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Saxena G.D.,Laboratory for Electro Optics Systems | Thamarai V.,Laboratory for Electro Optics Systems
Proceedings - 2011 International Conference on Computational Intelligence and Communication Systems, CICN 2011 | Year: 2011

MEMS fabrication process is an inherently rugged technology and has great potential to bring forth novel solutions on the harsh environment and critical applications. This paper reports on a very high performance closed-loop MEMS accelerometer targeted at inertial navigation applications. Motivation of this paper is to develop a high resolution inertial grade closed loop Accelerometer using the MEMS sensor fabricated at LEOS. The MEMS sensor with comb type structure has a sensitivity of 6 pF / g. This paper reports on the design and detailed simulation of signal conditioning circuit for MEMS accelerometer using a 6 th order Sigma-Delta IC ADS-1278 provided by Texas Instruments. The functionality and the performance of the system were studied by P-Spice simulation. Signal-to-noise ratio (SNR) of 97.8dB and effective number of bits (ENOB) of 16 bits over a measurement range of +/-1g was estimated with an over sampling ratio (OSR) of 128. © 2011 IEEE.

Reddy V.V.R.,Laboratory for Electro Optics Systems | Ravindra H.S.,Laboratory for Electro Optics Systems | Krishnamoorthy S.,Laboratory for Electro Optics Systems
Journal of Spacecraft Technology | Year: 2012

Spinning satellites need attitude sensors to compute spin rate and also for spin rate control and Spin Axis Orientation Control [SAOCJ The two spinning satellites viz. HAMSAT and ANUSAT had two LEOS developed attitude sensors onboard for the above tasks. These were the Tri-axial Mini Magnetometer [Mini-Mag ] and the Twin Slit Sun Sensor [TWSS]. Spin rate measured by TWSS was used by onboard AOCE to control spin rate of the satellite. It also gave sun aspect angle which was used for SAOC. The magnetometer outputs are used to activate magnetic torquers, which are the actuators used for spin rate control and spin axis orientation control. The magnetometer outputs are also used in the initial de-tumbling mode after launch, where the onboard computer uses "Negative B dot" control law to nullify the spacecraft body rates using magnetic torquers. Tri-axial Magnetometers were flown in many remote sensing missions as attitude sensors for a three axis stabilized control of spacecraft. For the spin-stabilised satellites HAMSAT & ANUSAT, LEOS developed and qualified the miniature Tri-axial Magnetometer which integrates the magnetic sensors and electronics in the same unit. The performance of both Mini-Mag & TWSS were extremely satisfactory in both these satellites. HAMSAT is in orbit since April 2005 and ANUSAT since April 2009. This paper describes the design, development and testing of both these attitude sensors and summarises their performance in both the spinning satellites.

Krishnamoorthy S.,Laboratory for Electro Optics Systems | Dinesh B.,Laboratory for Electro Optics Systems | Shila K.V.,Laboratory for Electro Optics Systems | Raju S.B.,Laboratory for Electro Optics Systems | Lohar K.A.,Laboratory for Electro Optics Systems
Journal of Spacecraft Technology | Year: 2011

High Accuracy Digital Sun Sensors (HDSS) are flown on many Indian remote sensing satellites as attitude sensors to measure spacecraft yaw error and give update to gyro over the poles. These sensors are equipped with neutral density filters (NDF) to attenuate Sun's intensity on board.Oceansat-2 satellite, the HDSS is reengineered without neutral density filter by successfully incorporating electronic gain switching.Oceansat-2, two HDSS were flown, one with NDF and another with built-in in electronic gain switching. The performance of both sensors onboard is extremely satisfactory. This paper describes the electronic gain switching scheme, the tests conducted in ground to verify the scheme and the onboard performance of both sensors.

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