 
 
MGS S/C CK File, Nominal Orientation for all ROTOs up to 2006-10-13
===========================================================================
 
     Created by Boris Semenov, NAIF/JPL, December 4, 2006
 
 
Orientation Data in the File
--------------------------------------------------------
 
     This file contains nominal orienation of the Mars Global Surveyor
     (MGS) spacecraft frame, 'MGS_SPACECRAFT', relative to the 'MARSIAU'
     inertial frame for the ROTO periods during the extended phase of the
     mission. The NAIF ID code for the 'MGS_SPACECRAFT' frame is -94000.
 
 
Status
--------------------------------------------------------
 
     This file provides nominal (``planned'') orientation for MGS
     observations in ROTO mode. It is intended to ``fill in'' some of the
     gaps in the archived reconstructed CKs for the extended phase of the
     mission. Note that since TLM orientation was available for most --
     about 90 percent -- ROTOs covered by this file, this file should be
     used only for those ROTOs for which the TLM data was not present. If
     this file is loaded together with the TLM-based CKs, it should always
     be loaded first to make sure that the data in it is accessed last.
 
 
Pedigree
--------------------------------------------------------
 
     While in general the coverage of the reconstructed CK files was very
     good, occasionally it had gaps due to the TLM outages. During the
     primary mapping mission and nadir pointing periods in the extended
     mission, science teams "worked around" gaps by assuming nominal nadir
     pointing. But this assumption did not work for the ROTO periods, when
     the s/c was intentionally slewed off nadir to image an area of special
     interest such as potential MER landing sites. For gaps during ROTOs,
     which there were a few of during the extended phase of the mission,
     science teams used commanded inertial orientation quaternions.
 
     At the time when the extended mission data was archived with PDS, the
     MOC science team contacted NAIF and suggested that it would be
     beneficial to include the commanded orientation for the ROTOs on the
     MGS SPICE PDS volumes. It provided NAIF with the times when the s/c
     was in the ROTO orientation and the commanded inertial quaternion for
     them (see Appendix 1).
 
     The times provided in the nominal ROTO pointing data were for the
     start of the slew from nadir to ROTO orientation and end of the slew
     from ROTO back to nadir. This CK attempts to model the slew by
     computing the nadir orientations at these times and the duration of
     the slews. The nadir orientation at the beginning and the end of each
     ROTO has been computed assuming the s/c +Z axis pointing exactly at
     the nearest point on the surface of Mars ellipsoid and the s/c -X axis
     pointing as close as possible to the s/c velocity vector. The slew
     have been modeled as the shortest uniform rotation from nadir-to-ROTO
     or ROTO-to-nadir orientation with average slew rate of 0.25 degrees
     per second.
 
 
Approximate Time Coverage
--------------------------------------------------------
 
     Although the boundaries of the segment contained in this file indicate
     that the file covers the following interval:
 
        COVERAGE BEGIN TIME (UTC):   2001-02-16T02:10:00.522
        COVERAGE END TIME (UTC):     2006-10-13T17:08:29.987
 
     in reality it covers only a set of short intervals, each corresponding
     to a particular ROTO observation.
 
     A table containing the complete list of ROTO intervals covered by the
     file is provided at the end of these comments.
 
 
Usage Note
--------------------------------------------------------
 
     In order to use this file an MGS SCLK file containing coefficients
     mapping MGS on-board time to ET must be loaded into a user's program.
 
 
Related Kernels
--------------------------------------------------------
 
     This file was created with LSK file naif0008.tls and MGS SCLK file
     MGS_SCLKSCET.00061.tsc.
 
 
Contacts
--------------------------------------------------------
 
     If you have any question regarding this data contact NAIF at JPL:
 
        Charles H. Acton, Jr
        (818)-354-3869
        chuck.acton@jpl.nasa.gov
 
        Boris V. Semenov
        (818)-354-8136
        boris.semenov@jpl.nasa.gov
 
 
Appendix 1: Nominal ROTO Orientation Provided by MSSS
--------------------------------------------------------
 
     The nominal ROTO orientation quaternions have been provided by MSSS in
     a text file containing 4-line block for each ROTO. The lines in each
     block were as follows:
 
        -- LINE 1 is a comment indicating the orbit during which ROTO
           took place;
 
        -- LINE 2 contains the time (ephemeris seconds past J2000) of the
           beginning of the slew from nadir to ROTO orientation and s/c
           inertial ROTO orientation quaternion components (iq(1) iq(2)
           iq(3) iq(4)), from which a matrix rotating vectors from the s/c
           to MARSIAU frame can be computed as follows:
 
              q(1) = -iq(4)
              q(2) =  iq(1)
              q(3) =  iq(2)
              q(4) =  iq(3)
              call q2m(q, m)
 
        -- LINE 3 contains approximate time (ephemeris seconds past J2000)
           of the end of the slew from ROTO back to nadir orientation
 
        -- LINE 4 is blank and is used to separate ROTO data blocks.
 
     This is the combined contents of the ROTO files provided by MSSS:
 
        # Orbit 8690
        35561464.708 6.678046E-01 9.297969E-02 -7.349624E-01 -7.226322E-02
        35562424.708 nadir
 
        # Orbit 8776
        36168268.873 4.164893E-01 8.449914E-04 -9.002700E-01 -1.266885E-01
        36169228.873 nadir
 
        (many lines were skipped here to reduce the example size)

        # Orbit 33946
        213975336.931 -9.39362E-01 -1.834417E-01 1.294238E-01 -2.592239E-01
        213976476.931 nadir
 
        # Orbit 33954
        214030235.170 6.771181E-01 2.088677E-01 -6.840977E-01 -1.729037E-01
        214031375.170 nadir
 
 
Appendix 2: MSOPCK Traceback Including Coverage Interval Table
--------------------------------------------------------
 
 
********************************************************************************
MSOPCK SETUP FILE: mgs_ext_roto_all_v9.msopck
********************************************************************************
 
 
   \begindata
 
      LSK_FILE_NAME           = 'naif0008.tls'
      SCLK_FILE_NAME          = 'MGS_SCLKSCET.00061.tsc'
 
      INTERNAL_FILE_NAME      = 'MGS ROTO NOM S/C ATT: EXTENDED MISSION UP TO 2006-10-13'
      COMMENTS_FILE_NAME      = 'mgs_ext_roto_all_v9.cmt'
 
      CK_TYPE                 = 3
      CK_SEGMENT_ID           = 'MGS ROTO NOM SC ATT UP TO 2006-10-13'
      INSTRUMENT_ID           = -94000
      REFERENCE_FRAME_NAME    = 'MARSIAU'
      ANGULAR_RATE_PRESENT    = 'MAKE UP/NO AVERAGING'
 
      MAXIMUM_VALID_INTERVAL  = 1200
 
      INPUT_TIME_TYPE         = 'UTC'
      INPUT_DATA_TYPE         = 'SPICE QUATERNIONS'
 
      PRODUCER_ID             = 'Boris Semenov, NAIF'
 
   \begintext
 
 
********************************************************************************
RUN-TIME OBTAINED META INFORMATION:
********************************************************************************
 
PRODUCT_CREATION_TIME = 2006-12-04T12:47:39
START_TIME            = 2001-02-16T02:10:00.521
STOP_TIME             = 2006-10-13T17:08:29.986
 
********************************************************************************
INTERPOLATION INTERVALS IN THE FILE SEGMENTS:
********************************************************************************
 
SEG.SUMMARY: ID -94000, COVERG: 2001-02-16T02:10:00.521 2006-10-13T17:08:29.986
--------------------------------------------------------------------------------
      2001-02-16T02:10:00.521    2001-02-16T02:26:00.521
      2001-02-23T02:43:24.687    2001-02-23T02:59:24.687

      (many lines were skipped here to reduce the example size)

      2006-10-13T01:34:31.747    2006-10-13T01:53:31.747
      2006-10-13T16:49:29.986    2006-10-13T17:08:29.986
 
 
********************************************************************************
 
