Satellite Communication: ISRO

Satellite Communication utilisation has become wide spread and ubiquitous throughout the country for such diverse applications like Television, DTH Broadcasting, DSNG and VSAT to exploit the unique capabilities in terms of coverage and outreach. The technology has matured substantially over past three decades and is being used on commercial basis for a large number of applications. Most of us are touched by satellite communication in more ways than we realise.

The potential of the technology for societal applications continue to fascinate ISRO and efforts are on to leverage the benefits of technology to the betterment of mankind. Important initiatives pursued by ISRO towards societal development include Tele-education, Tele-medicine, Village Resource Centre (VRC) and Disaster Management System (DMS) Programmes. The potential of the space technology for applications of national development is enormous.

Image Credits: ISRO

Telecommunication:

INSAT satellites have been traditionally supporting telecommunication applications for providing voice and data communications. Satellite links are the primary means of connectivity to remote and far-flung regions of the country and they are the backup links for large number of terrestrial connectivity in the mainland.

The satellite networks of modern age embrace, to a large extent, Very Small Aperture Terminals (VSATs) to cater to the traffic and application requirements of varied users. The VSAT networks are designed to support all kinds of applications supporting video, voice and data, with a wide range of data rates from few kilobits per second (kbps) to 8 megabits per seconds (mbps). A VSAT network comprises of a central hub and hundreds of terminals, which are further interfaced to computers and other peripheral devices. The hub acts as a gateway with interface to external connectivity and several application servers. Rapid technological advancements and reduction in the cost of user equipment are increasing the popularity of VSAT network. A VSAT network works out to be a cheaper option while establishing a network to cover a wide geographical area, state wide or nationwide. VSAT networks operate in C, Extended C and Ku-bands.

About 1400 Satellite Earth Stations of different size are operating in satellite network of BSNL, Government users, Closed user group, commercial users and broadcasters and are being utilised for telecommunications / broadcasting applications.Telecom services are being provided by BSNL to remote and inland through satellite media in C-band and Ku-band from main earth stations as backhaul point to point connections. BSNL is also providing GSM connectivity, ATM/Banking connectivity through around 20,000 IPSTAR VSATs as well as one by two voice channel connectivity to remote areas through around 6,000 Digital Satellite Phone Terminal (DSPTs).

Captive satellite based networks for NTPC, GAIL, Oil and Natural Gas Corporation Ltd., National Fertilizer Ltd., Coal India Ltd., ERNET, Karnataka Power Transmission Corporation Ltd., IOCL, BPCL, Jai Prakash Industries Ltd., Indian Railway Project Management Unit, ICAR, POLNET and Infotel Satcom are operational in INSAT system. The networks of Bombay Stock Exchange in Extended C Band are operational on INSAT system. A number of other captive government networks like Indian Coast Guard, Ministry of Defence, Cabinet Secretariat, DRDO, etc., are also working with INSAT satellites.

Image Credits: Google Image

Mobile Satellite Services:

An S-band Mobile Satellite Service (MSS) was added to INSAT system with the launch of INSAT-3C in 2002 and GSAT-2 in 2003. The following two classes of services were identified for MSS:

1.  A small portable satellite terminal that works with INSAT for voice/data communication has been developed with the participation of Indian industries. The terminal is useful for voice communication especially during disasters when other means of communication break down. It can be used from any location in India for emergency communication. Transmit and receive frequencies of the terminal are in S-Band.
2. The portable terminal is connected to the EPABX at central hub station through satellite channel and hence could be considered as an extension of EPABX and call could be made between any satellite terminals and local phones on EPABX. Central hub station is located at SAC, Ahmedabad.

Image Credits: Google Image

Radio Networking:

Radio Networking (RN) through INSAT provides a reliable high-fidelity programme channels for National as well as Regional Networking. At present, 326 All India Radio (AIR) stations have been equipped with receive terminals.

A total of 85 RN channels are being up-linked at present. For this, AIR is utilising one C-band transponder (C-11) of INSAT-3C. A total of 90 carriers in CxC band are being envisaged for up-linking by utilising a full transponder of INSAT-3C by the end of 12th five year plan.

In AIR network, a total of 32 earth stations are equipped with the facility to uplink in CxC band. The Central earth station at Broadcasting House, New Delhi, has been augmented to up-link 26 RN carriers in CxC band.

At present, AIR has 21 radio channels on DTH platform in Ku-band being uplinked with TV carriers from Todapur, New Delhi on INSAT-4B. Efforts are underway to augment this to 40 channels, and installation is in progress to uplink 6 radio channels on DTH C-Band to cover Andaman and Nicobar areas during XII Plan period.

Image Credits: Google Image

Satellite Navigation Programme:

GAGAN Stability tests were successfully completed in June 2013. The overall performance of the systems was reviewed by the review committee. As part of certification activity, DGCA personnel visited GAGAN complex, Kundalahalli in Bengaluru and carried out final inspection activities on Indian Land Uplink Station (INLUS), Indian Master Control Centre (INMCC), Indian Reference Earth Station (INRES) and other facilities.

The implementation of GAGAN has numerous benefits to the aviation sector in terms of fuel saving, saving in equipment cost, flight safety, increased air space capacity, efficiency, enhancement of reliability, reduction in work load for operators, coverage of oceanic area for air traffic control, high position accuracy, etc. The quantum of benefits in the aviation sector would depend on the level of utilisation of such benefits. 

S     Some of the benefits GAGAN is expected to bring for Civil Aviation sector are:

1. Safety benefits – Vertical guidance improves safety, especially in adverse weather conditions
2. Reduction of circling approaches
3. Environmental benefits–Approach with Vertical Guidance procedures will help facilitate better energy and descent profile management during the final approach
4. Global seamless navigation for all phases of flight including arrival, departure, oceanic and en route
5. Allow direct routings, multiple approaches resulting in considerable fuel savings to airlines and provide for capacity enhancement of airports and airspace
6. In addition to aviation sector, GAGAN is expected to bring benefits to other sectors like:
7. Navigation and Safety Enhancement in Railways, Roadways, Ships, Spacecraft
8. Geographic Data Collection
9. Scientific Research for Atmospheric Studies
10. Geodynamics
11. Natural Resource and Land Management
12. Location based services, Mobile, Tourism, etc