urn:nasa:pds:magellan_scvdr:data_sif:sif04355 1.0 1.23.0.0 Product_Observational 2025-09-19 1.0 Initial PDS4 version 1992-03-09T01:21:50.667Z 1992-03-09T01:37:17.195Z 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 sif04355_1.dat 1994-10-11T06:00:47Z The Sinusoidal Image Data File (SIF) contains the results of fitting the radar backscatter cross-section measurements of a single Magellan orbit, from the sinusoidal image file of the C-BIDR or F-BIDR product, to a quadratic function, along with a histogram of pixel values used in the fit. The SIF 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).

Sinusoidal Image Header Table 390 1 The single binary SIF header record contains constants that describe the fitting process, algorithm IDs, and the maximum sizes of arrays in the SIF data records. 11 1 60 SFDU_AGGREGATE_HEADER 1 1 ASCII_String 20 'NJPL1I00001000000040', the number '0010' is registered with the NJPL SFDU authority as the 'Image Header Record'. '00000040' indicates that the remainder of this SFDU is 40 bytes in length. ORBIT_NUMBER 2 21 UnsignedMSB4 4 The Magellan orbit number for the data represented in these data records. VERSION_NUMBER 3 25 UnsignedMSB4 4 The version of the image data file used for these results. Obtained from the VERSION_ID keyword of the corresponding C-BIDR (or F-BIDR) 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). NUMBER_OF_IMAGE_DATA_RECORDS 4 29 UnsignedMSB4 4 The number of image records that follow this header. NUMBER_OF_IMAGE_LINES_PER_RECORD 5 33 UnsignedMSB4 4 The number of C-BIDR (or F-BIDR) image lines compressed to form one output processed record (nominally 9). SOURCE_DATA_TYPE 6 37 UnsignedByte 1 Set to binary 0 if source data are from an F-BIDR, set to 1 if from a C-BIDR. FITTING_METHOD_FLAG 7 38 UnsignedByte 1 Zero for chi-square fitting to determine polynomial coefficients, 1 for linear least squares fitting. RMAP_MAJOR_SOFTWARE_VERSION 8 39 UnsignedMSB2 2 The major software version number of the Stanford program RMAP used to obtain the scattering function from the image data. RMAP_MINOR_SOFTWARE_VERSION 9 41 UnsignedMSB2 2 The minor software version number of the Stanford program RMAP used to obtain the scattering function from the image data. MAX_NUMBER_OF_ANGLES 10 43 UnsignedMSB2 2 The largest value of NUMBER_OF_ANGLES_IN_IR_BINS that will appear in this orbit. MAX_HISTOGRAM_SIZE 11 45 UnsignedMSB2 2 The largest value of NUMBER_OF_LEVELS_IN_I_COUNT that will appear in this orbit. 1 14 1 0 47 14 SPARE 1 1 UnsignedByte 1 Spare. Sinusoidal Image Data Table 538 2245 Each SIF data record contains the result of fitting the radar backscatter function derived from approximately 9 rasters of the C-BIDR image, or approximately 27 rasters of the F-BIDR image, to an n'th order polynomial. 34 9 2432 SFDU_AGGREGATE_HEADER 1 1 ASCII_String 20 'NJPL1I0000120000nnnn', the designator '0012' is registered with the NJPL SFDU authority as the 'Image 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 = 2412. FOOTPRINT_NUMBER 2 21 UnsignedMSB4 4 Starting from 1, the number of the Image Data Record by increasing Image Footprint Time (FOOTPRINT_TIME). BURST_COUNT_FOR_CLOSEST_BURST 3 25 UnsignedMSB4 4 The burst for which the Mid-Range Point is closest to the footprint center. FLAG_FIELDS 4 29 UnsignedMSB4 4 Stanford Image Data Record Flag Values. FOOTPRINT_TIME 5 33 IEEE754MSBDouble 8 second The burst start time (seconds of TDB since J2000) for the associated burst. 1 3 1 0 41 12 SPACECRAFT_POSITION_VECTOR 1 1 IEEE754MSBSingle 4 km The spacecraft position for the associated burst, relative to the Venus center of mass and expressed in the Venus Body Fixed 1985 coordinate system. 2 3 1 0 53 12 SPACECRAFT_VELOCITY_VECTOR 1 1 IEEE754MSBSingle 4 km/s The spacecraft velocity for the associated burst, relative to the Venus center of mass and expressed in Venus Body Fixed 1985 coordinates. 3 3 1 0 65 12 SAR_ANTENNA_UNIT_BORESIGHT_VECTOR 1 1 IEEE754MSBSingle 4 The unit vector along the axis of the SAR antenna for the associated burst, expressed in Venus Body Fixed 1985 coordinates. 4 3 1 0 77 12 BORESIGHT_INTERCEPT_POINT 1 1 IEEE754MSBSingle 4 km The position of the boresight intercept point on Venus' surface for the associated burst, expressed in Venus Body Fixed 1985 coordinates. FOOTPRINT_LATITUDE 6 89 IEEE754MSBSingle 4 degree The body-fixed latitude of the footprint center, in the range of -90 (South Pole) to +90 (North Pole). FOOTPRINT_LONGITUDE 7 93 IEEE754MSBSingle 4 degree The body-fixed longitude of the footprint center in the range of 0 - 360. AZIMUTH_FROM_FOOTPRINT_TO_S_C 8 97 IEEE754MSBSingle 4 degree At the footprint center (FOOTPRINT_LATITUDE, FOOTPRINT_LONGITUDE) the spacecraft azimuth measured positive toward the east from local north. POLARIZATION 9 101 ASCII_String 2 Horizontal transmitted and horizontal received ('HH') or vertical transmitted and vertical received ('VV'). 5 2 1 0 103 2 SPARE 1 1 UnsignedByte 1 Spare. ALONG_TRACK_FOOTPRINT_SIZE 10 105 IEEE754MSBSingle 4 km The along-track dimension of the Venus surface area described by this data record (nominally 9 C-BIDR image lines, or 2.025 km). CROSS_TRACK_FOOTPRINT_SIZE 11 109 IEEE754MSBSingle 4 km The across-track dimension of the Venus surface area described by this data record. MID_RANGE_POINT_LATITUDE 12 113 IEEE754MSBSingle 4 degree The latitude of the Mid-Range Point for the associated burst. MID_RANGE_POINT_LONGITUDE 13 117 IEEE754MSBSingle 4 degree The longitude of the Mid-Range Point for the associated burst. MID_RANGE_POINT_INCIDENCE_ANGLE 14 121 IEEE754MSBSingle 4 degree The incidence angle at the Mid-Range Point for the associated burst. MID_RANGE_POINT_C1_COORDINATE 15 125 UnsignedMSB4 4 The C1 coordinate at the Mid-Range Point for the associated burst in units of 225 m pixels. MID_RANGE_POINT_C2_COORDINATE 16 129 UnsignedMSB4 4 The C2 coordinate at the Mid-Range Point for the associated burst in units of 225 m pixels. BIP_LATITUDE 17 133 IEEE754MSBSingle 4 degree The latitude at the Boresight Intercept Point for the associated burst (the Boresight Intercept Point is the point on the Venus surface where the HGA boresight would intercept the surface, after accounting for atmospheric refraction and the Magellan-adopted model for topography). BIP_LONGITUDE 18 137 IEEE754MSBSingle 4 degree The longitude at the Boresight Intercept Point for the associated burst. BIP_INCIDENCE_ANGLE 19 141 IEEE754MSBSingle 4 degree The incidence angle at the Boresight Intercept Point for the associated burst. BIP_ELEVATION 20 145 IEEE754MSBSingle 4 km The elevation (above the 6051 km reference surface) at the Boresight Intercept Point for the associated burst. APPARENT_RANGE_S_C_TO_BIP 21 149 IEEE754MSBSingle 4 km The apparent slant range from the spacecraft to the Boresight Intercept Point for the associated burst. NORMALIZING_FACTOR_FOR_PIXELS 22 153 IEEE754MSBSingle 4 The Muhleman Law backscatter coefficient at the Mid-Range Point reported on the CBIDR tape. Note: this value was not computed correctly. LOWEST_INCIDENCE_ANGLE 23 157 IEEE754MSBSingle 4 degree The smallest angle represented by the scattering data array. HIGHEST_INCIDENCE_ANGLE 24 161 IEEE754MSBSingle 4 degree The largest angle represented by the scattering data array. LOWEST_ANGLE_FOR_FIT 25 165 IEEE754MSBSingle 4 Hz The smallest incidence angle for which at least one pixel was found in the block; the smallest incidence angle used in the polynomial fit. HIGHEST_ANGLE_FOR_FIT 26 169 IEEE754MSBSingle 4 degree The largest incidence angle for which at least one pixel was found in the block; the largest incidence angle used in the polynomial fit. LOWEST_VALID_BIN_FOR_ANGLE_FIT 27 173 UnsignedByte 1 The smallest bin number for which data were used in the polynomial fit (0 < LOWEST_VALID_BIN_FOR_ANGLE_FIT < 99). HIGHEST_VALID_BIN_FOR_ANGLE_FIT 28 174 UnsignedByte 1 The largest bin number for which data were used in the polynomial fit (0 < HIGHEST_VALID_BIN_FOR_ANGLE_FIT < 99). NUMBER_OF_ANGLES_IN_IR_BINS 29 175 UnsignedByte 1 The dimension of the array IR_BINS (equal to HIGHEST_VALID_BIN_FOR_ANGLE_FIT - LOWEST_VALID_BIN_FOR_ANGLE_FIT + 1). SIZE_OF_POLYNOMIAL_FIT 30 176 UnsignedByte 1 The number of coefficients in the fitted polynomial; one more than the highest power in the polynomial. CHI_SQUARE_VALUE_FROM_LINEAR_FIT 31 177 IEEE754MSBSingle 4 The residual from the weighted least-square error fit for the polynomial. 6 3 1 0 181 12 COEFFICIENTS_FOR_POLYNOMIAL_FIT 1 1 IEEE754MSBSingle 4 The coefficients for the fitted polynomial to the scattering function, which is expanded about (LOWEST_ANGLE_FOR_FIT + HIGHEST_ANGLE_FOR_FIT)/2. The first coefficient (COEFFICIENTS_FOR_POLYNOMIAL_FIT[0]) is the constant term, the second coefficient (COEFFICIENTS_FOR_POLYNOMIAL_FIT[1]) is the linear term. LOWEST_VALID_INTENSITY_BIN 32 193 UnsignedByte 1 The smallest pixel intensity represented by the pixel intensity histogram (0 < LOWEST_VALID_INTENSITY_BIN < 255). HIGHEST_VALID_INTENSITY_BIN 33 194 UnsignedByte 1 The highest pixel intensity represented by the pixel intensity histogram (0 < HIGHEST_VALID_INTENSITY_BIN < 255). NUMBER_OF_LEVELS_IN_IR_I_COUNT 34 195 UnsignedByte 1 The dimension of array HISTOGRAM_OF_PIXEL_VALUES (NUMBER_OF_LEVELS_IN_IR_I_COUNT = HIGHEST_VALID_INTENSITY_BIN - LOWEST_VALID_INTENSITY_BIN + 1). 7 13 1 0 196 13 SPARE 1 1 UnsignedByte 1 Spare. BACKSCATTER_DATA 8 100 3 0 For up to 100 Angles-at n=ir_nth angles the pixel intensity, number of pixels, and standard deviation of the weighted intensity. The angles are equally spaced from ir_thlo to ir_thhi, inclusive. 209 1200 CUMULATIVE_INTENSITY 1 1 IEEE754MSBSingle 4 The sum of the intensities of all pixels assigned to this incidence angle bin. 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 400 bytes. 999999.0 NUMBER_OF_PIXELS 2 5 UnsignedMSB4 4 The number of pixels assigned to this incidence angle bin. For the PDS4 migration, this field has been padded with a series of 4-byte integers (999999) to set the total field length to 400 bytes. 999999 STANDARD_DEVIATION 3 9 IEEE754MSBSingle 4 The standard deviation of the weighted intensities for this incidence angle bin. 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 400 bytes. 999999.0 9 256 1 0 1409 1024 HISTOGRAM_OF_PIXEL_VALUES 1 1 UnsignedMSB4 4 For up to 256 Intensity Levels, the number of pixels at each of m = NUMBER_OF_LEVELS_IN_IR_I_COUNT intensity levels. For the PDS4 migration, this field has been padded with a series of 4-byte integers (999999) to set the total field length to 1024 bytes. 999999