PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 FILE_RECORDS = 423 ^HGA_POINTING_HDR_TABLE = ("1013H00A.SRA",1) ^HGA_POINTING_TABLE = ("1013H00A.SRA",3) INSTRUMENT_HOST_NAME = "MARS GLOBAL SURVEYOR" TARGET_NAME = "MARS" INSTRUMENT_NAME = "RADIO SCIENCE SUBSYSTEM" DATA_SET_ID = "MGS-M-RSS-5-SDP-V1.0" PRODUCT_ID = "1013H00A.SRA" START_TIME = 2001-01-13T07:00:00 STOP_TIME = 2001-01-13T07:07:00 PRODUCT_CREATION_TIME = 2002-07-04T22:43:28 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 = 421 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