PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM LABEL_REVISION_NOTE = " 2012-10-30 NAIF:Semenov initial version; 2013-04-09 NAIF:Semenov updated for crash site SPK and FK, updated STOP_TIME; 2021-04-12 NAIF:Costa updated CITATION_DESC with DOI; " OBJECT = DATA_SET DATA_SET_ID = "GRAIL-L-SPICE-6-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "GRAIL SPICE KERNELS V1.0" DATA_SET_TERSE_DESC = " Navigation and ancillary data in the form of SPICE System kernel files for the GRAIL spacecraft. " ABSTRACT_DESC = " This data set includes the complete set of GRAIL SPICE data files (``kernel files''), which can be accessed using SPICE software. The SPICE data contain geometric and other ancillary information needed to recover the full value of science instrument data. In particular SPICE kernels provide spacecraft and planetary ephemerides, instrument mounting alignments, spacecraft orientation, and data needed for relevant time conversions. " CITATION_DESC = " Semenov, B.V., and C.H. Acton, GRAIL SPICE KERNELS V1.0, GRAIL-L-SPICE-6-V1.0, NASA Planetary Data System, 2012. https://doi.org/10.17189/1520110 " DATA_SET_COLLECTION_MEMBER_FLG = "N" START_TIME = 2011-09-10T13:08:52 STOP_TIME = 2012-12-17T22:29:15 DATA_SET_RELEASE_DATE = 2012-10-30 PRODUCER_FULL_NAME = "BORIS V. SEMENOV" DATA_OBJECT_TYPE = "SPICE KERNEL" DETAILED_CATALOG_FLAG = "Y" DATA_SET_DESC = " Data Set Overview ================= This data set includes the complete set of GRAIL SPICE data files (``kernel files''), which can be accessed using SPICE software. The SPICE data contain geometric and other ancillary information needed to recover the full value of science instrument data. In particular SPICE kernels provide spacecraft and planetary ephemerides, instrument mounting alignments, spacecraft orientation, and data needed for relevant time conversions. This data set is contained on a single virtual volume, GRLSP_1000, including data from all mission phases and covering from launch, 2011-09-10T13:08:52, through the end time of the latest spacecraft trajectory file supplied in the data set. Until the end of the spacecraft lifespan this data set is accumulating with new data added according the project archive release schedule. Data Types (SPICE kernel types) =============================== SPK kernels contain ephemerides for spacecraft, planets, satellites, comets and asteroids as well as for moving or fixed spacecraft and instrument structures. They provide position and velocity, given in a Cartesian reference frame. SPK files are located under the ``data/spk'' directory of this data set. PCK kernels contain certain physical, dynamical and cartographic constants for target bodies, such as size and shape specifications, and orientation of the spin axis and prime meridian. PCK files are located under the ``data/pck'' directory of this data set. IK kernels (Instrument description kernels) give descriptive and operational data peculiar to a particular scientific instrument, such as internal timing relative to the spacecraft clock and field-of-view model parameters. IK files are located under the ``data/ik'' directory of this data set. CK kernels describe pointing, containing a transformation traditionally called the C-matrix which is used to determine time-tagged pointing (orientation) angles for a spacecraft structure upon which science instruments are mounted. CK files are located under the ``data/ck'' directory of this data set. EK (Events) kernels are derived from the integrated sequence of events used to produce actual spacecraft commands. EK files are located under the ``data/ek'' directory of this data set. LSK (Leapseconds) kernels contain the leapseconds and the values of other constants required to perform a transformation between Universal Time Coordinated (UTC) and Ephemeris time (ET). LSK files are located under the ``data/lsk'' directory of this data set. SCLK (Spacecraft Clock) kernels contain on-board clock calibration data required to perform a mapping between Ephemeris time (ET) and spacecraft on-board time (SCLK). SCLK files are located under the ``data/sclk'' directory of this data set. FK (Frame Definitions) kernels contain information required to define reference frames, sources of frame orientation data and connections between these frames and other frames supported within the SPICE system. This includes mounting alignment information for each instrument. FK files are located under the ``data/fk'' directory of this data set. Kernel File Details =================== A brief overview of the different types of GRAIL kernels included in this data set is provided in the CONFIDENCE_LEVEL_NOTE section of this file while details specific to individual files are found in the ``*info.txt'' files in the corresponding data directory. The most detailed description of the data in each file is provided in metadata included inside the file -- in the description area of text kernels or in the comment area of binary kernels. Software ======== The SPICE Toolkit contains software modules needed to read SPICE kernel files. SPICE software is highly documented via internal headers. Additional documentation is available in separate ASCII text files called Required Reading files. For example, the S- and P- Kernel (SPK) Required Reading File, named SPK.REQ, describes use of the SPK kernel file readers and contains sample programs. The latest SPICE Toolkit for a variety of computer platforms such as PC, Mac, SUN, etc. is available at the NAIF Node of PDS electronically (via anonymous FTP and WWW servers). Refer to information in ``software/softinfo.txt'' for details regarding obtaining this software. Each version of the Toolkit is also archived at the NASA National Space Science Data Center. Loading Kernel Files into a SPICE-based Application =================================================== The easiest way to make data from a collection of SPICE kernels available to a SPICE-based application is to list these kernels in a meta-kernel and load it into the program using the high level SPICE data loader routine FURNSH. This data set provides such meta-kernel(s) under the ``extras/mk'' directory. For more information about the GRAIL meta-kernel(s), see the file ``extras/mk/mkinfo.txt''. " CONFIDENCE_LEVEL_NOTE = " This data set contains SPICE kernel files created during mission operations and after mission data reconstruction and analysis. Some general information about this collection follows here, but the prospective user is also referred to extensive descriptions about each file that are stored inside each kernel file. These metadata provide detailed information regarding the information source from which the data were derived, the type of processing applied to the source data, applicability of the data, etc. Metadata are located in the ``comment area'' for binary kernel types (SPK, CK, ESQ), accessible using either the COMMNT or SPACIT utility program found in the NAIF Toolkit. Metadata are located after ``\begintext'' markers within the text kernel types (PCK, IK, FK, LSK, SCLK, MK), accessible by using any available text file display tool such as a word processor, text editor, or the unix ``more'' or ``cat'' commands. Where there are questions about data accuracy or ``confidence'' not addressed herein the reader is invited to contact the NAIF node of the Planetary Data System for possible further information. SPK Files ========= Three kinds of SPK files are provided in this archive: SPK files for the spacecraft orbit, SPK files for the crash sites, and SPK files for the Solar System planets and satellites. The spacecraft orbit SPK files contain the spacecraft trajectory determined by the GRAIL Navigation (NAV) Team, JPL or by the GRAIL Science Team, JPL. The NAV spacecraft SPKs are available for all phases of the mission. Since the NAV team team did not have a formal trajectory reconstruction requirement, these SPKs contain a mix of reconstruction and short-term prediction segments with trajectory errors reaching up to a few hundred meters (based on segment boundary discontinuities). The science spacecraft SPKs are available for only for the science phases of the mission. They are based on Deep Space Network one-way Doppler and two-way Doppler tracking data and the inter-satellite range rate measurements. The gravity field used for the GRAIL science orbits was a GRAIL internal gravity field of degree and order 420 (420b8a), which had all primary mission inter-satellite range data included. The resulting orbit accuracy of the orbit in absolute sense is a the meter level and in relative range rate error between the spacecraft is better than 20 um/sec. The crash site SPKs included in this data set contain the locations of the spacecraft crash sites of the Moon surface relative to the Moon center, and fixed, zero-offset positions of the spacecraft relative to these sites, covering from the crash times far into the future. The 3-sigma accuracy of the crash site locations provided by the NAV team is 2.75 meters downtrack / 65 meters crosstrack for GRAIL-A and 3.33 meters downtrack / 17 meters crosstrack for GRAIL-B. The DE421 planetary ephemeris SPK file included in this data set contains ephemeris data for the Solar System planet barycenters, Sun, Mercury, Venus, Earth, Moon, and Mars. This version of ephemerides was officially used by the project during mission operations. The internal comments included this SPK file provide detailed accuracy information. More information about GRAIL SPK files is available in the file ``data/spk/spkinfo.txt''. This data set also includes the orbit number files generated by the NAIF's ORBNUM utility program using the archive spacecraft SPKs. These files are not SPICE kernels; for this reason they are provided in the ``extras/orbnum'' directory. For more information about the GRAIL orbit number files, see the file ``extras/orbnum/orbinfo.txt''. CK Files ======== One kind of C-kernel files is provided in this archive: the reconstructed spacecraft bus (SC) orientation CKs. The reconstructed spacecraft bus (SC) CK files were created from engineering telemetry downlinked from the spacecraft by NAIF. Neither formal nor informal accuracy estimates for the spacecraft bus attitude provided in these reconstructed CK files were available at the time when this archive was created. More information about GRAIL CK files is available in the file ``data/ck/ckinfo.txt''. PCK Files ========= Two PCK files are provided in this data set, one is a text PCK containing on the official IAU/IAG/COSPAR values accepted in 2006, the other is a binary PCK containing high-accuracy orientation data for the lunar principal axes (PA) reference frame, from the JPL Solar System Dynamics Group's planetary ephemeris DE-421. Both files were the versions used by the project during operations. More information about the PCK files included in this data set is available in the file ``data/pck/pckinfo.txt''. FK Files ======== This data set includes the GRAIL mission FK file, a generic Lunar FK file, and the crash site topocentric frame FK file. The GRAIL FK file defines the frames for the GRAIL spacecraft and their science instruments. The instrument frames defined in it incorporate the instrument mounting alignment data. The generic Lunar FK file defines a number of lunar body-fixed frames associated high-accuracy lunar orientation data provided by the JPL Solar System Dynamics Group's planetary ephemerides. The crash site topocentric frame FK file defines the topocentric frames at the spacecraft crash sites. More information about the GRAIL FK files is available in the file ``data/fk/fkinfo.txt''. IK Files ======== This data set includes IK files for instruments on the GRAIL spacecraft, including the Lunar Gravity Ranging System, MoonKAM cameras, and the star trackers. Because the sets of geometric parameters included in the IKs vary from instrument to instrument users are encouraged to carefully examine the IKs before using them. More information about GRAIL IK files is available in the file ``data/ik/ikinfo.txt''. SCLK Files ========== This data set includes the GRAIL Spacecraft Clock kernel files provide a tabulation of data needed for converting time measurements between ephemeris time (ET) and spacecraft clock time (SCLK). The GRAIL SPICE SCLK files were made from similar files--SCLK/SCET files, or SCLKvSCET files--produced by another mission entity. Each newly made SCLK file fully replaces the previous SCLK file. For GRAIL, the time correlation accuracy provided in the SCLK kernel files for the science phases is informally reported to be better than 40 milliseconds. SPICE software does not prohibit an SCLK file from being used for time conversions occurring for ``future times'' (or more accurately, for epochs that occur later than the epoch of the last telemetry data used in producing the last correlation coefficients found in the SCLK file). Such ``predict'' time conversions are likely to be inaccurate (changed somewhat) once the epoch of interest has been passed. More information about the GRAIL SCLK files is available in the file ``data/sclk/sclkinfo.txt''. LSK Files ========= Leapseconds kernel files provide a tabulation of ``leapseconds'' and some other terms used in converting time measurements between ephemeris time (ET) and Universal Time (UTC). ``Spacecraft Event Time'' (SCET) is the commonly used name for UTC events measured at the spacecraft. Metadata describing how the LSK data are obtained or computed is contained inside the LSK text file. The time conversion provided by SPICE LSK files is accurate to approximately 0.000030 seconds. More information about the LSK files is available in the file ``data/lsk/lskinfo.txt''. EK Files ======== The GRAIL project did not produce any EK files; therefore, no EKs are included in this data set. " END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_MISSION MISSION_NAME = "GRAVITY RECOVERY AND INTERIOR LABORATORY" END_OBJECT = DATA_SET_MISSION OBJECT = DATA_SET_TARGET TARGET_NAME = "MOON" END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = "GRAIL-A" INSTRUMENT_ID = SPICE END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = "GRAIL-B" INSTRUMENT_ID = SPICE END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "ACTON1994" END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END