CCSD3ZF0000100000001NJPL3IF0PDS200000001 = SFDU_LABEL RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 SPACECRAFT_NAME = MAGELLAN TARGET_NAME = VENUS OBJECT = TEXT PUBLICATION_DATE = 1992-03-20 BYTES = 80 NOTE = "MAGELLAN ARCDR MGMLIB DOCUMENTATION" END_OBJECT = TEXT END MGMLIB(3) Magellan A&R Subroutines MGMLIB(3) NAME read_arcdr, read_adf_rec, read_rdf_rec read_ohf_rec - access ARCDR data files SYNOPSIS #include "mgmlib.h" int read_arcdr(afile, rfile, ntype, type, ndim, nzero, array) char *afile, *rfile; int ntype, type[], ndim, nzero; float array[]; ar_rec *read_adf_rec(afile, nfoot); int write_adf_rec(afile, nfoot, ar); char *afile; int nfoot; ar_rec *ar; rr_rec *read_rdf_rec(rfile, burst); int write_rdf_rec(rfile, burst, rr); char *rfile; int burst; rr_rec *rr; oh_rec *read_oh_rec(ofile); char *ofile; mgm_setexit(proc) void (*proc)(); DESCRIPTION The read_arcdr subroutine reads the afile altimetry data file and the rfile radiometry data file, copying specified data fields to array. The number of distinct data fields is specified by ntype, and the data code of each type is supplied by the elements of the type array. Data codes are defined in the "mgm.h" include file. The output array is treated as a ntypexndim array of floats, i.e. float array[ntype][ndim]. Values are copied into array[n][m] from altimetry and radiometry records such that row n is filled by the data type defined by the n'th element of the type array, and column m is filled from footprint number ar_nfoot+nzero of altimetry records, and burst number rr_burst+nzero of radiometry records. The read_adf_rec and read_rdf_rec functions also read altimetry and radiometry data files, returning pointers to static structures representing, respectively, individual ar_rec or rr_rec data records, selected by their nfoot or burst values. The read_ohf_rec function reads the single binary data record from the file named ofile and returns a pointer to a static oh_rec structure. The write_adf_rec and write_rdf_rec functions update the existing nfoot or burst record, ar or rr, in afile or rfile. A&R mgmlib.man 2.3 Last change: 1/7/92 1 MGMLIB(3) Magellan A&R Subroutines MGMLIB(3) The static structures will be overwritten by subsequent calls to any of the read routines. In all cases, data fields are automati- cally transformed between external and internal binary representa- tions. If the ARCDR data file is unreadable, or if a requested record is missing, the updating routines will return a NULL value. Otherwise, if the file format is incorrect, the mgmerror error rou- tine will be called. The default action taken by mgmerror is to write an error message to the standard error stream stderr, and then call exit(1). This may be overridden by calling mgm_setexit with the name of an error handler, which will be called with a sin- gle character-string argument: the text of the error message. A typical use of this exit routine would be as follows: #include #include "mgmlib.h" static jmp_buf env; void recover(s) char *s; { /* print error message */ fprintf(stderr, "%s\n", s); /* cancel error handling */ mgm_setexit((void (*)()) NULL); /* return to setjmp() command */ longjmp(env, 1); } { ar_rec *ar; ... /* enable error handling */ mgm_setexit(recover); /* define error return */ if (setjmp(env)) { ... /* perform cleanup */ } /* call the mgmlib routine */ if ((ar = read_adf_rec(ifile, nfoot)) == NULL) fprintf(stderr, "missing footprint\n"); /* cancel error handling */ mgm_setexit((void (*)()) NULL); ... } AUTHOR Peter G. Ford, MIT CSR SEE ALSO A&R mgmlib.man 2.3 Last change: 1/7/92 1 MGMLIB(3) Magellan A&R Subroutines MGMLIB(3) MIT-MGN-ARCDR, Magellan Software Interface Specification, Altimetry & Radiometry Composite Data Record Tapes, P. Ford, MIT, Version 1.4, November 8, 1989. intro(2), artovax(3), ar_rec(5), rr_rec(5) DIAGNOSTICS If an error occurs when read_arcdr opens a data file, it returns one of the following integer values: 0 The altimetry and radiometry files were read successfully. 1 Could not open the altimetry file. All altimetry variables in array are set to zero. 2 Could not open the radiometry file. All radiometry vari- ables in array are set to zero. 3 Could not open either the altimetry or the radiometry file. All elements in array are set to zero. When the return value is non-zero, the extern int variable named errno will contain the system error code, as explained in intro(2). The read_adf_rec and read_rdf_rec functions will return NULL values if the file is missing or unreadable, or if the footprint or burst isn't present in the file. The write_adf_rec and write_rdf_rec functions will return a value of 1 if the file is missing or unreadable, or if the footprint or burst isn't present in the file. Otherwise, they return zero. Errors encountered in the contents of the data files cause read_arcdr, read_adf_rec, read_rdf_rec, and read_ohf_rec to call mgmerror and halt after writing one of the following messages: + LIB file: bad PRODUCT_TYPE: text an incorrect PRODUCT_TYPE keyword value was read from the key- word label of file. + LIB file: bad sfdu: text an incorrect SFDU header label was read from file. + LIB file: unknown CPU type: text an incorrect DATA_FORMAT keyword value was read from the keyword label of file. + LIB function: file: unexpected EOF an EOF was encountered while reading data records from file. The EMARKER SFDU was never found. A&R mgmlib.man 2.3 Last change: 1/7/92 1 AR_REC(5) Magellan A&R Data Structure AR_REC(5) NAME ar_rec - ARCDR Altimeter Data Record SYNOPSIS #define AR_FIT 0x0001 /* Values inserted by MGMTAC */ #define AR_EPHC 0x0002 /* Orbital geometry corrected */ #define AR_RHOC 0x0004 /* ar_rhocor computed from C-BIDR */ #define AR_RS2 0x0008 /* Range-sharpened to 2nd order */ #define AR_NRS2 0x0010 /* Non-range-sharpened to 2nd order */ #define AR_BAD 0x0020 /* Ignore this record entirely */ #define AR_RBAD 0x0040 /* Ignore ar_radius and ar_rsprof[] */ #define AR_CBAD 0x0080 /* Ignore ar_slope, ar_rho & ar_prof[] */ #define AR_TMARK 0x0100 /* Temporary ar_radius marker flag */ #define AR_CMARK 0x0200 /* Temporary ar_slope marker flag */ #define AR_FMARK 0x0400 /* Temporary ar_rho marker flag */ #define AR_HAGFORS 0x0800 /* ar_slope is Hagfors's C-parameter */ #define AR_BADALTA 0x1000 /* ALTA offset too large to correct */ #define AR_SLOPEBAD 0x2000 /* Ignore ar_slope and ar_prof[] */ #define AR_RHOBAD 0x4000 /* Ignore ar_rho */ #define AR_RHO2 0x8000 /* ar_radius2 and ar_rhofact are used */ #define AR_RAD2BAD 0x10000 /* ar_radius2 is incorrect */ #define AR_AMBIG 0x20000 /* ar_radius shifted by 10.02km */ #define AR_AMBIG2 0x40000 /* ar_radius2 shifted by 10.02km */ typedef struct { sfdu ar_sfdu; /* SFDU aggregate header label & length */ long ar_nfoot; /* Footprint number */ ulong ar_flag, /* Flag fields */ ar_flag2; /* Flag fields (unused) */ double ar_scet, /* S/C Altimetry Footprint Time (SCET) */ ar_pos[3], /* S/C Position Vector (km, J2000) */ ar_vel[3]; /* S/C Velocity Vector (km sec-1, J2000) */ float ar_lon, /* Footprint Longitude (deg, VBF85) */ ar_lat, /* Footprint Latitude (deg, VBF85) */ ar_xfoot, /* Along-track Footprint Size (km) */ ar_yfoot, /* Cross-track Footprint Size (km) */ ar_rcal, /* Receiver Noise Calibration (km-sq) */ ar_range, /* Uncorrected range to nadir (km) */ ar_atmos, /* Atmospheric correction to range (km) */ ar_radius, /* Derived Planetary Radius (km) */ ar_slope, /* Derived RMS Surface Slope (deg) */ ar_rho, /* Derived Fresnel Reflectivity */ ar_rhocor, /* Rho Diffuse Scattering Correction */ ar_error[3] /* Formal errors in Radius, Slope, Rho */ ar_correl[6],/* Formal correlations in same */ ar_drad, /* Ephemeris Radius Correction (km) */ ar_dlon, /* Longitude Correction (deg. VBF85) */ ar_dlat, /* Latitude Correction (deg. VBF85) */ ar_partl[3][6], /* Partials of rad/lon/lat */ ar_fit, /* Non-range-sharpened goodness of fit */ ar_scale; /* Scaling factors for fit and prof */ ulong ar_looks, /* Number of non-range-sharpened looks */ CTL ar_rec.man 2.3 Last change: 3/20/92 1 AR_REC(5) Magellan A&R Data Structure AR_REC(5) ar_nprof0; /* ar_prof element matching ar_tmpl[0] */ uchar ar_prof[302],/* Non-range-sharpened Echo Profile */ ar_tmpl[50]; /* Best non-range-sharp Model Template */ float ar_rsfit, /* Range-sharpened goodness-of-fit */ ar_rsscale; /* Scaling factors for rsfit and rsprof */ ulong ar_looks, /* Number of range-sharpened looks */ ar_rsnprof0; /* ar_rsprof elem. matching ar_rstmpl[0] */ uchar ar_rsprof[302], /* Range-sharpened Echo Profile */ ar_rstmpl[50]; /* Best range-sharpened Model Template */ float ar_rhofact, /* Multi-peak corrn applied to ar_rho */ ar_radius2, /* Radius from Threshold Detector (km) */ ar_sqi; /* Signal Quality Indicator (dB) */ long ar_thresh, /* Threshold Detector Index */ ar_spare[7]; /* Unused */ } ar_rec; DESCRIPTION ar_sfdu SFDU Label and Length: 'NJPL1I000nnn00001004'. ar_nfoot The Footprint Number-a signed integer value. The A&R pro- cessing program assigns footprint 0 to that observed at nadir 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 negative numbers, post-periapsis foot- prints will be assigned positive ones. A loss of several consecutive burst records from the ALT-EDR will result in missing footprint numbers. ar_flag Flag fields: AR_FIT Record contains footprint values that have been fitted in the A&R mgmtac processing phase. AR_EPHC Geometry values have been corrected for ephemeris errors in the mgmorb phase. AR_RHOC Reflectivity values have been corrected from C-BIDR backscatter values in the mgmgen phase. AR_RS2 Range-sharpened values have passed the 2nd-order template fitting criteria in the mgmtac phase. AR_NRS2 Non-range-sharpened values have passed the 2nd- order template fitting criteria in the mgmtac phase. AR_BAD Ignore this record entirely. AR_RBAD Ignore the range-sharpened profile ar_rsprof[] and CTL ar_rec.man 2.3 Last change: 3/20/92 2 AR_REC(5) Magellan A&R Data Structure AR_REC(5) the associated ar_radius and ar_radius2 values. AR_CBAD Ignore the non-range-sharpened profile ar_prof[] and the associated ar_slope and ar_rho values. AR_TMARK Temporary ar_radius marker flag, used in the mgmdqe phase. AR_CMARK Temporary ar_slope marker flag, used in the mgmdqe phase. AR_FMARK Temporary ar_rho marker flag, used in the mgmdqe phase. AR_HAGFORS The ar_slope parameter, and the value of ar_error[1], represent the value of Hagfors' C parameter, not slope. AR_BADALTA The altimetry antenna boresight was more than 3 degrees away from the location anticipated when the altimetry templates were calculated. The quoted value of ar_rho is therefore probably in error. AR_SLOPEBAD The ar_slope parameter value is suspect, and ar_prof should also be disregarded. AR_RHOBAD The ar_rho value is suspect. AR_RAD2 This record was created under software version 2 or higher, in which the data fields ar_rhofact, ar_radius2, ar_sqi, and ar_thresh are used. AR_RAD2BAD Ignore the ar_radius2 value. AR_AMBIG The value of ar_radius has been shifted by a multi- ple of the range ambiguity, (10.02 km) during the mgmdqe processing phase. AR_AMBIG2 The value of ar_radius2 has been shifted by a mul- tiple of the range ambiguity, (10.02 km) during the mgmdqe processing phase. CTL ar_rec.man 2.3 Last change: 3/20/92 3 AR_REC(5) Magellan A&R Data Structure AR_REC(5) ar_flag2 Additional flag fields (unused). ar_scet Altimetry Footprint Time (SCET)-the ephemeris time 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. ar_pos S/C Position Vector (km, J2000)-the S/C position at ar_scet, relative to the Venus center of mass, expressed in inertial coordinates. ar_vel S/C Velocity Vector (km sec-1, J2000)-the S/C velocity at ar_scet, relative to the Venus center of mass, expressed in inertial coordinates. 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 longitude by about 1.48' per day (about 0.2' per orbit). ar_lat Footprint Latitude (degrees, VBF85)-the crust-fixed lati- tude of the center of the altimeter footprint, in the range of -90' (South Pole) to +90' (North Pole). 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 mul- tiple of the doppler resolution of the altimeter (at this point in the S/C orbit) that is greater than 8 km. 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 altitude at this point in the orbit. ar_rcal Receiver Noise Calibration (km2)-a measure of the altimeter noise background, obtained from the pulse-compressed altim- eter signals by the mgmtac phase of the A&R data reduction program. ar_range Uncorrected range to nadir (km)-the `raw' measurement of range-to-surface, obtained from the pulse-compressed altim- eter signals by the MGMTAC phase of the A&R data reduction program. ar_atmos Atmospheric correction to range (km)-the correction applied CTL ar_rec.man 2.3 Last change: 3/20/92 4 AR_REC(5) Magellan A&R Data Structure AR_REC(5) to ar_radius to allow for the delay of signals passing through the atmosphere, calculated by the MGMOUT phase of the A&R data reduction program. 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. ar_slope Derived RMS Surface Slope (deg)-the root mean square meter-scale surface slope, averaged over the radar foot- print, obtained by fitting the altimeter echo to a suite of theoretical templates derived from the Hagfors scattering model. ar_rho Derived Fresnel Reflectivity-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. 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 allow for the effect of small-scale surface roughness. ar_error Formal errors in Radius, Slope, Rho-the 1-Y statistical errors expected in the determination of ar_radius, ar_slope, and ar_rho, respectively. ar_correl Formal correlations in same-the formal 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 correlations may not be symmetric. ar_drad Ephemeris Radius Correction (km)-the correction applied to the length of the ar_pos vector by the post-fitting MGMORB phase of the A&R reduction program. ar_dlon Ephemeris Longitude Correction (deg. VBF85)-the correction applied to the footprint longitude value by the post- fitting MGMORB phase of the A&R reduction program. ar_dlat Ephemeris Latitude Correction (deg. VBF85)-the correction applied to the footprint latitude value by the post-fitting MGMORB phase of the A&R reduction program. CTL ar_rec.man 2.3 Last change: 3/20/92 5 AR_REC(5) Magellan A&R Data Structure AR_REC(5) ar_partl Partials 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_fit Non-range-sharpened "goodness of fit"-a measure of the correlation between the observed profile ar_prof and the theoretical template ar_tmpl. 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^2. ar_looks Number of non-range-sharpened looks-the number of statisti- cally independent measurements of echo profile that were summed to produce the profile ar_prof. ar_nprof0 The index of the element in ar_prof that corresponds to the first element in ar_tmpl[0]. The indices start at zero. ar_prof Non-range-sharpened Echo Profile-the power vs. time echo profile, at half-baud (0.21 Msec) intervals, assembled from up to 16 frequency components, without shifting their time origins (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-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_rsfit Range-sharpened "goodness of fit" parameter-a measure of the correlation between the observed profile ar_rsprof and the theoretical template ar_rstmpl. 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^2. ar_rslooks Number of equivalent looks-the number of statistically independent measurements of echo profile that were summed to produce the range-sharpened profile ar_rsprof. CTL ar_rec.man 2.3 Last change: 3/20/92 6 AR_REC(5) Magellan A&R Data Structure AR_REC(5) ar_rsnprof0 The index of the element in ar_rsprof that corresponds to the first element in ar_rstmpl[0]. The indices start at zero. ar_rsprof Range-sharpened Echo Profile-the power vs. time echo pro- file, at half-baud (0.21 Msec) 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 of ar_radius. ar_rstmpl Best range-sharpened Model Template-the theoretical echo profile, at one-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_rhofact The correction factor that has been added to ar_rho to allow for multi-peaked echos. This field is unused in software version 1. ar_radius2 The planetary radius derived from threshold detection of the signal in ar_rsprof. This field is unused in software version 1. 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. This field is not used in software version 1. In version 2, it is always recorded in IEEE-754 format, even when the remaining "float" fields are in VAX format. ar_thresh The index in ar_rsprof at which the threshold detector has located the rising signal. This field is not used in software version 1. ar_spare Unused-reserved for future data fields. AUTHOR Peter G. Ford, MIT CSR SEE ALSO Magellan A&R Software Design Document, P. Ford and G. Pettengill, MIT CSR, Version 2.0, September 20, 1989. MIT-MGN-ARCDR, Magellan Software Interface Specification, Altimetry & Radiometry Composite Data Record Tapes, P. Ford, MIT, Version 2.3, September 12, 1991. oh_rec(5), rr_rec(5) CTL ar_rec.man 2.3 Last change: 3/20/92 7 OH_REC(5) Magellan A&R Data Structure OH_REC(5) NAME oh_rec - ARCDR Orbit Header Record SYNOPSIS typedef struct { sfdu oh_sfdu; /* SFDU label and length */ ulong oh_norbit, /* Orbit number */ oh_nalt, /* Number of Altimetry Data Records */ oh_nrad; /* Number of Radiometry Data Records */ double oh_alt_start, /* First Alt Footprint Time (SCET) */ oh_alt_end, /* Last Altim Footprint Time (SCET) */ oh_rad_start, /* First Radiom Footprint Time (SCET) */ oh_rad_end, /* Last Radiom Footprint Time (SCET) */ oe_rec oh_avg; /* Average Predicted Orbit elements */ } oh_rec; DESCRIPTION oh_sfdu SFDU Label and Length: 'NJPL1I00017800000092'. oh_norbit The Magellan Orbit Number corresponding to the following three files (ephemeris, altimetry, and radiometry). oh_nalt Number of Altimetry Data Records-the number of ar_rec SFDU's in this orbit's altimetry data file. oh_nrad Number of Radiometry Data Records-the number of rr_rec SFDU's in this orbit's radiometry data file. oh_alt_start First Altimetry Footprint Time (SCET)-the S/C ephemeris time that represents the first altimeter footprint of this orbit. It is equal to the ar_scet value in the first ar_rec record of this orbit's altimetry data file. oh_alt_end Last Altimetry Footprint Time (SCET)-the S/C ephemeris time that represents the last altimeter footprint of this orbit. It is equal to the ar_scet value in the last ar_rec record of this orbit's altimetry data file. oh_rad_start First Radiometer Footprint Time (SCET)-the S/C ephemeris time of the first radiometer measurement of this orbit. It is equal to the rr_scet value in the first rr_rec record of this orbit's radiometry data file. oh_rad_end Last Radiometer Footprint Time (SCET)-the S/C ephemeris time of the last radiometer measurement of this orbit. It is equal to the rr_scet value in the last rr_rec record of this orbit's radiometry data file. CTL oh_rec.man 1.6 Last change: 9/14/89 1 OH_REC(5) Magellan A&R Data Structure OH_REC(5) oh_avg.scet Periapsis Time (SCET)-the periapsis time of the predicted orbit. This orbit is based on the elements used to gen- erate the uplink commands for the current mapping pass. It represents an average over the entire orbit, and is not the result of post-orbit navigation solutions. The elements should be used for comparison purposes only, since they may involve large errors. The predicted orbit elements are copied from the orbit header file of the ALT-EDR tape. 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 sys- tem. 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. AUTHOR Peter G. Ford, MIT CSR SEE ALSO Magellan A&R Software Design Document, P. Ford and G. Pettengill, MIT CSR, Version 2.0, September 20, 1989. MIT-MGN-ARCDR, Magellan Software Interface Specification, Altimetry & Radiometry Composite Data Record Tapes, P. Ford, MIT, version 1.2, September 20, 1989. ar_rec(5), rr_rec(5) CTL oh_rec.man 1.6 Last change: 9/14/89 2 RR_REC(5) Magellan A&R Data Structure RR_REC(5) NAME rr_rec - ARCDR Radiometer Data Record SYNOPSIS #define RR_GEOC 0x0001 /* Orbital geometry corrected */ #define RR_RADC 0x0002 /* Radius corrected from ALT-EDR */ #define RR_NOS1 0x0004 /* rr_sar[0] value missing */ #define RR_NOS2 0x0008 /* rr_sar[1] value missing */ #define RR_BAD 0x0010 /* ignore the radiometer results */ #define RR_CAL 0x0020 /* radiometer calibration burst */ #define RR_NRAD 0x0040 /* no radius info from topo model */ #define RR_RAD2 0x8000 /* rr_dedrad through rr_acr used */ typedef struct { sfdu rr_sfdu; /* SFDU aggregate header label & length */ long rr_burst; /* SAB Number (from C-BIDR) */ ulong rr_flag, /* Flag fields */ rr_flag2; /* Flag fields (unused) */ double rr_scet, /* S/C Radiometry Epoch (SCET) */ rr_pos[3], /* S/C Position Vector (km, J2000) */ rr_vel[3]; /* S/C Velocity Vector (km sec-1, J2000) */ float rr_lon, /* Footprint Longitude (deg, VBF85) */ rr_lat, /* Footprint Latitude (deg, VBF85) */ rr_xfoot, /* Along Track Radiom Footprt Size (km) */ rr_yfoot, /* Cross Track Radiom Footprt Size (km) */ rr_sfoot[2], /* SAR Footprint Diameters (km) */ rr_sar[2], /* SAR Average Backscatter Values (dB) */ rr_angle, /* Incidence Angle (deg) */ rr_bright, /* Brightness Temperature (K) */ rr_radius, /* Average Planetary Radius (km) */ rr_anttemp, /* System Temperature of Antenna (K) */ rr_skytemp, /* Assumed Cold Sky Temperature (K) */ rr_rcvrtemp, /* System Temperature of Receiver (K) */ rr_surftemp, /* Surface Emission Temperature (K) */ rr_emiss, /* Surface Emissivity */ rr_partl[3][6], /* Partials of Lat,Lon,Radius */ rr_dedrad, /* Partial of Emissivity wrt Radius */ rr_phystemp, /* Physical Surface Temperature (K) */ rr_antval, /* Radiometer Antenna Value */ rr_loadval; /* Radiometer Load Value */ uchar rr_askip[2], /* Altimeter Skip Factor */ rr_again[2]; /* Altimeter Gain Factor */ long rr_acf, /* Altimeter Coarse Resolution */ rr_spare[4]; /* Unused */ } rr_rec; DESCRIPTION rr_sfdu SFDU header label 'NJPL1I000nnn00000212'. rr_burst SAB Number (from C-BIDR)-the number assigned by the MSPF SAR processor to the burst header that contains the CTL rr_rec.man 2.3 Last change: 9/12/91 1 RR_REC(5) Magellan A&R Data Structure RR_REC(5) radiometer measurement referenced by this rr_rec. rr_flag Flag fields: RR_GEOC Geometry values have been corrected for ephemeris errors in the phase. RR_RADC rr_radius has been corrected by altimeter radius values. RR_NOS1 rr_sar[0] value missing. RR_NOS2 rr_sar[1] value missing. RR_BAD The radiometer fields (rr_bright through rr_emiss) do not contain good values. RR_CAL The burst was taken for calibration purposes. The SAR antenna boresight was not pointed at the planet. rr_lon and rr_lat contain the right ascen- sion and declination, in degrees, of the boresight pointing vector. rr_radius, rr_surftemp, and rr_emiss contain zeros. RR_NRAD The footprint location was not contained in the topography file. rr_radius is set to the planetary average. RR_RAD2 This record was created under software version 2 or higher, in which data fields rr_dedrad through rr_acr are used. rr_flag2 Additional flag fields (unused). rr_scet S/C Radiometry Epoch (SCET)-the ephemeris time at which the radiometry measurement was made. rr_pos S/C Position Vector (km, J2000)-the S/C position at rr_scet, relative to the Venus center of mass expressed in inertial coordinates. rr_vel S/C Velocity Vector (km sec-1, J2000)-the S/C velocity at rr_scet, relative to the Venus center of mass, expressed in inertial coordinates. rr_lon Footprint Longitude (deg, VBF85)-the crust-fixed longitude, at rr_scet, of the intersection of the antenna boresight and the planetary surface (a sphere of radius rr_radius). rr_lat Footprint Latitude (deg, VBF85)-the crust-fixed latitude, at rr_scet, of the intersection of the antenna boresight CTL rr_rec.man 2.3 Last change: 9/12/91 2 RR_REC(5) Magellan A&R Data Structure RR_REC(5) and the planetary surface (a sphere of radius rr_radius). rr_xfoot Along Track Radiometry Footprint Size (km)-the along track dimension of the intersection of the SAR antenna (3dB one- way attenuation) cone with a sphere of radius rr_radius. rr_yfoot Cross Track Radiometry Footprint Size (km)-the cross track dimension of the intersection of the SAR antenna (3dB one- way attenuation) cone with a sphere of radius rr_radius. rr_sfoot SAR Footprint Diameters (km)-the approximate dimension of the surface footprints represented by the pair of SAR back- scatter values, rr_sar. rr_sar SAR Average Backscatter Values (dB)-a pair of running aver- ages 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. rr_angle Incidence Angle (deg)-the angle between the local vertical and the S/C direction, measured at the center of the radiometer footprint at rr_scet. rr_bright Brightness Temperature (K)-the planet brightness tempera- ture, derived from rr_anttemp. rr_radius Average Planetary Radius (km)-the planetary radius of the radiometer footprint, used to compute rr_lon and rr_lat, and also rr_surftemp and atmospheric corrections to rr_emiss. rr_anttemp System Temperature of the SAR Antenna (K)-the rr_rcvrtemp value compensated for thermal feed noise and losses. rr_skytemp Assumed Cold Sky Temperature (K)-the temperature assumed for the dominant portion of 'sky' reflected by the radiome- ter footprint. rr_rcvrtemp System Temperature of the receiver input (K)-the difference between the raw radiometer reading and the previous load reading, converted to equivalent noise temperature, and compensated for receiver temperature and attenuation. CTL rr_rec.man 2.3 Last change: 9/12/91 3 RR_REC(5) Magellan A&R Data Structure RR_REC(5) rr_surftemp Radiometric Emission Temperature (K)-the emission tempera- ture calculated for the planetary surface covered by the radiometer footprint. rr_emiss Surface Emissivity-derived from the above values, after correcting for atmospheric absorption. rr_partl Partials of rr_lat, rr_lon, and rr_radius with respect to rr_pos and rr_vel. rr_dedrad Partial of Emissivity wrt Radius-derived from a numerical differentiation. This may be used to correct the rr_emiss value when a more accurate value of rr_radius becomes available. rr_phystemp Physical Surface Temperature (K)-the temperature of the atmosphere in contact with the surface at a radius of rr_radius. rr_antval Radiometer Antenna Value-the raw radiometer reading when detecting a signal from the antenna, corrected for altime- ter leakage. rr_loadval Radiometer Load Value-the raw radiometer reading when detecting a signal from the load, corrected for altimeter leakage. rr_askip[2] Altimeter Skip Factor-the two skip factors taken from the SAB header during the bursts in which the antenna and load signals were measured. rr_again[2] Altimeter Gain Factor-the two gain factors taken from the SAB header during the bursts in which the antenna and load signals were measured. rr_acf Altimeter Coarse Resolution-the coarse range index taken from the SAB header during the burst in which the antenna signal was measured. rr_spare Unused-reserved for future data fields. CTL rr_rec.man 2.3 Last change: 9/12/91 4 RR_REC(5) Magellan A&R Data Structure RR_REC(5) AUTHOR Peter G. Ford, MIT CSR SEE ALSO Magellan A&R Software Design Document, P. Ford and G, Pettengill, MIT CSR, Version 2.0, September 20, 1989. MIT-MGN-ARCDR, Magellan Software Interface Specification, Altimetry & Radiometry Composite Data Record Tapes, P. Ford, MIT, version 2.2, January 1, 1991. HS513-5029, Magellan Radar Sensor Compensation Report, edited by C. Cuevas, Hughes Aircraft Co., August 18, 1989. oh_rec(5), ar_rec(5) CTL rr_rec.man 2.3 Last change: 9/12/91 5