KPL/FK
\beginlabel
PDS_VERSION_ID = PDS3
RECORD_TYPE = STREAM
RECORD_BYTES = "N/A"
^SPICE_KERNEL = "MGS_HGA_V10.TF"
MISSION_NAME = "MARS GLOBAL SURVEYOR"
SPACECRAFT_NAME = "MARS GLOBAL SURVEYOR"
DATA_SET_ID = "MGS-M-SPICE-6-V1.0"
KERNEL_TYPE_ID = FK
PRODUCT_ID = "MGS_HGA_V10.TF"
PRODUCT_CREATION_TIME = 2000-01-04T09:41:56
PRODUCER_ID = "NAIF/JPL"
MISSION_PHASE_NAME = "N/A"
PRODUCT_VERSION_TYPE = ACTUAL
PLATFORM_OR_MOUNTING_NAME = "MGS SPACECRAFT"
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 HIGH GAIN ANTENNA"
NAIF_INSTRUMENT_ID = "N/A"
SOURCE_PRODUCT_ID = "N/A"
NOTE = "See comments in the file for details"
OBJECT = SPICE_KERNEL
INTERCHANGE_FORMAT = ASCII
KERNEL_TYPE = FRAMES
DESCRIPTION = "MGS High Gain Antenna Frame Definitions SPICE
FRAMES Kernel File."
END_OBJECT = SPICE_KERNEL
\endlabel
Mars Global Surveyor Antenna Frames Kernel
================================================================================
This Frames Kernel file (FK) contains set of frame definitions for the
Mars Global Surveyor High and Low gain antennas.
If You're in a Hurry
-------------------------------------------------------------------------------
In case you are not interested in details and just looking for the right
name of the frame for a particular MGS antenna to use it in SXFORM or
SPKEZ call, here is the list:
'MGS_HGA'
'MGS_LGT1'
'MGS_LGT2'
'MGS_LGR1'
'MGS_LGR2'
In any of these frames the boresight vector of the corresponding MGS antenna
is pointing along frame's +Z axis.
Version and Date
-------------------------------------------------------------------------------
Version 1.0 -- March 1, 1999
Initial Release.
Contact Information
-------------------------------------------------------------------------------
Boris V. Semenov, NAIF/JPL, (818)-354-8136, bsemenov@spice.jpl.nasa.gov
References
-------------------------------------------------------------------------------
1. Complete Set of MGS Mechanical Drawings, 1997.
2. LMA IOM "S/C HGA phase center and line of boresight movements after
deployment with azimuth and elevation gimbal positions", by Mahendra
Jagjit, February 16, 1998
3. ``Frames Required Reading''
4. ``Kernel Pool Required Reading''
5. ``C-Kernel Required Reading''
6. MGS MISSION.CAT PDS document, version XX.X, 1998
7. E-mail memos regarding HGA kinematics and telemetry data by
Dave F. Eckart, LMA from January 31 and February 1, 1999
Implementation Notes
-------------------------------------------------------------------------------
This file is used by the SPICE system as follows: programs that make
use of this frame kernel must `load' the kernel, normally during program
initialization. The SPICELIB routine LDPOOL loads a kernel file into the
pool as shown below.
CALL LDPOOL ( frame_kernel_name )
This file was created and may be updated with a text editor or word
processor.
MGS Antennas Description
--------------------------------------------------------
The following description is based on the information provided in [2]
and [6]:
The MGS spacecraft is equipped with High Gain Antenna (HGA)
and four low-gain antennas (LGA), two for transmit and two
for receive.
The HGA is mounted on the boom attached by a hinge to the +X
side of the AFT deck of the spacecraft propulsion module. The
HGA boresight direction is fixed and co-aligned with the
spacecraft +X axis when antenna is in the stowed configuration
(during cruise and aerobraking phases of the mission.) After
the HGA is deployed for mapping operations, its pointing is
achieved by rotation of the azimuth and elevation gimbals.
Both transmitting LGA's are mounted to the TWA Enclosure Box
which is itself mounted to the HGA reflector. One of the
transmit LGA's (LGT1) is co-aligned with the HGA boresight
(nominally in the +X direction while the antenna is stowed),
while the other's (LGT2) boresight is oriented approximately
160 degrees away from this axis (near the -X axis while the
HGA is stowed).
The two receive LGAs are mounted on the -X panel of the
equipment module (LGR2) and the +X side of the propulsion
module (LGR1).
MGS HGA Hinge Geometry
-------------------------------------------------------------------------------
The following description is based on the information provided in [1], [2]
and [7]:
The MGS HGA deployment hinge is a mechanism attaching the HGA
boom to the +X side of the AFT deck of the propulsion module.
During transition from aerobraking to mapping, the locks
holding antenna in stowed configuration get released and,
driven by the spring, the hinge rotates from stowed to deployed
position and locks in deployed position for the rest of the
mission.
The hinge rotation axis is parallel to the s/c Y axis. In the
stowed configuration the antenna boom is parallel to the s/c
Z axis. In the deployed configuration the boom is parallel to
the s/c XZ plane and is rotated by 5 degrees from the s/c -Z axis
towards the s/c +X axis. The full nominal deployment angle between
stowed and deployed positions is 175 degrees.
There is no direct measurement of the hinge deployment angle
available in the s/c engineering telemetry after antenna is
deployed. The deployment actual angle is planned to be estimated
from signal strength during the initial HGA calibration tests.
MGS HGA Gimbal Geometry
-------------------------------------------------------------------------------
The following description is based on the information provided in [1], [2]
and [7]:
The MGS HGA Gimbal assembly is a mechanism attaching the HGA
reflector to the end of the HGA boom. It consists of two
independent gimbals -- elevation (EL) and azimuth (AZ) gimbals
-- and is used to achieve antenna pointing in deployed
configuration. The first of them -- EL gimbal -- is attached
to the antenna boom. The second -- AZ gimbal -- is attached
by one side to the first gimbal with a "corner-like" fitting
and by the opposite side to the antenna reflector.
The EL gimbal rotation axis is parallel to the deployment
hinge rotation axis. The AZ gimbal rotation axis is perpendicular
to the EL gimbal rotation axis and parallel to the s/c XZ and
the antenna reflector rim circle planes.
The gimbals have the following hard/soft stop positions
determining limits of the rotation ranges:
Soft Stops: azimuth: -8 deg ... +81 deg
elevation: -153 deg ... +153 deg
Hard stops: azimuth: -30 deg ... +190 deg
elevation: -158 deg ... +158 deg
"Zero" angle position (EL=0,AZ=0) puts the HGA boresight vector
parallel to the -Z axis of the spacecraft.
Other recognized antenna positions include:
Stowed Position: azimuth: +180 deg
elevation: -95 deg
Initial Deployed azimuth: 0 deg
Position: elevation: -90 deg
Park Position: azimuth: 80 deg
elevation: -120 deg
The antenna gimbal angle values are available in the spacecraft
engineering telemetry channels:
F-0190 (HGA_AZ_ANG), Azimuth Angles
F-0195 (HGA_EL_ANG), Elevation Angles
at the s/c housekeeping medium rate i.e. once every
32 seconds. The angle value are downlinked in radians.
There are also three additional HGA data telemetry channels:
F-0193 (HGA_AZ_TRG), Azimuth Targets
F-0198 (HGA_EL_TRG), Elevation Targets
F-0200 (HGA_STATS), HGA Status words
the first two of which give the expected final values +-0.04
degrees of the panels when motion is commanded and which are
unnecessary for the computation of the gimbal rotations.
During mapping, movement of the of the azimuth gimbal is in
general fixed for a given orbit. For a fixed azimuth position,
the elevation gimbal angle is varied to provide proper pointing
throughout the orbit.
MGS Antenna Frames
-------------------------------------------------------------------------------
The following MGS Antenna frames are defined in this kernel file (antenna
ID frame ID codes are -9407x):
Name Relative to Type NAIF ID
====================== =================== ============ =======
MGS_HGA_HINGE MGS_SPACECRAFT CK -94070
MGS_HGA_EL_GIMBAL MGS_HGA_HINGE CK -94071
MGS_HGA_AZ_GIMBAL MGS_HGA_EL_GIMBAL CK -94072
MGS_HGA MGS_HGA_AZ_GIMBAL FIXED -94073
MGS_LGT1 MGS_HGA FIXED -94074
MGS_LGT2 MGS_HGA FIXED -94075
MGS_LGR1 MGS_SPACECRAFT FIXED -94076
MGS_LGR2 MGS_SPACECRAFT FIXED -94077
In the list above ``CK'' means ``CK kernel based frame'' and ``FIXED''
means ``fixed offset frame''. Refer to [3] for more details regarding
supported frame types.
MGS Antenna Frames Hierarchy
-------------------------------------------------------------------------------
The diagram below shows MGS Antenna frames hierarchy:
"IAU_MARS" "IAU_EARTH"
MARS BFR(*) EARTH BFR(*)
------------ -------------
^ ^
| |
| <--pck | <--pck
| "J2000" INERTIAL(*) |
+-----------------------------------------------+
|
| <--ck
|
V
"MGS_SPACECRAFT"(**)
+-----------------------------------------------+
| | |
| <--fixed | <--ck | <--fixed
| | |
V V V
"MGS_LGR1" "MGS_HGA_HINGE" "MGS_LGR2"
---------- --------------- ----------
|
| <--ck
|
V
"MGS_HGA_EL_GIMBAL"
-------------------
|
| <--ck
|
V
"MGS_HGA_AZ_GIMBAL"
-------------------
|
| <--fixed
|
V
"MGS_HGA"
+-----------------------------------------------+
| |
| <--fixed | <--fixed
| |
V V
"MGS_LGT1" "MGS_LGT2"
---------- ----------
(*) Inertial and body-fixed rotation (BFR) frame are standard frames
frame supported with SPICE system and, therefore, they don't
require custom definitions (see [3]).
(**) for historical reasons MGS_SPACECRAFT frame is defined in an MGS
SCLK file.
MGS HGA Frame Definitions
--------------------------------------------------------
The MGS HGA deploy hinge frame is defined as follows:
- Z axis is along deploy hinge rotation axis, and is parallel to and
points in the same as the s/c frame +Y axis;
- X is perpendicular to the hinge rotation axis, parallel to the HGA
boom central axis and points long it from the deploy hinge side
towards the elevation gimbal side ;
- Y complements to the right hand frame;
- the origin of this frame is located at the intersection of the hinge
rotation axis and a plane perpendicular to the rotation axis and
containing central axis of the boom.
The MGS HGA elevation gimbal frame is defined as follows:
- Z axis is along the elevation gimbal rotation axis and points
from the HGA boom side towards the azimuth gimbal side;
- X is perpendicular to the elevation gimbal rotation axis, parallel
to the azimuth gimbal rotation axis and points from the
elevation gimbal side towards the HGA reflector mounting side;
- Y complements to the right hand frame;
- the origin of this frame is located at the intersection of the
elevation gimbal rotation axis and a plane perpendicular to this
rotation axis and containing the azimuth gimbal rotation axis.
The MGS HGA azimuth gimbal frame is defined as follows:
- Z axis is along the azimuth gimbal rotation axis and points
from the elevation gimbal side towards the HGA reflector
mounting side;
- X is perpendicular to the azimuth gimbal rotation axis, parallel to
a plane containing HGA reflector rim circle and points from the
azimuth gimbal towards the HGA rim circle center;
- Y complements to the right hand frame;
- the origin of this frame is located at the intersection of the
azimuth gimbal rotation axis and a plane perpendicular to this
rotation axis and containing the HGA reflector central symmetry
axis (boresight axis).
The MGS HGA boresight frame is defined as follows:
- Z axis is along the HGA reflector central symmetry axis (boresight
axis) and points from the reflector surface towards the feed horn;
- X is perpendicular to the boresight direction, perpendicular to
azimuth gimbal rotation axis and points from the antenna symmetry
axis towards the side of the reflector where azimuth gimbal is
attached;
- Y complements to the right hand frame;
- the origin of this frame is located at the intersection of the
antenna reflector symmetry axis and a plane containing HGA reflector
rim circle.
The diagram below illustrates HGA hinge/gimbal/boresight frame definitions
(the antenna is show as if boom would be fully extended along s/c +X axis,
elevation and azimuth gimbal axes will be in the s/c plane and antenna
boresight will be pointing along s/c +Z axis):
Top view (+Zsc view):
---------------------
* * * * *
* *
* *
* *
* *
* *
* *
* +Zb o----> +Yb *
* | *
* | *
* v +Xb *
* *
* ^ * ^ +Zel
* |+Xaz *____ |
* | __| |____|_
<----x__*___| +Xel<----o|+Yel
+Zaz +Yaz |_____| | |
azimuth _|_|_
____________ +Zh gimbal | | elev.
| ^ | | gimbal
+Ysc |_|__ |_____|
^ +Yh| |___________________________________| |
| | x---->___________________________________|
| +Xsc |_____| +Xh
o----> | deployment
+Zsc | hinge
|
|
|
____________|
Side view (-Ysc view):
----------------------
^ +Zb
|
| | +Yb
| ___________o---->______ +Yel
| \__ +Xb __/ ^
|___ \__ __/____ _|_
/+Zh\_______________\__+Xaz __/_| |_/ | \
____________| x---->____________<----x______| +Xel<---x +Zel
^+Zsc \_|_/ +Xh +Zaz | |_____| \___/
| \ | |
| +Xsc V +Yh v +Yaz
___x--->_\
+Ysc
On the diagram:
+Xsc,+Ysc,+Zsc -- axes of the s/c frame;
+Xh, +Yh, +Zh -- axes of the hinge frame;
+Xel,+Yel,+Zel -- axes of the elevation gimbal frame;
+Xaz,+Yaz,+Zaz -- axes of the azimuth gimbal frame;
+Xb, +Yb, +Zb -- axes of the HGA boresight frame;
"o" shows axes pointing "out of page", "x" shows axes pointing "into page"
As follows from the definition, the HGA boresight frame is rotated from the
azimuth gimbal frame by two rotation -- first by +90 degrees about +X axis
and second by +180 degrees about +Z axis.
Actual frame definition keyword sets for the HGA hinge/gimbal/boresight
frames (note opposite sign/order of rotations in the MGS_HGA definition
because the definition contains transformation from antenna
to reference frame, see [3]):
\begindata
FRAME_MGS_HGA_HINGE = -94070
FRAME_-94070_NAME = 'MGS_HGA_HINGE'
FRAME_-94070_CLASS = 3
FRAME_-94070_CLASS_ID = -94070
FRAME_-94070_CENTER = -94
CK_-94070_SCLK = -94
FRAME_MGS_HGA_EL_GIMBAL = -94071
FRAME_-94071_NAME = 'MGS_HGA_EL_GIMBAL'
FRAME_-94071_CLASS = 3
FRAME_-94071_CLASS_ID = -94071
FRAME_-94071_CENTER = -94
CK_-94071_SCLK = -94
FRAME_MGS_HGA_AZ_GIMBAL = -94072
FRAME_-94072_NAME = 'MGS_HGA_AZ_GIMBAL'
FRAME_-94072_CLASS = 3
FRAME_-94072_CLASS_ID = -94072
FRAME_-94072_CENTER = -94
CK_-94072_SCLK = -94
FRAME_MGS_HGA = -94073
FRAME_-94073_NAME = 'MGS_HGA'
FRAME_-94073_CLASS = 4
FRAME_-94073_CLASS_ID = -94073
FRAME_-94073_CENTER = -94
TKFRAME_-94073_SPEC = 'ANGLES'
TKFRAME_-94073_RELATIVE = 'MGS_HGA_AZ_GIMBAL'
TKFRAME_-94073_ANGLES = ( -90.0, 0.0, 180.0 )
TKFRAME_-94073_AXES = ( 1, 2, 3 )
TKFRAME_-94073_UNITS = 'DEGREES'
\begintext
MGS Transmit LGA Frame Definitions
--------------------------------------------------------
The MGS LGT1 boresight frame is defined as follows:
- Z axis is perpendicular the the antenna "patch" surface and points
away from the surface;
- X axis is parallel to the line connecting the "patch" center with
the "patch" corner furthest from both antenna connectors attached
to the bottom side of the patch and points from the center towards
the corner;
- Y axis complements to the right hand frame;
- the origin of this frame is located at the geometric center of
the antenna "patch" square.
The MGS LGT2 boresight frame is defined as follows:
- Z axis is perpendicular the the antenna "patch" surface and points
away from the surface;
- X axis is parallel to the line connecting the "patch" center with
the "patch" corner furthest from both antenna connectors attached
to the bottom side of the patch and points from the center towards
the corner;
- Y axis complements to the right hand frame;
- the origin of this frame is located at the geometric center of
the antenna "patch" square.
As follows from the definitions and [1], the LGT1 frame is rotated
from the HGA boresight frame by +214 degrees about +Z axis (34
degrees due to TWA box mounting on the HGA reflector plus 180 degrees
due to "patch" orientation with respect to the bracket of which it's
mounted.) The LGT2 frame is first rotated +34 degrees about +Z axis
(due to TWA bow mounting on the HGA reflector), after that it's
rotated by -130.88 degrees about new direction of +Y axis and at
last it's rotated -10.4 degrees about new direction of +X axis (last
two rotations are due to "sophisticated" geometry of the lower LGT2
mounting bracket.)
Actual frame definition keyword sets for the LGT1 and LGT2 frames, which
incorporate these rotations, are below (note opposite sign/order of
rotations because the definitions contains transformation from antenna
to reference frame, see [3]):
\begindata
FRAME_MGS_LGT1 = -94074
FRAME_-94074_NAME = 'MGS_LGT1'
FRAME_-94074_CLASS = 4
FRAME_-94074_CLASS_ID = -94074
FRAME_-94074_CENTER = -94
TKFRAME_-94074_SPEC = 'ANGLES'
TKFRAME_-94074_RELATIVE = 'MGS_HGA'
TKFRAME_-94074_ANGLES = ( -214.0, 0.0, 0.0 )
TKFRAME_-94074_AXES = ( 3, 2, 1 )
TKFRAME_-94074_UNITS = 'DEGREES'
FRAME_MGS_LGT2 = -94075
FRAME_-94075_NAME = 'MGS_LGT2'
FRAME_-94075_CLASS = 4
FRAME_-94075_CLASS_ID = -94075
FRAME_-94075_CENTER = -94
TKFRAME_-94075_SPEC = 'ANGLES'
TKFRAME_-94075_RELATIVE = 'MGS_HGA'
TKFRAME_-94075_ANGLES = ( -34.0, 130.0, 10.4 )
TKFRAME_-94075_AXES = ( 3, 2, 1 )
TKFRAME_-94075_UNITS = 'DEGREES'
\begintext
MGS Receive LGA Frame Definitions
--------------------------------------------------------
The MGS LGR1 boresight frame is defined as follows:
- Z axis is perpendicular the the antenna "patch" surface, and is
parallel and points in the same direction as the s/c +X axis;
- Y axis is parallel to and points in the same direction as the
s/c +Y axis;
- X axis complements to the right hand frame;
- the origin of this frame is located at the geometric center of
the antenna "patch" square.
The MGS LGR2 boresight frame is defined as follows:
- Z axis is perpendicular the the antenna "patch" surface, and is
parallel and points in the same direction as the s/c -X axis;
- Y axis is parallel to and points in the same direction as the
s/c +Y axis;
- X axis complements to the right hand frame;
- the origin of this frame is located at the geometric center of
the antenna "patch" square.
As follows from the definitions, the LGR1 frame is rotated from the
spacecraft frame by +90 degrees about +Y axis and the LRG2 frame is
rotated from the spacecraft frame by -90 degrees about +Y axis.
The diagram below illustrates LGR1 and LGR2 frame definitions:
Side View (-Ysc):
-----------------
LGT2 ____ LGT1
@=| |=@
| |_
|__ / |
___________ / |
+Xlgr2 | | / |
^ | | / |
| | || |
+Zlgr2 | | || | HGA
<----x=| || |
+Ylgr2|___________| \ |
| | \ |
| | \ |
| | \__|
| |
| +Ylgr1
| |=x---->
|___________| | +Zlgr1
+Zsc \ |
/ ^ \ v
/ | \ +Xlgr1
/ | \
/_____x---->
+Ysc +Xsc
On the diagram:
+Xsc, +Ysc, +Zsc -- axes of the s/c frame;
+Xlgr1, +Ylgr1, +Zlgr1 -- axes of the LGR1 frame;
+Xlgr2, +Ylgr2, +Zlgr2 -- axes of the LGR2 frame;
"x" shows axes pointing "into page"
Actual frame definition keyword sets for the LGR1 and LGR2 frames, which
incorporate these rotations, are below (note opposite sign/order of
rotations because the definitions contains transformation from antenna
to reference frame, see [3]):
\begindata
FRAME_MGS_LGR1 = -94076
FRAME_-94076_NAME = 'MGS_LGR1'
FRAME_-94076_CLASS = 4
FRAME_-94076_CLASS_ID = -94076
FRAME_-94076_CENTER = -94
TKFRAME_-94076_SPEC = 'ANGLES'
TKFRAME_-94076_RELATIVE = 'MGS_SPACECRAFT'
TKFRAME_-94076_ANGLES = ( 0.0, -90.0, 0.0 )
TKFRAME_-94076_AXES = ( 3, 2, 1 )
TKFRAME_-94076_UNITS = 'DEGREES'
FRAME_MGS_LGR2 = -94077
FRAME_-94077_NAME = 'MGS_LGR2'
FRAME_-94077_CLASS = 4
FRAME_-94077_CLASS_ID = -94077
FRAME_-94077_CENTER = -94
TKFRAME_-94077_SPEC = 'ANGLES'
TKFRAME_-94077_RELATIVE = 'MGS_SPACECRAFT'
TKFRAME_-94077_ANGLES = ( 0.0, 90.0, 0.0 )
TKFRAME_-94077_AXES = ( 3, 2, 1 )
TKFRAME_-94077_UNITS = 'DEGREES'
\begintext