KPL/IK \beginlabel PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM RECORD_BYTES = "N/A" ^SPICE_KERNEL = "MGS_MOLA_V22.TI" MISSION_NAME = "MARS GLOBAL SURVEYOR" SPACECRAFT_NAME = "MARS GLOBAL SURVEYOR" DATA_SET_ID = "MGS-M-SPICE-6-V1.0" KERNEL_TYPE_ID = IK PRODUCT_ID = "MGS_MOLA_V22.TI" PRODUCT_CREATION_TIME = 2000-01-04T09:41:59 PRODUCER_ID = "NAIF/JPL" MISSION_PHASE_NAME = "N/A" PRODUCT_VERSION_TYPE = ACTUAL PLATFORM_OR_MOUNTING_NAME = "MGS NADIR DECK" START_TIME = "N/A" STOP_TIME = "N/A" SPACECRAFT_CLOCK_START_COUNT = "N/A" SPACECRAFT_CLOCK_STOP_COUNT = "N/A" TARGET_NAME = MARS INSTRUMENT_NAME = "MARS ORBITER LASER ALTIMETER" NAIF_INSTRUMENT_ID = -94040 SOURCE_PRODUCT_ID = "N/A" NOTE = "See comments in the file for details" OBJECT = SPICE_KERNEL INTERCHANGE_FORMAT = ASCII KERNEL_TYPE = INSTRUMENT DESCRIPTION = "MGS Mars Orbiter Laser Altimeter instrument parameters SPICE I-Kernel File. This file also contains MOLA Frame definitions and location of the MGS antenna phase centers and center of gravity for some spacecraft configurations." END_OBJECT = SPICE_KERNEL \endlabel MOLA Instrument Kernel =========================================================================== This instrument kernel (I-kernel) contains the Mars Orbiter Laser Altimeter (MOLA) instrument mounting offset, intrument frame definition and instrument location. Version and Date -------------------------------------------------------- Version 2.2 -- May 27, 1998 Added section contaning coordinates of the HGA and LGAs geometric centers in stowed position. Version 2.1 -- August 25, 1997 Z coordinate of MOLA was changed to be 1.9202 meters (old value 1.9116 meters) after confirmation from Rich Hund of LMA. Version 2.0 -- August 19, 1997 Section specifying location of MOLA, s/c center of mass and s/c frame origin was added. Version 1.2 -- August 11, 1997 Frame definition was corrected to represent the correct transformation sense. Version 1.1 -- June 19, 1997 The MOLA frame definition section was added to support utilization of the SPICE system FRAMES capabilities. Version 1.0 -- November 26, 1996 Initial Release. References -------------------------------------------------------- 1. ``MGS Alignment Transformation'', by Richard A. Hund, November 26, 1996. 2. ``MGS Payload Data Sheet'' by C.Kloss, October 31, 1995, 3. ``C-kernel Required Reading'' 4. ``Kernel Pool Required Reading'' 5. ``Frames Required Reading'' 6. ``MGS Mission Specification. Mission Requirements and Vehicle Description'', MDC 95H0026B, MGS REV B. APRIL 1996. 7. ``Nadir Equipment Deck. Science Instrument Configuration" DWG, 23 Jan 1995; provived by Carl Kloss. 8. Phone message from Jon Nichols re. location of the spacecarft's center of mass during mapping phase of the mission; August 13, 1997. Implementation Notes -------------------------------------------------------- This file is used by the SPICE system as follows: programs that make use of this I-kernel must `load' the kernel, normally during program initialization. Loading the kernel associates data items with their names in a data structure called the `kernel pool'. The SPICELIB routine LDPOOL loads a kernel file into the pool as shown below. CALL LDPOOL ( I_kernel_name ) In order for a program or subroutine to extract data from the pool, the SPICELIB routines GDPOOL and GIPOOL are used. See [4] for more details. This file was created and may be updated with a text editor or word processor. Naming Conventions -------------------------------------------------------- All names referencing values in this I-kernel start with the characters `INS' followed by the NAIF Mars Global Surveyor spacecraft ID number (-94) followed by the NAIF three digit MOLA instrument reference number (040). The remainder of the name is an underscore character followed by the unique name of the data item. For example, the MOLA offset relative to the spacecraft frame, given as three Euler angles, is specified using two items: INS-94040_EULER_ANGLES INS-94040_EULER_AXES The upper bound on the length of the name of any data item is 32 characters. If the same item is included in more then one file, or if the same item appears more than once within a single file, the latest value supersedes any earlier values. MOLA mounting offset -------------------------------------------------------- This section describes the offset of the MOLA instrument fixed frame (the frame fixed to the alignment cube on the MOLA) relative to the Mars Global Surveyor spacecraft frame. From the offset, given as three rotation angles -- ROLL, PITCH and YAW, a rotation matrix can be constructed that will transform the components of a vector expressed in the spacecraft frame to components expressed in the MOLA instrument fixed frame. For example, if x y and z are the components of a vector expressed in the spacecraft frame, X Y and Z will be the components of the same vector expressed in the MOLA instrument fixed frame: [ X ] [ ] [ x ] | Y | = | ROT | | y | [ Z ] [ ] [ z ] where ROT is the rotation matrix constructed from the rotation angles as follows: [ ] [ ] [ ] [ ] [ ROT ] = [ YAW ] [ PITCH ] [ ROLL ] [ ] [ ] [ ] [ ] Z Y X where each of three matrixes on the right side represent a coordinate frame rotation by the given angle around the indicated axis. See the SPICELIB routine EUL2M for more information about constructing a rotation matrix from a set of rotation angles. The following measured values of ROLL, PITCH and YAW are provided in [1]: ROLL = 0.021 (degrees) PITCH = 359.995 (degrees) YAW = 0.059 (degrees) The keyword INS-94040_EULER_ANGLES contains these values, in radians, in the following order: INS-94040_EULER_ANGLES = ( ``ROLL'' ``PITCH'' ``YAW'' ) The keyword INS-94040_EULER_AXES contains integer codes of the corresponding axes of rotations (1 -- X, 2 -- Y, 3 -- Z). \begindata INS-94040_EULER_ANGLES = ( 0.000366519143 6.283098040717 0.001029744259 ) INS-94040_EULER_AXES = ( 1 2 3 ) \begintext Laser Transmitter -------------------------------------------------------- The laser transmitter beam divergence, from [2], is 0.25 mrad. Unit are in radians \begindata INS-94040_LASER_BEAM_DIVERGENCE = ( 0.00025 ) \begintext Altimeter Receiver -------------------------------------------------------- The altimeter receiver field of view (FOV), from [2], is cone of 0.85 mrad. Units are in radians \begindata INS-94040_RECEIVER_FOV = ( 0.00085 ) \begintext Platform ID -------------------------------------------------------- This number is the NAIF instrument ID of the platform on which the instrument is mounted. \begindata INS-94040_PLATFORM_ID = ( -94000 ) \begintext Instrument Frame Definition -------------------------------------------------------- The instrument frame definition for MOLA. This definiton will be utilized by SPICE's FRAMES subsystem to provide automatic state transformations to/from MOLA instrument frame frame. Note that SPICE toolkit version N0047 or higher is required to use fixed-offset frames. Note that angles in the frame definitions are specified for "from instrument to base (relative to) frame" transformation. \begindata FRAME_MGS_MOLA = -94040 FRAME_-94040_NAME = 'MGS_MOLA' FRAME_-94040_CLASS = 4 FRAME_-94040_CLASS_ID = -94040 FRAME_-94040_CENTER = -94 TKFRAME_-94040_SPEC = 'ANGLES' TKFRAME_-94040_RELATIVE = 'MGS_SPACECRAFT' TKFRAME_-94040_ANGLES = ( -0.000366519143, -6.283098040717, -0.001029744259 ) TKFRAME_-94040_AXES = ( 1, 2, 3 ) TKFRAME_-94040_UNITS = 'RADIANS' \begintext MOLA and s/c center of mass locations -------------------------------------------------------- The locations of the MOLA instrument [ref. 6,7] and the s/c center of mass for stowed (launch) [ref. 6] and nominal mapping [ref. 8] configuration are specified relative to the s/c fixed which is defined as follows: - origin of the frame is located at the intersection of the s/c--launch vehicle interface plane and the spacecraft's central axis, i.e at the center of the bottom of the propulsion unit nozzle; - Z axis is along s/c central axis; positive Z direction is from s/c bottom towards nadir equipment deck; - X axis is perpendicular to Z axis and points thought the side of the s/c which high gain antenna is mounted on; positive X direction is from the center of the s/c toward HGA side; - Y axis completes X and Z axes to right hand frame. The locations coordinates are given in meters. \begindata INS-94040_MOLA_LOC = ( 0.3383 0.3126 1.9202 ) INS-94040_SC_LAUNCH_CG_LOC = ( -0.0010 -0.0007 1.1320 ) INS-94040_SC_MAPPING_CG_LOC = ( 0.0298 0.0718 0.9970 ) \begintext MGS Antenna Locations (stowed configuration). -------------------------------------------------------- Three MGS antennas -- main HGA and "FRONT" and "BACK" LGAs -- in stowed position are shown on the diagrams below: MGS S/C "-Y" Side View: ------------------------------------------------- ^ S/C +Z Axis | | 39.318" |<----------->| | | | 39.318" | |<--------->| | | | | | 20.72" | | |<-->| | | | | LGAB __LGAF ---------- @=| |=@ -------- | | __ ^ ^ |__|/ | | | +-----------+ / | | | | | / | | | | | / | | 81.46" | | || | | |81.56" || HGA | ---- | | | || | ^ | | | | \ | | | | | | \ | | | | | | \ | | | | | | \__| | | | +----+-+----+ | | | / \ | | | / \ 66.15"| | v / \ v v ---- +----#----+ ----------------- ---> S/C Frame S/C +X Axis Origin MGS S/C Top View: ------------------------------------------------- ^ S/C +Y Axis | | __ / | +-----------+ / | | | / | | S/C Frame | / | | Origin || HGA | ---- | # ||__ | ---- ---> ^ | || | | ^ S/C +X Axis |30.05" || | | | | | || | | | | +----+-+----+| | | | 28.18" v | |\__| v --------------- @=|__|=@ ----- LGAB LGAF The HGA center, coordinates of which are given below, is considered to be at the geometric center of the outside (big diameter) circle of the antenna. The LGA centers coordinates of which are given below are considered to be at the geometric center of the 1.45" x 1.45" square-shaped active element of the antenna. In both cases, the "geometric" centers of the antennas probably don't match with antenna's phase centers, location of which have to be computed using complete antenna geometry. MGS Antenna Center locations, in inches: s/c X s/c Y s/c Z -------- -------- --------- HGA 39.318 0.0 66.15 "FRONT" LGA 39.318 -28.18 81.46 "BACK" LGA 20.72 -30.05 81.56 Same, in meters: s/c X s/c Y s/c Z -------- -------- --------- HGA 0.999 0.000 1.680 "FRONT" LGA 0.999 -0.716 2.069 "BACK" LGA 0.526 -0.763 2.072 Cooridnates in meters are the data keywords: \begindata INS-94040_HGA_STOWED_LOC = ( 0.999 0.000 1.680 ) INS-94040_FRONT_LGA_STOWED_LOC = ( 0.999 -0.716 2.069 ) INS-94040_BACK_LGA_STOWED_LOC = ( 0.526 -0.763 2.072 ) \begintext