KPL/IK
\beginlabel
PDS_VERSION_ID = PDS3
RECORD_TYPE = STREAM
RECORD_BYTES = "N/A"
^SPICE_KERNEL = "MGS_MHSA_V23.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_MHSA_V23.TI"
PRODUCT_CREATION_TIME = 2000-01-04T09:41:58
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 = "MGS HORIZON SENSOR ASSEMBLY"
NAIF_INSTRUMENT_ID = -94020
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 Horizon Sensor Assembly instrument
parameters SPICE I-Kernel File. This file also contains MHSA Frame
definitions."
END_OBJECT = SPICE_KERNEL
\endlabel
MHSA Instrument Kernel
===========================================================================
This MGS Horizon Sensor Assembly (MHSA) instrument kernel (I-kernel)
contains the instrument base mounting offset, and field of view
orientation data for four detectors of the instrument.
Version and Date
--------------------------------------------------------
Version 2.3 -- August 11, 1997
Revisions
--------------------------------------------------------
Version 2.3 -- August 11, 1997
Frame definitions were corrected to represent the correct
trasnformation sense.
Version 2.2 -- July 18, 1997
Direction of the FOV principal axis of each detector was changed
to point to the center of the middle lower element instead
of the geometrical center of the FOV (center of the circle
circumscribing all 4 elements). 2.7 degrees was subtracted
from ALPHA angle for each detector.
Version 2.1 -- July 9, 1997
Section containing MHSA frame definitions was added.
Version 2.0 -- January 27, 1997
Initial release.
References
--------------------------------------------------------
1. ``MGS Alignment Transformation'', by Richard A. Hund,
November 26, 1996.
2. Horizon Sensor Assembly Data Sheet, by EDO/BARNES Engineering
Department, 12/6/90 - 12/12/90
3. ``C-kernel Required Reading''
4. ``Kernel Pool Required Reading''
5. Memo "???", from ???, (provided by T.Martin, on January
10, 1997)
6. MHSA assembly drawing ??? provided by C.Connor and T.Martin,
on July 17, 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 MHSA 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 mounting alignment of
the MHSA is specified by
INS-94020_EULER_ANGLES
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.
MHSA mounting offset
--------------------------------------------------------
This section describes the offset of the MHSA instrument fixed frame
(the frame fixed to the alignment cube on the MHSA) 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 MHSA 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 MHSA 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 provided in [1]
give the alignment of the MHSA alignment cube:
ROLL = 359.967 (degrees)
PITCH = 0.037 (degrees)
YAW = 359.974 (degrees)
An additional -45 degrees offset must be applied in YAW because the
actual MHSA frame (or so called Barnes frame) in which the detector
field of view vectors are defined is rotated relative to the alignment
cube by that angle about Z axis. So
YAW = ( 359.974 - 45.0 ) = 314.974 (degrees)
The keyword INS-94020_EULER_ANGLES contains these values, in radians,
in the following order:
INS-94020_EULER_ANGLES = ( ``ROLL'' ``PITCH'' ``YAW'' )
The keyword INS-94020_EULER_AXES contains integer codes of the
corresponding axes of rotations (1 -- X, 2 -- Y, 3 -- Z).
\begindata
INS-94020_EULER_ANGLES = ( 6.282609348526 0.000645771823 5.497333358177 )
INS-94020_EULER_AXES = ( 1 2 3 )
\begintext
Orientation of the detector FOVs
--------------------------------------------------------
The following description the MHSA detector field of view vectors is
provided in [5]:
``...
For each MHSA quadrant, two angles are necessary to
describe the field of view vectors in Barnes(*) frame.
These angles are ALPHA and THETA. Following is the
table showing the Barnes data:
THETA ALPHA
----------- -----------
1 44.85583 65.68686
2 45.11277 65.62951
3 45.18111 65.62672
4 44.81861 65.72406
ALPHA (A) is defined as the angle from Barnes Z axis
to the field of view vector. In general, THETA (T)
defines an angle from Barnes +/-Y axis to the
projection of the field of view vector onto the Barnes
XY plane. However, the precise definition of the angle
depends on which quadrant it refers to. Following is
a table which specifies how the field of view vectors
were calculated in the Barnes frame, using the correct
quadrant dependent definition of THETA.
X Y Z
------------ ------------ -------
QUAD1 sin(A)sin(T) sin(A)cos(T) cos(A)
QUAD2 -sin(A)sin(T) -sin(A)cos(T) cos(A)
QUAD3 sin(A)sin(T) -sin(A)cos(T) cos(A)
QUAD4 -sin(A)sin(T) sin(A)cos(T) cos(A)
...''
The angles ALPHA and THETA provided in the first table above
in combination with the data from the second table can be easily
transformed into two other angles (ALPHA' and THETA'), defining the
rotations required to construct a rotation matrix that will transform
the components of a vector expressed in the MHSA instrument fixed frame
to the components of a vector expressed in a particular detector frame.
The first of these angles, THETA', is the angle between +X axis of the
Barnes frame and projection of the field of view vector onto the Barnes
XY plane. It can be derived from THETA and corresponds to the first
rotation about +Z axis of the Barnes frame. The second angle,
ALPHA', is the same as ALPHA, i.e. it the angle from Barnes Z axis
to the field of view vector. It corresponds to the second
rotation about new position of the +Y axis of the Barnes frame.
The derived values of the ALPHA' and THETA' are provided in the table
below:
THETA' ALPHA'
---------------------------- -----------
1 ( 90 - 44.85583 ) = 45.14417 65.68686
2 ( 270 - 45.11277 ) = 224.88723 65.62951
3 ( 270 + 45.18111 ) = 315.18111 65.62672
4 ( 90 + 44.81861 ) = 134.81861 65.72406
The FOV vectors defined in the table above go through the geometrical
centers of the detectors (i.e. centers of the circles circumscribing
4 elements of each FOV). To make the centers of the middle lower
elements be FOV vectors, 2.7 degrees offset must be subtracted
from ALPHA angle for each detector:
THETA' ALPHA' ALPHA1'
---------------------------- ----------- ----------
1 ( 90 - 44.85583 ) = 45.14417 65.68686 62.98686
2 ( 270 - 45.11277 ) = 224.88723 65.62951 62.92951
3 ( 270 + 45.18111 ) = 315.18111 65.62672 62.92672
4 ( 90 + 44.81861 ) = 134.81861 65.72406 63.02406
A rotation matrix transforming the components of a vector expressed in
the MHSA instrument fixed frame to the components of a vector expressed
in a particular detector frame can be constructed from these two
rotation angles as follows:
[ ] [ ] [ ]
[ ROTi ] = [ ALPHA'i ] [ THETA'i ]
[ ] [ ] [ ]
Y Z
where each of two 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.
Then given a X Y and Z, the components of a vector expressed in the
Barnes instrument fixed frame, the corresponding Xi Yi and Zi,
the components of the same vector expressed in the "i"th detector
frame, can be calculated as follows:
[ Xi ] [ ] [ x ]
| Yi | = | ROTi | | y |
[ Zi ] [ ] [ z ]
where ROTi is the rotation matrix constructed from the corresponding
rotation angles above
The keywords INS-94020_D<<i>>_EULER_ANGLES, where <<i>> is the detector
index (1,2,3 and 4), contain these values, in radians, in the following
order:
INS-94020_D<<i>>_EULER_ANGLES = ( ``THETA1i'' ``ALPHA1i'' 0 )
The third component is set to 0 for all four detectors since tilt of
the FOV is insignificant for processing of the data coming from a
detector.
The keywords INS-94020_D<<i>>_EULER_AXES contain integer codes of the
corresponding axes of rotations (1 -- X, 2 -- Y, 3 -- Z).
ALPHA angle values below are given for lower middle detector centers.
\begindata
INS-94020_D1_EULER_ANGLES = ( 0.7879144046 1.0993280925 0 )
INS-94020_D1_EULER_AXES = ( 3 2 3 )
INS-94020_D2_EULER_ANGLES = ( 3.9250226092 1.0983271462 0 )
INS-94020_D2_EULER_AXES = ( 3 2 3 )
INS-94020_D3_EULER_ANGLES = ( 5.5009481096 1.0982784515 0 )
INS-94020_D3_EULER_AXES = ( 3 2 3 )
INS-94020_D4_EULER_ANGLES = ( 2.3530286375 1.0999773550 0 )
INS-94020_D4_EULER_AXES = ( 3 2 3 )
\begintext
Platform ID
--------------------------------------------------------
This number is the NAIF instrument ID of the platform on which the
instrument is mounted.
\begindata
INS-94020_PLATFORM_ID = ( -94000 )
\begintext
Instrument Frame Definition
--------------------------------------------------------
The instrument frame definitions for MHSA base frame and for the frames
of a particular sensors. This definition will be utilized by SPICE's
FRAMES subsystem to provide automatic state transformations to/from
MHSA instrument frames.
The names of these frames are:
MGS_MHSA
MGS_MHSA_D1
MGS_MHSA_D2
MGS_MHSA_D3
MGS_MHSA_D4
Given that MGS SCLK file, MGS CK file containing orientation of the s/c and
this IK file loaded into the program, transformation matrix from inertial
J2000 frame to the detector 3 frame can be obtained with a single call to
SPICE's SXFORM subroutine:
CALL SXFORM ( 'J2000', 'MGS_MHSA_D3', ET, XFORM )
DO I = 1,3
DO J = 1,3
CMAT(I,J) = XFORM(I,J)
END DO
END DO
Note that angles in the frame definitions are specified for "from
instrument to base (relative to) frame" transformation.
Frame definitions:
\begindata
FRAME_MGS_MHSA = -94020
FRAME_-94020_NAME = 'MGS_MHSA'
FRAME_-94020_CLASS = 4
FRAME_-94020_CLASS_ID = -94020
FRAME_-94020_CENTER = -94
TKFRAME_-94020_SPEC = 'ANGLES'
TKFRAME_-94020_RELATIVE = 'MGS_SPACECRAFT'
TKFRAME_-94020_ANGLES = ( -6.282609348526, -0.000645771823, -5.497333358177 )
TKFRAME_-94020_AXES = ( 1, 2, 3 )
TKFRAME_-94020_UNITS = 'RADIANS'
FRAME_MGS_MHSA_D1 = -94021
FRAME_-94021_NAME = 'MGS_MHSA_D1'
FRAME_-94021_CLASS = 4
FRAME_-94021_CLASS_ID = -94021
FRAME_-94021_CENTER = -94
TKFRAME_-94021_SPEC = 'ANGLES'
TKFRAME_-94021_RELATIVE = 'MGS_MHSA'
TKFRAME_-94021_ANGLES = ( -0.7879144046, -1.0993280925, 0.0 )
TKFRAME_-94021_AXES = ( 3, 2, 3 )
TKFRAME_-94021_UNITS = 'RADIANS'
FRAME_MGS_MHSA_D2 = -94022
FRAME_-94022_NAME = 'MGS_MHSA_D2'
FRAME_-94022_CLASS = 4
FRAME_-94022_CLASS_ID = -94022
FRAME_-94022_CENTER = -94
TKFRAME_-94022_SPEC = 'ANGLES'
TKFRAME_-94022_RELATIVE = 'MGS_MHSA'
TKFRAME_-94022_ANGLES = ( -3.9250226092, -1.0983271462, 0.0 )
TKFRAME_-94022_AXES = ( 3, 2, 3 )
TKFRAME_-94022_UNITS = 'RADIANS'
FRAME_MGS_MHSA_D3 = -94023
FRAME_-94023_NAME = 'MGS_MHSA_D3'
FRAME_-94023_CLASS = 4
FRAME_-94023_CLASS_ID = -94023
FRAME_-94023_CENTER = -94
TKFRAME_-94023_SPEC = 'ANGLES'
TKFRAME_-94023_RELATIVE = 'MGS_MHSA'
TKFRAME_-94023_ANGLES = ( -5.5009481096, -1.0982784515, 0.0 )
TKFRAME_-94023_AXES = ( 3, 2, 3 )
TKFRAME_-94023_UNITS = 'RADIANS'
FRAME_MGS_MHSA_D4 = -94024
FRAME_-94024_NAME = 'MGS_MHSA_D4'
FRAME_-94024_CLASS = 4
FRAME_-94024_CLASS_ID = -94024
FRAME_-94024_CENTER = -94
TKFRAME_-94024_SPEC = 'ANGLES'
TKFRAME_-94024_RELATIVE = 'MGS_MHSA'
TKFRAME_-94024_ANGLES = ( -2.3530286375, -1.0999773550, 0.0 )
TKFRAME_-94024_AXES = ( 3, 2, 3 )
TKFRAME_-94024_UNITS = 'RADIANS'
\begintext