$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