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 = 2001-06-27T17:43:38 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