Transcript Preliminary Experiment with KHz SLR at Shanghai Observatory

Preliminary Results of Laser Ranging to
Un-cooperative Targets at Shanghai SLR Station
Yang FuMin, Zhang ZhongPing, Chen JuPing,
Chen WanZhen, Wu ZhiBo, Zhang HaiFeng
Shanghai Astronomical Observatory, Chinese
Academy of Sciences, Shanghai, China
Ivan Prochazka
Czech Technical University in Prague, Czech Republic
Email: [email protected]
Goals
 Investigation of the key techniques of
un-cooperative target laser ranging
 Experimental laser ranging to
un-cooperative targets
Estimate of the returned signal strength
The returned signal strength of laser ranging on uncooperative targets can be estimated by:
Et Ar  S cos   2
n0 

 T  Kt  K r  
2 4
hc
t R
q
Where
n0: Average number of photoelectrons received by detector
λ: Wavelength of laser, 532nm
ηq: Quantum efficiency of the C-SPAD detector, 0.2
h: Planck constant, 6.624×10-34 J·S
c:
Light speed, 2.998×108 m/s
Et: Energy of laser pulse, 2J
Ar: Effective area of receive telescope, 0.245m2
ρ: Reflectivity of the target’s surface
r:
Equivalent radius of the target, 1m
cos(): Suppose the targets are spherical, cos()=1
t: Divergency of laser beam from telescope, 12 arcsec
R: Range of the targets, 800Km
T: Atmospheric transmission, T2=0.6
Kt: Eff. of transmitting optics, 0.60
Kr: Eff. of receiving optics, 0.60
: Attenuation factor, 13dB
We have,
n0=0.198 (Photoelectron)
The probability of detection can be estimated:
P  1 e
 n0
 1 e
0.198
 0.18
So we can get 18 return signals in 5 second by the
laser with 20Hz repetition.
Oscillator
Isolator
Amplifier Unit 1
Amplifier Unit 2
Beams combination
1: HR mirror
8: Reflect mirror
2: E-Q Switch
3: Polarizer
9: Frequency doubler
Isolator
4: YAG rod
10: Optical coupler
5: Output mirror
6: Isolator
7: Compensator
11: Imaging lens
Diagram of the 40W laser (2J, 20Hz, 10ns)
Photo of the laser
Inner view of the laser
Laser firing
at Shanghai
Some results of
un-cooperative target laser ranging
at the Shanghai SLR station
Number of point: 127
RMS: 76cm
Returns from the discard Soviet rocket (ID 1987-38B) on July 7, 2008
Number of point: 79
RMS: 83cm
Returns from the discard US rocket (ID 2007-006G) on July 17, 2008
Number of point: 170
RMS: 68cm
Returns from the discard US rocket (ID 2007-006G) on July 18, 2008
距离值(公里)
Range (Km)
2008年07月07日
1000
950
900
850
800
750
700
46230
46250
46270
46290
46310
46330
时间(秒)
Time
(s)
Ranging data of ID 1987-38B on July 7, 2008
Range (Km)
距离值(公里)
2008年07月17日
880
850
820
790
760
730
700
71290
71300
71310
71320
71330
Time
(s)
时间(秒)
Ranging data of ID 2007-006G on July 17, 2008
71340
2008年07月18日
Range (Km)
距离值(公里)
900
850
800
750
700
650
70200
70220
70240
70260
Time
(s)
时间(秒)
70280
Ranging data of ID 2007-006G on July 18, 2008
16
of returns
Number
数据点个数
14
12
10
8
6
4
2
0
1
2
3
4
5
6
7
8 9 10 11 12 13 14 15 16 17
Time (5-second
bin)
时间/5s
Statistics of returns (5-second bin) on July 7, 2008
 12-14 returns in 5 seconds were obtained when tracking well,
and roughly coincide with the estimation of the returns signal
strength.
Future Plan
• Upgrading of the prediction of the targets
(now the error of range prediction is about
1km, too difficult to obtain the returns)
• Automatically scanning of range gate and
rapidly identify the return signals
• To track smaller targets and assessing the
ranging capability of the system
Summary
 The laser returns from the un-cooperative targets have
been obtained at the Shanghai SLR Station in July 2008.
 These targets are the discard Soviet and US rockets
with the ID 1987-38B and 2007-006G respectively.
 The return signals from the targets with the range of
900km were quite strong.
Thank You!