Denied by US,India launched its own GPS

SRIHARIKOTA: When Pakistani troops took positions in Kargil in 1999, one of the first things Indian military sought was GPS data for the region. The space-based navigation system maintained by the US government would have provided vital information, but the US denied it to India. A need for an indigenous satellite navigation system was felt earlier, but the Kargil experience made the nation realise its inevitability.

On Friday, the Indian Space Research Organisation took the nation closer to the goal, which it would achieve in less than two years. The result, the Indian Regional Navigation Satellite System (IRNSS) will be as good as any such space-based system, as India can keep a close watch of not just its boundaries, but up to 1,500km beyond that. It works on a combination of seven satellites which would 'look' at the region from different angles, and, in the process, helps calculate from relative data, real-time movement of objects by as less as 10m.

Isro launched the first of the satellites in the group, IRNSS-1A, in July last. "By mid-2015," said Isro chairman K Radhakrishnan, "we will have all the seven in place." The system will be functional by the beginning of 2016. Basic navigational services wouldn't have to wait that long—they can take off with just four satellites in orbit, which will be this year. "When we have four satellites by the end of this year, we will have an operational system and then we can go and test its accuracy to validate it," said K Radhakrishnan.>

Three of the seven satellites will be in geostationary orbits and the other four in inclined geosynchronous orbits. From ground, the three geostationary satellites will appear at a fixed point in the sky. However, the four geosynchronous satellites moving in inclined orbits in pairs will appear to move in the figure of '8' when 'seen' from ground. Apart from navigation, the system will help in precise time keeping, disaster management, fleet management and mapping.

"Geopolitical needs teach you that some countries can deny you the service in times of conflict. It's also a way of arm twisting and a country should protect itself against that," said S Ramakrishnan, director of Vikram Sarabhai Space Centre, Thiruvananthapuram. This is the reasoning behind two types of services that IRNSS will be offering. The first is called Standard Positioning Service (SPS) which is for civilian use. This will have an accuracy of 20m, while the second is called Restricted Services (RS), which can detect movement of objects by less than 10m.

"Many weapon systems like guided missiles and bombs also use such navigation systems. An indigenous system allows the development of such capabilities in a reliable manner," said Ramakrishnan. "There is also the need to have your own navigation system in the civilian and commercial domain since so many critical services and businesses depend on it. A system run by another country (like GPS) may be switched off in times of crisis leading to complete collapse of certain services."

It will put India in the company of select nations which have their own positioning systems. While the US operates the Global Positioning System (GPS), Russia has its own GLONASS and European Union, Galileo. China is also in the process of building Beidou Navigation Satellite System (BDS).

Too bad it is regional rather than worldwide. It would be nice to have back up systems in case our own government decides to screw with the system. Right now the tablet I’m using can track both the US and Russian systems.

Does anyone else get the impression the author doesn’t know the difference between “satellite navigation” and “satellite reconnaissance”?

Or am I missing something?

That system is going to require a lot of complex math — fortunately, the help desk will be a local call.

The US GPS system requires math that makes advanced calculus look like a sunday school picnic. Fortunately for users, the GPS receiver has the solutions built in and are not difficult to use.

Anyone can use the automotive ones, the hunting ones are more difficult, but not beyond the capabilities of any high school graduate.

I was thinking about the systems level — where you even need to incorporate special relativity. Then, it seemed to me that mixing Geo-stationary and NEO satellites together would make it even more complex. There are a lot of scary-smart engineers in India; so I have little doubt they'll pull it off (despite my cheap shot about call center help desks, which seem to be located mostly in India).

Then, it seemed to me that mixing Geo-stationary and NEO satellites together would make it even more complex.

"Three of the seven satellites will be in geostationary orbits and the other four in inclined geosynchronous orbits. From ground, the three geostationary satellites will appear at a fixed point in the sky. However, the four geosynchronous satellites moving in inclined orbits in pairs will appear to move in the figure of '8' when 'seen' from ground."

There are no NEO satellites. The 4 "inclined geosynchronous satellites" are at geosynch orbital distance, but are inclined with respect to the equator. This a very interesting solution to providing a regional positioning system, without taking up too many geosync "slots".

I am not certain if the math is easier or harder than the GPS system, but I wonder if a communications geosynch satellite could carry a piggyback positioning capability. And, are they going to start selling automotive receivers like in the rest of the world, or are those going to rely on regular old GPS.

“There are no NEO satellites. The 4 “inclined geosynchronous satellites”

You’re right of course. I replied from my ping list, without refreshing my memory by checking the article again. The kernel I had remembered was “different types of orbit”.

Perhaps the math won’t be more difficult than the original GPS system — but, it will be difficult enough. For one thing, the relative position of the signals from geosynchronous satellites will be constantly changing, with respect to those from the geostationary satellites. Also, they will have to work out their own equations, without any cribbing from the US GPS (the GLONASS, and Galileo systems are more similar to the GPS).

Given the greater satellite distances, I wonder whether the Indian system will have enough signal strength for civilian use.

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.