Sample Mars Express Spacecraft Orientation CK File ========================================================================= Created by Boris Semenov, NAIF/JPL, May 20, 2002 Abstract -------------------------------------------------------- This CK contains sample Mars Express spacecraft orientation for the first few mapping orbits. It's intended to be used ONLY for MEX SPICE interfaces try-outs and verification. This file generated by running prediCkt program on the set of setups provided in the section below. MEX SPICE Used in the prediCkt Run Generated This File -------------------------------------------------------- The following files were provided in support of the construction of the attitude given in this kernel: Type Name ---- ------------------------------------------ SPK de405.bsp SPK mex_map_sample_v3.bsp LSK naif0007.tls SCLK mex_fake.tsc FK mex_v02.tf Orientation Mode Definitions -------------------------------------------------------- This section defines MEX s/c orientation mode simulated in this file. These modes are based on the digram provided in MEX WWW site: http://sci.esa.int/content/doc/d4/2004_-4.jpg It also defines off-nadir pointing mode, in which the s/c points so many degrees off nadir to image particular location on Mars. Nadir-Pointed Orientation The directions needed to simulate the s/c orientation in nadir-pointed mode: -- vector from spacecraft to Mars (i.e. 'nadir') -- spacecraft velocity vector; \begindata DIRECTION_SPECS += ( 'ToMars = POSITION OF MARS -' ) DIRECTION_SPECS += ( 'FROM MEX -' ) DIRECTION_SPECS += ( 'CORRECTION LT+S' ) DIRECTION_SPECS += ( 'scVelocity = VELOCITY OF MEX -' ) DIRECTION_SPECS += ( 'FROM MARS -' ) DIRECTION_SPECS += ( 'CORRECTION NONE' ) \begintext This is how these directions for nadir-pointed mode relate to the s/c axes: -- s/c +Z axis points exactly along nadir direction; -- s/c +Y axis points (as close as possible) along the s/c velocity vector; \begindata ORIENTATION_NAME += 'NadirPointed' PRIMARY += '+Z = ToMars' SECONDARY += '+Y = scVelocity' BASE_FRAME += 'J2000' \begintext Off-Nadir Orientation In some cases the s/c will need to point so many degrees off nadir to image target locations on Mars. The directions needed to simulate this orientation are based on the Nadir-Pointed directions from the previous section. Note that the rotation by specified angle is about a vector normal to the nadir direction rather than about velocity vector (which, in general, is not normal to nadir direction.) The implementation below is based on the assumption that off-nadir angle is measured from the nadir direction in the plane that includes the nadir direction and is perpendicular to plane containing the nadir direction and the s/c velocity vectors. Of the three directions below, the last one -- OffNadirVec -- is going to be used in the orientation definition. The other two are intermediate steps needed to make sure that angle convention described above is adhered to. The "off nadir" angle used in the OffNadirVec direction specification is measured positive CCW as seen from the tip of the the s/c velocity vector. I.e. if you are flying on the s/c, angle of 10 degrees will be "looking 10 degrees left off nadir", while -15 degrees is "looking 15 degrees right off nadir." \begindata DIRECTION_SPECS += ( 'VelXNadir = CROSS PRODUCT -' ) DIRECTION_SPECS += ( 'scVelocity ToMars' ) DIRECTION_SPECS += ( 'AngRotAxis = CROSS PRODUCT -' ) DIRECTION_SPECS += ( 'ToMars VelXNadir' ) DIRECTION_SPECS += ( 'OffNadirVec = ROTATE ToMars -' ) DIRECTION_SPECS += ( '10 degrees -' ) DIRECTION_SPECS += ( 'ABOUT AngRotAxis' ) \begintext The OffNadirVec and scVelocity directions are used to built OffNadir orientation the same way as the NadirPointed one is done: -- s/c +Z axis points exactly along off nadir direction; -- s/c +Y axis points (as close as possible) along the s/c velocity vector; \begindata ORIENTATION_NAME += 'OffNadir' PRIMARY += '+Z = OffNadirVec' SECONDARY += '+Y = scVelocity' BASE_FRAME += 'J2000' \begintext Earth-Pointed Orientation These directions are important to simulate the s/c orientation in nadir-pointed mode: -- vector from spacecraft to Earth; -- vector from spacecraft to Sun; Note that Earth direction is pure geometric position (i.e. not corrected for LS+S.) Such definition results in a slight MEX off-pointing from the true MEX-to-Earth up-link line of sight. \begindata DIRECTION_SPECS += ( 'ToEarth = POSITION OF EARTH -' ) DIRECTION_SPECS += ( 'FROM MEX -' ) DIRECTION_SPECS += ( 'CORRECTION NONE' ) DIRECTION_SPECS += ( 'ToSun = POSITION OF SUN -' ) DIRECTION_SPECS += ( 'FROM MEX -' ) DIRECTION_SPECS += ( 'CORRECTION NONE' ) \begintext This is how these directions for Earth-pointed mode relate to the s/c axes: -- s/c -X axis points (HGA boresight) points exactly along direction to Earth; -- s/c -Z axis points (main engine side) point toward Sun (to make sure that both instruments on +Z and instrument radiator on +X are in the shadow); \begindata ORIENTATION_NAME += 'EarthPointed' PRIMARY += '-X = ToEarth' SECONDARY += '-Z = ToSun' BASE_FRAME += 'J2000' \begintext Limb-Pointed Orientation Directions and orientations for this mode are TBD. Lander-Comm Orientation Directions and orientations for this mode are TBD. Orientation Mode Definitions -------------------------------------------------------- This section defines simulated MEX orientation mode schedule. It is based on the assumption that the s/c points nadir for +/- 1 hour around pericenter and spend the rest of the orbit communicating with Earth. The s/c turns from one orientation mode to the other are assumed to take 5 minutes. These are pericenter times for orbit 3 through 20 taken from an ORBNUM file generated using data in the STAT-based SPK "mex_map_sample_v3.bsp": No. Periapsis UTC ____ ____________________ 3 2004 JAN 10 21:55:58 4 2004 JAN 11 05:30:44 5 2004 JAN 11 13:05:38 6 2004 JAN 11 20:40:28 7 2004 JAN 12 04:15:24 8 2004 JAN 12 11:50:20 9 2004 JAN 12 19:25:09 10 2004 JAN 13 03:00:03 11 2004 JAN 13 10:34:47 12 2004 JAN 13 18:09:31 13 2004 JAN 14 01:44:14 14 2004 JAN 14 09:18:53 15 2004 JAN 14 16:53:39 16 2004 JAN 15 00:28:22 17 2004 JAN 15 08:03:07 18 2004 JAN 15 15:38:02 19 2004 JAN 15 23:12:51 20 2004 JAN 16 06:47:47 The times in the schedule ETs computed for these 18 periapsis passes using the rules described above. This C-kernel matches the specification given below to 0.10000 degrees. \begindata CK-SCLK = 41 CK-SPK = -41 CK-FRAMES = -41000 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-10-15:27:19 CK-41000STOP += @2004-01-10-20:52:02 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-10-20:57:02 CK-41000STOP += @2004-01-10-22:57:02 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-10-23:02:02 CK-41000STOP += @2004-01-11-04:26:48 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-11-04:31:48 CK-41000STOP += @2004-01-11-06:31:48 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-11-06:36:48 CK-41000STOP += @2004-01-11-12:01:42 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-11-12:06:42 CK-41000STOP += @2004-01-11-14:06:42 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-11-14:11:42 CK-41000STOP += @2004-01-11-19:36:32 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-11-19:41:32 CK-41000STOP += @2004-01-11-21:41:32 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-11-21:46:32 CK-41000STOP += @2004-01-12-03:11:28 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-12-03:16:28 CK-41000STOP += @2004-01-12-05:16:28 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-12-05:21:28 CK-41000STOP += @2004-01-12-10:46:24 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-12-10:51:24 CK-41000STOP += @2004-01-12-12:51:24 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-12-12:56:24 CK-41000STOP += @2004-01-12-18:21:13 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-12-18:26:13 CK-41000STOP += @2004-01-12-20:26:13 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-12-20:31:13 CK-41000STOP += @2004-01-13-01:56:07 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-13-02:01:07 CK-41000STOP += @2004-01-13-04:01:07 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-13-04:06:07 CK-41000STOP += @2004-01-13-09:30:51 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-13-09:35:51 CK-41000STOP += @2004-01-13-11:35:51 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-13-11:40:51 CK-41000STOP += @2004-01-13-17:05:35 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-13-17:10:35 CK-41000STOP += @2004-01-13-19:10:35 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-13-19:15:35 CK-41000STOP += @2004-01-14-00:40:18 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-14-00:45:18 CK-41000STOP += @2004-01-14-02:45:18 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-14-02:50:18 CK-41000STOP += @2004-01-14-08:14:57 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-14-08:19:57 CK-41000STOP += @2004-01-14-10:19:57 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-14-10:24:57 CK-41000STOP += @2004-01-14-15:49:43 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-14-15:54:43 CK-41000STOP += @2004-01-14-17:54:43 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-14-17:59:43 CK-41000STOP += @2004-01-14-23:24:26 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-14-23:29:26 CK-41000STOP += @2004-01-15-01:29:26 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-15-01:34:26 CK-41000STOP += @2004-01-15-06:59:11 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-15-07:04:11 CK-41000STOP += @2004-01-15-09:04:11 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-15-09:09:11 CK-41000STOP += @2004-01-15-14:34:06 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-15-14:39:06 CK-41000STOP += @2004-01-15-16:39:06 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-15-16:44:06 CK-41000STOP += @2004-01-15-22:08:55 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-15-22:13:55 CK-41000STOP += @2004-01-16-00:13:55 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-16-00:18:55 CK-41000STOP += @2004-01-16-05:43:51 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-16-05:48:51 CK-41000STOP += @2004-01-16-07:48:51 CK-41000ORIENTATION += 'EarthPointed' CK-41000START += @2004-01-16-07:53:51 CK-41000STOP += @2004-01-16-13:18:45 CK-41000ORIENTATION += 'NadirPointed' CK-41000START += @2004-01-16-13:23:45 CK-41000STOP += @2004-01-16-15:23:45 \begintext