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), 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.
We propose a facile and combined methodology to develop magnetron sputtered various metals and alloy (e.g. tungsten, tin and nichrome), and metal oxide (indium tin oxide) thin film-based micro-patterns deposited on flexible and rigid substrates utilizing reusable patterned mask. CO 2 laser-cut glass-based mask is fabricated and assembled with the substrates for pattern printing by sputtered thin film deposition technique. Fabrication of mask is adopted with the rapid CO 2 laser-cut process aided with computer-aided design software. The laser-cut glass-based mask can easily fix on any type of substrates and any resistive materials deposition can be carried out. Currently, the developed thin film micropatterns show good uniformity, dense morphology and without sign of any discontinuity. Finally, a successful functional characterization of a typical nichrome line-heater also confirms the feasibility and proof of concept of the present proposed approach that is much facile, less time-consuming and economical.
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