urn:nasa:pds:magellan_scvdr:data_anf:anf04076 1.0 1.23.0.0 Product_Observational 2025-09-12 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 4076 Mapping Cycle 3 mg_2144 urn:nasa:pds:magellan_scvdr:document:scvdr_sis data_to_document urn:nasa:pds:magellan_scvdr:data_gmf:gmf04031 data_to_geometry anf04076_1.dat 1994-09-27T16:39:55Z The Altimetry Inversion Data File (ANF) contains the results of inverting the time and frequency spectra of a single orbit of Magellan altimetry, from the ALT-EDR product, by means of the accompanying Geometry Matrix File (GMF). The ANF 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.

20 372 7-Bit ASCII Text SFDU keyword label (K-type).

Altimetry Inversion Header Table 392 1 The single binary ANF header record contains constants that describe the inversion process, algorithm IDs, and the maximum sizes of arrays in the ANF data records. 23 1 72 SFDU_AGGREGATE_HEADER 1 1 ASCII_String 20 'NJPL1I00000500000052', the number '0005' is registered with the NJPL SFDU authority as the 'Altimetry Inversion Header Record'. '00000052' signifies that the remainder of this SFDU is 52 bytes in length. ORBIT_NUMBER 2 21 UnsignedMSB4 4 The Magellan orbit number for the data represented in these data records. ORBIT_VERSION 3 25 UnsignedMSB4 4 The version of the altimetry data file used for these results. Obtained from the VERSION_ID keyword of the corresponding ALT-EDR Orbit Header File (Note: This turns out not to be a good indicator of the version of the data file; the Orbit Header File itself is rarely updated). ALTINV_MAJOR_VERSION_NUMBER 4 29 UnsignedMSB2 2 The major software version number of the Stanford program ALTINV used to obtain the scattering function solution. ALTINV_MINOR_VERSION_NUMBER 5 31 UnsignedMSB2 2 The minor software version number of the Stanford program ALTINV used to obtain the scattering function solution. ALT_MAJOR_VERSION_NUMBER 6 33 UnsignedMSB2 2 The major software version number of the Stanford program ALT used to compute the range-Doppler array from the raw altimetry data. ALT_MINOR_VERSION_NUMBER 7 35 UnsignedMSB2 2 The minor software version number of the Stanford program ALT used to compute the range-Doppler array from the raw altimetry data. COVARIANCE_MATRIX_FLAG 8 37 UnsignedByte 1 If set (1) the upper triangular portion (in row-major order) of the covariance matrix is saved in COVARIANCE_MATRIX; if not set (0), only the diagonal is saved. INVERSION_METHOD_ID 9 38 UnsignedByte 1 The code number for the specific method of overdetermined least squares used to compute the inversions (see Section 5.4.1 of the SCVDR SIS). VARIANCE_ESTIMATION_METHOD_ID 10 39 UnsignedByte 1 The code number for the method used to estimate the statistical uncertainty in the input data. The resulting variance is used in a weighted least squares fit and propagated to form an estimate of the inverted uncertainty in the solution. CONSTRAINT_VARIANCE_METHOD_ID 11 40 UnsignedByte 1 The code number for the method used to assign weight to the smoothing constraint that controls the shape of the inversion. Determines the scale of smoothing parameter SMOOTHING_FACTOR (see Section 5.4.1 of the SCVDR SIS). THERMAL_NOISE_METHOD_ID 12 41 UnsignedByte 1 The code number for the method used to account for the effects of thermal noise on the observations. NON_DELTA_SPECTRAL_FILTER_FLAG 13 42 UnsignedByte 1 If set (1), the Doppler spectrum has been convolved with an FIR filter before the inversion process. The nominal filter is [0.25 0.50 0.25] but is not saved in the SCVDR. If not set (0), no filter has been used (preferred). DOPPLER_ROTATION_METHOD_ID 14 43 UnsignedByte 1 The code number for the method used to account for unexpected Doppler shifts in the observed echo spectrum (see Section 5.4.1 of the SCVDR SIS). SPARE 15 44 UnsignedByte 1 Spare. NUMBER_OF_DATA_RECORDS 16 45 UnsignedMSB4 4 The number of altimetry inversion records that follow this header. RANGE_ECHO_PROCESSING_ID 17 49 UnsignedByte 1 The code number for the method used to process the range echo before the inversion (see Section 5.4.1 of the SCVDR SIS). MAXIMUM_ANGLE_METHOD_ID 18 50 UnsignedByte 1 The code number for the method used to determine the maximum solution angle in the inversion (see Section 5.4.1 of the SCVDR SIS). PULSE_COMPRESSION_ID 19 51 UnsignedMSB2 2 The code number for the correlation kernel used in the radar pulse compression stage, before the range-Doppler array is computed (see Section 5.4.1 of the SCVDR SIS). COMP_MAJOR_VERSION_ID 20 53 UnsignedMSB2 2 The major version number of the Stanford calibration software COMP used to compensate the input data for amplitude and timing effects. COMP_MINOR_VERSION_ID 21 55 UnsignedMSB2 2 The minor version number of the Stanford calibration software COMP used to compensate the input data for amplitude and timing effects. MAX_NUMBER_OF_SOLUTION_ANGLES 22 57 UnsignedMSB2 2 The largest number of elements that will appear in any scattering function (SCATTERING_FUNCTION) in this orbit, equal to the largest value of NUMBER_OF_ANGLES_IN_SOLUTION. The maximum size in bytes is thus 4 * MAX_NUMBER_OF_SOLUTION_ANGLES. MAX_NUMBER_OF_ELEMENTS_IN_CVM 23 59 UnsignedMSB2 2 The largest number of elements that will appear in any covariance matrix (COVARIANCE_MATRIX) in this orbit, equal to the largest value of NUMBER_OF_ELEMENTS_SAVED_IN_CVM. The maximum size in bytes is thus 4 * MAX_NUMBER_OF_ELEMENTS_IN_CVM. 1 12 1 0 61 12 SPARE 1 1 UnsignedByte 1 Spare.