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Overview: Laboratory for Electro-Optics Systems (LEOS)

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Laboratory for Electro Optics Systems (LEOS) is actively engaged in design, development, production and delivery of Electro-Optic sensors and optics to Spacecrafts. The Electro-optic sensors are used for attitude determination, guidance and navigation of Low Earth Orbit (LEO), Geosynchronous Earth Orbit (GEO) and inter planetary Spacecrafts, Landers and Rovers. Optics both refractive and reflective of various dimensions are used for imaging and meteorological applications. LEOS is also actively engaged in developing laser based and other payloads for scientific/interplanetary missions, variety of thin film coatings for optics, detectors and micro electro-mechanical systems (MEMS).

The attitude sensors which are indigenously developed are Star tracker, Earth sensors, Sun sensors, Magnetometers and Fiber Optics Gyroscope (FOG). Star trackers are the very high accuracy attitude sensors and using charge coupled devices (CCD) and active pixel sensors (APS) have been developed and flown successfully. The advanced version of this sensor with accuracy of 1 arc second is recently flown. Presently sub arc second accuracy star sensor is under development. In addition, micro Star tracker and nano Star tracker have been developed for small satellites and nano satellites respectively. Earth sensors have been main attitude sensors for earth pointing till the development of Star trackers. Conical scanning Earth sensors for LEO spacecrafts and Scanning Earth sensor for GEO spacecrafts are the examples. Miniature version of conical scanning Earth sensor is still being used specifically in Earth pointing remote sensing satellites for back up and safe mode applications. More than 100 nos. of scanning Earth sensors have been flown on communication Spacecrafts. LEOS has realized different type Sun sensors based on accuracy and range viz., Four pi Sun sensor, Coarse analog sun sensor (CASS), Solar panel Sun sensor (SPSS), Digital Sun sensor (DSS), APS Sun sensor, Analog yaw Sun sensor, Twin slit Sun sensor. The newest addition is micro CASS using MEMS technology. Two axes micro DSS with linear CCD is also developed. Magnetometers are part of the LEO Spacecrafts from the days of IRS-1A. Presently digital magnetometer with resolution of 4nT and very high accuracy version as a payload under development. Standard design and the advanced version of high bias stability FOG is realized successfully and flown.

Multi-spectral refractive optical systems with moderate and wide field-of-view lens assemblies such as Linear Imaging Self Scanning Sensor (LISS-III), LISS-IV, Advanced Wide Field Sensor (AWiFS), Hyper Spectral Imager (HySi), Field Corrector Optics (FCO) and Terrain Mapping Camera (TMC) have been developed in-house and flown. Refractive optical elements for different versions of Star tracker, Navigation sensors and LEOS payloads have been designed and realized. Medium/High-resolution large-area light-weight telescope mirrors ranging from 200mm to 705mm have been successfully developed which has yielded sub-meter resolution Earth Observation pictures. LEOS carries the credit of realizing Ultra Violet Imaging Telescope (UVIT) optics which lead to the detection of best-ever UV stars in space based astronomy. Besides, Corner-Cube Retro-Reflector (CCRR) trays have been indigenously characterized and flown. Ultra-Light-weight 1200mm diameter mirror developed for high resolution camera and flown. Visible Emission Line Coronagraph (VELC) optics and Solar Ultraviolet Imaging Telescope (SUIT) optics are under development.

LEOS has developed wide variety of optical coatings viz., anti-reflection coating (ARC), reflection enhancement coating, filter coatings for different wavelengths on different materials. Black absorber coating for star sensor baffle vanes, photo masks for different sun sensors and encoders are other contributions from thin film group.

LEOS has indigenously developed Silicon photo-detector, Micro Coarse Analogue Sun Sensor (µ-CASS), Immersed Bolometer for Earth sensor, MEMS Inclinometer and MEMS seismometer. These have been flown on LEOS sensors/payloads successfully. Terra Hertz bolometer, UV detector, RF switch and micro valve are in advanced stages of development.

Over the years LEOS has specialized in laser based and optical fiber components based systems for space applications. The payloads that are realized and flown by LEOS for science mission are Lunar Laser Range Instrument (LLRI) and Lyman Alpha Photometer (LAP). LEOS is presently working on new payloads, navigation sensors for Lander and sensors for docking and rendezvous. Laser Induced Breakdown Spectroscopy (LIBS), Laser Altimeter (LASA), Horizontal velocity camera, docking cameras and Rover Navigation Camera developed and flown. Optical communication terminal for high speed data link, Laser Doppler Velocity-meter (LDV), which use laser and fiber optic components are advanced stage of development. Indigenous high energy laser source for Light Detection and Ranging (LIDAR) applications and pico second laser source for Altimeter application is under progress.