File: aareadme.txt Creation Date: 2006-08-04 Revised: 2020-04-11 (NJB) Revised: 2021-06-25 (NJB) Revised: 2022-12-14 (BVS) Revised: 2022-12-27 (NJB) (BVS) Revised: 2022-01-18 (NJB) (BVS) Revised: 2023-06-03 (NJB) Revised: 2023-06-25 (BVS) Authors: Nat Bachman (JPL/NAIF) Boris Semenov (JPL/NAIF) Contents of path pub/naif/generic_kernels/pck ============================================= Binary Earth PCKs ----------------- The following kernels provide Earth orientation data taking into account Precession Nutation Nutation corrections UT1-TAI Polar motion See the comment areas of these kernels (using the SPICE utility COMMNT) for additional documentation. High accuracy EOP-based kernel, updated at least twice per week: earth_000101_yymmdd_yymmdd.bpc earth_latest_high_prec.bpc The first two dates in the first file name are the file's coverage start and stop times. The third date in that file name is the epoch of the last datum in the source EOP file: earth orientation from this date forward is predicted. The second file is a copy of the first. The name of this file remains unchanged. Low accuracy, long term predict kernel. The extended predict region of this kernel---the time interval following the end of the predict region of the input EOP file---does not estimate changes in UT1-TAI. The dates in the file name are the file's coverage start and stop times: earth_200101_990825_predict.bpc High accuracy, historical kernel. The dates in the file name are the start time and stop time, which is also the epoch of last datum. earth_720101_230601.bpc Binary Lunar PCKs ----------------- DE440 version ------------- DE440 based kernel, providing orientation of Lunar Principal Axis (PA) reference frame: moon_pa_de440_200625.bpc Reference: [1] Ryan S. Park, et al, "The JPL Planetary and Lunar Ephemerides DE440 and DE441," The Astronomical Journal, Volume 161, Number 3. 2021 AJ 161 105. URL: https://iopscience.iop.org/article/10.3847/1538-3881/abd414/meta The data source for this kernel was the NAVIO file de440.nio The approximate time coverage is 1550-2650 This kernel is to be used with the lunar frame kernel moon_de440_220930.tf This frame kernel is located in the path pub/naif/generic_kernels/fk/satellites See the cited frame kernel for a detailed discussion of lunar reference frames and associated SPICE kernels. DE-421 version -------------- DE-421 based kernel, providing orientation of Lunar Principal Axis (PA) reference frame: moon_pa_de421_1900-2050.bpc The data source for this kernel was the NAVIO file de421.nio The approximate time coverage is indicated by the dates in the file name. This kernel is to be used with the lunar frame kernel moon_080317.tf This frame kernel is located in the path pub/naif/generic_kernels/fk/satellites See the cited frame kernel for a detailed discussion of lunar reference frames and associated SPICE kernels. Version preceding DE-421 ------------------------ DE-418 based kernel, providing orientation of Lunar Principal Axis (PA) reference frame: moon_pa_de418_1950-2050.bpc The data source for this kernel was the NAVIO file de418.nio The approximate time coverage is indicated by the dates in the file name. This kernel is to be used with the lunar frame kernel moon_071218.tf This frame kernel is located in the path pub/naif/generic_kernels/fk/satellites See the cited frame kernel for a detailed discussion of lunar reference frames and associated SPICE kernels. Generic text PCKs ----------------- These kernels contain orientation data for planets, natural satellites, the Sun, and selected asteroids. The latest files, released December 27, 2022, are: pck00011.tpc pck00011_n0066.tpc Reading the Mars system orientation data in pck00011.tpc *requires* SPICE Toolkit version N0067 (current as of December 2022) or later. The file pck00011_n0066.tpc is compatible with SPICE Toolkit versions N0066 and earlier. In this file, orientation data for Phobos has been modified slightly in order to be usable by these earlier Toolkit versions. Kernel variables for the Mars system have been modified, but only the orientation of Phobos is affected. See the documentation in the file for details. All other data in the file match those in pck00011.tpc. Most data in both files are from article Archinal, B.A., Acton, C.H., A'Hearn, M.F., Conrad, A., Consolmagno, G.J., Duxbury, T., Hestroffer, D., Hilton, J.L., Kirk, R.L., Klinoner, S.A., McCarthy, D., Meech, K., Oberst, J., Ping., J., Seidelmann, P.K., Tholen, D.J., Thomas, P.C., and Williams, I.P., "Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2015," Celestial Mechanics and Dynamical Astronomy 130, Article number 22 (2018). DOI: https://doi.org/10.1007/s10569-017-9805-5 This article presents data for some bodies, including Mercury, Mars and its satellites, and Neptune, that are very different from those of the previous IAU WGCCRE report. NAIF recommends careful inspection of the data prior to use. The preceding version of the generic text PCK file is pck00010.tpc which was released September 21, 2011. Most data in that file are from the article Archinal, B.A., A'Hearn, M.F., Bowell, E., Conrad, A., Consolmagno, G.J., Courtin, R., Fukushima, T., Hestroffer, D., Hilton, J.L., Krasinsky, G.A., Neumann, G., Oberst, J., Seidelmann, P.K., Stooke, P., Tholen, D.J., Thomas, P.C., and Williams, I.P. "Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2009." All of these kernels are text files; see the documentation in the files for details concerning the files' contents. WARNING: Mars system orientation data in the PCK files pck00011*.tpc listed above are incompatible with corresponding data from older PCK files. Loading either of the pck00011*.tpc files, and then loading older PCK files, including mars_iau2000_v0.tpc pck00010.tpc will make Mars system orientation data from the later loaded files unusable. After this sequence of kernel loads, calls to SPICE APIs that require the orientation of Mars, Phobos, or Deimos, for example calls to the SPICE APIs PXFORM or SXFORM, will cause the error SPICE(INSUFFICIENTANGLES) to be signaled. Mars system orientation data in the file pck00011.tpc cannot be used with SPICE Toolkit versions earlier than N0067. The text PCK mars_iau2000_v1.tpc is provided to work around this compatibility problem. See the section "Mars system text PCK" below. Mars system text PCK -------------------- The file mars_iau2000_v1.tpc was released on January 12, 2023. This file contains data only for Mars and its natural satellites. Orientation data in this file are identical to those in mars_iau2000_v0.tpc pck00010.tpc Body shape data in this file are identical to those in pck00011.tpc pck00011_n0066.tpc This file was created to work around compatibility problems with Mars system orientation data in the files pck00011*.tpc listed above. This update of mars_iau2000_v0.tpc contains variables that enable Mars system orientation data in this file to be safely used when this file is loaded after either pck00011.tpc or pck00011_n0066.tpc. After this file is loaded, it is safe to load other, older PCKs and use the Mars system orientation data from those files, even if one of the pck00011*.tpc files had been loaded before this file. This kernel may be used by any SPICE Toolkit version. NORAD two-line element kernel ----------------------------- This kernel supports creation of SPK files containing type 10 (NORAD two-line element) segments: geophysical.ker See the MKSPK User's Guide for further information. GM/mass kernels --------------- The file gm_de440.tpc gives "GM" (gravitational constant times mass) values for the sun, planets, planetary system barycenters, and selected satellites asteroids. These values are based on DE-440 and latest satellite ephemeris release memos. This file combines data from two PCKs provided to NAIF on 11/28/22 and 11/30/22 by Jon D. Giorgini, Solar System Dynamics group. See file comments for details. The file gm_de431.tpc gives "GM" (gravitational constant times mass) values for the sun, planets, planetary system barycenters, and selected satellites asteroids. These values are based on DE-431 and latest satellite ephemeris release memos. This file was provided to NAIF on 04/16/14 by Jon D. Giorgini, Solar System Dynamics group. The file de-403-masses.tpc gives "GM" (gravitational constant times mass) values for the sun, planets, and planetary system barycenters. These values are based on DE-403. The file Gravity.tpc contains data of uncertain provenance. Use at your own risk. NAIFers: consider deleting this file? EARTH_FIXED Alias Kernel ------------------------ This is a kernel used to map the reference frame alias EARTH_FIXED to a specific reference frame: earth_fixed.tf Using the alias EARTH_FIXED in code allows applications to select the earth-fixed frame to use at run time via the frame specification in this kernel. The default association is with the frame IAU_EARTH The file contains instructions for changing the association to ITRF93. Getting help ============ SPICE tutorials are available on the NAIF web site: http://naif.jpl.nasa.gov/naif/ The following tutorials may be of particular interest: Intro to Kernel Files PCK (Planetary cartographic and physical constants) FK (Reference frame specifications) Also see the following Required Reading documents provided with the SPICE Toolkit: Frames Kernel PCK Many SPICE kernels contain internal documentation. Text kernels may be viewed with a text editor or web browser. Comments in binary kernels may be viewed using the SPICE utility COMMNT. Coverage of binary PCKs may be viewed using the SPICE utility SPACIT. See the COMMNT and SPACIT User's Guides (provided with the SPICE Toolkit) for details.