Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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!