urn:nasa:pds:magellan_scvdr:data_gmf:gmf02000 1.0 1.23.0.0 Product_Observational 2025-09-15 1.0 Initial PDS4 version Magellan Mission urn:nasa:pds:context:investigation:mission.magellan data_to_investigation The Magellan Spacecraft Host urn:nasa:pds:context:instrument_host:spacecraft.mgn is_instrument_host Magellan Spacecraft Radar System Instrument urn:nasa:pds:context:instrument:mgn.rdrs is_instrument Venus Planet urn:nasa:pds:context:target:planet.venus data_to_target SCVDR 1 2000 Mapping Cycle 1 urn:nasa:pds:magellan_scvdr:document:scvdr_sis data_to_document gmf02000_1.dat 1992-09-22T02:00:52Z The Geometry Matrix Data File (GMF) contains the values of the G-matrices used to invert the delay and frequency spectra of the Magellan altimeter. The GMF contains a CCSD header, a keyword and value SFDU, a binary header record SFDU, and one or more binary data record SFDUs, sandwiched between starting and ending marker SFDUs.

0 20 7-Bit ASCII Text CCSD header.

20 308 7-Bit ASCII Text SFDU keyword label (K-type).

Geometry Matrix Header Table 328 1 The single binary GMF header record contains the maximum sizes of arrays in the GMF data records. 7 1 44 SFDU_AGGREGATE_HEADER 1 1 ASCII_String 20 'NJPL1I00002300000024', the number '0023' is registered with the NJPL SFDU authority as the 'G-Matrix Header Record'. '00000024' signifies that the remainder of this SFDU is 24 bytes in length. NUMBER_OF_G_MATRICES 2 21 UnsignedMSB2 2 The number of G-matrices contained in this file. MAX_DIM_ANGLE_VECTOR 3 23 UnsignedMSB2 2 The largest value of NUMBER_OF_ANGLES in this file. MAX_DIM_RANGE_VECTOR 4 25 UnsignedMSB2 2 The largest value of NUMBER_OF_RANGES in this file. MAX_DIM_FREQUENCY_VECTOR 5 27 UnsignedMSB2 2 The largest value of NUMBER_OF_FREQUENCIES in this file. MAX_DIM_ANGLE_RANGE_G_MATRIX 6 29 UnsignedMSB4 4 The largest value of the product NUMBER_OF_ANGLES * NUMBER_OF_RANGES in this file. MAX_DIM_ANGLE_FREQUENCY_G_MATRIX 7 33 UnsignedMSB4 4 The largest value of the product NUMBER_OF_ANGLES * NUMBER_OF_FREQUENCIES in this file. 1 8 1 0 37 8 SPARE 1 1 UnsignedByte 1 Spare. Geometry Matrix Data Table 458 168 Each GMF data record contains the matrices used to invert the altimeter delay or frequency spectrum to yield the scattering functions in the ANF data records. 12 11 35320 SFDU_AGGREGATE_HEADER 1 1 ASCII_String 20 'NJPL1I0000240000nnnn', the number '0024' is registered with the NJPL SFDU authority as the 'G-Matrix Data Record'. 'nnnn' is the length in bytes of the remainder of the SFDU, which varied from record to record in the original data file. After padding for PDS4 migration, nnnn = 35300. G_MATRIX_ID_NUMBER 2 21 UnsignedMSB2 2 The identifier for the G-matrix. G-matrices are indexed from 0. ORBIT_NUMBER 3 23 UnsignedMSB2 2 The orbit number for which the G-matrix was computed. BURST_NUMBER_WITHIN_ORBIT 4 25 UnsignedMSB4 4 The burst number within orbit ORBIT_NUMBER for which the G-matrix was computed. 1 4 1 0 29 4 SPARE 1 1 UnsignedByte 1 Spare. BURST_TIME 5 33 IEEE754MSBDouble 8 second The time at which burst BURST_NUMBER_WITHIN_ORBIT was transmitted (seconds past J2000). NADIR_LATITUDE 6 41 IEEE754MSBSingle 4 degree The latitude at the nadir point for the G-matrix calculation. NADIR_LONGITUDE 7 45 IEEE754MSBSingle 4 degree The longitude at the nadir for the G-matrix calculation. 2 3 1 0 49 24 SPACECRAFT_POSITION 1 1 IEEE754MSBDouble 8 km The spacecraft position at BURST_TIME, relative to the Venus center of mass, expressed in inertial coordinates. 3 3 1 0 73 24 SPACECRAFT_VELOCITY 1 1 IEEE754MSBDouble 8 km/s The spacecraft velocity at BURST_TIME, relative to the Venus center of mass, expressed in inertial coordinates. 4 3 1 0 97 24 ALTIMETER_POINTING_VECTOR 1 1 IEEE754MSBDouble 8 The unit vector along the axis of the altimetry antenna at BURST_TIME, expressed in inertial coordinates. 5 3 1 0 121 24 SAR_POINTING_VECTOR 1 1 IEEE754MSBDouble 8 The unit vector along the axis of the high-gain (SAR) antenna at BURST_TIME, expressed in inertial coordinates. NUMBER_OF_ANGLES 8 145 UnsignedMSB2 2 The number of angles in the calculated G-matrix. NUMBER_OF_RANGES 9 147 UnsignedMSB2 2 The number of ranges in the calculated G-matrix. NUMBER_OF_FREQUENCIES 10 149 UnsignedMSB2 2 The number of frequencies in the calculated G-matrix (an odd number). HIGHEST_RANGE_ALIASING_INCLUDED 11 151 UnsignedMSB2 2 The highest order of range aliasing included in the computation of the G-matrix. If 0, no aliasing was considered; if 1, the contribution due to the first range ambiguity, etc. HIGHEST_FREQ_ALIASING_INCLUDED 12 153 UnsignedMSB2 2 The highest order of frequency aliasing included in the computation of the G-matrix. If 0, no aliasing was considered; if 1, the contributions due to the first positive and negative frequency aliasing, etc. 6 18 1 0 155 18 SPARE 1 1 UnsignedByte 1 Spare. 7 51 1 0 173 204 ANGLE_VECTOR 1 1 IEEE754MSBSingle 4 radians The vector of nb = NUMBER_OF_ANGLES angles for which the G-matrix was calculated (radians). Entries in ANGLE_VECTOR are monotonically increasing from an initial 0 radians, which is implicit and not included in the vector. Entries ANGLE_VECTOR[n] and ANGLE_VECTOR[n+1] thus bound the nth angle interval, which has nominal value (ANGLE_VECTOR[n] + ANGLE_VECTOR[n+1])/2. For the PDS4 migration, this field has been padded with a series of 4-byte floats (999999.0) to set the total field length to 204 bytes. 999999.0 8 151 1 0 377 604 RANGE_VECTOR 1 1 IEEE754MSBSingle 4 seconds The vector of nr = NUMBER_OF_RANGES ranges for which the G-matrix was calculated (seconds). Entries in R ANGE_VECTOR are monotonically increasing from an initial 0 seconds, which is implicit and not included in the vector. Entries RANGE_VECTOR[n] and RANGE_VECTOR[n+1] thus bound the nth range interval, which has nominal value (RANGE_VECTOR[n] + RANGE_VECTOR[n+1])/2. For the PDS4 migration, this field has been padded with a series of 4-byte floats (999999.0) to set the total field length to 604 bytes. 999999.0 9 17 1 0 981 68 FREQUENCY_VECTOR 1 1 IEEE754MSBSingle 4 Hz The vector of nf = NUMBER_OF_FREQUENCIES frequencies for which the G-matrix was calculated (Hz). Entries in FREQUENCY_VECTOR are monotonically increasing and denote frequencies at the centers of nominal frequency bins. FREQUENCY_VECTOR has an odd number of elements; the center element is zero and the remainder are symmetric (positive and negative frequencies) about this center value. For the PDS4 migration, this field has been padded with a series of 4-byte floats (999999.0) to set the total field length to 68 bytes. 999999.0 10 7701 1 0 1049 30804 ANGLE_RANGE_G_MATRIX 1 1 IEEE754MSBSingle 4 The (aliased) G-matrix in angle-range space, with NUMBER_OF_RANGES rows and NUMBER_OF_ANGLES columns, stored in row-major order for a total of nrb = NUMBER_OF_RANGES * NUMBER_OF_ANGLES entries. The first row is associated with the first element in RANGE_VECTOR, and each element in a row is associated with the corresponding element in ANGLE_VECTOR. For the PDS4 migration, this field has been padded with a series of 4-byte floats (999999.0) to set the total field length to 30804 bytes. 999999.0 11 867 1 0 31853 3468 ANGLE_DOPPLER_G_MATRIX 1 1 IEEE754MSBSingle 4 The (aliased) G-matrix in angle-frequency space, with NUMBER_OF_FREQUENCIES rows and NUMBER_OF_ANGLES columns, stored in row-major order for a total of nfb = NUMBER_OF_FREQUENCIES * NUMBER_OF_ANGELES entries. The first row is associated with the first element in FREQUENCY_VECTOR, and each element in a row is associated with the corresponding element in ANGLE_VECTOR. For the PDS4 migration, this field has been padded with a series of 4-byte floats (999999.0) to set the total field length to 3468 bytes. 999999.0