KPL/IK PMIRR Instrument kernel =========================================================================== This instrument kernel (I-kernel) contains the Pressure Modulator Infrared Radiometer (PMIRR) instrument mounting offset and mirror articulation parameters. This is a preliminary version. Version and Date --------------------------------------------------------------------------- Version 1.0 -- July 26, 1999 -- Boris Semenov, NAIF/JPL Initial Release. References --------------------------------------------------------------------------- 1. ``IDC for PMIRR'', Revision B1, September 14, 1998 2. ``MSPSAL009SS Spreadsheet: Final PMIRR Summary Sheet'', September 29, 1998 3. ``C-kernel Required Reading'' 4. ``Kernel Pool Required Reading'' 3. MCO Web pages describing the mission science objectives and science instrument payload; July 1999. Implementation Notes -------------------------------------------------------- User programs that need I-kernel data must `load' the I-kernel file, normally during program initialization. Loading the kernel using SPICELIB routine LDPOOL causes the data items and their associated values present in the kernel to become associated with a data structure called the ``kernel pool''. Then a user's program can obtain the value(s) for any data item using the SPICELIB routines GDPOOL, GIPOOL and GCPOOL. See [4] for details. This file was created and can 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 MCO spacecraft ID number (-127) followed by the NAIF three digit PMIRR instrument reference number (020). The remainder of the name is an underscore character followed by the unique name of the data item. For example, the PMIRR mirror step size is specified by INS-127020_MIRROR_STEP_SIZE 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. PMIRR Overview -------------------------------------------------------- From [3]: "PMIRR is a nine-channel limb and nadir scanning atmospheric sounder designed to vertically profile atmospheric temperature, dust, water vapor and condensate clouds and to quantify surface radiative balance. PMIRR observes in a broadband visible channel, calibrated by observations of a solar target mounted on the instrument, and in eight spectral intervals between 6 and 50 mkm in the thermal infrared. High spectral discrimination in the 6.7 mkm water vapor band and in two parts of the 15 mkm carbon dioxide bands is achieved by employing pressure (density) modulation cells in front of selected spectral detectors. Adequate signal-to-noise in these channels is ensured through the placement of their detectors on a cold focal plane assembly cooled to 80 K by a passive radiative cooler. The PMIRR Principal Investigator is Dr. Daniel McCleese (JPL/Caltech); Vasily Moroz (IKI/Russia) is Joint Principal Investigator. PMIRR science observations will commence only after the PMIRR radiator door is fully opened. Once PMIRR is deployed in the mapping orbit, vertical profiles of atmospheric properties are constructed from observations in three fields-of-view (FOV) stepped across the limb and onto the planet using a two-axis scan mirror in front of the primary telescope. Nominally, PMIRR views the aft limb, referenced to the spacecraft, except for the polar regions where it routinely views in and out of the plane of the spacecraft track to quantify the polar surface albedo by observing much of the bi-direction reflectance distribution function. PMIRR can also view to the side limb, acquiring observations characterized by different local times. PMIRR's vertical resolution is 5 km." PMIRR Mounting Offset --------------------------------------------------------------------------- This section describes the offset of the PMIRR instrument fixed frame (defined below) relative to the MCO spacecraft frame. Nominal PMIRR Frame Orientation ------------------------------- The PMIRR instrument fixed frame is defined as follows: +X direction is along the boresight vector, +Y is along scan mirror elevation gimbal axis and points the direction opposite to the cooler side (or in same direction as the s/c +Y axis, and +Z is completing to right hand frame (and is nominally along scan mirror azimuth axis). Nominal orientation of the PMIRR axis relative to the MCO S/C frame is shown on the diagram below: MCO S/C Frame: +Zsc | +Xs | _- | _- | _- ________|- +Ysc PMIRR Frame: +Zpmirr \ / +Xpmirr (boresight) (nadir) \ / \ / \ / \/ _- _- _- _- +Ypmirr This orientation can be achieved by two subsequent rotations (see [1]) -- first about +X axis of the S/C frame by -5 degreees: +Z' ^ +Zsc \ | \ | \<-* -5 degrees \ | +Ysc \| <--------_* +Xsc (+X') _- (into page) _- _- +Y' and second rotation by -10 degrees about new positon of the Y axis: +Zpmirr ^+Z' \ | \ | _- +Xpmirr -10 \<-| _- degrees \ | _- \|_- *---------> +Y'(+Ypmirr) +X' (into page) From these rotations which represent Euler angles, a rotation matrix can be constructed that will transform the components of a vector expressed in the spacecraft frame to components expressed in the PMIRR instrument fixed frame: [ X ] [ ] [ ] [ ] [ x ] | Y | = [ 0.0 ] [-10.0] [-5.0 ] | y | [ Z ] [ ] [ ] [ ] [ z ] PMIRR Z Y X S/C Note that the third rotation angle -- about Z -- is nominally equal to zero. Actual PMIRR Frame Orientation ------------------------------- Actual PMIRR frame orientaion was measred during multuple metrology sessions during S/C assembly and testing at LMA facilities in Denver. The following adjusted values for three rotation angles described above were specified in [2]: first rotation (about X): -5.0 degrees (nominal value) second rotation (about Y): -10.0 degrees (nominal value) third rotation (about Z): 0.0 degrees (nominal value) I-Kernel variables below store these values in radians: INS-127020_EULER_ANGLES = ( -0.0872664626 -0.1745329252 0.0 ) INS-127020_EULER_AXES = ( 1 2 3 ) Note that the keywords above are NOT enclosed between \begindata -- \begintext tokens and, therefore, they are NOT available to SPICE System toolkit. This is done to encourage use of the SPICE Frames subsystem that provides a more flexible interface to instrument mounting alignment information. Refer to the latest MCO Frames Kernel file for details. PMIRR Scan Mirror Gimbal Geometry --------------------------------------------------------------------------- This section describes the PMIRR scan mirror gimbal geometry such as orientation of the mirror gimbal axes relative to the PMIRR instrument frame, location of the axes relative to the instrumet boresight, mirror step count vs. reflection angle calibration tables, etc. Scan Mirror axes Orientation -------------------------------- PMIRR scan mirror can rotate independenly about two perpendicular axes -- elevation axis and azimuth axis. The elevation axis is defind to be along +Y axis of the PMIRR instrument frame: a) Elevation Axis (Azimuth=0) ----------------------------- Mirror Normal PMIRR Axes +PI/2 +Zpmirr (nominally nadir) ^ ^ | | | | | +Ypmirr | 0 <-------+-------> (into page)+--------> | +Xpmirr | (PMIRR boresight and | nominally s/c v velocity vector) -PI/2 b) Azimuth Axis (Elevation=0) ----------------------------- Mirror Normal Spacecraft Axes -PI/2 ^ | | | PI <-------+-------> 0 +--------> | +Xpmirr | (PMIRR boresight and | nominally s/c v velocity vector) +PI/2 In this preliminary version, nominal values will be used. Angles below are given in radians. \begindata \begintext Scan Mirror Step Size and --------------------------------------------------------------------------- The instrument scan mirror moves in units of `steps' in both the azimuth and elevation directions. There are 7680 steps in a 360 degree rotation [1]. The size of one step is given below in radians. \begindata INS-127020_MIRROR_STEP_SIZE = ( 8.1812308687234199E-04 ) \begintext The maximum and minimum step numbers in both azimuth and elevation directions are given below. \begindata INS-127020_MIRROR_STEP_RANGE_AZ = ( -3840 3840 ) INS-127020_MIRROR_STEP_RANGE_EL = ( -3840 3840 ) \begintext PMIRR Detectors Geometry --------------------------------------------------------------------------- This section describes the PMIRR detectors geometry such as detector orientation relative to the PMIRR instrument frame, detector size and relative alignment, etc. PMIRR Detectors Orientation --------------------------- TBD PMIRR Detectors Shape, Size and Relative Alignment -------------------------------------------------- TBD Platform ID --------------------------------------------------------------------------- This number is the NAIF instrument ID of the platform on which the instrument is mounted. \begindata INS-127020_PLATFORM_ID = ( -127000 )