DAWN SPK files. =========================================================================== This ``aareadme.txt'' file describes contents of the kernels/spk directory of the DAWN SPICE data server. It was last modified on October 14, 2011. Contact Chuck Acton (818-354-3869, Chuck.Acton@jpl.nasa.gov) or Boris Semenov (818-354-8136, Boris.Semenov@jpl.nasa.gov) if you have any questions regarding this data. Brief summary -------------------------------------------------------- This directory contains the SPICE SP-Kernel files for the DAWN mission. The following files are present in this directory. (Only file names are shown; the file name extensions of the binary SPK files are always ``.bsp''): DAWN spacecraft trajectory SPK files: dawn_rec_BEG-END_DEL[_ext][_vN] Reconstructed trajectory SPK files produced by DAWN NAV. These files, delivered on DEL date, contain reconstructed spacecraft trajectory data, covering from BEG date to END date, with all three dates specified in YYMMDD format. ext is an optional additional information token. N indicates the file version; N is optional and, if omitted, assumed ``1''. dawn_ql_BEG-END_DEL[_ext][_vN] Quick-look trajectory SPK files produced by DAWN NAV. These files, delivered on DEL date, contain reconstructed spacecraft trajectory data covering from BEG date to ~DEL date and predicted spacecraft trajectory data covering from ~DEL date to END date, with all three dates specified in YYMMDD format. ext is an optional additional information token. N indicates the file version; N is optional and, if omitted, assumed ``1''. dawn_ref_BEG-END_DEL[_ext][_vN] Reference trajectory SPK files produced by DAWN NAV. These files, delivered on DEL date, contain predicted spacecraft trajectory data, covering from BEG date to END date, with all three dates specified in YYMMDD format. ext is an optional additional information token. N indicates the file version; N is optional and, if omitted, assumed ``1''. dawn_dsn_BEG-END_DEL[_ext][_vN] Predicted trajectory SPK files for DSN produced by DAWN NAV. These files, delivered on DEL date, contain predicted spacecraft trajectory data, covering from BEG date to END date, with all three dates specified in YYMMDD format. ext is an optional additional information token. N indicates the file version; N is optional and, if omitted, assumed ``1''. Small body and planetary ephemeris SPK files: sb_TARG_DEL Small body ephemeris SPK files for DAWN targets. TARG is the target name (ceres, vesta) and DEL is the delivery date in YYMMDD format. de405s DE 405 planetary ephemeris SPK file. DAWN spacecraft structures SPK file: dawn_struct_vN SPK file containing relative locations of DAWN solar array and HGA structures. Supplementary/Meta Information Files. -------------------------------------------------------- There are two types of supplementary/meta information files provided with the SPK files: detached label files and orbit number files. SPK Label Files. Detached label files have the same names as the corresponding SPK files with the additional extension ``.lbl'' appended at the end. For all files except the merged products created by NAIF, the labels do NOT have any specific structure and they contain rather ``raw'' information combined from the following sources: file SFDU label (if such was present), contents of the comment area and file summary output by the BRIEF utility program. Most of these labels are created automatically ``on the fly'' and are planned to be re-processed before final data archiving with the PDS. For the merged products created by NAIF, the label contains more structured and organized information including detailed description of the data sources, the way the file was created, etc. Orbit Number Files. Orbit number files created by NAIF based on the reconstructed trajectory (*_rec_* spacecraft SPKs) are provided only for the orbital phases of the mission and are named: dawn_BODY_vNN.norb where BODY is either ``vesta'' or ``ceres'', ``NN'' is the file version, and ``.norb'' is the standard NAIF extension for the orbit number files following the ``node-to-node'' orbit numbering scheme. For the DAWN Vesta mission with the orbit number is changing at the ascending node crossings with the first orbit starting at the first crossing after July 16, 2011. From that point the orbits are numbered continuously till the end of the Vesta mission without resets at the orbit phase boundaries. The information contained in the orbit number files includes the orbit number, ascending node UTC and SCLK time, descending node UTC time and additional information for the ascending node such as the subsolar and subspacecraft longitudes and latitudes, spacecraft altitude, and solar distance. The longitudes and latitudes are given in the body-fixed frame with the frame orientation computed using the PCK file by the project science team at the time when the orbit number file was made.