | length | +---+---+----------------------------------------+--------------+ | . | V | | | | . | A | Keywords | | | . | L | Catalog and Keyword Information | | | . | U | and Values | | | . | E | | | +---+---+----------------------------------------+--------------+ | . | T | CCSD1R000003 | Start marker | +---+---+----------------------------------------+--------------+ | . | L | 000000xx | length | +---+---+----------------------------------------+--------------+ | . | V | DELIMITER=SMARKER | | | . | . | PRODUCT_NAME=cccccccc | Start value | | . | . | TYPE=NJPL1I000nnn | | +---+---+----------------------------------------+--------------+ | Data Record SFDU's | +---+--------------------------------------------+--------------+ | T | CCSD1R000003 | End marker | +---+--------------------------------------------+--------------+ | L | 000000xx | length | +---+--------------------------------------------+--------------+ | V | DELIMITER=EMARKER | End value | | . | PRODUCT_NAME=cccccccc | | +---+--------------------------------------------+--------------+ 5.2. Volume Header File Each ARCDR product tape begins with a Volume Header File (VHF)--a set of SFDU volume descriptors and catalog keywords. It only appears on the first reel of a multi-reel product volume. It identifies the number and sequence of orbits on this multi-orbit product. +---------------------------------------------------------------+ | Figure 5-3. MIT Volume Header File (VHF) Format | +---+--------------------------------------------+--------------+ | T | CCSD1Z000001 | CCSD label | +---+--------------------------------------------+--------------+ | L | 00000xxx | length | +---+---+----------------------------------------+--------------+ | . | T | NJPL1K00KL00 | Keywd label | +---+---+----------------------------------------+--------------+ | . | L | 00000xxx | length | +---+---+----------------------------------------+--------------+ | . | . | DATA_SET_NAME=ARCDR.nnnnn-nnnnn.v | | | . | . | DATA_OBJECT_TYPE=ARCDR | | | . | . | PRODUCT_SEQUENCE_NUMBER=nnnnn | | | . | V | MISSION_ID=4 | | | . | A | MISSION_NAME=MAGELLAN | Keywords | | . | L | SPACECRAFT_ID=18 | and | | . | U | SPACECRAFT_NAME=MAGELLAN | Values | | . | E | PROCESS_TIME=yyyy-mm-ddThh:mm:ss.fff | | | . | . | ORBIT_NUMBER=(nnnnn[,nnnnn,...]) | | | . | . | HARDWARE_VERSION_ID=nn | | | . | . | SOFTWARE_VERSION_ID=nn | | | . | . | DATA_FORMAT_TYPE=VAX | | +---+---+----------------------------------------+--------------+ | . | T | CCSD1R000003 | Start marker | +---+---+----------------------------------------+--------------+ | . | L | 000000xx | length | +---+---+----------------------------------------+--------------+ | . | V | DELIMITER=SMARKER | Start value | | . | . | PRODUCT_NAME=ARCDR | | +---+---+----------------------------------------+--------------+ * CCSDS Label 'CCSD1Z000001', the CCSDS primary SFDU label. * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the remainder of the Volume Header File. * Keyword Label 'NJPL1K00KL00', the SFDU Catalog/Keyword label, where '1' indicates that an ASCII length field follows. * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the keyword/value field, including two bytes per keyword/value pair for the (unillustrated) carriage return and line feed, and a possible trailing blank if required to make this length an even number. * DATA_SET_NAME= 'ARCDR.nnnnn-nnnnn.v', the external volume identifier of the tape product that contains this file. See Section 2.3.2. for details. * DATA_OBJECT_TYPE= The character string 'ARCDR'. * PRODUCT_SEQUENCE_NUMBER= A 5-character numeric string, with leading zeroes, that is incremented by 1 for each ARCDR product. The first will be numbered '00001'. ARCDR products with identical sequence numbers can be assumed to be identical. * MISSION_ID= The single character '4'. * MISSION_NAME= The character string 'MAGELLAN'. * SPACECRAFT_ID= For real data, the 2-digit number '18'. For simulated data, the number '28'. * SPACECRAFT_NAME= The character string 'MAGELLAN'. * PROCESS_TIME= The local EST or EDT time at which the product tape was written by the MIT A&R processing system. * ORBIT_NUMBER= A list of 5-digit numbers, separated by commas, enclosed in parentheses, denoting the order of Magellan orbit numbers of the data files contained in this product. Orbits begin at apoapsis. The numbers are copied from the header files of the corresponding ALT-EDR input tapes. * HARDWARE_VERSION_ID= A 2-digit number, 'nn', identifying the hardware version number of the MIT A&R data processing system used to create this file or volume. * SOFTWARE_VERSION_ID= A 2-digit number, 'nn', identifying the software version number of the MIT A&R data processing system used to create this file or volume. * DATA_FORMAT_TYPE= Either 'VAX' or 'IEEE', depending on the format in which binary fields are represented in the data records. For all ARCDR products sent to DMAT, this will be 'VAX'. * Start Marker 'CCSD1R000003', the SFDU Aggregate Marker label, indicating the start of a data aggregate of unspecified length. This aggregate consists of the remainder of the product, and is matched by an ending marker in the Volume Trailer File. * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the remainder of the aggregate marker SFDU. * DELIMITER= The character string 'SMARKER', indicating that this is the start of a data aggregate. * PRODUCT_NAME= The character string 'ARCDR'. 5.3. Orbit Header Record File Each Orbit Header Record File (OHF) identifies the orbit number, time frame, and orbital geometry for one Magellan orbit. The OHF data block is depicted in Table 5-5 and has a fixed length of 112 bytes. The file format is illustrated in Figure 5-4. +---------------------------------------------------------------+ | Figure 5-4. MIT Orbit Header Record File (OHF) - Block Format | +---+--------------------------------------------+--------------+ | T | CCSD1Z000001 | CCSD label | +---+--------------------------------------------+--------------+ | L | 00000xxx | length | +---+---+----------------------------------------+--------------+ | . | T | NJPL1K00KL00 | Keywd label | +---+---+----------------------------------------+--------------+ | . | L | 00000xxx | length | +---+---+----------------------------------------+--------------+ | . | . | PRODUCT_FILE_NAME=OHFnnnnn.v | | | . | . | PRODUCT_TYPE=ORBIT_HEADER_RECORD | | | . | . | MISSION_ID=4 | | | . | V | MISSION_NAME=MAGELLAN | | | . | A | SPACECRAFT_ID=18 | Keywords | | . | L | SPACECRAFT_NAME=MAGELLAN | and | | . | U | PROCESS_TIME=yyyy-mm-ddThh:mm:ss.fff | Values | | . | E | ORBIT_NUMBER=nnnnn | | | . | . | HARDWARE_VERSION_ID=nn | | | . | . | SOFTWARE_VERSION_ID=nn | | | . | . | DATA_FORMAT_TYPE=ccc | | | . | . | UPLOAD_ID=cccccc | | +---+---+----------------------------------------+--------------+ | . | | Orbit | | . | Orbit Header Record SFDU (see Table 5.5) | Header | | . | | Record | +---+--------------------------------------------+--------------+ * CCSDS Label 'CCSD1Z000001', the CCSDS primary SFDU label. * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the remainder of the Orbit Header File. * Keyword Label 'NJPL1K00KL00', the SFDU Catalog/Keyword label, where '1' indicates that an ASCII length field follows. * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the keyword/value field, including two bytes per keyword/value pair for the (unillustrated) carriage return and line feed, and a possible trailing blank if required to make this length an even number. * PRODUCT_FILE_NAME= 'OHFnnnnn.v', the external file name of this OHF. 'nnnn' is a 5-digit orbit number and 'v' a decimal version number. For test OHF files, 'v' consists of the letter 'T' followed by a decimal version number. * PRODUCT_TYPE= The character string 'ORBIT_HEADER_RECORD'. * MISSION_ID= The single character '4'. * MISSION_NAME= The character string 'MAGELLAN'. * SPACECRAFT_ID= For real data, the 2-digit number '18'. For simulated data, the number '28'. * SPACECRAFT_NAME= The character string 'MAGELLAN'. * PROCESS_TIME= The local EST or EDT time at which the Orbit Header Record File was created by the MIT A&R processing system. * ORBIT_NUMBER= A 5-digit number, denoting the Magellan orbit number of this and the following three data files. * HARDWARE_VERSION_ID= A 2-digit number, 'nn', identifying the hardware version number of the MIT A&R data processing system used to create this file or volume. * SOFTWARE_VERSION_ID= A 2-digit number, 'nn', identifying the software version number of the MIT A&R data processing system used to create this file or volume. * DATA_FORMAT_TYPE= Either 'VAX' or 'IEEE', depending on the format in which binary fields are represented in the orbit header record. For all ARCDR products sent to DMAT, this will be 'VAX'. * UPLOAD_ID= 6 characters 'ABBBBC', where 'A' is the mission phase, 'BBBB' is the upload number within each phase, and 'C' is a revision indicator in the range A-Z. * Orbit Header Record See Table 5-5 and the definition following it. +---------------------------------------------------------------------------+ | Table 5-5. MIT Orbit Header Record SFDU (oh_rec) | +-----+-----+--------+--------------+---------------------------------------+ | Off | Len | Type | Name | Description | +-----+-----+--------+--------------+---------------------------------------+ | +0 | 20 | sfdu | oh_sfdu | SFDU label and length | | 20 | 4 | ulong | oh_norbit | Orbit number | | 24 | 4 | ulong | oh_nalt | Number of Altimetry Data Records | | 28 | 4 | ulong | oh_nrad | Number of Radiometry Data Records | | 32 | 8 | double | oh_alt_start | First Alt Footprint Time (SCET, TDB) | | 40 | 8 | double | oh_alt_end | Last Alt Footprint Time (SCET, TDB) | | 48 | 8 | double | oh_rad_start | First Rad Footprint Time (SCET, TDB) | | 56 | 8 | double | oh_rad_end | Last Rad Footprint Time (SCET, TDB) | | 64 | 8 | double | oh_avg.scet | Predicted Periapsis Time (SCET, TDB) | | 72 | 8 | double | oh_avg.sma | Predicted Semi-Major Axis (km) | | 80 | 8 | double | oh_avg.ecc | Predicted Eccentricity | | 88 | 8 | double | oh_avg.incl | Predicted Inclination (deg) | | 96 | 8 | double | oh_avg.long | Predicted Lon of Ascending Node (deg) | | 104 | 8 | double | oh_avg.arg | Predicted Argument of Periapsis (deg) | | 112 +-----+--------+--------------+---------------------------------------+ +-----+ Element Name Type Length Description * oh_sfdu sfdu 20 SFDU Label and Length: 'NJPL1I00017800000092'. The number '0178' is registered with the NJPL SFDU authority as the "MIT Orbit Header Record Aggregate". * oh_norbit ulong 4 The Magellan Orbit Number corresponding to the following three files (ephemeris, altimetry, and radiometry). An orbit begins at apoapsis, and the number is copied from the orbit header file of the input ALT-EDR tape. * oh_nalt ulong 4 Number of Altimetry Data Records--the number of ar_rec SFDU's in this orbit's altimetry data file. * oh_nrad ulong 4 Number of Radiometry Data Records--the number of rr_rec SFDU's in this orbit's radiometry data file. * oh_alt_start double 8 First Altimetry Footprint Time (SCET)--the S/C ephemeris time (seconds of TDB since J2000; see 1.5.4.2) that represents the first altimeter footprint of this orbit. It is equal to the ar_scet value in the first ar_rec record of this orbit's altimetry data file. * oh_alt_end double 8 Last Altimetry Footprint Time (SCET)--the S/C ephemeris time (seconds of TDB since J2000; see 1.5.4.2) that represents the last altimeter footprint of this orbit. It is equal to the ar_scet value in the last ar_rec record of this orbit's altimetry data file. * oh_rad_start double 8 First Radiometer Footprint Time (SCET)--the S/C ephemeris time (seconds of TDB since J2000; see 1.5.4.2) of the first radiometer measurement of this orbit. It is equal to the rr_scet value in the first rr_rec record of this orbit's radiometry data file. * oh_rad_end double 8 Last Radiometer Footprint Time (SCET)--the S/C ephemeris time (seconds of TDB since J2000; see 1.5.4.2) of the last radiometer measurement of this orbit. It is equal to the rr_scet value in the last rr_rec record of this orbit's radiometry data file. * oh_avg.scet double 8 Periapsis Time (SCET)--the periapsis time (seconds of TDB since J2000; see 1.5.4.2) of the predicted orbit. * oh_avg.sma double 8 Semi-Major Axis (km)--the semi-major axis of the predicted orbit. * oh_avg.ecc double 8 Eccentricity--the eccentricity of the predicted orbit. * oh_avg.incl double 8 Inclination (deg)--the inclination of the predicted orbit with respect to the xy-plane of the J2000 coordinate system. * oh_avg.long double 8 Longitude of Ascending Node (deg)--the angle in the xy-plane of the J2000 coordinate system to the ascending node of the predicted orbit. * oh_avg.arg double 8 Argument of Periapsis (deg)--the angle in the plane of the predicted orbit from the ascending node in the xy-plane of the J2000 coordinate system to the periapsis. 5.4. Ephemeris File The information recorded in the ephemeris files is in the NAIF S&P Kernel format (SPK), and is therefore not immediately interpretable. It is designed to be accessed by Fortran subroutines distributed by NAIF in its NESYS/SPICELIB system (see Applicable Documents [10] and [12]). This access is a two-step process. 5.4.1. Convert the EDF to Binary The SPICELIB routines expect their input data to be in the form of a binary direct-access file, so the ASCII Ephemeris Data File (as described in figure 5-5) must be reformatted. This is performed by first stripping off the SFDU header and trailer labels, and then invoking SEFU--an interactive program distributed by NAIF that prompts the user to specify the names of the input (ASCII) and output (binary) ephemeris files. 5.4.2. Call the SPICELIB Subroutines As an example, a Fortran 77 program that wishes to know the Magellan spacecraft position and velocity vectors, relative to the center of Venus, at time ScET, might be linked with the SPICELIB library and contain the following code: Parameter (Venus = -18) Parameter (Magellan = 2) Integer*4 Handle Double Precision State(6), Starg(6), ScET Call ClPool () Call LdPool ('LEAPSECONDS') Call LdPool ('CONSTANTS') Call Spklef ('/tmp/spk', Handle) Call Spkssb (Venus, ScET, 'J2000', State) Call Spkapp (Magellan, ScET, 'J2000', State, 'LT+S', Starg, Lt) The required vector will be returned in the Starg array. ScET is expressed in seconds of ephemeris time (TDB) since J2000, and will therefore be a large negative number. The SPICELIB subroutine UTC2ET will convert a UTC date expressed as an ASCII character string into TDB. UTC2ET routine is capable of interpreting a wide variety of UTC character string formats. Character*30 Utc Double Precision ScET Utc = '1991 JUN 21 18:21:33.914' Call Utc2Et (Utc, ScET) +-------------------------------------------------------------------+ | Figure 5-5. NAIF Ephemeris File (EPF) - Block Format | +---+------------------------------------------------+--------------+ | T | CCSD1Z000001 | CCSD label | +---+------------------------------------------------+--------------+ | L | 00000xxx | length | +---+---+--------------------------------------------+--------------+ | . | T | NJPL1K00KL00 | Keywd label | +---+---+--------------------------------------------+--------------+ | . | L | 00000xxx | length | +---+---+--------------------------------------------+--------------+ | . | . | DATA_OBJECT_TYPE=EPHEMERIS | | | . | . | PRODUCT_VERSION_TYPE=ACTUAL | | | . | . | DATA_SET_NAME=MGNnnnnn.TSP | | | . | . | MISSION_ID=4 | | | . | . | MISSION_NAME=MAGELLAN | | | . | . | SPACECRAFT_NAME=MAGELLAN | | | . | . | SPACECRAFT_ID=18 | | | . | . | PROCESS_TIME=yyyy-mm-ddThh:mm:ss.fff | | | . | . | VERSION_ID=nn | | | . | . | UPLOAD_ID=cnnnnc | | | . | . | ORBIT_NUMBER=nnnnn | | | . | . | OBJECT=ORBIT_TIME_RANGE_GROUP | | | . | . | TIME_RANGE_NUMBER=1 | | | . | . | ORBIT_START_TIME=yyyy-mm-ddThh:mm:ss.fff | | | . | . | ORBIT_STOP_TIME=yyyy-mm-ddThh:mm:ss.fff | | | . | . | END_OBJECT=ORBIT_TIME_RANGE_GROUP | | | . | . | OBJECT=MAPPING_TIME_RANGE_GROUP | | | . | . | TIME_RANGE_NUMBER=1 | | | . | . | MAPPING_START_TIME=yyyy-mm-ddThh:mm:ss.fff | | | . | . | MAPPING_STOP_TIME=yyyy-mm-ddThh:mm:ss.fff | | | . | . | END_OBJECT=MAPPING_TIME_RANGE_GROUP | | | . | . | EFFECTIVE_TIME=yyyy-mm-ddThh:mm:ss.fff | | | . | . | NAV_UNIQUE_ID="cccccccc " | | +---+---+--------------------------------------------+--------------+ | . | T | NJPL1S00KL00 | SFDU label | +---+---+--------------------------------------------+--------------+ | . | L | 00000000 | length | +---+---+--------------------------------------------+--------------+ | . | T | CCSD1S000002 | SFDU label | +---+---+--------------------------------------------+--------------+ | . | L | 00000xxx | length | +---+---+--------------------------------------------+--------------+ | . | V | | | | . | A | Comments (usually omitted | ASCII text | | . | L | | | +---+---+--------------------------------------------+--------------+ | . | T | CCSD1R000003 | Start marker | +---+---+--------------------------------------------+--------------+ | . | L | 000000xx | length | +---+---+--------------------------------------------+--------------+ | . | V | DELIMITER=SMARKER | | | . | A | PRODUCT_NAME=NAIF_SPK_FILE | Start value | | . | L | TYPE=NJPL1I000152 | | | . | . | PROTOCOL=NONE | | +---+---+--------------------------------------------+--------------+ | | | | SPK Ephemeris Data Records | variable | | | | +---+------------------------------------------------+--------------+ | T | CCSD1R000003 | End marker | +---+------------------------------------------------+--------------+ | L | 000000xx | length | +---+------------------------------------------------+--------------+ | V | DELIMITER=EMARKER | End value | | . | PRODUCT_NAME=NAIF_SPK_FILE | | +---+------------------------------------------------+--------------+ 5.5. Altimetry Data File +-------------------------------------------------------------------+ | Figure 5-6. MIT Altimetry Data File (ADF) - Block Format | +---+------------------------------------------------+--------------+ | T | CCSD1Z000001 | CCSD label | +---+------------------------------------------------+--------------+ | L | 00000xxx | length | +---+---+--------------------------------------------+--------------+ | . | T | NJPL1K00KL00 | Keywd label | +---+---+--------------------------------------------+--------------+ | . | L | 00000xxx | length | +---+---+--------------------------------------------+--------------+ | . | . | PRODUCT_FILE_NAME=ADFnnnnn.v | | | . | . | PRODUCT_TYPE=ALTIMETRY_FILE | | | . | . | MISSION_ID=4 | | | . | . | SPACECRAFT_NAME=MAGELLAN | | | . | . | SPACECRAFT_ID=18 | | | . | V | MISSION_NAME=MAGELLAN | Keywords | | . | A | PROCESS_TIME=yyyy-mm-ddThh:mm:ss.fff | and | | . | L | ORBIT_NUMBER=nnnnn | Values | | . | U | HARDWARE_VERSION_ID=nn | | | . | E | SOFTWARE_VERSION_ID=nn | | | . | . | TEMPLATE_VERSION_NUMBER=nn | | | . | . | DATA_FORMAT_TYPE=ccc | | | . | . | UPLOAD_ID=cccccc | | | . | . | NAV_UNIQUE_ID="cccccccccc " | | +---+---+--------------------------------------------+--------------+ | . | T | CCSD1R000003 | Start marker | +---+---+--------------------------------------------+--------------+ | . | L | 000000xx | length | +---+---+--------------------------------------------+--------------+ | . | V | DELIMITER=SMARKER | Start value | | . | A | PRODUCT_NAME=ALTIMETRY_DATA_RECORD | | | . | L | TYPE=NJPL1I000177 | | +---+---+--------------------------------------------+--------------+ | | | | Altimetry Data Record SFDUs (see Table 5-6) | Variable | | | | +---+------------------------------------------------+--------------+ | T | CCSD1R000003 | End marker | +---+------------------------------------------------+--------------+ | L | 000000xx | length | +---+------------------------------------------------+--------------+ | V | DELIMITER=EMARKER | End value | | . | PRODUCT_NAME=ALTIMETRY_DATA_RECORD | | +---+------------------------------------------------+--------------+ * CCSDS Label 'CCSD1Z000001', the CCSDS primary SFDU label. * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the remainder of the Altimetry Data File header. * Keyword Label 'NJPL1K00KL00', the SFDU Catalog/Keyword label, where '1' indicates that an ASCII length field follows. * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the keyword/value field, including two bytes per keyword/value pair for the (unillustrated) carriage return and line feed, and a possible trailing blank if required to make this length an even number. * PRODUCT_FILE_NAME= 'ADFnnnnn.v', the external file name of this ADF. 'nnnnn' is a 5-digit orbit number and 'v' a decimal version number. For test ADF files, 'v' consists of the letter 'T' followed by a decimal version number. * PRODUCT_TYPE= The character string 'ALTIMETRY_FILE'. * MISSION_ID= The single character '4'. * MISSION_NAME= The character string 'MAGELLAN'. * SPACECRAFT_ID= For real data, the 2-digit number '18'. For simulated data, the number '28'. * SPACECRAFT_NAME= The character string 'MAGELLAN'. * PROCESS_TIME= The local EST or EDT time at which the Altimetry Data File was created by the MIT A&R processing system. * ORBIT_NUMBER= A 5-digit number, denoting the Magellan orbit number of this Altimetry Data File. * HARDWARE_VERSION_ID= A 2-digit number, 'nn', identifying the hardware version number of the MIT A&R data processing system used to create this file or volume. * SOFTWARE_VERSION_ID= A 2-digit number, 'nn', identifying the software version number of the MIT A&R data processing system used to create this file or volume. * TEMPLATE_VERSION_NUMBER= A 2-digit number, 'nn', denoting the version number of the altimetry echo templates used to fit the altimetry profiles and generate this file. * DATA_FORMAT_TYPE= Either 'VAX' or 'IEEE', depending on the format in which binary fields are represented in the altimetry data records. For all ARCDR products sent to DMAT, this will be 'VAX'. * UPLOAD_ID= 6 characters 'ABBBBC', where 'A' is the mission phase, 'BBBB' is the upload number within each phase, and 'C' is a revision indicator in the range A-Z. * NAV_UNIQUE_ID= See Applicable Document [4]. * Start Marker 'CCSD1R000003', the SFDU Aggregate Marker label, indicating the start of a data aggregate of unspecified length. This aggregate consists of a varying number of Altimetry Data Record SFDU's (ar_rec), as shown in Table 5-6. * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the remainder of the aggregate marker SFDU. * DELIMITER= The character string 'SMARKER', indicating that this is the start of a data aggregate. * PRODUCT_NAME= The character string 'ALTIMETRY_DATA_RECORD'. * TYPE= The character string 'NJPL1I000177', where '0177' indicates that the data between the SMARKER and EMARKER labels comprise a registered SFDU aggregate, composed of a set of registered NJPL aggregates. * Altimetry Data Record See Table 5-6. * End Marker 'CCSD1R000003', the SFDU Aggregate Marker label, indicating the end of a data aggregate of unspecified length. This matches the above "Start Marker". * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the remainder of the aggregate marker SFDU. * DELIMITER= The character string 'EMARKER', indicating that this is the end of a data aggregate. * PRODUCT_NAME= The character string 'ALTIMETRY_DATA_RECORD'. +---------------------------------------------------------------------------- | Table 5-6. MIT Altimetry Data Record SFDU (ar_rec) +-----+-----+--------+----------------+-------------------------------------- | Off | Len | Type | Name | Description +-----+-----+--------+----------------+-------------------------------------- | +0 | 20 | sfdu | ar_sfdu | SFDU header label and length | 20 | 4 | long | ar_nfoot | Footprint number | 24 | 4 | ulong | ar_flag | Flag fields (see Table 5-7) | 28 | 4 | ulong | ar_flag2 | Additional flag fields (unused) | 32 | 8 | double | ar_scet | Altimetry Footprint Time (SCET, TDB) | 40 | 24 | double | ar_pos[3] | S/C Position Vector (km, J2000) | 64 | 24 | double | ar_vel[3] | S/C Velocity Vector (km/sec, J2000) | 88 | 4 | float | ar_lon | Footprint Longitude (deg, VBF85) | 92 | 4 | float | ar_lat | Footprint Latitude (deg, VBF85) | 96 | 4 | float | ar_xfoot | Along-track Alt Footprint Size (km) | 100 | 4 | float | ar_yfoot | Cross-track Alt Footprint Size (km) | 104 | 4 | float | ar_rcal | Receiver Noise Calibration (km^2) | 108 | 4 | float | ar_range | Uncorrected range to nadir (km) | 112 | 4 | float | ar_atmos | Atmospheric correction to range (km) | 116 | 4 | float | ar_radius | Derived Planetary Radius (km) | 120 | 4 | float | ar_slope | Derived RMS Surface Slope (deg) | 124 | 4 | float | ar_rho | Derived Fresnel Reflectivity | 128 | 4 | float | ar_rhocor | ar_rho corrected for Diffuse Scat. | 132 | 12 | float | ar_error[3] | Formal errors in Radius, Slope, Rho | 144 | 24 | float | ar_correl[6] | Formal parameter correlations | 168 | 4 | float | ar_drad | Ephemeris Radius Correction (km) | 172 | 4 | float | ar_dlon | Ephemeris Lon Correction (deg, VBF85) | 176 | 4 | float | ar_dlat | Ephemeris Lat Correction (deg, VBF85) | 180 | 72 | float | ar_partl[3][6] | Partials of rlon, lat and radius | 252 | 4 | float | ar_fit | Non-range-sharpened goodness of fit | 256 | 4 | float | ar_scale | Scaling factors for ar_tmpl & ar_prof | 260 | 4 | ulong | ar_looks | Number of non-range-sharpened looks | 264 | 4 | ulong | ar_nprof0 | ar_prof index matching ar_tmpl[0] | 268 | 302 | uchar | ar_prof[302] | Non-range-sharpened Echo Profile | 570 | 50 | uchar | ar_tmpl[50] | Best non-range-sharp Model Template | 620 | 4 | float | ar_rsfit | Range-sharpened goodness of fit | 624 | 4 | float | ar_rsscale | ar_rstmpl & ar_rsprof scaling factors | 628 | 4 | ulong | ar_rslooks | Number of range-sharpened looks | 632 | 4 | ulong | ar_rsnprof0 | ar_rsprof index matching ar_rstmpl[0] | 636 | 302 | uchar | ar_rsprof[302] | Range-sharpened Echo Profile | 938 | 50 | uchar | ar_rstmpl[50] | Best range-sharpened Model Template | 988 | 4 | float | ar_rhofact | Multi-peak correction to ar_rho | 992 | 4 | float | ar_radius2 | Radius from Threshold Detector (km) | 996 | 4 | float | ar_sqi | Signal Quality Indicator (dB) |1000 | 4 | ulong | ar_thresh | Threshold Detector Index |1004 | 28 | long | ar_spare[7] | Unused |1032 +-----+--------+----------------+-------------------------------------- +-----+ Element Name Type Size Description * ar_sfdu sfdu 20 SFDU Label and Length: 'NJPL1I00017900001012'. The number '0179' is registered with the NJPL SFDU authority as the "MIT Altimetry Data Record Aggregate". * ar_nfoot long 4 The Footprint Number--a signed integer value. The A&R processing program assigns footprint 0 to that observed at nadir at periapsis. The remaining footprints are located along the S/C nadir track, with a separation that depends on the doppler resolution of the altimeter at the epoch at which that footprint is observed. Pre-periapsis footprints will be assigned negative numbers, post-periapsis footprints will be assigned positive ones. A loss of several consecutive burst records from the ALT-EDR will result in missing footprint numbers. * ar_flag ulong 4 Flag fields--see Table 5P7. * ar_flag2 ulong 4 Unused flag fields. * ar_scet double 8 Altimetry Footprint Time (SCET)--the ephemeris time (seconds of TDB since J2000; see 1.5.4.2) at which the S/C passed directly over the center of the footprint. As each footprint is composed of data collected from several altimeter bursts, this epoch doesn't necessarily coincide with a particular burst. * ar_pos double 3*8 S/C Position Vector (km, J2000)--the S/C position at ar_scet, relative to the Venus center of mass, expressed in inertial coordinates. * ar_vel double 3*8 S/C Velocity Vector (km sec^1, J2000)--the S/C velocity at ar_scet, relative to the Venus center of mass, expressed in inertial coordinates. * ar_lon float 4 Footprint Longitude (deg, VBF85)--the crust-fixed longitude of the center of the altimeter footprint, in the range 0E - 360E longitude. Periapsis nadir increases in longitude by about 1.48 degrees per day (about 0.2 degrees per orbit). * ar_lat float 4 Footprint Latitude (degrees, VBF85)--the crust-fixed latitude of the center of the altimeter footprint, in the range of -90 degrees (South Pole) to +90 degrees (North Pole). * ar_xfoot float 4 Along-track Altimetry Footprint Size (km)--the along-track dimension of the Venus surface area whose mean radius, RMS slope, and reflectivity are reported in this data record. The along track dimension is chosen to be the smallest multiple of the doppler resolution of the altimeter (at this point in the S/C orbit) that is greater than 8 km. * ar_yfoot float 4 Cross-track Altimetry Footprint Size (km)--the cross-track footprint dimension is determined solely by the radar baud length and the S/C altitude at this point in the orbit. * ar_rcal float 4 Receiver Noise Calibration (km^2)--a measure of the altimeter noise background, obtained from the pulse-compressed altimeter signals by the MGMTAC phase of the A&R data reduction program. * ar_range float 4 Uncorrected range to nadir (km)--the "raw" measurement of range-to-surface, obtained from the pulse-compressed altimeter signals by the MGMTAC phase of the A&R data reduction program. * ar_atmos float 4 Atmospheric correction to range (km)--the correction applied to ar_radius to allow for the delay of signals passing through the atmosphere, calculated by the MGMOUT phase of the A&R data reduction program. * ar_radius float 4 Derived Planetary Radius (km)--the mean Venus radius for this radar footprint, obtained by subtracting (ar_range - ar_atmos) from the length of the ar_pos vector. * ar_slope float 4 Derived RMS Surface Slope (deg)--the root mean square meter-scale surface slope, averaged over the radar footprint, obtained by fitting the altimeter echo to a suite of theoretical templates derived from the Hagfors scattering model. * ar_rho float 4 Derived Fresnel Reflectivity--the bulk reflectivity of the surface material, averaged over the radar footprint, obtained by fitting the altimeter echo to a suite of theoretical templates derived from the Hagfors scattering model, but ignoring the effect of small-scale surface roughness. * ar_rhocor float 4 Rho correction factor for Diffuse Scattering--a factor which must be added to ar_rho (but only if AR_RHOC is set in ar_flag), to allow for the effect of small-scale surface roughness. * ar_error float 3*4 Formal errors in Radius, Slope, Rho--the 1-sigma statistical errors expected in the determination of ar_radius, ar_slope, and ar_rho, respectively. * ar_correl float 6*4 Formal correlations in same--the formal correlations between ar_radius and ar_slope, between ar_slope and ar_rho, and between ar_rho and ar_radius, respectively. As the profile fitting algorithm is non-linear, the correlations may not be symmetric. * ar_drad float 4 Ephemeris Radius Correction (km)--the correction applied to the length of the ar_pos vector by the post-fitting MGMORB phase of the A&R reduction program. * ar_dlon float 4 Ephemeris Longitude Correction (deg. VBF85)--the correction applied to the footprint longitude by the post-fitting MGMORB phase of the A&R reduction program. * ar_dlat float 4 Ephemeris Latitude Correction (deg. VBF85)--the correction applied to the footprint latitude by the post-fitting MGMORB phase of the A&R reduction program. * ar_partl float 18*4 Partials of ar_lon, ar_lat, and ar_radius with respect to ar_pos and ar_vel--the partial derivatives of the footprint coordinates with respect to changes in the S/C position and velocity. See Appendix B for a discussion of the definition and use of these numbers. * ar_fit float 4 Non-range-sharpened "goodness of fit"--a measure of the correlation between the observed profile ar_prof and the theoretical template ar_tmpl. * ar_scale float 4 Scaling factors for ar_tmpl and ar_prof--the conversion factor that multiplies the integer array elements of ar_tmpl and ar_prof to yield their physical values, expressed as equivalent radar cross-sections in units of km^2. * ar_looks ulong 4 Number of non-range-sharpened looks--the number of statistically independent measurements of echo profile that were summed to produce the profile ar_prof. * ar_nprof0 ulong 4 The index of the element in ar_prof that corresponds to the first element in ar_tmpl. The indices start at zero. * ar_prof uchar 302*1 Non-range-sharpened Echo Profile--the power vs. time echo profile, at half-baud (0.21 micsec) intervals, assembled from up to 16 frequency components, without shifting their time origins (see ar_rsprof, below). This profile yields the best estimate of the time dispersion of the echo, and hence of ar_slope and ar_rho. * ar_tmpl uchar 50*1 Best non-range-sharp Model Template--the theoretical echo profile, at half-baud (0.21 micsec) intervals, that best approximates the peak of the ar_prof array. The optimal fit is made by matching ar_tmpl[i] with ar_prof[i+ar_nprof0], i = 0,49. * ar_rsfit float 4 Range-sharpened "goodness of fit" parameter--a measure of the correlation between the observed profile ar_rsprof and the theoretical template ar_rstmpl. * ar_rsscale float 4 Scaling factors for ar_rstmpl and ar_rsprof--the conversion factor that multiplies the integer array elements ar_rstmpl and ar_rsprof to yield their physical values, expressed as specific radar cross-sections in units of km^2. * ar_rslooks ulong 4 Number of equivalent looks--the number of statistically independent measurements of echo profile that were summed to produce the range- sharpened profile ar_rsprof. * ar_rsnprof0 ulong 4 The index of the element in ar_rsprof that corresponds to the first element in ar_rstmpl. The indices start at zero. * ar_rsprof uchar 302*1 Range-sharpened Echo Profile--the power vs. time echo profile, at half-baud (0.21 msec) intervals, assembled from up to 16 frequency components, each shifted in time so as to align their rising edges. * ar_rstmpl uchar 50*1 Best range-sharpened Model Template--the theoretical echo profile, at half-baud (0.21 micsec) intervals, that best approximates the peak of the ar_rsprof array. This profile yields the best estimate of the two-way echo time, and hence of ar_radius. The optimal fit is made by matching ar_rstmpl[i] with ar_rsprof[i+ar_rsnprof0], i = 0,49. * ar_rhofact float 4 Multi-peak correction applied to ar_rho-- the raw ar_rho value has been multiplied by a factor (1+ar_rhofact) to allow for multi- peaked echoes. This field is unused in software version 1. * ar_radius2 float 4 Radius from Threshold Detector (km)-- the planetary radius derived from threshold detection of the signal in ar_rsprof. This field is unused in software version 1. * ar_sqi float 4 Signal Quality Indicator (dB)--the ratio between the sum of the 10 range bins starting 10 bins after the threshold range bin and the sum of the 10 range bins starting 20 bins before the threshold bin. This field is not used in software version 1. In version 2, it is always recorded in IEEE-754 format, even when the remaining "float" fields are in VAX format. * ar_thresh ulong 4 Threshold Detector Index -- the index in ar_rsprof at which the threshold detector has located the rising signal. This field is not used in software version 1. * ar_spare long 7*4 Unused--reserved for future data fields. +---------------------------------------------------------------------------+ | Table 5-7. MIT Altimetry Data Record Flag Values (ar_flag) | | (for details, see Applicable Document [7]) | +------------+-------+------------------------------------------------------+ | Name | Value | Flag Description | +------------+-------+------------------------------------------------------+ | AR_FIT | 1 | Record contains footprint values that have been | | | | fitted in the A&R MGMTAC processing phase. | +------------+-------+------------------------------------------------------+ | AR_EPHC | 2 | Geometry values have been corrected for | | | | ephemeris errors (MGMORB phase). | +------------+-------+------------------------------------------------------+ | AR_RHOC | 4 | Reflectivity correction ar_rhocor has been deter- | | | | mined from SAR backscatter values (MGMORB phase). | +------------+-------+------------------------------------------------------+ | AR_RS2 | 8 | Range-sharpened values have passed the 2nd-order | | | | template fitting criteria (MGMTAC phase). | +------------+-------+------------------------------------------------------+ | AR_NRS2 | 16 | Non-range-sharpened values have passed the 2nd- | | | | order template fitting criteria (MGMTAC phase). | +------------+-------+------------------------------------------------------+ | AR_BAD | 32 | Ignore this record entirely. | +------------+-------+------------------------------------------------------+ | AR_RBAD | 64 | Ignore the range-sharpened profile ar_rsprof[] | | | | and the associated ar_radius value. | +------------+-------+------------------------------------------------------+ | AR_CBAD | 128 | Ignore the non-range-sharpened profile ar_prof[] | | | | and the associated ar_slope and ar_rho values. | +------------+-------+------------------------------------------------------+ | AR_TMARK | 256 | Temporary ar_radius marker flag, used by MGMDQE. | +------------+-------+------------------------------------------------------+ | AR_CMARK | 512 | Temporary ar_slope marker flag, used by MGMDQE. | +------------+-------+------------------------------------------------------+ | AR_FMARK | 1024 | Temporary ar_rho marker flag, used by MGMDQE. | +------------+-------+------------------------------------------------------+ | AR_HAGFORS | 2048 | ar_slope and its errors and correlations are | | | | expressed as Hagfors' C parameter instead of | | | | degrees of RMS slope. This flag will not be set | | | | in any standard ARCDR products. It is solely used | | | | during some phases of internal MIT processing. | +------------+-------+------------------------------------------------------+ | AR_BADALTA | 4096 | The altimetry antenna was pointed more than 3 deg | | | | from its expected location as given by the nominal | | | | look-angle profile. | +------------+-------+------------------------------------------------------+ | AR_SLOPEBAD| 8192 | The ar_slope parameter value is suspect, and | | | | ar_prof should also be disregarded. | +------------+-------+------------------------------------------------------+ | AR_RHOBAD | 16384 | The ar_rho value is suspect. | +------------+-------+------------------------------------------------------+ | AR_RAD2 | 32768 | This record was created under software version | | | | 2 or higher, in which the data fields ar_rhofact, | | | | ar_radius2, ar_sqi, and ar_thresh are significant. | +------------+-------+------------------------------------------------------+ | AR_RAD2BAD | 65536 | The ar_radius2 value is suspect. | +------------+-------+------------------------------------------------------+ | AR_AMBIG |131072 | The value of ar_radius has been shifted by a | | | | multiple of the range ambiguity (10.02 km) during | | | | the MGMDQE processing phase. | +------------+-------+------------------------------------------------------+ | AR_AMBIG2 |262144 | The value of ar_radius2 has been shifted by a | | | | multiple of the range ambiguity (10.02 km) during | | | | the MGMDQE processing phase. | +------------+-------+------------------------------------------------------+ 5.6. Radiometry Data File +-------------------------------------------------------------------+ | Figure 5-7. MIT Radiometry Data File (RDF) - Block Format | +---+------------------------------------------------+--------------+ | T | CCSD1Z000001 | CCSD label | +---+------------------------------------------------+--------------+ | L | 00000xxx | length | +---+---+--------------------------------------------+--------------+ | . | T | NJPL1K00KL00 | Keywd label | +---+---+--------------------------------------------+--------------+ | . | L | 00000xxx | length | +---+---+--------------------------------------------+--------------+ | . | . | PRODUCT_FILE_NAME=RDFnnnnn.v | | | . | . | PRODUCT_TYPE=RADIOMETRY_FILE | | | . | . | MISSION_ID=4 | | | . | . | SPACECRAFT_NAME=MAGELLAN | | | . | V | SPACECRAFT_ID=18 | | | . | A | MISSION_NAME=MAGELLAN | Keywords | | . | L | PROCESS_TIME=yyyy-mm-ddThh:mm:ss.fff | and | | . | U | ORBIT_NUMBER=nnnnn | Values | | . | E | HARDWARE_VERSION_ID=nn | | | . | . | SOFTWARE_VERSION_ID=nn | | | . | . | DATA_FORMAT_TYPE=ccc | | | . | . | UPLOAD_ID=cnnnnc | | | . | . | NAV_UNIQUE_ID="cccccccccc " | | +---+---+--------------------------------------------+--------------+ | . | T | CCSD1R000003 | Start marker | +---+---+--------------------------------------------+--------------+ | . | L | 000000xx | length | +---+---+--------------------------------------------+--------------+ | . | V | DELIMITER=SMARKER | Start value | | . | A | PRODUCT_NAME=RADIOMETRY_DATA_RECORD | | | . | L | TYPE=NJPL1I000177 | | +---+---+--------------------------------------------+--------------+ | | | | Radiometry Data Record SFDUs (see Table 5-8) | Variable | | | | +---+------------------------------------------------+--------------+ | T | CCSD1R000003 | End marker | +---+------------------------------------------------+--------------+ | L | 000000xx | length | +---+------------------------------------------------+--------------+ | V | DELIMITER=EMARKER | End value | | . | PRODUCT_NAME=RADIOMETRY_DATA_RECORD | | +---+------------------------------------------------+--------------+ * CCSDS Label 'CCSD1Z000001', the CCSDS primary SFDU label. * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the remainder of the Radiometry Data File header. * Keyword Label 'NJPL1K00KL00', the SFDU Catalog/Keyword label, where '1' indicates that an ASCII length field follows. * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the keyword/value field, including two bytes per keyword/value pair for the (unillustrated) carriage return and line feed, and a possible trailing blank if required to make this length an even number. * PRODUCT_FILE_NAME= 'RDFnnnnn.v', the external file name of this RDF. 'nnnn' is a 5-digit orbit number and 'v' is a decimal version number. For test RDF files, 'v' consists of the letter 'T' followed by a decimal version number. * PRODUCT_TYPE= The character string 'RADIOMETRY_FILE'. * MISSION_ID= The single character '4'. * MISSION_NAME= The character string 'MAGELLAN'. * SPACECRAFT_ID= For real data, the 2-digit number '18'. For simulated data, the number '28'. * SPACECRAFT_NAME= The character string 'MAGELLAN'. * PROCESS_TIME= The local EST or EDT time at which the Radiometry Data File was created by the MIT A&R processing system. * ORBIT_NUMBER= A 5-digit number, denoting the Magellan orbit number of this Radiometry Data File. * HARDWARE_VERSION_ID= A 2-digit number, 'nn', identifying the hardware version number of the MIT A&R data processing system used to create this file or volume. * SOFTWARE_VERSION_ID= A 2-digit number, 'nn', identifying the software version number of the MIT A&R data processing system used to create this file or volume. * DATA_FORMAT_TYPE= Either 'VAX' or 'IEEE', depending on the format in which binary fields are represented in the altimetry data records. For all ARCDR products sent to DMAT, this will be 'VAX'. * UPLOAD_ID= 6 characters 'ABBBBC', where 'A' is the mission phase, 'BBBB' is the upload number within each phase, and 'C' is a revision indicator in the range A-Z. * NAV_UNIQUE_ID= See Applicable Document [4]. * Start Marker 'CCSD1R000003', the SFDU Aggregate Marker label, indicating the start of a data aggregate of unspecified length. This aggregate consists of a varying number of Radiometry Data Record SFDU's (rr_rec), as shown in Table 5-8. * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the remainder of the aggregate marker SFDU. * DELIMITER= The character string 'SMARKER', indicating that this is the start of a data aggregate. * PRODUCT_NAME= The character string 'RADIOMETRY_DATA_RECORD'. * TYPE= The character string 'NJPL1I000177', where '0177' indicates that the data between the SMARKER and EMARKER labels comprise a registered SFDU aggregate, composed of a set of registered NJPL aggregates. * Radiometry Data Record See Table 5-8. * End Marker 'CCSD1R000003', the SFDU Aggregate Marker label, indicating the end of a data aggregate of unspecified length. This matches the above "Start Marker". * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the remainder of the aggregate marker SFDU. * DELIMITER= The character string 'EMARKER', indicating that this is the end of a data aggregate. * PRODUCT_NAME= The character string 'RADIOMETRY_DATA_RECORD'. +---------------------------------------------------------------------------+ | Table 5-8. MIT Radiometry File Record SFDU (rr_rec) | +-----+-----+--------+----------------+-------------------------------------+ | Off | Len | Type | Name | Description | +-----+-----+--------+----------------+-------------------------------------+ | +0 | 20 | sfdu | rr_sfdu | SFDU header label and length | | 20 | 4 | long | rr_burst | Radar Burst Number (periapsis=0) | | 24 | 4 | ulong | rr_flag | Flag fields (see Table 5-9) | | 28 | 4 | ulong | rr_flag2 | Additional flag fields (unused) | | 32 | 8 | double | rr_scet | S/C Radiometry Epoch (SCET, TDB) | | 40 | 24 | double | rr_pos[3] | S/C Position Vector (km, J2000) | | 64 | 24 | double | rr_vel[3] | S/C Velocity Vector (km/sec, J2000) | | 88 | 4 | float | rr_lon | Footprint Longitude (deg, VBF85) | | 92 | 4 | float | rr_lat | Footprint Latitude (deg, VBF85) | | 96 | 4 | float | rr_xfoot | Along Track Rad Footprint Size (km) | | 100 | 4 | float | rr_yfoot | Cross Track Rad Footprint Size (km) | | 104 | 8 | float | rr_sfoot[2] | Footprint Diameters of rr_sar (km) | | 112 | 8 | float | rr_sar[2] | Average Backscatter Values (dB) | | 120 | 4 | float | rr_angle | Incidence Angle (deg) | | 124 | 4 | float | rr_bright | Brightness Temperature (K) | | 128 | 4 | float | rr_radius | Average Planetary Radius (km) | | 132 | 4 | float | rr_anttemp | System Temperature of Antenna (K) | | 136 | 4 | float | rr_skytemp | Assumed Sky Temperature (K) | | 140 | 4 | float | rr_rcvrtemp | System Temperature of Receiver (K) | | 144 | 4 | float | rr_surftemp | Physical Surface Temperature (K) | | 148 | 4 | float | rr_emiss | Surface Emissivity | | 152 | 72 | float | rr_partl[3][6] | Partials of rlon, lat, and radius | | 224 | 4 | float | rr_dedrad | Partial of rr_emiss wrt rr_radius | | 228 | 4 | float | rr_phystemp | Physical Surface Temperature (K) | | 232 | 4 | float | rr_antval | Radiometer Antenna Value | | 236 | 4 | float | rr_loadval | Radiometer Load Value | | 240 | 2 | uchar | rr_askip[2] | Altimeter Skip Factors | | 242 | 2 | uchar | rr_again[2] | Altimeter Gain Factors | | 244 | 4 | long | rr_acr | Altimeter Coarse Resolution | | 248 | 16 | long | rr_spare[4] | Unused | | 264 +-----+--------+----------------+-------------------------------------+ +-----+ Element Name Type Size Description * rr_sfdu sfdu 20 SFDU header label 'NJPL1I00018000000244'. The number '0180' is registered with the NJPL SFDU authority as the "MIT Radiometry Data Record Aggregate". * rr_burst long 4 SAB Number--the number assigned by MGMSAR processor to the burst header that contains the radiometer measurement referenced by this rr_rec. * rr_flag ulong 4 Flag fields--see Table 5P9. * rr_flag2 ulong 4 Additional flag fields (unused). * rr_scet double 8 S/C Radiometry Epoch (SCET)--the ephemeris time (seconds of TDB since J2000; see 1.5.4.2) at which the radiometry measurement was made. * rr_pos double 3*8 S/C Position Vector (km, J2000)--the S/C position at rr_scet, relative to the Venus center of mass, expressed in inertial coordinates. * rr_vel double 3*8 S/C Velocity Vector (km/sec, J2000)--the S/C velocity at rr_scet, relative to the Venus center of mass, expressed in inertial coordinates. * rr_lon float 4 Footprint Longitude (deg, VBF85)--the crust-fixed longitude, at rr_scet, of the intersection of the antenna boresight and the planetary surface (a sphere of radius rr_radius). If the RR_CAL flag is set in rr_flag (see table 5-9), rr_lon is expressed in inertial (J2000) coordinates. * rr_lat float 4 Footprint Latitude (deg, VBF85)--the crust-fixed latitude, at rr_scet, of the intersection of the antenna boresight and the planetary surface (a sphere of radius rr_radius). If the RR_CAL flag is set in rr_flag (see table 5-9), rr_lon is expressed in inertial (J2000) coordinates. * rr_xfoot float 4 Along Track Radiometry Footprint Size (km)--the along track dimension of the intersection of the SAR antenna (3dB one-way attenuation) cone with a sphere of radius rr_radius. * rr_yfoot float 4 Cross Track Radiometry Footprint Size (km)--the cross track dimension of the intersection of the SAR antenna (3dB one-way attenuation) cone with a sphere of radius rr_radius. * rr_sfoot float 2*4 SAR Footprint Diameters (km)--the approximate dimension of the surface areas represented by the pair of SAR backscatter values, rr_sar. * rr_sar float 2*4 SAR Average Backscatter Values (dB)--a pair of running averages of SAR image pixel values, rr_sar[0] taken from pixels lying westward of the antenna boresight, and rr_sar[1] taken from pixels lying to the east of it. * rr_angle float 4 Incidence Angle (deg)--the angle between the local vertical and the S/C direction, measured at the center of the radiometer footprint at rr_scet. * rr_bright float 4 Brightness Temperature (K)--the planet brightness temperature, derived from rr_anttemp, after correcting for antenna efficiency and side-lobe gain. * rr_radius float 4 Average Planetary Radius (km)--the planetary radius of the radiometer footprint, used to compute rr_lon and rr_lat, and also rr_surftemp and atmospheric corrections to rr_emiss. * rr_anttemp float 4 System Temperature of the SAR Antenna (K)--the rr_rcvrtemp value compensated for cable noise and losses. * rr_skytemp float 4 Sky Temperature (K)--the temperature assumed for the dominant portion of 'sky' reflected in the radiometer footprint, including atmospheric absorption and emission. * rr_rcvrtemp float 4 System Temperature of the receiver input (K)--the difference between rr_antval and rr_loadval, converted to equivalent noise temperature, and compensated for receiver gain and temperature. * rr_surftemp float 4 Radiometric Emission Temperature (K)--the emission temperature of the planetary surface covered by the radiometer footprint, derived by correcting rr_bright for atmospheric emission and absorption. * rr_emiss float 4 Surface Emissivity--defined by the following expression: rr_surftemp - rr_skytemp ------------------------ rr_phystemp - rr_skytemp * rr_partl float 18*4 Partials of rr_lat, rr_lon, and rr_radius with respect to rr_pos and rr_vel. * rr_dedrad float 4 Partial of rr_emiss with respect to rr_radius-- obtained by numerical differentiation. This may be used to correct the rr_emiss value when a more accurate value of rr_radius becomes available. * rr_phystemp float 4 Physical Surface Temperature (K)--the temper- ature of the atmosphere in contact with the surface at a radius of rr_radius. * rr_antval float 4 Radiometer Antenna Value--the raw radiometer reading when detecting a signal from the antenna, corrected for altimeter leakage. * rr_loadval float 4 Radiometer Load Value--the raw radiometer reading when detecting a signal from the load, corrected for altimeter leakage. * rr_askip uchar 2 Altimeter Skip Factors--the two skip factors taken from the SAB header during the bursts in which antenna and load signals were measured. * rr_again uchar 2 Altimeter Gain Factors--the two gain factors taken from the SAB header during the bursts in which antenna and load signals were measured. * rr_acr long 4 Altimeter Coarse Resolution--the coarse range index taken from the SAB header during the burst in which the antenna signal was measured. * rr_spare long 4*4 Unused--reserved for future data fields. +---------------------------------------------------------------------------+ | Table 5-9. MIT Radiometry Data Record Flag Values (rr_flag) | | (for details, see Applicable Document [7]) | +---------+-------+---------------------------------------------------------+ | Name | Value | Flag Description | +---------+-------+---------------------------------------------------------+ | RR_GEOC | 1 | Geometry values have been corrected for ephemeris | | | | errors (MGMORB phase). | +---------+-------+---------------------------------------------------------+ | RR_RADC | 2 | rr_radius value has been corrected by altimeter radius | | | | values. Otherwise, its value is taken from the Magellan | | | | topography model (see Applicable Document [9]). | +---------+-------+---------------------------------------------------------+ | RR_NOS1 | 4 | rr_sar[0] value missing. | +---------+-------+---------------------------------------------------------+ | RR_NOS2 | 8 | rr_sar[1] value missing. | +---------+-------+---------------------------------------------------------+ | RR_BAD | 16 | The rr_rec fields rr_bright through rr_emiss should be | | | | ignored. | +---------+-------+---------------------------------------------------------+ | RR_CAL | 32 | The spacecraft is operating in its "radiometric calib- | | | | ration" mode, in which the SAR boresight is pointed | | | | away from the planet. The rr_lat and rr_lon fields | | | | contain the boresight latitude and longitude in the | | | | inertial (J2000) coordinate system, not in VBF85. | +---------+-------+---------------------------------------------------------+ | RR_NRAD | 64 | The rr_radius value could not be estimated from the | | | | topography model. | +---------+-------+---------------------------------------------------------+ | RR_RAD2 | 32768 | This record was created under software version 2 | | | | or higher, in which data fields rr_dedrad through | | | | rr_acr are significant. | +---------+-------+---------------------------------------------------------+ 5.7. Volume Trailer File +-------------------------------------------------------------------+ | Figure 5-8. MIT Volume Trailer File (VTF) Format | +---+------------------------------------------------+--------------+ | T | CCSD1Z000001 | CCSD label | +---+------------------------------------------------+--------------+ | L | 00000xxx | length | +---+---+--------------------------------------------+--------------+ | . | T | CCSD1R000003 | End marker | +---+---+--------------------------------------------+--------------+ | . | L | 00000xxx | length | +---+---+--------------------------------------------+--------------+ | . | V | DELIMITER=EMARKER | End value | | . | . | PRODUCT_NAME=ARCDR | | +---+---+--------------------------------------------+--------------+ * CCSDS Label 'CCSD1Z000001', the CCSDS primary SFDU label.. * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the remainder of the trailer file. * End Marker 'CCSD1R000003', the SFDU Aggregate Marker label, indicating the end of a data aggregate of unspecified length. This matches the Aggregate Marker in the Volume Header File. * Length Eight bytes, ASCII, with leading zeroes mandatory; the length of the remainder of the aggregate marker SFDU. * DELIMITER= The character string 'EMARKER', indicating that this is the end of a data aggregate. * PRODUCT_NAME= The character string 'ARCDR'.