 
 
Stardust Spacecraft Orientation CK File, OPNAV Solution for Wild 2 Encounter
===========================================================================
 
     Created on May 13, 2004 by Boris Semenov, NAIF/JPL.
 
 
Orientation Data in the File
--------------------------------------------------------
 
     This file contains orientation and angular velocity data for the
     Stardust (SDU) spacecraft frame, 'SDU_SPACECRAFT', relative to the
     'J2000' inertial frame. The NAIF ID code for the 'SDU_SPACECRAFT'
     frame is -29000.
 
 
Status
--------------------------------------------------------
 
     This file has been prepared for archiving with the Planetary Data
     System.
 
 
Pedigree
--------------------------------------------------------
 
     This file contains actual spacecraft orientation data adjusted
     using attitude corrections computed by Shyam Bhaskaran, SDU
     Optical Navigation (OPNAV) team.
 
 
Original Attitude Data
 
     The original un-adjusted spacecraft orientation data came from two
     different sources:
 
          -- regular operational spacecraft orientation C-Kernel
             file(s),
 
          -- Small Forces File (SFF).
 
     During mission operation both types of files were produced by
     NAIF/JPL. Both inputs contained spacecraft orientation quaternions
     computed by the AACS flight s/w on-board the spacecraft.
 
     The regular operational CK file(s) were generated by an automated
     process that extracted spacecraft orientation quaternions and
     angular rates from the channelized telemetry stream.
 
     The SFF file(s), containing spacecraft thruster activity
     information, were generated by an automated process that
     decomutated the small forces packets. Each of these packets
     included spacecraft orientation quaternion.
 
     At the time of the archiving data from regular CK have been
     "dumped" into a text file using CK3DUMP program and the
     orientation data from the SFF have been extracted into another
     text file using a simple Perl script. After that the two data
     streams have been merged together, sorted, cleaned to remove
     duplicate records, and written to this CK file using MSOPCK
     program (see MSOPCK setup at the end of these comments.)
 
     Only "on-change" records from SFF were used because the
     orientation for the "other mode" SFF records was not
     representative of the instantaneous spacecraft orientation neither
     at the record start not at the record stop time. While the total
     quantity of SFF data was small compared the quantity of data from
     the ops CKs -- from 5% for the high downlink rate periods (when
     the spacecraft was close to Earth) to about 30% for the low rate
     downlink periods (when the spacecraft was far away), -- the SFF
     data were usually more dense for the periods when the spacecraft
     was not communicating with Earth. This and the fact that SFF data
     points were usually at the "edges" of AACS deadband made them very
     valuable for providing a better estimate of orientation for such
     periods.
 
     While both sources contained the actual telemetered orientation
     data (quaternions), the actual angular rates were available only
     in the CK file. The angular rates for the SFF attitude stream have
     been "manufactured" using MSOPCK program assuming uniform constant
     rotation between the adjacent SFF quaternions. These manufactured
     rates were verified to be close to the actual rates when the two
     data streams were merged together.
 
 
Application of OPNAV Correction
 
     Shyam Bhaskaran provided the following description of the OPNAV
     solution for s/c trajectory and attitude during the encounter:
 
         "The trajectory segment surrounding the closest approach to
          Wild 2 (time span from Jan 2, 2004 18:22:36 ET to Jan 2, 2004
          20:22:36) is specific and distinct from the the rest of the
          spacecraft trajectory. It was computed by fitting optical
          image data of Wild 2 taken by the spacecraft through closest
          approach, adjusting the position and attitude of the
          spacecraft relative to Wild 2 to achieve the best fit.
          Because it simultaneously solved for position and attitude,
          it must be used in conjunction with the special flyby
          attitude kernel in order to get the most accurate pointing
          information of the camera and other instruments.  Note that
          because of the method in which this trajectory segment was
          computed, it does not provide an accurate representation of
          the heliocentric location of the spacecraft; only its
          location relative to Wild 2 is accurate. Thus, it should only
          be used for the purpose of obtaining geometric and pointing
          information of Wild 2 relative to the spacecraft in the short
          time span surrounding the encounter."
 
     The attitude corrections applied to the telemetry attitude were
     expressed as delta angels that had to be added to the RA, DEC and
     TWIST of the s/c +X axis pointing direction. The delta angles
     values were:
 
          dRA    = -0.07 deg
          dDEC   = -0.06 deg
          dTWIST = -0.55 deg
 
     To apply these corrections each original attitude quaternion
     during the time period between the first image used in the OPNAV
     solution (image #2002, SCLK=757537019, not included into the
     downlink) and the last image (image #2115) was converted first to
     matrix, then to Euler angles assuming this rotation order:
 
          M = R3[TWIST]x * R2[DEC]y * R1[RA]z
 
     The angles were updated by adding deltas, and converted back to
     matrix using the same convention, and then to quaternions. The
     quaternions were written to this CK file using MSOPCK program.
 
 
Approximate Time Coverage
--------------------------------------------------------
 
     This file covers the following time span, UTC:
 
          START_TIME (UTC) = 2004-01-02T18:50:00.001
          STOP_TIME  (UTC) = 2004-01-02T19:34:59.999
 
     This file is a type 3 CK file (segment) which provides linear
     interpolation between orientation data points. Since the time
     spacing between the data points stored in this file is very small,
     especially during high rate attitude telemetry period around the
     flyby, the interpolation is permitted during the whole period
     covered by the file.
 
 
Usage Note
--------------------------------------------------------
 
     In order to use this file an SDU SCLK file, containing
     coefficients mapping SDU on-board time to ET, and standard LSK
     file, providing UTC to ET mapping, must be loaded into a user's
     program.
 
 
Contacts
--------------------------------------------------------
 
     If you have any question regarding this data contact NAIF at JPL:
 
        Boris V. Semenov
        (818)-354-8136
        boris.semenov@jpl.nasa.gov
 
 
MSOPCK Setup Information
--------------------------------------------------------
 
 
********************************************************************************
MSOPCK SETUP FILE: sdu_sc_rec_w2_opnav.msopck
********************************************************************************
 
\begindata
 
PRODUCER_ID             = 'NAIF/JPL'
 
LSK_FILE_NAME           = 'naif0007.tls'
SCLK_FILE_NAME          = 'SD_SCLKSCET.00105.tsc'
INTERNAL_FILE_NAME      = 'SDU SC BUS ADJUSTED ORIENTATION CK FILE BY NAIF/JPL'
 
CK_TYPE                 = 3
CK_SEGMENT_ID           = 'SDU SC BUS ADJUSTED ORIENTATION'
INSTRUMENT_ID           = -29000
REFERENCE_FRAME_NAME    = 'J2000'
ANGULAR_RATE_PRESENT    = 'YES'
 
INPUT_DATA_TYPE         = 'SPICE QUATERNIONS'
INPUT_TIME_TYPE         = 'TICKS'
ANGULAR_RATE_FRAME      = 'REFERENCE'
 
MAXIMUM_VALID_INTERVAL  = 60
 
\begintext
 
********************************************************************************
RUN-TIME OBTAINED META INFORMATION:
********************************************************************************
 
PRODUCT_CREATION_TIME = 2004-05-13T11:32:13
START_TIME            = 2004-01-02T18:50:00.001
STOP_TIME             = 2004-01-02T19:34:59.999
 
********************************************************************************
INTERPOLATION INTERVALS IN THE FILE SEGMENTS:
********************************************************************************
 
SEG.SUMMARY: ID -29000, COVERG: 2004-01-02T18:50:00.001 2004-01-02T19:34:59.999
--------------------------------------------------------------------------------
      2004-01-02T18:50:00.001    2004-01-02T19:34:59.999
 
 
********************************************************************************
 
 
