PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM LABEL_REVISION_NOTE = " 1999-03-10 NAIF:Semenov Initial entry; 2002-11-01 NAIF:Semenov Updated for PDS-D; 2003-10-15 NAIF:Semenov Updated for ROTO CKs; 2005-05-10 NAIF:Semenov Added ABSTRACT_DESC and CITATION_DESC and a note regarding corrected SA CKs; 2006-03-06 NAIF:Semenov Added required DATA_SET_MISSION object; 2007-02-20 NAIF:Semenov Numerous revisions for the end of the mission and additional products; 2007-06-11 NAIF:Semenov removed ARCHIVE_STATUS keyword; 2008-01-10 NAIF:Semenov set INSTRUMENT_ID to SPICE; 2008-05-13 NAIF:Semenov set STOP_TIME; 2013-01-07 NAIF:Semenov updated PCK description; " OBJECT = DATA_SET DATA_SET_ID = "MGS-M-SPICE-6-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "MGS MARS SPICE KERNELS V1.0" DATA_SET_TERSE_DESC = " Navigation and ancillary data in the form of SPICE System kernel files for the Mars Global Surveyor. " ABSTRACT_DESC = " This data set includes the complete set of Mars Global Surveyor SPICE data files (``kernel files''), which can be accessed using SPICE software. The SPICE data contains 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, spacecraft sequences of events, and data needed for relevant time conversions. " CITATION_DESC = " Semenov, B.V., L.S. Elson, and C.H. Acton, MARS GLOBAL SURVEYOR SPICE KERNELS V1.0, MGS-M-SPICE-6-V1.0, NASA Planetary Data System, 1998. " DATA_SET_COLLECTION_MEMBER_FLG = "N" START_TIME = 1996-11-06T08:00:00 STOP_TIME = 2006-11-02T23:24:48 DATA_SET_RELEASE_DATE = 2002-11-01 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 Mars Global Surveyor SPICE data files (``kernel files''), which can be accessed using SPICE software. The SPICE data contains 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, spacecraft sequences of events, and data needed for relevant time conversions. This data set is contained on a single virtual volume, MGSP_1000, including data from all mission phases and covering from launch, 1996-11-06T08:00:00, 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 approximately every three to six months. Initially this data set was released on multiple volumes, each containing the complete set of SPICE kernels for two or more mission phases, a single mission phase or a portion of a mission phase. During the transition to the PDS on-line distribution system at the end of 2002 the data from all volumes were segregated on a single volume, MGSP_1000. The coverages of the original volumes are summarized in the table: VOLUME ID START TIME STOP TIME --------- ------------------- ------------------- MGSP_0001 1996-11-06T08:00:00 1998-05-28T00:00:00 MGSP_0002 1998-05-28T00:00:00 1999-03-09T00:00:00 MGSP_0003 1999-03-09T01:00:00 1999-06-02T00:00:00 MGSP_0004 1999-06-02T00:00:00 1999-08-25T00:00:00 MGSP_0005 1999-08-25T00:00:00 1999-11-17T00:00:00 MGSP_0006 1999-11-17T00:00:00 2000-02-09T00:00:00 MGSP_0007 2000-02-09T00:00:00 2000-05-03T00:00:00 MGSP_0008 2000-05-03T00:00:00 2000-07-26T00:00:00 MGSP_0009 2000-07-26T00:00:00 2000-10-18T00:00:00 MGSP_0010 2000-10-18T00:00:00 2001-02-01T00:00:00 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 inter-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 MGS 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. SPICELIB 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 MGS 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 (reconstructed and nominal post-mission trajectory), SPK files for Phobos, Deimos, Mars, Earth and Sun, and SPK files for the solar array and high gain antenna structures and the locations of the MAG/ER instrument components on the solar arrays. Each of these kinds is briefly described below; more information is available in the file ``data/spk/spkinfo.txt''. Spacecraft Orbit SPK Files -------------------------- Most of the included SPK files provide the orbit of the MGS spacecraft. Most missions had a single source for this kind of data, but for MGS there were three sources: the Mars Surveyor Operations Project (MSOP) Navigation Team (NAV), the Mars Orbiter Laser Altimeter (MOLA) Team based at the Goddard Space Flight Center (GSFC), and the Inner Planet Navigation and Gravity Group (IPNG) based at JPL. The MOLA and IPNG groups produced multiple solutions for some of the mission phases, presumably yielding ever more accurate results as the gravity model used and other data handling improvements come into play. It is possible that any or all of these three groups will produce yet more--and presumably further improved--solutions in the future; these should eventually be available from NAIF. For all three solution sets, each archival SPK file covering a particular mission phase was made by merging together numerous shorter duration individual files. The component files used to make a merged product can be discerned by reading the descriptive information (metadata) found in the comment area of each file. The subset of SPKs to be used in a particular application should be picked from the archived set considering these factors: 1) Completeness of coverage: are there gaps in the orbit data, or missing mission phases? 2) Discontinuities: are position and velocity data continuous across individual orbit data fits comprising the merged product? More particularly, how large are these discontinuities? 3) What kinds of data were used in producing the orbit solutions? (In all cases, doppler and range data were used. For the MOLA/GSFC solutions, laser range points were also used.) 4) What models were used (particularly what Mars gravity model) and how might this affect the orbit solution? Based on these factors NAIF recommends that, unless there are special circumstances, the MGS NAV SPKs providing the most complete coverage and the latest SPKs produced by IPNG (version MGS95J) providing the most accurate solution are used together. The two sets of files should be loaded in such way that the IPNG MGS95J SPKs have higher priority (loaded last) and provide data for all interval that they cover while the MGS NAV SPKs have lower priority (loaded first) and provide coverage during the gaps in the IPNG MGS95J set. This data set also includes the orbit number files generated during the mission using the NAIF's ORBNUM utility program for each of the NAV spacecraft trajectory SPK files for the orbital phases of the mission. These files are not SPICE kernels; for this reason they are provided in the ``extras/orbnum'' directory. For more information about the MGS orbit number files, see the file ``extras/orbnum/orbinfo.txt''. Post-mission Nominal Spacecraft Orbit SPK ----------------------------------------- This data set also includes the post-mission nominal trajectory SPK file provided by the MGS NAV team and covering 50 years into the future starting at the end of the mission. Since this file provides an extremely long term prediction it should only be used to get a rough idea where the MGS orbit plane might be years after the end of the mission. Solar System Body SPK Files --------------------------- The MAR033 Martian satellite ephemeris SPK files provided in this data set were used by the project up to the fall of 2006. They contain ephemeris data for Phobos, Deimos, Earth and the sun. Formal one-sigma accuracy information for Phobos and Deimos are reported as follows: Body Downtrack Crosstrack Radial Uncertainty Uncertainty Uncertainty ------ ----------- ----------- ----------- Phobos 15 km 7 km 3 km Deimos 30 km 16 km 3 km The MAR063 Martian satellite ephemeris SPK file provided in this data set superseded the MAR033 files and was used by the project starting in the fall of 2006. As the MAR033 files the MAR063 SPK contain ephemeris data for Phobos, Deimos, Earth and the sun. Formal one-sigma accuracy information for Phobos and Deimos are reported as follows: Body Downtrack Crosstrack Radial Uncertainty Uncertainty Uncertainty ------ ----------- ----------- ----------- Phobos 5 km 2 km 2 km Deimos 10 km 3 km 3 km Accuracies for Mars-Sun and Mars-Earth directions (positions obtained from SPK files) are at the level of 0.001 arc-sec (1 sigma). Spacecraft Solar Array, High Gain Antenna and MAG/ER SPK Files -------------------------------------------------------------- Included in the SPK archive are two files containing location information (fixed offsets) for spacecraft structures--the high gain antenna and the Magnetometer instrument components mounted on solar arrays. See the metadata for each of these files--found in the comment area--for detailed descriptions of how the files were produced. CK Files ======== Three kinds of C-kernel files are provided in this archive: the spacecraft bus orientation CKs (reconstructed and nominal orientation for ROTO observations), the solar arrays orientation CKs (reconstructed only) and the high gain antenna orientation CKs (reconstructed only). Each of these kinds is briefly described below; more information is available in the file ``data/ck/ckinfo.txt''. All three kinds of reconstructed CK files are produced from engineering telemetry downlinked from the spacecraft while the ROTO CK file was produced from the commanded attitude for each of the ROTO observations. As is often the case with spacecraft engineering telemetry-based measurements, considerable uncertainty exists as to the accuracy of such measurements, and, data quality (accuracy and completeness) can vary significantly. Spacecraft Bus CK Files ----------------------- CK files providing the orientation of the spacecraft bus (``the spacecraft'') can be used to support interpretation of data obtained by all science experiments. The stated requirement on spacecraft orientation knowledge is better than three mrad per axis, 3-sigma. It has been informally reported that the achieved orientation knowledge is significantly better than this, but at the time of this archive production there are no known reports substantiating this or providing further details. Processing of the Mars Orbiter Laser Altimeter (MOLA) data by the MOLA Team at GSFC led to a determination that the spacecraft clock time tags assigned to the downlinked spacecraft orientation quaternions that comprise these CK files had a time bias. This assessment was verified by the Lockheed Martin Astronautics (LMA) spacecraft control team, although firm determination of the magnitude has been illusive. The situation was further complicated by knowledge that on-board AACS software filter settings that resulted in this timing bias varied during the mission. The magnitude of this bias has been estimated in the range of 1 to nearly 2.5 seconds. Based on this analysis a constant timing correction was applied to the time tags of the attitude data points stored in the CK files. The correction value used in creating the spacecraft bus CK files was set to -1.15 seconds for the data before 1999-02-26T11:45, switched between -1.15 and -2.3 seconds for the data between 1999-02-26 and 1999-03-31, and was set to -2.3 seconds for the data after 1999-03-31. The internal comments in each of the CK files specifically state which value(s) was(were) used for the data in the file. Unfortunately the MOLA team later concluded that applying the larger offset (-2.3 seconds) to the Mapping, Extended and Extended-Extended mission attitude time tags might have been a mistake and that the smaller value (-1.15 seconds) should have been used instead. They suggested that to compensate for the ``over-corrected'' timing of the CK data a half of the -2.3 second offset should be ``taken back'' during reading of the CK files by subtracting -1.15 seconds from the CK pointing request time. This small diagram illustrates how the MOLA team compensated this in their instrument processing software: CK request time at ``true'' which correct s/c observation orientation is stored time | | | <...................... | | 1.15 seconds must | | be subtracted to get | | correct orientation | | | | V V ............................................ . 2.3 seconds were subtracted . . by the ground s/w making CK files . V . @ @ ......................> @ ^ ^ 1.15 seconds were ^ | | added by AACS filter | | | | | | | time tag ``true'' time for time tag in CK file which s/c orientation in s/c TLM was determined Other than computing the spacecraft attitude at the observation time minus 1.15 seconds as the diagram suggests, the offset can be also ``taken out'' by processing each of the Mapping, Extended and Extended-Extended mission spacecraft CK files through the CKSMRG program with the ``-C'' argument set to +1.15 seconds. Nominal ROTO Orientation Spacecraft Bus CK Files ------------------------------------------------ This data set also includes CK files providing predict orientation for the spacecraft bus for ``ROTO'' observations during Extended and Extended-Extended phases of the mission. These files should be used only for the times when reconstructed orientation is not available. Solar Array CK Files -------------------- CK files providing orientation of the solar arrays relative to the spacecraft bus are included to support interpretation of data collected by the MAG/ER instruments mounted on these arrays. The situation is complicated somewhat due to the non-complete deployment of one of the two arrays. There is no currently known mechanism for estimating the accuracy of the solar array CK files; however it is assumed that they nevertheless satisfy the requirements of the MAG/ER experiment. The first version of the solar array CKs for Cruise, Aerobraking 1, Science Phasing 1, and Science Phasing 2 mission phases, released in 1998, contained incorrect angular rate data resulted from the bug in the process that generated daily solar array CKs during operations. This was discovered in 2005 and version 2 of these files with corrected angular rate data was added to the data set. Pointing data was correct and is the same in both versions. High Gain Antenna CK Files -------------------------- CK files providing orientation of the high gain antenna (HGA) relative to the spacecraft bus are included to support the Radio Science experiment. They may also be used to help with calibration or data processing for the MAG/ER experiment. There is no currently known mechanism for estimating the accuracy of the HGA CK files. (It may be possible that the Radio Science experiment will later yield some assessment of this accuracy.) Caution on Using CK Files ------------------------- While not a data accuracy issue, the CK user is nevertheless cautioned to understand and properly use the data found and tolerance arguments that are inputs to the CK reader provided in the SPICE Toolkit. Descriptions about how to read CK files are found in the CK reader routine headers (top of the source code files) and in the ``CK Required Reading'' document; these are contained in each SPICE Toolkit package. PCK Files ========= PCK files provide size, shape and orientation data for ``target'' bodies such as Mars, Phobos and Deimos. A description of these data items and reference to their source is provided inside the PCK file, which is a simple text file that can be viewed using any word processor, text editor or text display utility. Of the three PCK files provided in this data set, the first PCK file ``pck00006.tpc'' is based on the official IAU/IAG/COSPAR values accepted in 1994. This file has been distributed and used during pre-mapping and mapping phases of the mission. The data in the file is generally rather old and in any case certainly do not reflect any new parameter determinations achieved as a result of science instrument data processing for the MGS mission. The second PCK file ``mars_iau2000_v0.tpc'' is based on the IAU/IAG/COSPAR values accepted in 2000. It contains constants only for Mars and Martian satellites. Many of these constants have been determined as the result of the MGS science data processing. The third PCK file ``pck00009.tpc'' is based on the IAU/IAG/COSPAR values accepted in 2006. It contains constants for for Mars and Martian satellites as well as for other Solar System planets and satellites. The Mars and Martian satellites constants provided in the PCK file are the same those in the second PCK file ``mars_iau2000_v0.tpc''. More information about the PCK files included in this data set is available in the file ``data/pck/pckinfo.txt''. FK Files ======== Frames kernel files provide specifications for how one reference frame is defined relative to another frame. In one case--that of fixed offset frames such as used for defining the mounting alignment of each antenna relative to the spacecraft--the FK file contains the actual parameter values. Metadata describing these mounting alignment estimates are provided in the one FK file included in this archive. There are no (known) accuracy estimates for these data at the time of this archive preparation. Historically the frame definitions for MGS were not provided in a single FK file as they were for many other missions. Instead some of the frames were defined in the SCLK files, others -- in the IK files, and yet more frames were defined in the HGA FK file. At the end of of the mission all of the frame definitions were collected in a single FK file included in this data set along with the older HGA FK file. More information about the MGS FK files is available in the file ``data/fk/fkinfo.txt''. IK Files ======== Instrument kernel files provide specifications for the mounting alignment and--where applicable--field-of-view size, shape and orientation for the named instrument. Metadata describing these estimates are provided in each IK file included in this archive. Parameter values were determined from pre-launch measurements or from manufacturing blueprints. (An update for the MOLA alignment using in-flight measurements is expected later in the mission.) There are no (known) accuracy estimates for these data at the time of this archive preparation. Although this data set includes an IK file(s) for each of the MGS instruments -- MAG/ER, MHSA, MOC, MOLA, and TES, -- not all of them are equally well developed. On one side of the ``spectrum'' are the latest MOC and MOLA IK files containing the most up to date geometric calibration data, FOV definitions, etc. while on the other side is the TES IK still providing bare minimum of information based on the pre-launch measurements (a better TES IK may be added to the data set at a later date.) Because of that users are encouraged to carefully examine the IKs before using them. More information about MGS FK files is available in the file ``data/ik/ikinfo.txt''. SCLK Files ========== Spacecraft Clock kernel files provide a tabulation of data needed for converting time measurements between ephemeris time (ET) and spacecraft clock time (SCLK). A SPICE SCLK file is made from a similar file--SCLK/SCET file, or SCLKvSCET file--produced by another mission entity. Each newly made SCLK file fully replaces the previous SCLK file. For MGS the time correlation accuracy provided in SCLK/SCET files is informally reported by the Lockheed Martin spacecraft team to be better than 100 milliseconds during cruise and better than 10 milliseconds during orbital phases. (NAIF has not attempted to obtain or produce an independent corroboration of these LMA estimates.) The SPICE SCLK file has essentially the same accuracy as the SCLK/SCET file. 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 MGS 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 ======== Two kinds of Events kernel (EK) files are included in this archive: Experimenter's Notebook EKs and Sequence EKs. Each of these kinds is briefly described below; more information is available in the file ``data/ek/ekinfo.txt''. Experimenter's Notebook EKs kernels are a digital analog to the traditional paper laboratory notebook. Hence Experimenter's Notebook entries represent truth only as seen by the author of the notes--there is no attempt made to independently validate any aspect of Experimenter's Notebook information. Sequence EKs comprise a summary of all commands sent to the spacecraft as well as some ground system events and instrument state (status) summaries. All Sequence EK entries are time tagged. In this archive includes Sequence EKs created the automated process for providing ``as run'' inputs reflecting what was actually sent to the spacecraft, and what execution times were used, was not yet implemented for the in-orbit mission phases. The cruise ESQ was produced from a cruise phase Predicted Events File (PEF) that was hand edited to reflect ``as run'' status. Consequently the validity of this ESQ is uncertain, but there is some reason to imagine that the handwork was well done. " END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_MISSION MISSION_NAME = "MARS GLOBAL SURVEYOR" END_OBJECT = DATA_SET_MISSION OBJECT = DATA_SET_TARGET TARGET_NAME = MARS END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = MGS INSTRUMENT_ID = "SPICE" END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = UNK END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END