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Laser Retro-reflector Arrays on the
Compass Satellites
Chen WanZhen, Yang FuMin,
Wang YuanMing, Li Pu
Shanghai Observatory, Chinese Academy of Sciences
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“COMPASS” (or “BeiDou”) is the regional satellite
navigation system in China, which will cover the
most areas of the East Asia region, and expect to be
operational by 2011.
The Compass constellation will consist of 12
satellites all equipped with LRA:
GEO 5
IGSO 3
MEO 4
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Drawing of COMPASS-M1 Navigation Satellite
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LRA
Location of the LRA on COMPASS-M1
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The LRA on Compass-M1 The LRA on Compass-M1 (MEO)(MEO)
Size 31.628 cm
Diameter of corner cube 33mm
Number 42
Reflective area 360cm2
Material fused silica
Weight 2.45 kg
The corner cubes are uncoated both front and back surfaces
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The LRA on Compass The LRA on Compass GEO/IGSOGEO/IGSO
Size 4943cm
Diameter of corner cube 33mm
Number 90
Reflective area 770cm2
Material Fused silica
Weight 5.0 kg
The corner cubes are uncoated both front and back surfaces
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Testing of LRA’s Testing of LRA’s
optical performance optical performance
with ZYGO with ZYGO
interferometerinterferometer
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Environment Environment
testing of LRA testing of LRA
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Cross section, range and signal for different satellites
By David Arnold*Sat. Cross
sectionRange
(0 deg.)
Range**4
Signal strength
Range
(45 deg.)
Range**4
Signal strength
Lageos 15 5.8 1 1.000 6.8 1 1.000
Etalon 55 19.0 115 .032 20.5 82 .044
GPS 19 20.0 141 .009 21.5 100 .012
GIOVE-A 45 23.9 288 .010 25.4 195 .015
Glonass 80 19.0 115 .046 20.5 82 .065
Compass 80 21.0 189 .028 23.0 131 .041
ETS-8 140 36.0 1484 .0063 37.6 935 .010
* Private communication
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Parameters of LRA on satellites*Satellite Cube
NumberDiameter
(inch)
Coating Dihedral
Offset
Vendor
Lageos1 422 1.5 uncoat 1.25 Perkin-Elmer
Lageos2 422 1.5 uncoat 1.25 Zygo
Etalon 2140 1.06 coat - IPIE
GPS 32 1.06 coat - IPIE
GIOVE-A 76 1.06 coat - IPIE
Glonass 132 1.06 coat - IPIE
Compass 42 1.3 uncoat 0.6 SHAO
ETS-8 36 1.6 uncoat 0.5 ITE
* From David Arnold, private communication
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Manufacturer of LRAs
ITE ITE, Inc., Laurel, MD, USA
ZYGO Zygo Corp., Middlefield, CT, USA
IPIE Institute for Precision Instrument
Engineering, Russia
Perkin-Elmer Headquarters-- Waltham, MA, USA
SHAO Shanghai Astronomical Observatory,
China. The fused silica was made by the
Shanghai LengGuang Co., China
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New Laser and Transmitter for Compass-M1 ranging at Changchun
The new laser was loaned from the NCRIEO in BeijingThe new laser was loaned from the NCRIEO in Beijing
- - Active-active mode locked Nd:YAG laserActive-active mode locked Nd:YAG laser
- - 100-150mJ in 532nm, 250ps, 20Hz100-150mJ in 532nm, 250ps, 20Hz
-- 10ns firing jitter 10ns firing jitter
New Coude mirrorsNew Coude mirrors
New 210mm diameter transmitting telescopeNew 210mm diameter transmitting telescope
10 aresec laser beam divergency10 aresec laser beam divergency
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Real-time display for Compass-M1 trackingReal-time display for Compass-M1 tracking
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Range residuals of Compass-M1 on Sept. 5, 2007Range residuals of Compass-M1 on Sept. 5, 2007
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Range residuals after data fittingRange residuals after data fitting
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Conclusions
The parameters of 12 sets of COMPASS LRA
arrays are introduced in this paper
The performance of the Compass M1 LRA is
excellent. It is shown in the ranging experiment
that the returned signal strength from the
Compass-M1 LRA is much stronger than those
from GPS-35/36 and GIOVE-A
The uncoated corner cubes are fine for high orbit
satellites
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Thank you
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Active-active mode-locked Nd:YAG laserActive-active mode-locked Nd:YAG laser100-150mJ (532nm), 250ps,20Hz100-150mJ (532nm), 250ps,20Hz
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Changchun SLR Telescope
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Changchun SLR Control Room