Laboratory for Electro Optics Systems

Bangalore, India

Laboratory for Electro Optics Systems

Bangalore, India
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Thamatam N.,Laboratory for Electro Optics Systems | John J.,BITS Pilani K. K. Birla Goa Campus | Sridhara S.,Vellore Institute of Technology | Prakash K.V.,BITS Pilani K. K. Birla Goa Campus | And 7 more authors.
2015 International Conference on Smart Sensors and Systems, IC-SSS 2015 | Year: 2017

This paper presents a detailed study of offset drift of a capacitive inertial sensor with temperature. The goal is to analyze the contribution to the overall drift component by the sensor and the signal conditioning circuit. The relevance of the study lies in the fact that the offset drift with temperature affects the overall accuracy of the sensor. The device selected for the case study is a bulk micro-machined single axis inclinometer with differential capacitive sensing mechanism. To assess the temperature dependence of capacitance, a numerical analysis has been done. Finite element method is used to simulate thermal, electrostatic and electro-thermo mechanical behavior of the sensor assembly. Simulations are performed to understand the advantages of silicone material based mounting technique, where a silicone based encapsulant is used to attach sensor to package. An experimental approach to segregate the offset drift contribution has been proposed. © 2015 IEEE.

Sumesh M.A.,Laboratory for Electro Optics Systems | Karanth S.P.,Laboratory for Electro Optics Systems | Thomas B.,Laboratory for Electro Optics Systems | Narayanamurthy H.R.N.,Laboratory for Electro Optics Systems | And 5 more authors.
2015 International Conference on Smart Sensors and Systems, IC-SSS 2015 | Year: 2017

High performance and reliable infrared detector are ever-sought in spacecraft attitude determination sensor. The most proven 'Earth Horizon sensor' based on the infrared detector operating in the wavelength region of 14-16 μm (CO2 atmospheric emission) essentially calls for IR detector performance; high sensitivity ≥400V/W at low operating bias, fast response ≤ 2 ms, NEP∼200pw/√Hz and long term durability in compliance with space specific conditions. Even though Optically Immersed Bolometer measuring Earth limb radiation budget @14-16μm wavelength region is widely adopted for the Indian Spacecraft ES applications, the sensor reliability was skeptical owing to the inherent disadvantages of materials used and conventional thick film detector technology. Novel fabrication technology for infrared detector has been developed in LEOS to overcome the issue of on-board reliability while achieving better infrared detector performance suitable for same Earth sensor configuration. Detailed design, material studies and characterization were carried out. Fabricated detectors were subjected to environmental tests according to MIL-STD-883F, MIL-STD-810F and MIL-STD-202F as per the Quality Assurance Plan, and their electro optics performance was evaluated. Finally, in house developed and Qualified Bolometer performance has been verified in the spacecraft ES. The paper provides all its details design to application and its specific performance in Earth Horizon Sensor. © 2015 IEEE.

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.

Sumesh M.A.,Laboratory for Electro Optics Systems | Karanth S.P.,Laboratory for Electro Optics Systems | Thomas B.,Laboratory for Electro Optics Systems | Rao G.M.,Indian Institute of Science | And 3 more authors.
Journal of Infrared, Millimeter, and Terahertz Waves | Year: 2016

Terahertz (THz) radiation perception using uncooled detectors are gaining importance due to the increasing demands in the areas of military, space, and industrial, medical, and surveillance applications. In spite of the efforts of researchers to fill the THz gap, there exists a need for detectors in the range between 15 THz and 30 THz. In this paper, we discuss the development of bolometric detectors whose performance is enhanced by an optical immersion technique and their characterization in the aforesaid range of frequencies. These detectors are characterized by high specific detectivity (D*) of 1.28 × 109 cmHz1/2 W−1 and high radiometric resolution (noise-equivalent temperature difference = 26 mK) and are fast enough for bolometric detectors (time constant = 1.7 ms), which make them suitable for spectroscopic and imaging applications. © 2016 Springer Science+Business Media New York

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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