Lunar ranging instrument for Chandrayaan-1

Journal of Earth system science

R Ranjith1¹  R Venketeswaran1¹  K V S Bhaskar1¹  J A Kamalakar1¹  A S Laxmi Prasad1¹  K A Lohar1¹  T K Alex1¹ 

[1] Laboratory for Electro-Optics Systems, Indian Space Research Organization (ISRO), Bangalore 560 058, India.$$

关键词: Nd:YAG laser;    Si APD;    laser altimeter.;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

Lunar Laser Ranging Instrument (LLRI)proposed for the first Indian lunar mission Chandrayaan-1 is aimed to study the topography of the Moon ’s surface and its gravitational field by precisely measuring the altitude from a polar orbit around the Moon.Altimetry data close to the poles of the Moon would also be available from the instrument,which was not covered by earlier missions. This instrument supplements the terrain mapping camera and hyper-spectral imager payloads on Chandrayaan-1.The instrument consists of a diode pumped Nd:YAG pulsed laser transmitter having 10 nsec pulse width and a receiver system.The receiver system features 17 cm diameter Ritchey –Chrétien collecting optics,Si Avalanche Photo Detector (APD),preampli fiers,constant fraction discriminators,time-of-flight measurement unit and spacecraft interface.Altimeter resolution of better than 5 m is targeted.The received signal strength of LLRI depends on laser pulse backscatter from the Moon ’s surface.Moon ’s surface being a poor re flector,the choice of receiver size and its type and the selection of detector play an important role in getting a good signal-to-noise ratio and in turn achieving the target resolution.At the same time,the spacecraft puts a limitation on payload size and weight.This paper discusses the proposed LLRI system for Chandrayaan-1 and signal-to-noise ratio estimation.

【 授权许可】

Unknown