DIF SPK file for the EPOCh Part of the EPOXI Mission =========================================================================== Created by Brian Rush, EPOXI NAV/JPL on February 4, 2009. Comments were added by Boris Semenov, NAIF/JPL, February 16, 2009. Objects in the Ephemeris -------------------------------------------------------- This file contains ephemeris data for Deep Impact Flyby (DIF) spacecraft (NAIF ID -140), DIXI mission's target comet HARTLEY 2 (NAIF ID 1000041), Sun, and planets and planet barycenters. Approximate Time Coverage -------------------------------------------------------- The DIF trajectory and comet and planetary ephemerides provided in this file cover from the beginning of to the nominal end -- Hartley 2 flyby plus three months -- of the EPOXI mission: COVERAGE BEGIN TIME (TDB): 2006 FEB 10 00:00:00.000 COVERAGE END TIME (TDB): 2011 JAN 31 00:00:00.000 Status -------------------------------------------------------- This file was created by merging reconstructed OD SPK files produced during the EPOCh part (February 2006 to December 2008) of the EPOXI mission and the latest (as of December 2008) predicted SPK for the DIXI part of the EPOXI mission for into a single file intended for archiving with the Planetary Data System (PDS). Pedigree -------------------------------------------------------- This file was created by Brian Rush, EPOXI NAV/JPL on February 4, 2009 and was originally named ``epoxi_merged.bsp''. Appendix 1 of these comments provides Brian's notes on how this file was made, including the list of source SPKs, SPKMERGE command file, etc. Segment Boundary Discontinuities -------------------------------------------------------- This SPK file contains a number of spacecraft trajectory SPK segments that came from original individual SPK files. Although, each segment provides continuous trajectory within the interval that it covers, in general a position and velocity discontinuity exists at the boundary of the segment and the segments whose coverage immediately precede and follow it. The times and magnitudes of discontinuities at the boundaries of the segments containing DIF trajectory relative to the Sun are provided in the Appendix 2 of these comments. There are no discontinuities at the boundaries of segments that provide DIF trajectory with respect to different centers. Contacts -------------------------------------------------------- If you have questions regarding this data contact Boris V. Semenov (818)-354-8136 Boris.Semenov@jpl.nasa.gov or EPOXI NAV Team: Brian P. Rush (818)-354-8124 Brian.P.Rush@jpl.nasa.gov Appendix 1: SPK Pedigree Notes by Brian Rush -------------------------------------------------------- This file was made by merging the following files. =============================================================================== SOLUTION NAMES AND DATA ARCS ------------------------------------------------------------------------------- Solution in /nav/epoxi/ops/od/ DATA EPOCH (ET) DATA CUTOFF (ET) ------------------------------------------------------------------------------- cruise1/070129=od212 10-FEB-2006 00:00 19-JAN-2007 08:00 efb/071219_short=od218 25-SEP-2007 21:05 20-DEC-2007 00:00 tcm12/080313_08jan01~od219.25 01-JAN-2008 07:02 14-MAR-2008 00:00 tcm12/080501_PostSafing~od219.75 01-MAR-2008 00:00 01-MAY-2008 00:00 tcm12/080623_epoch080418=od221 18-APR-2008 09:00 24-JUN-2008 00:00 ega2/081002_epoch080620~od221.75 20-JUN-2008 00:00 03-OCT-2008 00:00 ega2/081202_epoch080902=od223 02-SEP-2008 11:25 03-DEC-2008 00:00 $DELOD/od223/pfile_drm223_with_tcms.nio 02-SEP-2008 00:00 03-DEC-2008 00:00 ------------------------------------------------------------------------------- The DATA EPOCH AND DATA CUTOFF represent the filter span used in the solution, i.e., the dates during which tracking data will be used. The actual tracking data used fall within these limits, usually by a few hours on each end. =============================================================================== DATA GAPS AND POSITION DIFFERENCES ------------------------------------------------------------------------------- Solution in /nav/epoxi/ops/od/ GAP^1 DIF^2 ------------------------------------------------------------------------------- cruise1/070129=od212 efb/071219_short=od218 249 311 tcm12/080313_08jan01~od219.25 12 23 tcm12/080501_PostSafing~od219.75 -13 2.4 tcm12/080623_epoch080418=od221 -13 1.6 ega2/081002_epoch080620~od221.75 -4 20 ega2/081202_epoch080902=od223 -31 8.8 $DELOD/od223/pfile_drm223_with_tcms.nio 0 0 ------------------------------------------------------------------------------- ^1 GAP = data gap in days, from end of earlier solution data arc, to beginning of latter solution data arc; negative = overlap ^2 DIF = 3-D rss position difference between previous and latter solution, at epoch of latter solution =============================================================================== The output/pv.nio files from the above directories were all copied to /nav/epoxi/ops/od/epoxi_merged_spk/, then converted to BSP files, and then merged with spkmerge, using the following inputs: spk_kernel = epoxi_merged.bsp leapseconds_kernel = /nav/epoxi/import/leapsec/naif0009.tls source_spk_kernel = pv00_060210_to_070119.bsp begin_time = 2006 FEB 10 00:00 TDB end_time = 2007 SEP 25 21:05 TDB bodies = -140 source_spk_kernel = pv01_070925_to_071220.bsp begin_time = 2007 SEP 25 21:05 TDB end_time = 2008 JAN 01 07:02 TDB bodies = -140 source_spk_kernel = pv02_080101_to_080314.bsp begin_time = 2008 JAN 01 07:02 TDB end_time = 2008 MAR 01 00:00 TDB bodies = -140 source_spk_kernel = pv03_080301_to_080501.bsp begin_time = 2008 MAR 01 00:00 TDB end_time = 2008 APR 18 09:00 TDB bodies = -140 source_spk_kernel = pv04_080418_to_080624.bsp begin_time = 2008 APR 18 09:00 TDB end_time = 2008 JUN 20 00:00 TDB bodies = -140 source_spk_kernel = pv05_080620_to_081003.bsp begin_time = 2008 JUN 20 00:00 TDB end_time = 2008 SEP 02 11:25 TDB bodies = -140 source_spk_kernel = pv06_080902_to_081203.bsp begin_time = 2008 SEP 02 11:25 TDB end_time = 2008 DEC 09 00:00 TDB bodies = -140 source_spk_kernel = pv06_080902_to_081203_runout.bsp begin_time = 2008 DEC 09 00:00 TDB end_time = 2011 JAN 31 00:00 TDB bodies = -140 source_spk_kernel = /nav/epoxi/import/ephem/sb-103p-49.bsp begin_time = 2006 FEB 10 00:00 TDB end_time = 2011 JAN 31 00:00 TDB bodies = 1000041 source_spk_kernel = /nav/common/import/ephem/de405s.bsp begin_time = 2006 FEB 10 00:00 TDB end_time = 2011 JAN 31 00:00 TDB Appendix 2: Spacecraft Trajectory Segment Boundary Discontinuity Summary -------------------------------------------------------- This SPK file contains a number of spacecraft trajectory SPK segments that came from original individual SPK files. Although, each segment provides continuous trajectory within the interval that it covers, in general a position and velocity discontinuity exists at the boundary of the segment and the segments whose coverage immediately precede and follow it. The times and magnitudes of discontinuities at the boundaries of the segments containing DIF trajectory relative to the Sun are provided in this Appendix. The top portion of the table contains the name of this SPK file. All descriptive lines in the top portion of the file start with the ``#'' character to allow direct plotting of the data in the freeware ``gnuplot'' application. The table consists of 4 columns. The first column contains the UTC time of that segment boundary. The last three columns (2..4) contain view coordinate frame components -- ``down track'' (this direction is parallel to the velocity vector), ``normal to plane'' (this direction is computed as cross product of position vector by velocity vector) and ``in plane'' (this direction is computed as a cross product of ``down track'' by ``normal to plane'') -- of the difference between the state vectors computed at that UTC time defining segment boundary at which a discontinuity exists. The pairs of segments and discontinuity times are determined using an algorithm that emulates the standard SPK loading priority -- ``last loaded segment takes precedence''. Therefore, the discontinuities summarized in the file are those which a user reading file would actually see. The difference components in the view coordinate frame were computed for each discontinuity using the following algorithm: -- A single state was computed from each pair of segment the J2000 frame at the time of discontinuity. -- For this pair of states, a position difference vector was computed by subtracting the state computed from the segment with higher priority from the state computed from segment with lower priority. Then, a frame transformation matrix rotating these difference vectors from J2000 to the view coordinate frame defined by the state obtained from the higher priority segment was computed, and the position difference vector was rotated to the view frame coordinates using this matrix. The spacecraft trajectory segment boundary discontinuities for this file are: # # Summary of discontinuities at segment boundaries for # SPK file dif_epoch_nav_v1.bsp: # # BOUNDARY TIME (UTC) DOWNTRK INPLANE NORMAL #----------------------- ------- ------- ------- 2007-09-25T21:03:54.817 -294.388 -20.816 -97.421 2008-02-29T23:58:54.814 -1.055 -2.138 -0.505 2008-04-18T08:58:54.814 -0.269 -1.561 -0.312 2008-06-19T23:58:54.815 -0.112 7.761 -18.349 2008-09-02T11:23:54.817 1.269 2.729 8.253 2008-12-08T23:58:54.816 0.000 -0.000 -0.000