$File FOOTPRINT_HEADER.DOC November 25, 1991 ; file: /ansa4/simmons/info/hdr_formats/footprint_header.doc Updated Apr 9, 2007 - kes ------------------------------------------------------------------------------ The following list documents the contents of SPICE derived "FOOTPRINT" file data records. All values and reference locations are DOUBLE PRECISION values ( eight byte VMS floating point values ). Each record contains 180 elements which can be accessed using an associate variable in IDL (now using the option '/vax_float') or a FORTRAN associated read. Files generated on the unix machine (most of them now) are accessed in IDL with the Fortran 77 unformated option. For example: IDL> close,1 & openr,1,'j0cd_urt_g1aura12.dat', /f77_unformatted IDL> a=dblarr(180) & readu,1,a The unix footprint data files were generated in 2007 using the original Vax footprint source code modified to execute on the unix platform. The source code is in /ansa4/gllsoft/foot/src. Each footprint data file also has a log file that lists the data sources for the generated data. This file has the same name as the data file, but with a "_log" file extension. The target bodies of the observations are referenced by a numeric code. The NAIF body code numbers are cross referenced with their body names in the file: DISKH:[GLL_RAW.INFO]SPICE_BODY_CODES.DOC, or /ansa4/simmons/info/seq_info/spice_body_codes.doc_4. The UVS field of view is defined by 9 vectors and viewing data for each vector is contained in the footprint. The field of view vector definition can be found in the UVS SPICE I kernel. This I kernel is currently located in: /vixen2/ggs/Kernels/Constants/gll34001.ti. (When reviewing this file for the size of the FOV used, be sure to look at the data statements toward the end of the file, and not at the diagrams, for the true value used by the SPICE routines.) If you find any errors or have any questions contact Karen Simmons at (303) 492-8363 [PISCES::SIMMONS] or Kirk Benell at 492-5877 [PISCES::BENELL] . Revision Date: November 25, 1991 KDB Updated January 07, 1992 KDB Updated June 16, 1992 KDB Updated July 08, 1992 KDB Updated March 23, 1993 KES Updated March 30, 1993 KDB Updated April 06, 1993 KES DETAILED DESCRIPTION OF FOOTPRINT DATA --------------------------------------- The following section provides a detailed description of the data that is contained in a footprint record (See also the NAIF SPICELIB library documents; look for these with the system logical SPICE$LIB after running the SPICE_LOGICALS.COM file). All angles are in degrees. All latitude and longitude values are PLANETOCENTRIC unless otherwise specified. All Jupiter longitudes are System III longitudes. NAV (and POINTER) software uses a Jupiter radius value of 71492 km (the one Bar value) to produce Jupiter SPP data. Some people prefer Rj as 71398 km (the IAU value). Since Rj is not used to calculate values herein, the only effect will be that of the SPP kernel. ERT(Earth Receive Time) - This is the time that an event is received on earth. The UTC time value has been corrected for one way light time. SCE(SpaceCraft Event time) - This is the time that an event occurs on the spacecraft. This time has not been corrected for one way light time. SCLK(SpaceCraft cLocK) - This is the time value of the spacecraft's clock. This time value has been broken up into three elements. The first is the reset counter of the clock. The second is the major frame counter and the last is the minor frame counter of the clock. The minor frame counter also contains the mod 10 and mod 8 counter values. These values have been converted into decimal minor frames. File Generation Date & Time - This is the date and time that the footprint data file was created by the footprint or GGGS program. NAIF target body code - All bodies are given a numeric code by NAIF. This number is the code for the target body used during the evaluation. Distance from S/C to target - This is the distance in kilometers from the spacecraft to the target body's center. Body Center Right Ascension - This is the Ra to the center of the target body from the spacecraft.This value is in degrees. Body Center Declination - This is the Dec to the center of the target body from the spacecraft. This value is in degrees. Sub-S/C latitude - This is the latitude on the target where the surface intercepts a line from the spacecraft to the body center. The value is in degrees and in planetocentric format. Sub-S/C longitude - This is the longitude on the target where the surface intercepts a line from the spacecraft to the body center. The value is in degrees and in planetocentric format. A "west" format is also used. (This format counts from left to right from the 0 longitude line.) Sub-Solar latitude - This is the latitude on the target where the surface intercepts a line from the sun center to the body center. The value is in degrees and in planetocentric format. Sub-Solar longitude - This is the longitude on the target where the surface intercepts a line from the sun center to the body center. The value is in degrees and in planetocentric format. A "west" format is also used. Target State Vector - This is the state vector for the target body. This vector includes the position and velocity of the body, sun centered. Earth State Vector - This is the state vector for the earth Spacecraft State Vector - This is the state vector for Galileo Polarization Angle - The polarization angle of the UVS field of view in degrees. It is measured from the line through the slit length, in a Right Hand Rule pointing out the optic axis, with zero degrees at the slit top midpoint, as 8-5 midpoint shown below. Also referred to as "chi". Delta Phi - The value of delta phi in degrees. An atmospheric parameter defined by Bob West in his memo of April 22,88. Field of View representation: The UVS field of view is represented by 9 vectors. One for the boresight, 4 for the corners of the F channel and 4 for the corners of the N/G channel. Data is given for each of these vectors. The following describes this data. All angles are in degrees. Field of view layout: 8 ----> +---------+ <---- 5 (N/G channel) | | | | | | 4 ----> +---------+ <---- 1 (F channel) | | | | | | | X <-|--- Boresight | | | | | | 3 ----> +---------+ <---- 2 (F channel) | | | | | | 7 ----> +---------+ <---- 6 (N/G channel) Intersection Flags - If a FOV vector intercepts with the target body this flag is a -1, but if no intersection occurs, the value is set to 0. Ra - This is the Ra of the field of view vector. Declination - This is the Dec of the field of view vector. Intersection Lat - This is the Latitude where the vector intercepts the target body. If no intersection occurs, this value will be zero Intersection Long - This is the longitude where the vector intercepts the target body. This value is in "west" format. If no intersection occurs, this value will be zero. Solar angle - This is the angle between the sun vector to the target body surface normal and the point of intersection. If no intersection occurs, this value will be zero. Phase angle - This is the angle between the sun vector to the vector from the body to the viewing location( the FOV vector ) and the point of the intersection. If no intersection occurs, this value will be zero. Emission angle - This is the angle between the vector from the body to the viewing location and the body surface normal at the point of intersection. If no intersection occurs, this value will be zero. Mu - This is the value of the cosine of the emission angle at the point of intersection. If no intersection occurs, this value will be zero. Mu 0 - This is the value of the cosine of the solar angle at the point of intersection. If no intersection occurs, this value will be zero. Intercept Altitude - This is the distance from the spacecraft to the point of intersection. If no intersection occurs, this value will be the altitude above the target of the tangent of the "look" vector. This value is in kilometers. Altitude Above surface - This is the distance from the FOV vector to the closet point on the body surface. This can be thought of the distance until the vector intercepts the body. This value is only given if the vector does NOT intersect with the target. Footprint record locations: ------------------------------------------------------------------------------ Index Values in: IDL FORTRAN Description 00 01 ERT Year 01 02 Day of year 02 03 Hour 03 04 Minute 04 05 Second 05 06 MSecond 06 07 SCE Year 07 08 Day of year 08 09 Hour 09 10 Minute 10 11 Second 11 12 MSecond 12 13 SCLK Reset counter (Starts at 1) 13 14 Major frames 14 15 Minor frames 15 16 Spare 16 17 Spare 17 18 File generation date MMDDYR. 18 19 File generation time HHMMSS. 19 20 Spare > GGGS version number 20 21 Spare 21 22 Spare 22 23 NAIF target body code number ( ie 399 = Earth ) 23 24 Distance from S/C to body center (km) 24 25 Body center RA (deg) 25 26 Body center DEC (deg) 26 27 Sub-S/C planetocentric Latitude (deg) 27 28 Sub-S/C Longitude (deg) In WEST longitude format. 28 29 Sub-Solar planetocentric Latitude (deg) 29 30 Sub-Solar Longitude (deg) In WEST longitude format. 30 31 X - State vector of the target body. 31 32 Y 32 33 Z 33 34 Vx 34 35 Vy 35 36 Vz 36 37 X - State vector of the Earth 37 38 Y 38 39 Z 39 40 Vx 40 41 Vy 41 42 Vz 42 43 X - State vector of the Spacecraft 43 44 Y 44 45 Z 45 46 Vx 46 47 Vy 47 48 Vz 48 49 Distance to the sun from target body (km) 49 50 Distance to the sun from spacecraft (km) 50 51 Distance to the sun from the earth (km) 51 52 Ra of the sun as seen from the Spacecraft (Deg) 52 53 Dec of the sun as seen from the Spacecraft (Deg) 53 54 Inertial reference (1=J2000, 2=B1950) 54 65 Boresight intersection flag (-1=contact,0=nocontact) 55 66 Intersection RA (deg) 56 67 Intersection DEC (deg) 57 68 Intersection LAT (deg) 58 69 Intersection LON (deg) In WEST Longitude format 59 60 Solar angle (deg) 60 61 Phase angle (deg) 61 62 Emission angle (deg) 62 63 Mu 63 64 Mu 0 64 65 Contact - Intercept Altitude Nocontact - Altitude above the target body 65 66 Delta Phi 66 67 Polarization Angle of the FOV 67 68 Spare 68 69 FOV corner 1 intersection flag(-1=contact,0=nocontact) 69 70 Intersection RA (deg) 70 71 Intersection DEC (deg) 71 72 Intersection LAT (deg) 72 73 Intersection LON (deg) In WEST Longitude format 73 74 Solar angle (deg) 74 75 Phase angle (deg) 75 76 Emission angle (deg) 76 77 Mu 77 78 Mu 0 78 79 Contact - Intercept Altitude Nocontact - Altitude above the target body 79 80 Delta Phi 80 81 Spare 81 82 Spare 82 83 FOV corner 2 intersection flag(-1=contact,0=nocontact) 83 84 Intersection RA (deg) 84 85 Intersection DEC (deg) 85 86 Intersection LAT (deg) 86 87 Intersection LON (deg) In WEST Longitude format 87 88 Solar angle (deg) 88 89 Phase angle (deg) 89 90 Emission angle (deg) 90 91 Mu 91 92 Mu 0 92 93 Contact - Intercept Altitude Nocontact - Altitude above the target body 93 94 Delta Phi 94 95 Spare 95 96 Spare 96 97 FOV corner 3 intersection flag(-1=contact,0=nocontact) 97 98 Intersection RA (deg) 98 99 Intersection DEC (deg) 99 100 Intersection LAT (deg) 100 101 Intersection LON (deg) In WEST Longitude format 101 102 Solar angle (deg) 102 103 Phase angle (deg) 103 104 Emission angle (deg) 104 105 Mu 105 106 Mu 0 106 107 Contact - Intercept Altitude Nocontact - Altitude above the target body 107 108 Delta Phi 108 109 Spare 109 110 Spare 110 111 FOV corner 4 intersection flag(-1=contact,0=nocontact) 111 112 Intersection RA (deg) 112 113 Intersection DEC (deg) 113 114 Intersection LAT (deg) 114 115 Intersection LON (deg) In WEST Longitude format 115 116 Solar angle (deg) 116 117 Phase angle (deg) 117 118 Emission angle (deg) 118 119 Mu 119 120 Mu 0 120 121 Contact - Intercept Altitude Nocontact - Altitude above the target body 121 122 Delta Phi 122 123 Spare 123 124 Spare 124 125 FOV corner 5 intersection flag(-1=contact,0=nocontact) 125 126 Intersection RA (deg) 126 127 Intersection DEC (deg) 127 128 Intersection LAT (deg) 128 129 Intersection LON (deg) In WEST Longitude format 129 130 Solar angle (deg) 130 131 Phase angle (deg) 131 132 Emission angle (deg) 132 133 Mu 133 134 Mu 0 134 135 Contact - Intercept Altitude Nocontact - Altitude above the target body 135 136 Delta Phi 136 137 Spare 137 138 Spare 138 139 FOV corner 6 intersection flag(-1=contact,0=nocontact) 139 140 Intersection RA (deg) 140 141 Intersection DEC (deg) 141 142 Intersection LAT (deg) 142 143 Intersection LON (deg) In WEST Longitude format 143 144 Solar angle (deg) 144 145 Phase angle (deg) 145 146 Emission angle (deg) 146 147 Mu 147 148 Mu 0 148 149 Contact - Intercept Altitude Nocontact - Altitude above the target body 149 150 Delta Phi 150 151 Spare 151 152 Spare 152 153 FOV corner 7 intersection flag(-1=contact,0=nocontact) 153 154 Intersection RA (deg) 154 155 Intersection DEC (deg) 155 156 Intersection LAT (deg) 156 157 Intersection LON (deg) In WEST Longitude format 157 158 Solar angle (deg) 158 159 Phase angle (deg) 159 160 Emission angle (deg) 160 161 Mu 161 162 Mu 0 162 163 Contact - Intercept Altitude Nocontact - Altitude above the target body 163 164 Delta Phi 164 165 Spare 165 166 Spare 166 167 FOV corner 8 intersection flag(-1=contact,0=nocontact) 167 168 Intersection RA (deg) 168 169 Intersection DEC (deg) 169 170 Intersection LAT (deg) 170 171 Intersection LON (deg) In WEST Longitude format 171 172 Solar angle (deg) 172 173 Phase angle (deg) 173 174 Emission angle (deg) 174 175 Mu 175 176 Mu 0 176 177 Contact - Intercept Altitude Nocontact - Altitude above the target body 177 178 Delta Phi 178 179 Spare 179 180 Spare