Current Science

Kurian Mathew ¹, S. S. Sarkar ¹, A. R. Srinivas ¹, Moumita Dutta ¹, Minal x Minal Rohit ¹, Harish Seth ¹, Rajiv Kumaran ¹, Kshitij Pandya ¹, Ankush Kumar ¹, Jitendra Sharma ¹, Jalshri Desai ¹, Amul Patel ¹, Vishnu Patel ¹, Piyush Shukla ¹, S. Manthira Moorthi ¹, Aravind K. Singh ¹, Ashutosh Gupta ¹, Jaya Rathi ¹, P. Narayana Babu ¹, Saji A. Kuriakose ¹, D. R. M. Samudraiah ¹, A. S. Kiran Kumar ¹

Affiliations
1 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 058, IN

Abstract

Methane Sensor for Mars (MSM), on-board Mars Orbiter Mission is a differential radiometer based on Fabry–Perot Etalon (FPE) filters which measures column density of methane in the Martian atmosphere. It is the first FPE sensor ever flown to space. Spectral, spatial and radiometric performances of the sensor were characterized thoroughly during the pre-launch calibration. Geophysical calibration of the sensor was carried out using the data acquired over Sahara desert during Earth Parking Orbit phase. Retrieval algorithm for MSM, which is based on the linearization of radiative transfer equations, gets simultaneous solutions for CH4 and CO2 concentrations in the Martian atmosphere.

Keywords

Differential radiometer, Fabry–Perot Etalon, geophysical calibration, methane sensor, retrieval algorithm.

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R. P. Singh ¹, Somya S. Sarkar ¹, Manoj Kumar ¹, Anish Saxena ¹, U. S. H. Rao ¹, Arun Bhardwaj ¹, Jalshri Desai ¹, Jitendra Sharma ¹, Amul Patel ¹, Yogesh Shinde ¹, Hemant Arora ¹, A. R. Srinivas ¹, Jaya Rathi ¹, Hitesh Patel ¹, Meenakshi Sarkar ¹, Arpita Gajaria ¹, S. Manthira Moorthi ¹, Mehul R. Pandya ¹, Ashwin Gujrati ¹, Prakash Chauhan ¹, Kuriakose A. Saji ¹, D. R. M. Samudraiah ¹, A. S. Kiran Kumar ²

Affiliations
1 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 058, IN
2 Indian Space Research Organisation, Bengaluru 560 231, IN

Abstract

Thermal Infrared Imaging Spectrometer (TIS), which operates in the infrared spectral region (7-13 μm), is one of the five instruments on-board the Mars Orbiting Mission (MOM). TIS was designed to detect emitted thermal infrared radiation from the Martian environment, which would enable the estimation of ground temperature of the surface of Mars and also map its surface composition. TIS instrument is a grating-based spectrometer which has spatial resolution of 258 m at periapsis (372 km). TIS hardware was realized with light-weight miniaturized components (total weight 3.2 kg) with power requirement of 6 W. Observations from TIS instrument were carried out during Earth-bound manoeuvres and cruise phase operations of MOM and the results were found to be in agreement with the laboratory measurements.

Keywords

Aerosol Optical Thickness, Mars Orbiter, Minerals Detection, Thermal Infrared Spectroscopy.

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Arup Roy Chowdhury ¹, Arup Banerjee ¹, S. R. Joshi ¹, Moumita Dutta ¹, Ankush Kumar ¹, Satadru Bhattacharya ¹, Amitabh ¹, Sami Ur Rehman ¹, Sunil Bhati ¹, J. C. Karelia ¹, Amiya Biswas ¹, Anish R. Saxena ¹, Satish Sharma ¹, Sandip R. Somani ¹, H. V. Bhagat ¹, Jitendra Sharma ¹, D. N. Ghonia ¹, B. B. Bokarwadia ¹, Ajay Parasar ¹

Affiliations
1 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN

Abstract

Imaging Infrared Spectrometer (IIRS) is an imaging hyperspectral instrument for mineralogy of the lunar surface (including the hydroxyl signature). IIRS operates in the 0.8–5 μm spectral range with about 250 contiguous bands. It has 80 m ground sampling distance and 20 km swath at nadir from 100 km orbit altitude. Optical design is based on fore-optics and Offner (convex multi-blazed grating)-type spectrometer. Focal plane array is HgCdTe (mercury–cadmium–telluride)- based actively cooled to 90 K, having 500 × 256 pixels format with 30 μm pixel size. Electronics comprises proximity, logic and control, power supply and cooler drive electronics. Mechanical system is realized to house various subsystems, namely optics, detector, electronics and thermal components meeting the structural, opto-mechanical thermal component and alignment requirements. Thermal system is designed such that the instrument is cooled and maintained at fixed temperature to reduce and control instrument background. Aluminum-based mirror, grating and housing are developed to maintain structural as well as opto-mechanical and thermal requirements. This article presents IIRS realization and spectroradoimetric performance.

Keywords

Hyperspectral Imaging, Infrared Spectrometer, Moon, Orbiter.

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Arup Roy Chowdhury ¹, Manish Saxena ¹, Ankush Kumar ¹, S. R. Joshi ¹, Amitabh ¹, Aditya Dagar ¹, Manish Mittal ¹, Shweta Kirkire ¹, Jalshri Desai ¹, Dhrupesh Shah ¹, J. C. Karelia ¹, Anand Kumar ¹, Kailash Jha ¹, Prasanta Das ¹, H. V. Bhagat ¹, Jitendra Sharma ¹, D. N. Ghonia ¹, Meghal Desai ¹, Gaurav Bansal ¹, Ashutosh Gupta ¹

Affiliations
1 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN

Abstract

Orbiter High Resolution Camera (OHRC) onboard Chandrayaan-2 Orbiter-craft, is a very high spatial resolution camera operating in visible panchromatic band. OHRC’s primary goal is to image the landingsite region prior to landing for characterization and finding hazard-free zones. Post landing operation of the OHRC will be for scientific studies of small-scale features on the lunar surface. OHRC makes use of the time delay integration detector to have good signal-tonoise ratio under low illumination condition and less integration time due to very high spatial resolution. Ground sampling distance (GSD) and swath of OHRC (in nadir view) are 0.25 m and 3 km respectively, from 100 km altitude. GSD is better than 0.32 m in oblique view (25° pitch angle) during landing site imaging from 100 km altitude in two stereo views in consecutive orbits. This article includes the details of the configuration, sub-systems, imaging modes, and optical, spectral and radiometric characterization performance.

Keywords

Ground Sampling Distance, Orbiter High Resolution Camera, Relative Spectral Response, Square Wave Response, Time Delay Integration.

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Arup Roy Chowdhury ¹, Vishnukumar D. Patel ¹, S. R. Joshi ¹, A. S. Arya ¹, Ankush Kumar ¹, Sukamal Paul ¹, Dhrupesh Shah ¹, Pradeep Soni ¹, J. C. Karelia ¹, Minal Sampat ¹, Satish Sharma ¹, Sandip Somani ¹, H. V. Bhagat ¹, Jitendra Sharma ¹, Amitabh ¹, K. Suresh ¹, R. P. Rajasekhar ¹, B. B. Bokarwadia ¹, Mukesh Kumar ¹, D. N. Ghonia ¹

Affiliations
1 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN

Abstract

The paper presents the design and development of Terrain Mapping Camera-2 (TMC-2) for Chandrayaan- 2 including science objectives; system and sub-system configuration along with the realized performance of the camera; payload characterization; aspects related to data products, etc. TMC-2, onboard Chandrayaan-2 orbiter-craft is a follow-on of the Terrain Mapping Camera (TMC) onboard Chandrayaan- 1. It operates in visible panchromatic band. It comprises three identical electro-optical chains aligned for three views (–25, 0 and +25 degree) along track direction for generation of stereo images. It provides data with 5 m horizontal ground sampling distance to generate digital elevation model. TMC-2 based on the new configuration and sub-system designs has reduction in mass and power by more than 40% compared to TMC, without compromising the performance.

Keywords

Digital Elevation Model, Light Transfer Characteristics, Relative Spectral Response, Signal-to-noise Ratio, Stereo Imaging, Square Wave Response, Terrain Mapping Camera-2.

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