The Indian Space Research Organisation (ISRO) is getting ready to launch of Radar Imaging Satellite RISAT-2BR1 on Wednesday at around 3.25pm (IST) from Satish Dhawan Space Centre (SDSC), Sriharikota. Onboard the fiftieth PSLV QL mission, there will be nine other commercial purpose foreign satellites from countries including six from the US, and one each from Italy, Japan and Israel, under a commercial contract with New Space India Limited (NSIL). The RISAT-2BR1 is a 628 kg Earth observation satellite and shall be positioned in the 576 km orbit and is a part of the sequence of similar dual-purpose satellites which have been positioned for India specific surveillance since 2009. The latest one was launched in May this year.
"With a robust space surveillance network along with ISRO’s Position, Navigation and Timing services, India joins the select group of nations capable of advance intelligence gathering from outer space," says Milind Kulshreshtha, C4I expert.
ISRO's Positioning, Navigation & Timing Services
Countries are trying to evolve their own captive Global Positioning System (like Russia's GLONASS and China's Beidou) since these technologies play an important role in various activities like booking a cab, aircraft navigation and military applications like the launch of a Surface to Surface missile.
"These PNT (Positioning, Navigation and Timing) services are efficiently available through space technologies. A disruption of PNT services or their spoofing by a non-friendly service provider nation can jeopardise a nations key commercial and defence services and these ISRO’s indigenous PNT services are crucial for India’s growth in near future," explains Kulshreshtha.
Precision Timing Services
According to him, the Indian space agency provides a Standard Time and Frequency Signal Dissemination Service through INSAT satellites. "This technology has been implemented by National Physical Laboratory. This Time synchronization signal is available for commercial use and gives a precision of better than one microsecond with an accuracy of better than 20 microseconds. For military applications, these Timing signals shall be crucial for advanced solutions like Multi-platform Multi-sensor data fusion."
Aircraft Navigation System GAGAN
GAGAN is part of Airport Authority of India (AAI) project for Satellite-Based Augmentation System (SBAS). The system is inter-operable with international systems from US, UK, Japan and has a geo-footprint from Africa to Australia region for achieving a seamless navigation. It’s the first SBAS system in the world to serve the equatorial region. For the aviation industry, GAGAN improves the reliability of GPS during all phases of flight and for Air Traffic Management (ATM).
According to the C4I expert, "GAGAN is primarily supported by GSAT satellites and uses ISRO’s proprietary GAGAN ionospheric algorithm. India is the third country in the world to have this precision approach capability. The Ground segment of GAGAN comprises of an Uplink Station, Master Control Centre and Reference Earth Station (network of ground reference stations strategically positioned across the country)."
The calculated GPS error correction messages are uplinked for broadcast back to Earth using the same frequency as GPS for aviation purposes. The GAGAN’s error correction signals have been also enabled for Railways, Highways and Maritime services.
Indian Regional Navigation Satellite System (IRNSS)
IRNSS is satellite-based navigation system to provide Positioning, Navigation and Timing services for users over Indian Region for land, air and sea transportation services. The system, called NavIC (Navigation Indian Constellation), uses a constellation of seven satellites and a wide network of ground stations.
"The IRNSS services can be run on a mobile phone for vehicle tracking. Further, Mapping services for capturing Geodetic survey data too shall benefit from IRNSS. As a strategy, IRNSS is designed with two types of positioning services viz. public use Standard Positioning Service (SPS) with 20m accuracy and an encrypted Restricted Service for Military use. To achieve this service, a network of Geostationary Earth Orbit (GEO) and Geo Synchronous Orbit (GSO) satellites is used for providing the positional accuracy," he says.
The first dedicated IRNSS-1A satellite weighing 1425kg for its Space segment was launched in July, 2013 and this has been followed with a series of IRNSS satellite launches over the last four years. For its commercial exploitation, ISRO has released the ‘Signal-in-Space’ Interface Control Document for NavIC Receiver manufacturers.
How does NavIC Receiver work?
Explaining about the technology involved, Kulshreshtha, says "It uses the IRNSS signals of opportunity for navigation purposes. These receivers have inbuilt software to integrate navigation services with other commercial Map providers like Google maps for compatibility for Mobile app (Android/IOS versions) and Web apps. For the Restricted Service military users, NavIC uses robust encryption for improved security, with the system encryption keys exchanged regularly to avoid crypto-hack by unauthorized users. To make NavIC available for use by the public, ISRO has collaborated with Qualcomm Technologies to develop the chipset to support NavIC Receivers."
Indian military shall be the ultimate beneficiary of these space endeavours since the future wars are going to be highly Information-centric, and their outcomes may be significantly dependent upon space-based Surveillance, Navigation and Timing services.