urn:nasa:pds:magellan_arcdr:data_altimetry:adf03565_1 1.0 1.20.0.0 Product_Observational 2024-02-03 1.0 Initial PDS4 version 1991-11-22T19:11:10Z 1991-11-22T19:27:15Z Magellan Mission urn:nasa:pds:context:investigation:mission.magellan data_to_investigation Magellan Host urn:nasa:pds:context:instrument_host:spacecraft.mgn is_instrument_host Radar System for Magellan Instrument urn:nasa:pds:context:instrument:mgn.rdrs is_instrument Venus Planet urn:nasa:pds:context:target:planet.venus data_to_target ARCDR 1 2 3565 Mapping Cycle 2 mg_2014 1991-11-22T19:11:10Z 1991-11-22T19:27:15Z Center -48.7605 -85.3233 255.9134 358.0900 adf03565_1.dat 1992-05-12T00:37:53.000Z Created with ARCDR processing software version 02 Altimetry_File Altimetry_File 0 243 This file contains binary records describing, in time order, each altimeter footprint measured during an orbit of the Magellan radar mapper. 31 10 1032 SFDU 1 1 ASCII_String 20 The SFDU identifies the label and length of the Standard Format Data Unit (SFDU). Footprint_Number 2 21 SignedLSB4 4 The footprint_number element provides a signed integer value. The altimetry and radiometry processing program assigns footprint 0 to that observed at nadir at periapsis. The remaining footprints are located along the spacecraft nadir track, with a separation that depends on the Doppler resolution of the altimeter at the epoch at which that footprint is observed. Pre-periapsis footprints will be assigned negative numbers, post-periapsis footprints will be assigned positive ones. A loss of several consecutive burst records from the ALT-EDR will result in missing footprint numbers. Flag 3 25 UnsignedLSB4 4 The Flag element identifies processing flag fields. Each bit in the Flag element has its own meaning and can be combined bitwise. See the ARCDR SIS Table 5-7 for a list of values and their meanings. Flag2 4 29 UnsignedLSB4 4 Additional flag fields (unused). Footprint_TDB_Time 5 33 IEEE754LSBDouble 8 The altimetry footprint_tdb_time element provides the ephemeris time at which the spacecraft passed directly over the center of the footprint. As each footprint is composed of data collected from several altimeter bursts, this epoch doesn't necessarily coincide with a particular burst. 1 3 1 0 41 24 Spacecraft_Position_Vector 1 1 IEEE754LSBDouble 8 km The spacecraft_position_vector element provides spacecraft position at altimetry footprint_tdb_time, relative to the Venus center of mass, expressed in inertial coordinates in the J2000 coordinate system. 2 3 1 0 65 24 Spacecraft_Velocity_Vector 1 1 IEEE754LSBDouble 8 km/s The spacecraft_velocity_vector element provides the spacecraft velocity at altimetry footprint_tdb_time, relative to the Venus center of mass, expressed in inertial coordinates in the J2000 coordinate system. Footprint_Longitude 6 89 IEEE754LSBSingle 4 degree The footprint_longitude (VBF85) element provides the crust-fixed longitude of the center of the altimeter footprint, in the range of 0 - 360 easterly longitude. Periapsis nadir increases in longitude by about 1.48 deg per day (about 0.2 deg per orbit). Footprint_Latitude 7 93 IEEE754LSBSingle 4 degree The footprint_latitude (VBF85) element provides the crust-fixed latitude of the center of the altimeter footprint, in the range of -90 (South Pole) to 90 (North Pole). Along_Track_Footprint_Size 8 97 IEEE754LSBSingle 4 km The along_track_footprint_size element provides the along-track dimension of the Venus surface area whose mean radius, RMS slope, and reflectivity are reported in this data record. The along track dimension is chosen to be the smallest multiple of the Doppler resolution of the altimeter (at this point in the spacecraft orbit) that is greater than 8 km. Cross_Track_Footprint_Size 9 101 IEEE754LSBSingle 4 km The cross_track_footprint_size element provides the cross-track footprint dimension determined solely by the radar baud length and the spacecraft altitude at this point in the orbit. Receiver_Noise_Calibration 10 105 IEEE754LSBSingle 4 km**2 The receiver_noise_calibration element provides a measure of the altimeter noise background, obtained from the pulse-compressed altimeter signals by the mgmtac phase of the altimetry and radiometry data reduction program. Uncorrected_Distance_to_Nadir 11 109 IEEE754LSBSingle 4 km The uncorrected_distance_to_nadir element provides the "raw" measurement of range-to-surface, obtained from the pulse-compressed altimeter signals by the MGMTAC phase of the altimetry and radiometry data reduction program. Atmos_Correction_to_Distance 12 113 IEEE754LSBSingle 4 km The atmos_correction_to_distance element provides the correction applied to derived_planetary_radius to allow for the delay of signals passing through the atmosphere, calculated by the MGMOUT phase of the altimetry and radiometry data reduction program. Derived_Planetary_Radius 13 117 IEEE754LSBSingle 4 km The derived_planetary_radius element provides the mean Venus radius for this radar footprint, obtained by subtracting (uncorrected_range_to_nadir - atmospheric_correct_to_range) from the length of the spacecraft_position_vector element. Radar_Derived_Surface_Roughness 14 121 IEEE754LSBSingle 4 degree The radar_derived_surface_roughness element provides the root mean square meter-scale surface slope, averaged over the radar footprint, obtained by fitting the altimeter echo to a suite of theoretical templates derived from the Hagfors scattering model. Derived_Fresnel_Reflectivity 15 125 IEEE754LSBSingle 4 The derived_fresnel_reflectivity element provides the bulk reflectivity of the surface material, averaged over the radar footprint, obtained by fitting the altimeter echo to a suite of theoretical templates derived from the Hagfors scattering model, but ignoring the effect of small-scale surface roughness. Derived_Fresnel_Reflect_Corr 16 129 IEEE754LSBSingle 4 The derived_fresnel_reflect_corr element provides the derived_fresnel_reflectivity correction factor for diffuse scattering which is a factor which must be added to the derived_fresnel_reflectivity (but only if the AR_RHOC flag is set in alt_flag_group), to allow for the effect of small-scale surface roughness. 3 3 1 0 133 12 Formal_Errors 1 1 IEEE754LSBSingle 4 The formal_errors group element provides the 1-sigma statistical errors expected in the determination of the derived_planetary_radius, the radar_derived_surf_roughness, and the derived_fresnel_reflectivity elements, respectively. 4 6 1 0 145 24 Formal_Correlations 1 1 IEEE754LSBSingle 4 The formal_correlations group provides the formal correlations between the derived_planetary_radius and the derived_rms_surface_fresnel_reflect elements, and between the derived_fresnel_reflectivity and the derived_planetary_radius elements, respectively. As the profile fitting algorithm is non-linear, the correlations may not be symmetric. Ephemeris_Radius_Correction 17 169 IEEE754LSBSingle 4 km The ephemeris_radius_correction element provides the correction applied to the length of the spacecraft_position_vector element by the post-fitting MGMORB phase of the altimetry and radiometry reduction program. Ephemeris_Longitude_Correction 18 173 IEEE754LSBSingle 4 degree The ephemeris_longitude_correction (VBF85) element provides the correction applied to the footprint longitude value by the post-fitting MGMORB phase of the altimetry and radiometry reduction program. Ephemeris_Latitude_Correction 19 177 IEEE754LSBSingle 4 degree The ephemeris_latitude_correction (VBF85) element provides the correction applied to the footprint latitude value by the post-fitting MGMORB phase of the altimetry and radiometry reduction program. 5 18 1 0 181 72 Partials_Group 1 1 IEEE754LSBSingle 4 The partials_group of the footprint_longitude, footprint_latitude, and the derived_planetary_radius with respect to the spacecraft_position_vector and spacecraft_velocity_vector elements provides the partial derivatives of the footprint coordinates with respect to changes in the spacecraft position and velocity. Non_Range_Sharp_Fit 20 253 IEEE754LSBSingle 4 The non_range_sharp_fit element provides the value of the 'goodness of fit' measuring the correlation between the observed profile non_range_sharp_echo_prof and the theoretical template best_non_range_sharp_model_tpt elements. Scaling_Factor 21 257 IEEE754LSBSingle 4 km**2 The scaling_factor element provides the conversion factor for the best_non_range_sharp_model_tpt and the non_range_sharp_echo_prof element that multiplies the integer array elements of the best_non_range_sharp_model_tpt and the non_range_sharp_echo_prof to yield their physical values, expressed as equivalent radar cross-sections in units of km**2. Non_Range_Sharp_Looks 22 261 UnsignedLSB4 4 The non_range_sharp_looks element provides the number of statistically independent measurements of echo profile that were summed to produce the value for the profile non_range_sharp_echo_prof element. Non_Range_Prof_Corrs_Index 23 265 UnsignedLSB4 4 The non_range_prof_corrs_index element provides the index of the element in non_range_sharp_echo_prof that corresponds corresponds to the first element in best_non_range_sharp_model_tpt[0]. The indices start at zero. 6 302 1 0 269 302 Non_Range_Sharp_Echo_Prof 1 1 UnsignedByte 1 The non_range_sharp_echo_prof element provides the power vs. time echo profile, at half-baud (0.21 microsecond) intervals, assembled from up to 16 frequency components, without shifting their time origins (see range_sharp_echo_profile element). This profile yields the best estimate of the time dispersion of the echo, and hence the value of the radar_derived_surf_roughness and derived_fresnel_reflectivity element. 7 50 1 0 571 50 Best_Non_Range_Sharp_Model_TPT 1 1 UnsignedByte 1 The best_non_range_sharp_model_tpt provides the theoretical echo profile, at half-baud (0.21 microsecond) intervals, that best approximates the peak of the non_range_sharp_echo_prof array. The optimal fit is made by matching best_non_range_sharp_model_tpt[i] with non_range_sharp_echo_prof[i+non_range_prof_corrs_index], where i is a value from 0 to 49. Range_Sharp_Fit 24 621 IEEE754LSBSingle 4 The range_sharp_fit element provides the parameter that measures the correlation between the observed range_sharp_echo_profile and the theoretical template best_range_sharp_model_tmplt elements. Range_Sharp_Scaling_Factor 25 625 IEEE754LSBSingle 4 km**2 The range_sharp_scaling_factor element provides the conversion factor for the best_range_model_tmplt and the range_sharp_echo_profile element that multiplies the integer array of the best_range_model_tmplt and range_sharp_echo_profile elements to yield their physical values, expressed as specific radar cross-sections in units of km**2. Range_Sharp_Looks 26 629 UnsignedLSB4 4 The range_sharp_looks element provides the number of equivalent looks of statistically independent measurements of echo profile that were summed to produce the values for the range_sharp_echo_profile element. Range_Sharp_Prof_Corrs_Index 27 633 UnsignedLSB4 4 The range_sharp_prof_corrs_index element provides the index of the element in range_sharp_echo_profile that corresponds to the first element in best_range_sharp_model_tmplt[0]. The indices start at zero. 8 302 1 0 637 302 Range_Sharp_Echo_Profile 1 1 UnsignedByte 1 The range_sharp_echo_profile element provides the power vs. time echo profile, at half-baud (0.21 microsecond) intervals, assembled from up to 16 frequency components, each shifted in time so as to align their rising edges. This profile yields the best estimate of the two-way echo time, and hence the value of the derived_planetary_radius element. 9 50 1 0 939 50 Best_Range_Sharp_Model_Tmplt 1 1 UnsignedByte 1 The best_range_sharp_model_tmplt element provides the the theoretical echo profile, at one-baud (0.21 microsecond) intervals, that best approximates the peak of the range_sharp_echo_profile array. The optimal fit is made by matching the best_range_sharp_model_tmplt[i] element with the range_sharp_echo_profile[i+range_sharp_prof_corrs_index] element, where i is a value from 0 to 49. Mult_Peak_Fresnel_Reflect_Corr 28 989 IEEE754LSBSingle 4 The mult_peak_fresnel_reflect_corr element provides the correction factor that has been applied to derived_fresnel_reflectivity to allow for radar echoes possessing more than an single peak. Derived_Planetary_Thresh_Radi 29 993 IEEE754LSBSingle 4 km The derived_planetary_thresh_radi element provides the threshold Venus radius for this radar footprint, obtained from the value of the derived_thresh_detector_index element, after correcting for atmospheric delay. Signal_Quality_Indicator 30 997 IEEE754MSBSingle 4 dB The signal_quality_indicator element provides a measure of the signal-to-noise ratio of the measurement of the derived_thresh_detector_index value. It is the ratio between the sum of the 10 successive values of range_sharp_echo_profile, starting 10 values after the element numbered by the derived_thresh_detector_index element value, to the 10 successive values of range_sharp_echo_profile, starting 20 values before the element numbered by the derived_thresh_detector_index element value. This ratio is expressed in decibels. Derived_Thresh_Detector_Index 31 1001 UnsignedLSB4 4 The derived_thresh_detector_index element provides the element in range_sharp_echo_profile that satisfies the altimeter threshold detection algorithm, representing the distance to the nearest object in this radar footprint in units of 33.2 meters, modulus a 10.02 kilometer altimeter range ambiguity. 10 28 1 0 1005 28 Spare 1 1 UnsignedByte 1 Spare bytes.