Lunar ranging instrument for Chandrayaan-1 |
| |
| Authors: | J A Kamalakar K V S Bhaskar A S Laxmi Prasad R Ranjith K A Lohar R Venketeswaran T K Alex |
| |
| Institution: | (1) Laboratory for Electro- Optics Systems, Indian Space Research Organization (ISRO), 560 058 Bangalore, India |
| |
| Abstract: | 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 hyperspectral 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), preamplifiers, 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 reflector, 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. |
| |
| Keywords: | Nd:YAG laser Si APD laser altimeter |
| 本文献已被 SpringerLink 等数据库收录！ |
|
