ASTROG Subsystems VSOP2 ANTENNA AND ITS STRUCTURE

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ASTRO-G Sub-system VSOP-2 ANTENNA AND ITS
STRUCTURE VSOP-2 Symposium Dec.7, 2007
Ken Higuchi (ISAS/JAXA) and VSOP-2 Antenna
Working Group
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HALCAETS8
Heritage and Trend of Large-scale Deployable
Reflector (LDR) Technology for Mesh Antenna
VSOP-1 (HALCA) LDR (Launched 1997)
VSOP-2 (ASTRO-G) LDR (under Design)
ETS-VIII (Kiku-8) LDR (Launched 2006)
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VSOP-1 HALCA
Center-fed Cassegrain Antenna Deployment Test on
Ground
Main Reflector about 10m tip-to-tip Diameter of
Projected Inscribing Circle 7200mm Maximum
Design Frequency for Observation 22GHz Launched
in 1997
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Engineering Test Satellite VIII (ETS-VIII
Kiku-8)
Communication Test Satellite Connected Modular
Mesh Reflector - Good Surface Accuracy
(2.4mmRMS) - Light-weight Structure - Easy
for Ground Test and Adjustment - Easy for
Upsizing
Deployed LDR on Orbit
Outer Dimension of Reflector 19m x 17m (14
modules each) Communication Frequency S-band
(TX, RX)
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(No Transcript)
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VSOP-2

• A Large-scale Deployable Antenna of Offset
• Cassegrain Type
• - Maximum Observation Frequency 43GHz
• - Target Surface Accuracy of Main Reflector
  0.4mmRMS
• (includes thermal deformation and
  vibration)
• - Equivalent Diameter of Projected Area 9.56m

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Structure and Mechanism of Main Reflector

• The main reflector is composed of seven
  deployable modular antennas.
• Each of the modules employs a new idea of
  radial-rib/hoop-cable construction to stretch
  metal mesh as a reflector surface, and to satisfy
  the required surface accuracy.
• Heritage of deployable truss technology for the
  backside structure of ETS-VIII LDR is used for
  ASTRO-G.

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1/1-Scale Full Model
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Radial-rib/Hoop-cable Construction
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ASTRO-G Satellite Configuration
Launching Configuration
On-orbit Configuration
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Geometry of Antenna Subsystem
Focus of Main Reflector
FAAM
Focus of Sub-reflector
Mechanical Axis of Main Reflector
Antenna Coordinate
Satellite Coordinate
Origin of Parabola
AAM
AAM Alignment Adjustment Mechanism FAAM Focus
and Alignment Adjustment Mechanism
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Fundamental Specification
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Components
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Utility of Radial Ribs on Reflector Surface

• To suppress pillow effect of convex curved
  surface
• To avoid tangling of cables
• To suppress accumulation of error of connected
  modules

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Japanese Traditional Umbrella
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Differnces between Two Modular Mesh Reflectors
Surface Cables
Hoop Cables
Tie Cables
Radial Ribs
Center Stand-Off
Peripheral Cable
Peripheral Stand-Off
Deployable Truss
Tie Cables
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Differnces between Two Modular Mesh Reflectors
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Deployment Sequence
Rotation of Boom-1 Hinge-1
Twist of Boom-1 Hinge-2
BOOM-1
FIXED HINGE
BOOM-2
Rotation of Boom-3 Hinge
BOOM-3
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FAAM
AAM
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Antenna Performance Degradation Cause
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ENDING