urn:nasa:pds:magellan_scvdr:data_anf:anf04355 1.0 1.23.0.0 Product_Observational 2025-09-12 1.0 Initial PDS4 version 1992-03-09T01:21:50.064Z 1992-03-09T01:37:27.881Z 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 4355 Mapping Cycle 3 mg_2145 urn:nasa:pds:magellan_scvdr:document:scvdr_sis data_to_document urn:nasa:pds:magellan_scvdr:data_gmf:gmf04300 data_to_geometry anf04355_1.dat 1994-10-11T06:00:47Z 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.

20 370 7-Bit ASCII Text SFDU keyword label (K-type).

Altimetry Inversion Header Table 390 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. Altimetry Inversion Data Table 554 210 Each ANF data record contains measurements of the surface scattering cross-section at various incidence angles, obtained by inverting the altimeter's delay and frequency spectra using the geometry matrices in the file 'GMF04300.1'. 47 17 1584 SFDU_AGGREGATE_HEADER 1 1 ASCII_String 20 'NJPL1I0000060000nnnn', the number '0006' is registered with the NJPL SFDU authority as the 'Altimetry Inversion 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 = 1564. FOOTPRINT_NUMBER 2 21 UnsignedMSB4 4 Starting from 1, the number of the Altimetry Inversion Record in increasing order of Altimetry Footprint Time (FOOTPRINT_TIME). BURST_NUMBER 3 25 UnsignedMSB4 4 The logical record number from the ALT-EDR burst SFDU most closely associated with this footprint. If the number of bursts averaged (NUMBER_OF_BURSTS_AVERAGE) is odd, the middle burst; if NUMBER_OF_BURSTS_AVERAGED is even, the earlier of the two middle bursts. FLAG_FIELDS 4 29 UnsignedMSB4 4 Stanford Altimetry Inversion Record Flag Values (see Table 5-5a of the SCVDR SIS). FOOTPRINT_TIME 5 33 IEEE754MSBDouble 8 second The burst start time (seconds of TDB since J2000; see Section 1.5.4.2 of the SCVDR SIS) for the burst given by BURST_NUMBER. GROSS_DOPPLER_SHIFT 6 41 IEEE754MSBDouble 8 Hz The Doppler shift resulting from motion of the spacecraft toward nadir at FOOTPRINT_TIME (GROSS_DOPPLER_SHIFT > 0 means the spacecraft altitude is decreasing). 1 3 1 0 49 24 SPACECRAFT_POSITION_VECTOR 1 1 IEEE754MSBDouble 8 km The spacecraft position at FOOTPRINT_TIME, relative to the Venus center of mass, expressed in inertial coordinates. 2 3 1 0 73 24 SPACECRAFT_VELOCITY_VECTOR 1 1 IEEE754MSBDouble 8 km/s The spacecraft velocity at FOOTPRINT_TIME, relative to the Venus center of mass, expressed in inertial coordinates. 3 3 1 0 97 24 SUB_SPACECRAFT_POSITION_VECTOR 1 1 IEEE754MSBDouble 8 km The position of the nadir point (on a reference sphere of 6051 km radius) at FOOTPRINT_TIME, relative to the Venus center of mass, expressed in inertial coordinates. 4 3 1 0 121 24 ALTIMETRY_ANTENNA_BORESIGHT_VECTOR 1 1 IEEE754MSBDouble 8 Unit vector along the axis of the altimetry antenna at FOOTPRINT_TIME, expressed in inertial coordinates. 5 3 1 0 145 24 SAR_ANTENNA_BORESIGHT_VECTOR 1 1 IEEE754MSBDouble 8 Unit vector along the axis of the high-gain (SAR) antenna at FOOTPRINT_TIME, expressed in inertial coordinates. BIN_0_ROUND_TRIP_TIME 7 169 IEEE754MSBDouble 8 second The round-trip light time corresponding to the first range bin (before peak detection and rotation) in the averaged altimetry echo at FOOTPRINT_TIME. INCREMENTAL_ROUND_TRIP_TIME 8 177 IEEE754MSBDouble 8 second The position of the echo peak with respect to the range bin used in BIN_0_ROUND_TRIP_TIME (each range bin represents an additional 0.442 microseconds of round-trip delay beyond BIN_0_ROUND_TRIP_TIME). LATITUDE_OF_NADIR 9 185 IEEE754MSBSingle 4 degree The body-fixed latitude of the nadir at FOOTPRINT_TIME, in the range of -90 (South Pole) to +90 (North Pole); the nominal latitude of the footprint. LONGITUDE_OF_NADIR 10 189 IEEE754MSBSingle 4 degree The body-fixed longitude of the nadir at FOOTPRINT_TIME, in the range of 0-360. Periapsis nadir increases in longitude by about 1.48 degrees per day (about 0.2 degrees per orbit); the nominal footprint longitude. ALONG_TRACK_ALTIMETRY_FOOTPRINT 11 193 IEEE754MSBSingle 4 km The along-track dimension of the intersection of the 3-dB (two-way) altimetry antenna pattern with the surface when the antenna boresight is aimed at nadir (a very approximate measure of the along-track footprint dimension). CROSS_TRACK_ALTIMETRY_FOOTPRINT 12 197 IEEE754MSBSingle 4 km The cross-track dimension of the intersection of the 3-dB (two-way) altimetry antenna pattern with the surface when the antenna boresight is aimed at nadir (a very approximate measure of the across-track footprint dimension). PIONEER_VENUS_RADIUS_AT_NADIR 13 201 IEEE754MSBSingle 4 km Radius of Venus at the nadir point as determined from Pioneer Venus data (provided by MIT in GIPS image format). FIRST_ALT_BURST_USED 14 205 UnsignedMSB4 4 The number of the first burst included in the average altimetry echo for this record. LAST_ALT_BURST_USED 15 209 UnsignedMSB4 4 The number of the last burst included in the average altimetry echo for this record. NUMBER_OF_BURSTS_AVERAGED 16 213 UnsignedMSB2 2 The total number of altimeter bursts averaged to make this record. G_MATRIX_ID_NUMBER 17 215 UnsignedMSB2 2 Identifies the range-Doppler-angle array used to invert the range-Doppler data in this averaged echo. G-matrices are indexed from 0. NUMBER_OF_ANGLES_IN_SOLUTION 18 217 UnsignedMSB2 2 Number of angle increments in the solution for the scattering function from this average echo. NUMBER_OF_ELEMENTS_SAVED_IN_CVM 19 219 UnsignedMSB2 2 The number of covariance values stored in COVARIANCE_MATRIX (depends on COVARIANCE_MATRIX_FLAG in the ANF TABLE_HEADER). SMOOTHING_FACTOR 20 221 IEEE754MSBSingle 4 The value of the parameter used to minimize second differences in the scattering function solution for this average echo. CHI_SQUARE_RESIDUAL_FROM_SOLUTION 21 225 IEEE754MSBSingle 4 The residual from the weighted least-square error inversion for the scattering function. RMS_SURFACE_TILT_FROM_DATA 22 229 IEEE754MSBSingle 4 degree RMS surface tilt theta-zero calculated from the NUMBER_OF_ANGLES_IN_SOLUTION points in the solution. This value is very sensitive to the value of NUMBER_OF_ANGLES_IN_SOLUTION. THERMAL_NOISE_ESTIMATE 23 233 IEEE754MSBSingle 4 Watts Thermal noise power estimate calculated as one of many variables in the chi-square solution for the surface scattering function SCATTERING_FUNCTION. Likely to be an overestimate since there is no attempt to account for radar clutter; THERMAL_NOISE_ESTIMATE includes contributions from Venus' surface, the radar equipment, and aliased echo signal in both time/range and frequency. ESTIMATED_VARIANCE_OF_TN_SOL 24 237 IEEE754MSBSingle 4 Watts Estimate of variance in THERMAL_NOISE_ESTIMATE from propagation of errors through solution procedure. SMALLEST_RANGE_DOPPLER_ARRAY_VALUE 25 241 IEEE754MSBSingle 4 Watts Smallest value in averaged 16 by 151 (frequency by range, respectively) array of processor output power. Likely to be an underestimate, since statistical variations will force the 'minimum' below the average. AVERAGE_OF_SMALL_VALUES 26 245 IEEE754MSBSingle 4 Watts The average of range echo bin values from 10-20 range bins before the echo peak (divided by 16). MINIMUM_IN_RANGE_ECHO 27 249 IEEE754MSBSingle 4 Watts The minimum value in the range echo, divided by 16. 6 16 1 0 253 16 SPARE 1 1 UnsignedByte 1 Spare. DOPPLER_CENTROID 28 269 IEEE754MSBSingle 4 Hz The calculated center of the spectrum of the radar receiver signal. VARIANCE_OF_DOPPLER_CENTROID 29 273 IEEE754MSBSingle 4 Hz Estimated variance of DOPPLER_CENTROID. DOPPLER_ROTATION_USED_FOR_SOLUTION 30 277 IEEE754MSBSingle 4 Hz The offset of the echo from its nominal center bin position assumed to be due to surface effects (an integral multiple of 935 Hz, the width of a single frequency bin). TRANSMITTER_A_FLAG 31 281 UnsignedByte 1 If set (1), transmitter A was used; if not set (0), transmitter B was used. RECEIVER_A_FLAG 32 282 UnsignedByte 1 If set (1), receiver A was used; if not set (0), receiver B was used. 7 2 1 0 283 2 SPARE 1 1 UnsignedByte 1 Spare. END_TO_END_SYSTEM_CORRECTION 33 285 IEEE754MSBSingle 4 The end-to-end gain of the complete altimetry radar system for a closed loop test [if the antenna were removed and the outgoing (transmitted) signal were turned directly back to the receiver--including processing at Stanford. The value of END_TO_END_SYSTEM_CORRECTION is the measured attenuation during this test. CROSS_STRAPPING_CORRECTION 34 289 IEEE754MSBSingle 4 The attenuation caused by using transmitter A with receiver B, or vice versa. TRANSMITTER_POWER_CORRECTION 35 293 IEEE754MSBSingle 4 An estimated attenuation of the available power, relative to END_TO_END_SYSTEM_CORRECTION based on telemetered measurements of transmitter and output network temperatures. TRANSMITTER_STAGE_1_TEMPERATURE 36 297 IEEE754MSBSingle 4 K The telemetered temperature of the Transmitter Stage 1 Driver temperature, used to compute the transmit power. ONU_ALTIMETER_TEMPERATURE 37 301 IEEE754MSBSingle 4 K The telemetered temperature of the ONU Altimeter temperature, used to compute the transmit power. ATMOSPHERIC_ATTENUATION 38 305 IEEE754MSBSingle 4 The expected attenuation due to the atmosphere for this nadir elevation (PIONEER_VENUS_RADIUS_AT_NADIR). ANTENNA_PATTERN 39 309 IEEE754MSBSingle 4 Always zero because the gain pattern of the antenna is accounted for in the G-matrix calculation. RECEIVER_TEMPERATURE 40 313 IEEE754MSBSingle 4 K Telemetered temperature of the receiver. RECEIVER_TEMPERATURE_ATTENUATION 41 317 IEEE754MSBSingle 4 The portion of receiver attenuation that is dependent on receiver temperature. COMMANDABLE_ATTENUATION_CODE 42 321 UnsignedByte 1 The 3-bit code specifying the amount of attenuation used in the receiver front end. 8 3 1 0 322 3 SPARE 1 1 UnsignedByte 1 Spare. RECEIVER_COMMANDABLE_ATTENUATION 43 325 IEEE754MSBSingle 4 The actual receiver attenuation specified by the attenuation code COMMANDABLE_ATTENUATION_CODE. TOTAL_AMPLITUDE_CORRECTION 44 329 IEEE754MSBSingle 4 The total amplitude correction expressed as an attenuation. JPL_SYNC_CODE 45 333 UnsignedMSB4 4 The JPL Sync code 0x03915ed3. 9 24 1 0 337 24 BFQ_THRESHOLD_VALUES 1 1 UnsignedByte 1 Block Floating Point Thresholds from the SAR burst header. 10 2 1 0 361 2 SPARE 1 1 UnsignedByte 1 Spare. RADIOMETER_READING 46 363 UnsignedMSB2 2 Raw value of the radiometer, measuring noise power of the high-gain antenna or, on alternating bursts, of a load at a known temperature. 11 8 1 0 365 8 RADAR_CLOCK 1 1 UnsignedByte 1 The 52-bit spacecraft clock value. 12 2 1 0 373 2 SPARE 1 1 UnsignedByte 1 Spare. 13 10 1 0 375 10 BIT_FIELDS 1 1 UnsignedByte 1 Radar instrument status fields. BUFFER_MEMORY_CHECKOUT 47 385 UnsignedMSB2 2 Buffer memory checkout flag. 14 18 1 0 387 18 SPARE 1 1 UnsignedByte 1 Spare. 15 21 1 0 405 84 SCATTERING_FUNCTION 1 1 IEEE754MSBSingle 4 The Sigma-zero function obtained by inverting the average altimetry radar echo from bursts FIRST_ALT_BURST_USED through LAST_ALT_BURST_USED. The function is a vector of n = NUMBER_OF_ANGLES_IN_SOLUTION numbers for the (effective) incidence angles given by SOLUTION_ANGLES. 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 84 bytes. 999999.0 16 21 1 0 489 84 SOLUTION_ANGLES 1 1 IEEE754MSBSingle 4 radian The n = NUMBER_OF_ANGLES_IN_SOLUTION angles at which the scattering function solution has been obtained. The default angles are spaced by 0.5 degrees, starting at 0.25. That is, the solution angles are 0.25, 0.75, 1.25, 1.75, ... NUMBER_OF_ANGLES_IN_SOLUTION * 0.5-0.25 degrees; note, however, that SOLUTION_ANGLES is given in radians. 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 84 bytes. 999999.0 17 253 1 0 573 1012 COVARIANCE_MATRIX 1 1 IEEE754MSBSingle 4 Matrix of estimated covariances of SCATTERING_FUNCTION and thermal noise estimates. 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 1012 bytes. 999999.0