CCSD3ZF0000100000001NJPL3IF0PDS200000001 = SFDU_LABEL RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 OBJECT = TEXT PUBLICATION_DATE = 1992-02-27 BYTES = 80 NOTE = "Description of the ARCDRLST program supplied with the Magellan ARCDR CD-ROM set" END_OBJECT = TEXT END ARCDRLST A Program to List Magellan Altimetry and Radiometry Composite Data Records Peter G. Ford Center for Space Research Massachusetts Institute of Technology Version 2.2 February 27, 1992 ======================================================================== INTRODUCTION The purpose of this command is to prepare ASCII listings of selected binary data fields in the Magellan Altimetry and Radiometry Composite Data Records. The program is line-oriented, i.e. it prompts the user to enter a set of parameters and then displays the result as lines of ASCII characters on the screen. On an Apple Macintosh, ARCDRLST creates a new window for this purpose, and removes it when it terminates. Within other graphical interfaces, the user must first create a suitable window, and then type the necessary commands into that window to invoke ARCDRLST. ARCDRLST recognizes the four types of ARCDR data file based on the first letter of the file name, 'O', 'E', 'A', or 'R', and their lower-case equivalents (after striping off any device or directory prefixes) OHFnnnnn.v orbit header file for orbit nnnnn, version v, EPFnnnnn.vv ephemeris file for orbit nnnnn, version vv, ADFnnnnn.v altimetry data file for orbit nnnnn, version v, RDFnnnnn.v radiometry data file for orbit nnnnn, version v, Each file contains two sections-a keyword label and a set of one or more data records. ARCDRLST prompts the user to specify which file, label, data fields, and data records are to be extracted. After satisfying the request, it prompts for another combination. The first time a particular prompt message is displayed, it is accompanied by a longer description of the possible replies. On subsequent occasions, the longer form is suppressed, unless the user replies with "?". The following sections explain the ARCDRLST prompts and give examples of output from the four types of ARCDR data file. Note that when a "+" sign is prefixed to the arcdr> response, ARCDRLST displays the contents of the keyword labels, not the data records themselves. The following brief glossary of technical terms may be of help in understanding the data field descriptions: A&R Altimetry and Radiometry dB Decibels, i.e. 10 * log10(gain). deg Angle in degrees. HGA High-Gain (SAR and Radiometry) antenna. J2000 IAU-approved celestial coordinate system. K Temperature in degrees Kelvin. km Kilometers. km-sq Square kilometers. S/C Spacecraft, i.e. Magellan. TDB Ephemeris time (date/time or seconds past J2000). VBF85 IAU-approved (1985) Venus body-fixed coordinate system. ======================================================================== ARCDRLST PROMPTING MESSAGES arcdr> At this point, the user must type one of the following replies. In each case, the response must be terminated with the RETURN key. * the name of an ARCDR data file, with optional device and directory or folder prefixes. The syntax depends on the operating system, and most recognize the concept of a "working directory" within which only the file name need be entered. MacOS disk:folder:folder:name MS-DOS disk:\dir\dir\name.ext UNIX /dir/dir/dir/name VMS node::device:[dir.dir.dir]name.ext;ver For instance, if you have mounted a CD-ROM on VMS logical device "MG_2001:", you might refer to a particular ADF file as "MG_2001:[03610380]ADF00378.4;1", whereas the same file on a UNIX system, mounted on directory "/cdrom", would be specified "/cdrom/03610380/adf00378.4", or mounted on MS- DOS disk "L:" would be "L:\03610380\ADF00378.4", or mounted on an Apple Macintosh as the device named "MG_2001" would be called "MG_2001:03610380:ADF00378.4;1". * an empty line (i.e. a single carriage return) to signify that you want to continue to read the previous ARCDR data file. * "<" followed by the name of a directory (Macintosh: folder) that will be prefixed to subsequent file names. If the directory name is omitted, this will revert to the default directory. i.e. the one that was current when ARCDRLST was invoked. On a Macintosh, this will be the folder that contains the ARCDRLST application itself. * ">" followed by the name of an output file to receive subsequent listings. If a file of that name already exists, it will be overwritten (except in VMS, where a new version will be created). Any previously open output file will be closed. If the file name is omitted, all listings will be displayed at the console, which is the state when ARCDRLST begins. * "+" followed by the name of an ARCDR data file, to list the label keyword values of the file. (If the file name is omitted, ARCDRLST will list the header keyword values of the most recently specified ARCDR data file) * "!" followed by a system command will execute that command without leaving the ARCDRLST program. This is particularly useful if you have forgotten the name of the data file you want to examine, but don't want to quit ARCDRLST while executing a "DIRECTORY" command (MS-DOS or VMS), or "ls" (UNIX). This command is not implemented on the Apple Macintosh version since the same functionality can be achieved by running ARCDRLST within Multi-Finder (or version 7 of Finder.) * "?", to repeat the initial long introductory message. * CTRL-Z (MS-DOS, VMS) or CTRL-D (UNIX) or COMMAND-. (MacOS) to terminate this program and return control to the operating system. In MS-DOS, you must follow the CTRL-Z with a carriage return. In the other systems, termination is immediate. In MacOS, the ARCDRLST window is removed from the screen. latitude limits> This prompt only appears when ADF or RDF files are specified at the arcdr> prompt. Enter one of the following replies. In each case, the response must be terminated with the RETURN key. * The desired latitude range, in degrees. The two values must be separated by one or more spaces. The order is unimportant. * An empty line (i.e. a single carriage return) to retain the previous range. When ARCDRLST first starts, the limits are set to 90 and -90. * "?" to display the initial long form of the prompting message, * CTRL-Z (MS-DOS, VMS) or CTRL-D (UNIX) or COMMAND-. (MacOS) to terminate this program and return control to the operating system. In MS-DOS, you must follow the CTRL-Z with a carriage return. In the other systems, termination is immediate. In MacOS, the ARCDRLST window is removed from the screen. data codes> This prompt only appears when ADF or RDF files are specified at the arcdr> prompt. Enter one of the following replies. In each case, the response must be terminated with the RETURN key. * The code numbers of the data fields you wish to extract. The ADF codes are shown in table 1, and the RDF codes in table 3, below. * "?" for a list of available code numbers and fields, simi- lar to tables 1 and 3. * "echo" (ADF only)--print the 302 altimeter echo profile ele- ments and the corresponding values of the model template that best approximates them. * "prof" (ADF only)--draw a graph of 50 elements of the alti- meter echo profile and of the corresponding values of the model template that best approximates them. * "rsprof" (ADF only)--same function as prof, but displays the range-sharpened profile and template. * An empty line (i.e. a single carriage return) to use the same codes as last time. ARCDRLST begins with no code table, and clears the table whenever the user switches from ADF to RDF files. Entering an empty line when there is no code table defined causes ARCDRLST to return to the arcdr> prompt. * CTRL-Z (MS-DOS and VMS) or CTRL-D (UNIX) or COMMAND-. (MacOS) to terminate this program and return control to the operating system. In MS-DOS, you must follow the CTRL-Z with a carriage return. In the other systems, termination is immediate. In MacOS, the ARCDRLST window is removed from the screen. Once the codes have been accepted, ARCDRLST will begin to read the input file. If output is directed to the console, the program will fill the screen and then prompt the user to either hit the RETURN key to view the next full screen, or enter any other character, followed by a carriage return, to terminate the output. ARCDRLST then closes the input file and displays the arcdr> prompt. ======================================================================== ORBIT HEADER FILES OHF Label keywords PRODUCT_FILE_NAME= 'OHFnnnnn.v', the external file name of this OHF. 'nnnn' is a 5-digit orbit number and 'v' a decimal version number. For test OHF files, 'v' consists of the letter 'T' followed by a decimal version number. PRODUCT_TYPE= The character string 'ORBIT_HEADER_RECORD'. MISSION_ID= The single character '4'. MISSION_NAME= The character string 'MAGELLAN'. SPACECRAFT_ID= For real data, the 2-digit number '18'. For simulated data, the number '28'. SPACECRAFT_NAME= The character string 'MAGELLAN'. PROCESS_TIME= The local EST or EDT time at which the Orbit Header Record File was created by the MIT A&R processing system. ORBIT_NUMBER= A 5-digit number, denoting the Magellan orbit number of this and the following three data files. HARDWARE_VERSION_ID= A 2-digit number, 'nn', identifying the hardware version number of the MIT A&R data processing system used to create this file or volume. SOFTWARE_VERSION_ID= A 2-digit number, 'nn', identifying the software version number of the MIT A&R data processing system used to create this file or volume. DATA_FORMAT_TYPE= Either 'VAX' or 'IEEE', depending on the format in which binary fields are represented in the orbit header record. For all published ARCDR products, this will be 'VAX'. UPLOAD_ID= 6 characters 'ABBBBC', where 'A' is the mission phase, 'BBBB' is the upload number within each phase, and 'C' is a revision indicator in the range A-Z. Example arcdr> +ohf03713.1 PRODUCT_FILE_NAME=OHF03713.1 PRODUCT_TYPE=ORBIT_HEADER_RECORD MISSION_ID=4 MISSION_NAME=MAGELLAN SPACECRAFT_ID=18 SPACECRAFT_NAME=MAGELLAN PROCESS_TIME=1992-01-24T18:45:20.000 ORBIT_NUMBER=03713 HARDWARE_VERSION_ID=01 SOFTWARE_VERSION_ID=02 DATA_FORMAT_TYPE=VAX UPLOAD_ID=M1340N OHF Data Record Each OHF file contains a single data record. When ARCDRLST is asked to display the record, it lists the value of each field. In the following descriptions, the italicized field names correspond to C language structure elements defined in the 'ARCDR.H' file located in the SOFTWARE directory of each ARCDR CD-ROM disk. oh_norbit The Magellan orbit number-orbits begins at apoapsis. This number is copied from the orbit header file of an ALT-EDR tape. oh_nalt Number of Altimetry Data Records-the number of footprint records in this orbit's altimetry data file. oh_nrad Number of Radiometry Data Records-the number of burst records in this orbit's radiometry data file. oh_alt_start First Altimetry Footprint Time (SCET)-the S/C ephemeris time (seconds of TDB since J2000) that represents the first altimeter footprint of this orbit. It is equal to the ar_scet value in the first record of this orbit's altimetry data file. oh_alt_end Last Altimetry Footprint Time (SCET)-the S/C ephemeris time (seconds of TDB since J2000) that represents the last altimeter foot-print of this orbit. It is equal to the ar_scet value in the last record of this orbit's altimetry data file. oh_rad_start First Radiometer Footprint Time (SCET)-the S/C ephemeris time (seconds of TDB since J2000) of the first radiometer measurement of this orbit. It is equal to the rr_scet value in the first record of this orbit's radiometry data file. oh_rad_end Last Radiometer Footprint Time (SCET)-the S/C ephemeris time (seconds of TDB since J2000) of the last radiometer measurement of this orbit. It is equal to the rr_scet value in the last record of this orbit's radiometry data file. oh_avg.scet Periapsis Time (SCET)-the periapsis time (seconds of TDB since J2000) of the predicted orbit, i.e. the estimated orbit ellipse that was used to generate up-link radar commands. oh_avg.sma Semi-Major Axis (km)-the semi-major axis of the predicted orbit. oh_avg.ecc Eccentricity-the eccentricity of the predicted orbit. oh_avg.incl Inclination (deg)-the inclination of the predicted orbit with respect to the xy-plane of the J2000 coordinate system. oh_avg.long Longitude of Ascending Node (deg)-the angle in the xy- plane of the J2000 coordinate system to the ascending node of the predicted orbit. oh_avg.arg Argument of Periapsis (deg)-the angle in the plane of the predicted orbit from the ascending node in the xy- plane of the J2000 coordinate system to the periapsis. Example arcdr> ohf03713.1 Orbit Number = 3713 Altimetry Footprint Count = 0 Radiometry Burst Count = 1252 Altimetry Start Time (ET) = 0.000 (N/A) Altimetry End Time (ET) = 0.000 (N/A) Radiometry Start Time (ET) = -254155073.336 (1991-12-12T21:22:06.664) Radiometry End Time (ET) = -254153657.122 (1991-12-12T21:45:42.878) Periapsis Time (ET) = -254155261.647 (1991-12-12T21:18:58.353) Semi-Major Axis (km) = 10424.347402 Eccentricity of Orbit = .394047614192 Orbit Inclination (deg) = 96.3691794715 Long. of Asc. Node (deg) = 300.801398669 Arg. of Periapsis (deg) = 149.479678617 ======================================================================== EPHEMERIS FILES EPF Label Keywords EPF label keywords are defined in the following document distributed by the JPL Navigation Ancillary Information Facility (NAIF): * SFOC-2-DPS-CDB-Ephemeris, NAIF Ephemeris File, JPL Navigation Ancillary Information Facility, July 15, 1988. Example arcdr> +epf03713.01 DATA_OBJECT_TYPE=EPHEMERIS PRODUCT_VERSION_TYPE=ACTUAL DATA_SET_NAME=MGN04424.TSP MISSION_ID=4 MISSION_NAME=MAGELLAN SPACECRAFT_NAME=MAGELLAN SPACECRAFT_ID=18 PROCESS_TIME=1992-01-06T12:35:39.000 VERSION_ID=01 UPLOAD_ID=M1340N ORBIT_NUMBER=03713 OBJECT=ORBIT_TIME_RANGE_GROUP TIME_RANGE_NUMBER=1 ORBIT_START_TIME=1991-12-12T20:39:52.133 ORBIT_STOP_TIME=1991-12-12T23:55:24.133 END_OBJECT=ORBIT_TIME_RANGE_GROUP OBJECT=MAPPING_TIME_RANGE_GROUP TIME_RANGE_NUMBER=1 MAPPING_START_TIME=1991-12-12T21:21:12.133 MAPPING_STOP_TIME=1991-12-12T21:44:47.200 END_OBJECT=MAPPING_TIME_RANGE_GROUP EFFECTIVE_TIME=1992-01-06T12:35:39.000 NAV_UNIQUE_ID="ID = M1345G12 " EPF Data File The data in EPF files are intended to be read by the Fortran SPICELIB subroutines distributed by NAIF. These routines expect their input data to be in the form of a binary Fortran direct-access file, so the EPF must be reformatted according to the particular requirements of your local Fortran I/O library. This is performed by instructing ARCDRLST to save the data portion of the EPF to disk, stripping off the header and trailer labels which are not strictly part of the SPICELIB format. Then you must process the saved file through SEFU, a utility program included in the SPICELIB distribution. Example A program needs to know the Magellan spacecraft inertial position and velocity vectors relative to the center of Venus at a particular time during orbit 3713. ARCDRLST would be used as follows: arcdr> epf03713.01 'NAIF/DAF' 2 6 'MGN04424.TSP ' 1 'ID = M1345G12 ' -254158722.88362 -254144644.48362 -18 2 14 1 100 -254157262.01987 75.299352765083 225.89805835485 376.49676394463 527.09546953440 677.69417512417 828.29288071394 978.89158630371 1112.7571023703 1246.6226184368 1380.4881345034 1499.4797043204 1618.4712741375 1737.4628439546 1856.4544137716 1975.4459835887 . . to verify that the data exists, then arcdr> > spka3713.01 arcdr> epf03713.01 to create an ASCII file named spka3713.01. The user then terminates the ARCDRLST session, and runs SEFU to convert spka3713.01 to a binary ephemeris file, e.g. spkb3713.01, which can be read directly into a Fortran 77 program that has been linked with the SPICELIB library. That program might contain the following : Parameter (Venus = -18) Parameter (Magellan = 2) Integer*4 Handle Double Precision State(6), Starg(6), ScET Call ClPool () Call LdPool ('LEAPSECONDS') Call LdPool ('CONSTANTS') Call Spklef ('spkb3713.01', Handle) Call Spkssb (Venus, ScET, 'J2000', State) Call Spkapp (Magellan, ScET, 'J2000', State, 'LT+S', Starg, Lt) The required vector will be returned in the Starg array. ScET is expressed in seconds of ephemeris time (TDB) since J2000, and will therefore be a large negative number. A SPICELIB subroutine UTC2ET will convert a UTC date expressed as an ASCII character string into TDB. For further instruction in SPICELIB, refer to * An Introduction to SPICELIB, Volumes I and II, Navigation Ancillary Information Facility, JPL Planetary Data System, September 3, 1988. ======================================================================== ALTIMETRY DATA FILES ADF Label Keywords PRODUCT_FILE_NAME= 'ADFnnnnn.v', the external file name of this ADF. 'nnnnn' is a 5-digit orbit number and 'v' a decimal version number. For test ADF files, 'v' consists of the letter 'T' followed by a decimal version number. PRODUCT_TYPE= The character string 'ALTIMETRY_FILE'. MISSION_ID= The single character '4'. MISSION_NAME= The character string 'MAGELLAN'. SPACECRAFT_ID= For real data, the 2-digit number '18'. For simulated data, the number '28'. SPACECRAFT_NAME= The character string 'MAGELLAN'. PROCESS_TIME= The local EST or EDT time at which the Altimetry Data File was created by the MIT A&R processing system. ORBIT_NUMBER= A 5-digit number, denoting the Magellan orbit number of this Altimetry Data File. HARDWARE_VERSION_ID= A 2-digit number, 'nn', identifying the hardware version number of the MIT A&R data processing system used to create this file or volume. SOFTWARE_VERSION_ID= A 2-digit number, 'nn', identifying the software version number of the MIT A&R data processing system used to create this file or volume. TEMPLATE_VERSION_NUMBER= A 2-digit number, 'nn', denoting the version number of the altimetry echo templates used to fit the altimetry profiles and generate this file. DATA_FORMAT_TYPE= Either 'VAX' or 'IEEE', depending on the format in which binary fields are represented in the altimetry data records. For all published ARCDR products, this will be 'VAX'. UPLOAD_ID= 6 characters 'ABBBBC', where 'A' is the mission phase, 'BBBB' is the upload number within each phase, and 'C' is a revision indicator in the range A-Z. NAV_UNIQUE_ID= A 32-byte ASCII string supplied by JPL's Navigation Ancillary Information Facility (NAIF) that uniquely characterizes the ephemeris used to determine the spacecraft location. Example arcdr> +adf03212.1 PRODUCT_FILE_NAME=ADF03212.1 PRODUCT_TYPE=ALTIMETRY_FILE MISSION_ID=4 SPACECRAFT_NAME=MAGELLAN SPACECRAFT_ID=18 MISSION_NAME=MAGELLAN PROCESS_TIME=1991-12-17T04:59:28.000 ORBIT_NUMBER=03212 HARDWARE_VERSION_ID=01 SOFTWARE_VERSION_ID=02 TEMPLATE_VERSION_NUMBER=02 DATA_FORMAT_TYPE=VAX UPLOAD_ID=M1277N NAV_UNIQUE_ID="ID = M1278-OCC " ADF Data Records The ADF contains one data record for each altimeter "footprint", i.e. each independent measurement of surface properties. Each record contains many fields, most of which are assigned data code numbers and can be extracted by ARCDRLST. If you reply to the data codes> prompt with a question mark, you will see the following listing: Table 1 - ADF data codes 1 Altimeter Footprint Number 23 Formal Error in Radius (km) 2 ADF Record Flag Field (hex) 24 Formal Error in Slope (deg) 3 ADF Record Flag Field (ASCII) 25 Formal Error in Rho 4 Echo Time (hh:mm:ss, TDB) 26 Sensitivity: Radius vs. Slope 5 Echo Time (hh:mm:ss, TDB) 27 Sensitivity: Slope vs. Rho 6 S/C X-Coordinate (km, J2000) 28 Sensitivity: Rho vs. Radius 7 S/C Y-Coordinate (km, J2000) 29 Sensitivity: Slope vs. Radius 8 S/C Z-Coordinate (km, J2000) 30 Sensitivity: Rho vs. Slope 9 S/C X-Velocity (km/sec, J2000) 31 Sensitivity: Radius vs. Rho 10 S/C Y-Velocity (km/sec, J2000) 32 Ephem Radius Corrn (km) 11 S/C Z-Velocity (km/sec, J2000) 33 Ephem Longitude Corrn (deg, VBF85) 12 Footprint Longitude (deg, VBF85) 34 Ephem Latitude Corrn (deg, VBF85) 13 Footprint Latitude (deg, VBF85) 35 Non-range-sharp Goodness-of-Fit 14 Along-track Footprint Size (km) 36 Range-sharp Goodness-of-Fit 15 Cross-track Footprint Size (km) 37 Multi-peak Corrn applied to ar_rho 16 Rcvr Noise Calibration (km-sq) 38 Radius from Thresh Detector (km) 17 Uncorrected Range to Nadir (km) 39 Signal Quality Indicator (dB) 18 Atmospheric Corrn to Range (km) 40 Profile Scaling Factor (km-sq) 19 Derived Planetary Radius (km) 41 Range-sharp Scaling Factor (km-sq) 20 Derived RMS Surface Slope (deg) 42 Number of non-range-sharp Looks 21 Derived Fresnel Reflectivity 43 Number of range-sharp Looks 22 Rho Diffuse Scatter Corrn Factor 44 Threshold Detector Index Detailed description of fields Code Name Description 1 ar_nfoot The Footprint Number-a signed integer value. The A&R processing program assigns number 0 to the nadir footprint at periapsis. The remaining footprints are located along the S/C 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 nega- tive numbers, post-periapsis footprints will be assigned positive ones. A loss of several con- secutive burst records from the ALT-EDR will result in missing footprint numbers. 2,3 ar_flag Flag fields-see table 2, below. 4,5 ar_scet Altimetry Footprint Time (SCET)-the ephemeris time (seconds of TDB since J2000) at which the S/C 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. 6-8 ar_pos S/C Position Vector (km, J2000)-the S/C posi- tion at ar_scet, relative to the Venus center of mass, expressed in inertial coordinates. 9-11 ar_vel S/C Velocity Vector (km/sec, J2000)-the S/C velocity at ar_scet, relative to the Venus center of mass, expressed in inertial coordi- nates. 12 ar_lon Footprint Longitude (deg, VBF85)-the crust- fixed longitude of the center of the altimeter footprint, in the range of 0 - 360 easterly longitude. Periapsis nadir increases in longi- tude by about 1.48 deg per day (about 0.2 deg per orbit). 13 ar_lat Footprint Latitude (degrees, VBF85)-the crust- fixed latitude of the center of the altimeter footprint, in the range of +90 deg (North Pole) to -90 deg (South Pole). 14 ar_xfoot Along-track Altimetry Footprint Size (km)-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 al- timeter (at this point in the S/C orbit) that is greater than 8 km. 15 ar_yfoot Cross-track Altimetry Footprint Size (km)-the cross-track footprint dimension is determined solely by the radar baud length and the S/C al- titude at this point in the orbit. 16 ar_rcal Receiver Noise Calibration (km-sq)-a measure of the altimeter noise background, obtained from the pulse-compressed range-migrated altimeter profile (ar_rsprof). 17 ar_range Uncorrected range to nadir (km)-the "raw" meas- urement of range-to-surface, obtained from the pulse-compressed range-migrated altimeter pro- file (ar_rsprof). 18 ar_atmos Atmospheric correction to range (km)-the correction to be applied to ar_range to allow for the delay of signals passing through the atmosphere. 19 ar_radius Derived Planetary Radius (km)-the mean Venus radius for this radar footprint, obtained by subtracting (ar_range - ar_atmos) from the length of the ar_pos vector. 20 ar_slope Derived RMS Surface Slope (deg)-the root mean square meter-scale surface slope, averaged over the radar footprint, obtained by fitting the altimeter echo profile (ar_prof) to a suite of theoretical templates derived from the Hagfors scattering model. 21 ar_rho Derived Fresnel Reflectivity-the bulk reflec- tivity of the surface material, averaged over the radar footprint, obtained by fitting the altimeter echo profile (ar_prof) to a suite of theoretical templates derived from the Hagfors scattering model, but ignoring the effect of small-scale surface roughness. 22 ar_rhocor Rho correction factor for Diffuse Scattering-a factor which should be added to ar_rho (but only if AR_RHOC is set in ar_flag), to compen- sate for small-scale surface roughness. 23-25 ar_error Formal errors in Radius, Slope, Rho-the 1-sigma statistical errors expected in the determina- tion of ar_radius, ar_slope, and ar_rho, respectively. 26-31 ar_correl Formal Parameter Sensitivities-the theoretical correlations between ar_radius and ar_slope, between ar_slope and ar_rho, and between ar_rho and ar_radius, respectively. As the profile fitting algorithm is non-linear, the correla- tions may not be symmetric. 32 ar_drad Ephemeris Radius Correction (km)-the correction applied to ar_radius by ephemeris-correction post-processing. 33 ar_dlon Ephemeris Longitude Correction (deg. VBF85)-the correction applied to ar_lon by ephemeris- correction post-processing. 34 ar_dlat Ephemeris Latitude Correction (deg. VBF85)-the correction applied to ar_lat by ephemeris- correction post-processing. 35 ar_fit Non-range-sharpened "goodness of fit"-a measure of the correlation between the observed profile ar_prof and the theoretical template ar_tmpl. 36 ar_rsfit Range-sharpened "goodness of fit" parameter-a measure of the correlation between the observed profile ar_rsprof and the theoretical template ar_rstmpl. 37 ar_rhofact Multi-peak correction applied to ar_rho-the original ar_rho value has been multiplied by a factor (1+ar_rhofact) to allow for multi-peaked echoes. This field is unused unless the AR_RAD2 flag is set in ar_flag. 38 ar_radius2 Radius from Threshold Detector (km)-the plane- tary radius derived from threshold detection of the signal in ar_rsprof. 39 ar_sqi Signal Quality Indicator (dB)-the ratio between the sum of the 10 range bins following the threshold range bin and the sum of the 10 range bins preceding the threshold bin. 40 ar_scale Scaling factors for ar_tmpl and ar_prof-the conversion factor that multiplies the integer array elements of ar_tmpl and ar_prof to yield their physical values, expressed as equivalent radar cross-sections in units of km-sq. 41 ar_rsscale Scaling factors for ar_rstmpl and ar_rsprof-the conversion factor that multiplies the integer array elements ar_rstmpl and ar_rsprof to yield their physical values, expressed as specific radar cross-sections in units of km-sq. 42 ar_looks Number of non-range-sharpened looks-the number of statistically independent measurements of echo profile that were summed to produce the profile ar_prof. 43 ar_rslooks Number of equivalent looks-the number of sta- tistically independent measurements of echo profile that were summed to produce the range- sharpened profile ar_rsprof. 44 ar_thresh Threshold Detector Index-the index in ar_rsprof at which the threshold detector has located the rising signal. Example arcdr> +adf03212.1 latitude limits> latitude range: 90 to -90 data codes> 1 4 12 13 19 20 21 ADF file: adf03212.1 norb foot echo-time lon lat radius slope rho 3212 210 1991-10-05T20:31:14.467 180.257 -5.502 6052.368 0.600 0.1081 3212 211 1991-10-05T20:31:15.354 180.262 -5.568 6052.384 1.318 0.0989 3212 212 1991-10-05T20:31:16.244 180.267 -5.635 6052.387 2.064 0.0840 3212 213 1991-10-05T20:31:17.135 180.273 -5.701 6052.429 0.810 0.0908 3212 214 1991-10-05T20:31:18.028 180.278 -5.768 6052.429 1.771 0.1020 3212 215 1991-10-05T20:31:18.923 180.284 -5.835 6052.456 0.927 0.1094 . . Table 2 - ADF Record Flags AR_FIT Record contains footprint values that have been fitted in the altimetry processing phase. AR_EPHC Geometry values have been corrected for ephemeris errors. AR_RHOC Reflectivity correction ar_rhocor has been determined from SAR backscatter values. AR_RS2 Range-sharpened values have passed the 2nd-order template fitting criteria. AR_NRS2 Non-range-sharpened values have passed the 2nd-order template fitting criteria. AR_BAD Ignore this record entirely. AR_RBAD Ignore the range-sharpened profile ar_rsprof[] and the associated ar_radius value. AR_CBAD Ignore the non-range-sharpened profile ar_prof[] and the associated ar_slope and ar_rho values. AR_TMARK Temporary ar_radius flag. AR_CMARK Temporary ar_slope flag. AR_FMARK Temporary ar_rho flag. AR_HAGFORS ar_slope and its errors and correlations are expressed as Hagfors' C parameter instead of degrees of RMS slope. This flag will not be set in any standard ARCDR products. It is solely used during MIT processing. AR_BADALTA The altimetry antenna was pointed more than 3 deg from its expected location as given by the nominal look-angle profile. ar_rho values are probably inaccurate. AR_SLOPEBAD Ignore the ar_slope value and the corresponding ar_prof array. AR_RHOBAD Ignore the ar_rho value. AR_RAD2 This record was created under software version 2 or higher, in which the altimetry data fields ar_rhofact, ar_radius2, ar_sqi, and ar_thresh are significant. AR_RAD2BAD Ignore the ar_radius2 value. AR_AMBIG The value of ar_radius has been shifted by a multiple of the range ambiguity (10.02 km). AR_AMBIG2 The value of ar_radius2 has been shifted by a multiple of the range ambiguity (10.02 km). Unaccessed ADF Fields The ADF data record contains several fields that are ignored by ARCDRLST. They can be accessed via the read_adf_rec subroutine in the MGMLIB library that is included in the SOFTWARE directory of each ARCDR CD-ROM. ar_flag2 Unused flag fields. ar_partl An array of 6 partial derivatives of ar_lon, ar_lat, and ar_radius with respect to ar_pos and ar_vel-the partial derivatives of the footprint coordinates with respect to changes in the S/C position and velocity. ar_nprof0 The index (0-301) of the element in ar_prof that corresponds to the first element in ar_tmpl. ar_prof Non-range-sharpened Echo Profile-a 302-element array containing the power vs. time echo profile, sampled at half-baud (0.21 Msec) intervals, assembled from up to 16 frequency components, without shifting their relative delays (see ar_rsprof, below). This profile yields the best estimate of the time dispersion of the echo, and hence of ar_slope and ar_rho. ar_tmpl Best non-range-sharpened Model Template-a 50-element array containing the theoretical echo profile, at half- baud (0.21 Msec) intervals, that best approximates the peak of the ar_prof array. The optimal fit is made by matching ar_tmpl[i] with ar_prof[i+ar_nprof0], i = 0,49. ar_rsnprof0 The index (0-301) of the element in ar_rsprof that corresponds to the first element in ar_rstmpl. ar_rsprof Range-sharpened Echo Profile-a 302-element array containing the power vs. time echo profile, at half-baud (0.21 Msec) intervals, assembled from up to 16 frequency components, each range-migrated so as to align their leading edges. This profile yields the best estimate of the two-way echo time, and hence of ar_radius. ar_rstmpl Best range-sharpened Model Template-a 50-element array containing the theoretical echo profile, at half-baud (0.21 Msec) intervals, that best approximates the peak of the ar_rsprof array. The optimal fit is made by matching ar_rstmpl[i] with ar_rsprof[i+ar_rsnprof0], i = 0,49. ar_spare Unused-reserved for up to 7 future data fields. Echo Profile Values Individual altimeter echo profile values may be listed by replying echo to the data codes> prompt. The output consists of 302 lines of 7 columns, one line per delay index. + Orbit number (from the file label) + Footprint number, ar_nfoot. + Delay index (in units of 0.5/bandwidth = 0.221 microsec). + Non-range-sharpened echo cross section, ar_prof (km-sq). + Best matching non-range-sharpened template, ar_tmpl (km-sq). + Range-sharpened echo cross section, ar_rsprof (km-sq). + Best matching range-sharpened template, ar_rstmpl (km-sq). Only 50 of the template values will be non-zero, since the remainder are not written to the ADF records. As the spacecraft altitude changes, the peak echo will move through the 302 delay indices, which are cyclical-i.e. index 0 immediately follows index 301. Example arcdr> adf03212.1 latitude limits> latitude range: 90 to -90 data codes> prof ADF file: adf03212.1 norb foot del prof tmpl rsprof rstmpl 3212 215 203 39.83 199.14 316.54 557.58 3212 215 204 677.06 1553.25 2321.27 2389.62 3212 215 205 4022.53 4699.59 8493.74 5376.65 3212 215 206 8881.43 7845.92 13400.07 9120.39 3212 215 207 10116.07 9996.58 10234.70 7129.04 3212 215 208 7168.87 6730.77 4484.27 3664.09 3212 215 209 4022.53 4500.45 2321.27 2110.83 3212 215 210 2787.89 3305.64 1529.93 1433.77 3212 215 211 2270.14 2548.93 738.59 1075.33 3212 215 212 1792.22 2071.01 633.07 836.37 3212 215 213 1752.39 1712.56 791.34 677.06 . . Echo Profile Graphs Altimeter echo profiles may be displayed by replying prof or rsprof to the data codes> prompt. They display the stored tem- plate; values and their overlapping profiles, and are therefore restricted to 50 delay values, typically with 10 before the rising edge and 40 after it. The following characters are used to display the echo: o profile and template match - profile less than template + profile greater than template Example arcdr> adf03212.1 latitude limits> latitude range: 90 to -90 data codes> prof ADF file: adf03212.1 | | o + o | +o | +o | +o Orbit Number | oo 3212 + oo+ Footprint | ooo 215 | ooo Latitude | ooo -5.835 | ooo Longitude + -ooo 180.284 | -ooo- Radius | ooooo 6052.456 | ooooo- R.M.S. Slope | oooooo 0.927 + oooooo- Reflectivity | ooooooo- 0.1094 | -oooooooooo+ ++ NRS Scale | -ooooooooooooo+++ 10155.9 | oooooooooooooooooooo--oo+++ ++ |----+----|----+----|----+----|----+----|----+----| Echo Delay: 0 10 20 30 40 50 ======================================================================== RADIOMETRY DATA FILES RDF Label Keywords PRODUCT_FILE_NAME= 'RDFnnnnn.v', the external file name of this RDF. 'nnnn' is a 5-digit orbit number and 'v' is a decimal version number. For test RDF files, 'v' consists of the letter 'T' followed by a decimal version number. PRODUCT_TYPE= The character string 'RADIOMETRY_FILE'. MISSION_ID= The single character '4'. MISSION_NAME= The character string 'MAGELLAN'. SPACECRAFT_ID= For real data, the 2-digit number '18'. For simulated data, the number '28'. SPACECRAFT_NAME= The character string 'MAGELLAN'. PROCESS_TIME= The local EST or EDT time at which the Radiometry Data File was created by the MIT A&R processing system. ORBIT_NUMBER= A 5-digit number, denoting the Magellan orbit number of this Radiometry Data File. HARDWARE_VERSION_ID= A 2-digit number, 'nn', identifying the hardware version number of the MIT A&R data processing system used to create this file or volume. SOFTWARE_VERSION_ID= A 2-digit number, 'nn', identifying the software version number of the MIT A&R data processing system used to create this file or volume. DATA_FORMAT_TYPE= Either 'VAX' or 'IEEE', depending on the format in which binary fields are represented in the altimetry data records. For all published ARCDR products, this will be 'VAX'. UPLOAD_ID= 6 characters 'ABBBBC', where 'A' is the mission phase, 'BBBB' is the upload number within each phase, and 'C' is a revision indicator in the range A-Z. NAV_UNIQUE_ID= A 32-byte ASCII string supplied by JPL's Navigation Ancillary Information Facility (NAIF) that uniquely characterizes the ephemeris used to determine the spacecraft location. Example arcdr> +rdf03716.1 PRODUCT_FILE_NAME=RDF03716.1 PRODUCT_TYPE=RADIOMETRY_FILE MISSION_ID=4 SPACECRAFT_NAME=MAGELLAN SPACECRAFT_ID=18 MISSION_NAME=MAGELLAN PROCESS_TIME=1992-01-24T18:51:21.000 ORBIT_NUMBER=03716 HARDWARE_VERSION_ID=01 SOFTWARE_VERSION_ID=02 DATA_FORMAT_TYPE=VAX UPLOAD_ID=M1340N NAV_UNIQUE_ID="ID = M1346G12 " RDF Data Records The RDF contains one data record for each radiometer "footprint", i.e. each independent measurement of surface properties. Each record contains many fields, some of which are assigned data code numbers and can be listed by ARCDRLST. If you reply to the data codes> prompt with a question mark, you will see the following listing: Table 3 - RDF data codes 1 Radiometer Burst Number 17 SAR #2 Footprint Diameter (km) 2 RDF Record Flag Field (hex) 18 SAR #1 Average Backscatter (dB) 3 RDF Record Flag Field (ASCII) 19 SAR #2 Average Backscatter (dB) 4 Burst Time (hh:mm:ss, TDB) 20 Incidence Angle (deg) 5 Burst Time (sec, TDB) 21 Brightness Temperature (K) 6 S/C X-Coordinate (km, J2000) 22 Average Planetary Radius (km) 7 S/C Y-Coordinate (km, J2000) 23 Antenna System Temperature (K) 8 S/C Z-Coordinate (km, J2000) 24 Assumed Sky Temperature (K) 9 S/C X-Velocity (km/sec, J2000) 25 Receiver System Temperature (K) 10 S/C Y-Velocity (km/sec, J2000) 26 Physical Surface Temperature (K) 11 S/C Z-Velocity (km/sec, J2000) 27 Surface Emissivity 12 Footprint Longitude (deg, VBF85) 28 Partial of Emissivity wrt Radius 13 Footprint Latitude (deg, VBF85) 29 Physical Surface Temperature (K) 14 Along Track Footprint Size (km) 30 Raw Antenna Signal 15 Cross Track Footprint Size (km) 31 Raw Load Signal 16 SAR #1 Footprint Diameter (km) 32 Altimeter Coarse Range Detailed description of fields Code Name Description 1 rr_burst Burst Number-the number assigned to the burst header that contains the radiometer measurement referenced by this record. 2,3 rr_flag Flag fields-see table 4, below. 4,5 rr_scet S/C Radiometry Epoch (SCET)-the ephemeris time (seconds of TDB since J2000) at which the ra- diometry measurement was made. 6-8 rr_pos S/C Position Vector (km, J2000)-the S/C posi- tion at rr_scet, relative to the Venus center of mass, expressed in inertial coordinates. 9-11 rr_vel S/C Velocity Vector (km/sec, J2000)-the S/C velocity at rr_scet, relative to the Venus center of mass, expressed in inertial coordi- nates. 12 rr_lon Footprint Longitude (deg, VBF85)-the crust- fixed longitude, at rr_scet, of the intersec- tion of the HGA boresight and the planetary surface (a sphere of radius rr_radius). If the RR_CAL flag is set in rr_flag, rr_lon is ex- pressed in inertial (J2000) coordinates. 13 rr_lat Footprint Latitude (deg, VBF85)-the crust-fixed latitude, at rr_scet, of the intersection of the HGA boresight and the planetary surface (a sphere of radius rr_radius). If the RR_CAL flag is set in rr_flag, rr_lon is expressed in iner- tial (J2000) coordinates. 14 rr_xfoot Along Track Radiometry Footprint Size (km)-the along track dimension of the intersection of the HGA (3dB attenuation) cone with a sphere of radius rr_radius. 15 rr_yfoot Cross Track Radiometry Footprint Size (km)-the cross track dimension of the intersection of the HGA (3dB attenuation) cone with a sphere of radius rr_radius. 16,17 rr_sfoot SAR Footprint Diameter (km)-the approximate di- mension of the surface areas represented by the pair of SAR backscatter values, rr_sar. 18,19 rr_sar SAR Average Backscatter Values (dB)-a pair of running averages of SAR image pixel values, rr_sar[0] taken from pixels lying westward of the antenna boresight, and rr_sar[1] taken from pixels lying to the east of it. 20 rr_angle Incidence Angle (deg)-the angle between the lo- cal vertical and the S/C direction, measured at the center of the radiometer footprint at rr_scet. 21 rr_bright Brightness Temperature (K)-the planet bright- ness temperature, derived from rr_anttemp after correcting for antenna efficiency and side-lobe gain. 22 rr_radius Average Planetary Radius (km)-the planetary ra- dius of the radiometer footprint, used to com- pute rr_lon and rr_lat, and also rr_surftemp and atmospheric corrections to rr_emiss. 23 rr_anttemp System Temperature of the HGA (K)-the rr_rcvrtemp value compensated for cable noise and losses. 24 rr_skytemp Sky Temperature (K)-the temperature assumed for the dominant portion of "sky" reflected in the radiometer footprint, including atmospheric ab- sorption and emission. 25 rr_rcvrtemp System Temperature of the receiver input (K)- the difference between rr_antval and rr_loadval, converted to equivalent noise tem- perature, and compensated for receiver gain and temperature. 36 rr_surftemp Radiometric Emission Temperature (K)-the emis- sion temperature of the planetary surface covered by the radiometer footprint, derived by correcting rr_bright for atmospheric emission and absorption. 27 rr_emiss Surface Emissivity-defined by the following ex- pression: rr_surftemp - rr_skytemp ------------------------ rr_phystemp - rr_skytemp 28 rr_dedrad Partial derivative of rr_emiss with respect to rr_radius-obtained by numerical differentia- tion. This may be used to correct the rr_emiss value when a more accurate value of rr_radius becomes available. 29 rr_phystemp Physical Surface Temperature (K)-the tempera- ture of the atmosphere in contact with the sur- face at a radius of rr_radius. 30 rr_antval Radiometer Antenna Value-the raw radiometer reading when detecting a signal from the HGA, corrected for altimeter leakage. 31 rr_loadval Radiometer Load Value-the raw radiometer read- ing when detecting a signal from the load, corrected for altimeter leakage. 32 rr_acr Altimeter Coarse Resolution-the coarse range index taken from the burst header during the burst in which the HGA signal was measured. Example arcdr> rdf03716.1 latitude limits> latitude range: 90 to -90 data codes> 1 3 5 12 13 27 RDF file: rdf03716.1 norb burst flags burst-time lon lat emiss 3716 -1043 0x0000c00c -254120714.943 281.590 57.381 0.894 3716 -1042 0x0000c00c -254120712.943 281.592 57.254 0.898 3716 -1041 0x0000c000 -254120710.054 281.595 57.069 0.888 3716 -1040 0x0000c000 -254120709.008 281.596 57.003 0.892 3716 -1039 0x0000c000 -254120707.962 281.597 56.936 0.889 3716 -1038 0x0000c000 -254120706.918 281.598 56.869 0.893 3716 -1037 0x0000c000 -254120705.874 281.599 56.802 0.890 3716 -1036 0x0000c000 -254120704.831 281.600 56.735 0.892 3716 -1035 0x0000c000 -254120703.788 281.601 56.669 0.886 3716 -1034 0x0000c000 -254120702.817 281.602 56.606 0.898 3716 -1033 0x0000c000 -254120701.916 281.603 56.549 0.898 . . Table 4 - RDF Record Flags RR_GEOC Geometry values have been corrected for ephemeris errors. RR_RADC rr_radius value has been corrected by ADF radius values. Otherwise, its value is taken from a less-precise topography model. RR_NOS1 rr_sar[0] value missing. RR_NOS2 rr_sar[1] value missing. RR_BAD The rr_rec fields rr_bright through rr_emiss should be ignored. RR_CAL The spacecraft is operating in "radiometric calibration" mode, in which the HGA boresight is pointed away from the planet. The rr_lat and rr_lon fields contain the HGA boresight latitude and longitude in the inertial (J2000) coordinate system, not in VBF85. RR_NRAD The rr_radius value could not be estimated from the topography model. RR_RAD2 This record was created under software version 2 or higher, in which data fields rr_dedrad through rr_acr are significant. Unaccessed ADF Fields The RDF data record contains several fields that are ignored by ARCDRLST. They can be accessed via the read_rdf_rec subroutine in the MGMLIB library that is included in the SOFTWARE directory of each ARCDR CD-ROM. rr_flag2 Additional flag fields (unused). rr_partl A 6-element array of partial derivatives of rr_lat, rr_lon, and rr_radius with respect to rr_pos and rr_vel.. rr_askip Altimeter Skip Factors-from the bursts in which the antenna and load signals were measured. rr_again Altimeter Gain Factors-from the bursts in which the antenna and load signals were measured. rr_spare Unused-reserved for up to 4 future data fields. ========================================================================