SAC : Overview
Space Applications Centre (SAC) is one of the major centres of the Indian Space Research Organisation (ISRO). SAC focuses on the design of space-borne instruments for ISRO missions and development and operationalisation of applications of space technology for societal benefits. The applications cover communication, broadcasting, navigation, disaster monitoring, meteorology, oceanography, environment monitoring and natural resources survey. SAC designs and develops all the transponders for the INSAT and GSAT series of communication satellites and the optical and microwave sensors for IRS series of remote sensing satellites. Further, SAC develops the ground transmit/receive systems (earth stations/ground terminals) and data/image processing systems. In order to carry out the above tasks, SAC has highly sophisticated payload integration laboratories, electronic and mechanical fabrication facilities, environmental test facilities, systems reliability/assurance group, image processing and analysis facilities, project management support group and a well-stocked library. SAC works with industry for sourcing and indigenization involves Indian universities in space research and propagates space technology and applications amongst students and public through in-house and mobile exhibitions. The Centre also conducts nine-month post graduate diploma courses for students from the Asia Pacific region under the aegis of the Centre for Space Science and Technology Education (CSSTEAP) in satellite meteorology and communication.
The Centre has its origin in the establishment of the Experimental Satellite Communication Earth Station (ESCES), in 1966 by late Dr Vikram Sarabhai in Ahmedabad.
Satellite Communications Technology and Applications
Payload development activity at SAC was started with the India’s first experimental communication satellite APPLE. Since then SAC has involved in the Conceptualization, design & development of advanced communication systems. About 38 transponders are added to the INSAT fleet in the last year. GSAT-14, Navigation payloads IRNSS-1A & 1B were developed and delivered. GSAT-14 communications satellite has the domestic communications capacity at Extended C and Ku-Bands. It will also carry two Ka Band beacons for propagation studies. IRNSS-1A will provide time and position signals across the Indian subcontinent and ocean region, enabling these services on a completely indigenous footing. Assembly, Integration and delivery of payloads for INSAT-3DR, GSAT-15, GSAT-16 and IRNSS-1C are in progress. New technologies like ETM Rubidium Atomic clock, Optical terminal for 1 GPS Link, Establishment of SAC-Bopal Free Space Optical link and System engineering for advanced communication payloads were developed.
In the area of antenna systems, SAC has developed various types of antenna systems like large Cassegrain antenna systems with tracking feed, short back fire antenna systems for earth stations, antennas of different sizes and for various frequencies for INSAT and GSAT satellites, multi frequency scanning antenna systems for Oceansat-1, slotted array fan-beam antenna for airborne radar systems, shaped beam antennas etc. SAC has also established a state-of-the-art Compact Antenna Test Facility (CATF). All the antennae & feed systems for the payloads under SATCOM, Navigation, Microwave remote sensing was realized and developed indigenously.
Beginning with the establishment of the first Experimental Satellite Communication Earth Station (ESCES) in 1966 at SAC to Maitri in Antarctica, SAC has built many earth stations including the one at the Master Control Facility at Hassan. Delhi Earth Station (DES) provides Type-D & Type-C INSAT Mobile Satellite Services, DMS VPN network services and Ka/Ku-band propagation studies. BES–Bopal Earth Station facility at Bopal SAC Campus caters to EUMETCAST and VHRR data reception from INSAT series of Satellites. Ahmedabad Earth Station (AES) is mainly involved in SATCOM based operations and Experiments including Special events at SAC main campus and Bopal campus through BES. It supports Space-Net based Video Conferencing Facility, VHRR data reception, SATCOM course under CSSTEAP.
SAC has undertaken a major applications project viz., EDUSAT applications Project for country-wide education via satellite. More than 33000 installations of user terminals for tele-education are operational in the country. SAC is also pursuing Telemedicine and extending communication support for Disaster management in the country.
Remote Sensing Technology Development
SAC plays a very important role in the Remote Sensing programme. Payload development was started with balloon experiments followed by aerial photography for remote sensing. In the last 25 years there is significant development in the Optical, mechanical & electronic systems. Several sensors were flown on all the IRS series of satellites starting from the first operational satellite IRS-1A.
Meteorological satellite INSAT 3D has a six-channel imaging radiometer to sense radiant and reflected solar energy and an IR radiometer for sensing atmospheric vertical temperature, moisture profiles, surface and cloud top temperature distribution.
Resourcesat-2, a follow on mission for the Resourcesat-1, payloads LISS-4, AWIFS A & B and LISS-3* cameras were developed & qualified at SAC is configured to provide continuity of data with enhanced performance. Youthsat is proposed to study the solar activities and its effect on earth upper atmosphere contain a Limb Viewing Hyper Spectral Imager (LiVHySI) developed by SAC. Three Electro-optical instruments: Terrain Mapping Camera-2 (TMC-2, Imaging IR Spectrometer (IIRS) and Rover Imager are being developed for Chandrayaan-2 mission. INSAT-3DR & S are follow-on to INSAT-3D and its subsystem developments are in progress. SAC is responsible for design and development of Detection systems of Adithya-1, the Science and Planetary satellite. Integration and payload development of MARS Mission is in final stage.
Over the last almost three decades, Microwave Remote Sensing (MRS) programme has evolved in SAC. From the modest beginning of development of SAMIR payloads for Bhaskara series of satellites for scientific understanding, payloads like MSMR and Scatterometers have been designed for providing operational services of atmospheric and oceanographic applications. At the same time, ISRO initiated collaborative development of payloads, like Megha-Tropiques (joint Indo-French collaboration between ISRO and CNES), with established space agencies, to consolidate expertise available in the development of complex technologies. Megha-Tropiques has 3 payloads: MADRAS (Microwave Analysis and Detection of Rain and Atmospheric Structures), SAPHIR, and SCARAB is used for climate studies in tropical regions with a repetivity of 6 hours. Ku-band Scatterometer, onboard Oceansat-II (2009) is aimed to gather information about the near surface winds over oceans at a global level and feed to global weather forecasting system. DMSAR – Airborne SAR for Disaster Management was developed with operational requirement in view. Recently an improved DMSAR Version-2 has been tested and delivered to NRSC, Hyderabad. Radar Imaging Satellite-1 (RISAT-1), carrying India’s first indigenously developed space-borne, C-Band active antenna based, Multi-mode Synthetic Aperture Radar (SAR) payload was launched on 26th April, 2012 by PSLV-C19 flight. Since the start of payload operation on May 1, 2012, SAR images of good quality have been continuously received. Target applications for RISAT-1 include agricultural crop acreage and yield estimates (Rice, Jute etc.), disaster monitoring like flood affected area estimation, hydrology, geology, land use, terrain studies, change detection and oceanography, bathymetry, wave spectra, etc. Work is initiated for Scatterometer Repeat (Scatsat-1/Oceansat-3) and RISAT-1A SAR Repeat missions.
Remote Sensing – Image Processing and Applications
SAC has been developing the algorithms and the software required for processing and product generation of data acquired from IRS satellites. It involves the design, development, operationalization and maintenance of software for remote sensing data processing related to earth, planetary and astronomical observations for Indian as well as International user community. The software is transferred to NRSC, Hyderabad for operational dissemination of data products to users.
RISAT-1, Scatterometer, Meghatropiques, YOUTHSAT, OCM-2 Data Products Generation softwares and FASAL-SOFT (SAR component) operationalised at MNCFC, Delhi. Resourcesat-2 DP software was operationalized at NRSC in IMGEOS environment from August, 2011 to provide high quality data products to remote sensing application users. Developed & Installed Level-1 DP software & Quick Look Display at ISSDC and Level-2 software at MOSDAC for all MADRAS, SAPHIR & SCARAB payloads of Megha-Tropiques satellite and achieved near real time processing capability for data products generation. IMDPS—INSAT Meteorological Data Processing System software has been indigenously designed, developed, installed and commissioned at IMD, New Delhi and the Mirror Site at BES, Bopal, SAC. Oceansat-2 scatterometer DP processing software operationalised at MOSDAC.
RISAT-1 Level-1 & 2 data products software was operationalised in October 2012.
In the area of remote sensing applications, SAC aims at identifying Earth Observational (EO) needs, development of techniques to model and analyse data for applications related to land, ocean, atmospheric and planetary sciences. It involves retrieval of biophysical and geophysical parameters from space borne imaging sensors, assimilation of remote sensing derived parameters, in-process modelling pertaining to interactions within the geosphere-biosphere system and atmosphere.
SAC has established the methodology for pre-harvest estimation of production of major crops like wheat, rice, cotton, mustard etc. This has led to establishment of multi-agency FASAL project for production forecast of major crops. Methodology has been developed for estimation of Kharif rice production using radar data. SAC developed the methodology for potential fishing zone forecasts using OCM and other satellite data and this has led to operational services for fishermen of maritime states. Glaciers of Himalayas have been studied systematically over the last decade and information on status of snow cover and inventory of glaciers is provided to the concerned ministries. Methodology for tracking cyclones has been developed and used for predicting the direction of movement and land falls for cyclones like Gonu, Nargis etc. Various algorithms have also been developed to derive ocean parameters like sea surface temperature, wind speed, wave heights etc as well as atmospheric parameters such as water vapour, cloud liquid water content etc. A facility to disseminate meteorology and oceanography data to interested users has been established. A major thrust is being provided to the utilization of microwave data in view of their ability to see through the clouds.
SAC was instrumental in setting up the Mahalanobis National Crop Forecast Centre (MNCFC) under the DAC, MOA in April, 2012 in the Pusa campus, New Delhi.
Fabrication and Test Facilities
In order to competently support the research & development activities, SAC has established excellent electronic and mechanical fabrication & test facilities. New Technologies/Process development activities in the areas of Antenna, Electronic & Mechanical Services & Support have been taken up to cater the need of future payloads requirements.
Four new laboratories were setup at SAC Bopal Campus. Installation & commissioning of curing chamber for PAAF under technical support of CTSD completed and chamber operationalised. TIMCD labs becomes first to get 2nd time NABL accredition amongst ISRO units (valid till June 2014). Installation & commissioning of upgradation of CATF for mm-waves completed.
A strong Systems Reliability group recognizes need for continuous update of tools, techniques and procedures to be employed for assuring quality and reliability of increasingly complex and miniaturized payloads with very aggressive development schedule.
Library and Information services
SAC has a well stocked library to support the R&D activities. Most of the functions are computerized and connected through the campus-wide network called SACNET to facilitate the users. Library also provides bibliographic and current awareness services.
Projects and Programme Management
To ensure advanced R&D activities and time bound projects with large budgets are executed systematically a management support group is established for project planning and monitoring. In addition, the functions related to patents & IPR filing, technology transfer & industrial interface, human resources development, management information systems, networks planning & operations as well as managing the IT facilities are carried out by a dedicated group.