India Launches Its Second Navigation Satellite | Hacker News Reader

India Launches Its Second Navigation Satellite

space.com

91 pointsmiddleclick15 comments

"Preliminary data showed the rocket placed the spacecraft in an orbit with a high point of 12,807 miles, a low point of 176 miles and an inclination of 19.2 degrees."

Maybe I'm reading this wrong, but this appears to be a very elliptical orbit with a the difference between the high and the low being more than 70x.

Does someone here know what the purpose of such an orbit is? Obviously it states navigation but I guess that's not enough for me to understand why they would pick such an orbit.

Geostationary satellites have a circular equatorial orbit, at 35,786 km above the Earth. Launch vehicles can only place satellites in an elliptical orbit with some degree of inclination from equator. So, geostationary satellites are placed in elliptical "geostationary transfer orbits". And, satellite's onboard propulsion system is used to:

1) Gradually raise the apogee

2) Transform elliptical orbit into circular orbit

3) Reduce inclination to zero degree with respect to equator.

Orbit's apogee is raised by firing onboard motor at perigee. Circular transformation is done by firing onboard motor at apogee.

If a launch vehicle can place satellite in a geostationary transfer orbit with calculated apogee of 35, 786 km itself, the the apogee raising operation (i.e. perigee firing) is not required. Satellite can just start firing at apogee to transfrom elliptical orbit to circular orbit.

ISRO's PSLV-XL placed IRNSS-1B at an apogee of 20,630 km. So, ISRO needs to do apogee raising before transforming into circular orbit.

ISRO's bigger rocket GSLV Mk2 can launch satellites directly to geostationary transfer orbit (calculated apogee of 35,786 km), so there's no need to do orbit raising manoeuvres.

Here's an article from Planetary Society blog about getting geostationary satellites to geostationary orbits:

http://www.planetary.org/blogs/jason-davis/20140116-how-to-g...

It is Geosynchronous Transfer Orbit I assume(http://en.wikipedia.org/wiki/Geostationary_transfer_orbit) (but wiki article's suggested apogee doesn't match) as there 5 more orbit manoeuvres remaining which will put it to final position.

From what I know, this is dues to lower capacity of PSLV which was used for this launch. GSLV being developed has more power but it is not as dependable as PSLV yet.

Launch video: http://www.youtube.com/watch?v=LtdgrcF1nFg

As an indian citizen I've never understood how these technologies ever reach me. I know GPS is by the US government, is any one commercializing these technologies in India?

"Indian officials say the independent navigation service will aid marine traffic, emergency response officials, vehicle tracking applications, mobile communications, mapping, and civilian drivers."

IRNSS wiki page[1] sums up nicely, on why indigenous navigation system is required:

  The requirement of such a navigation system is driven by the fact that access to foreign government-controlled global navigation satellite systems is not guaranteed in hostile situations.

Two more IRNSS satellites will be launched by the end of 2014, and remaining three will be launched by mid 2015. So, the 7 satellite constellation will be ready by 2015. IRNSS receivers (akin to GPS receivers) can be tested by 2014 itself (4 satellites are sufficient for determining position). I've come across few vendors who already have industrial/commercial grade IRNSS receivers[2]. So, it's only a matter of time until we start seeing IRNSS receiver chips in consumer electronic devices.

Missiles use satellite navigation to determine their targets. So, relying on external navigation systems is undesirable.

[1] http://en.wikipedia.org/wiki/Indian_Regional_Navigational_Sa...

[2] http://gpsworld.com/novatel-supplies-reference-receivers-for...

This just moves the problem to space warfare, so things work...until your satellites are knocked out in space.

But, I understand the premise.

Personally I think another angle is important: more competition, hopefully leading to more accurate navigational data streams.

Do we know if IRNSS will be backwards compatible with GPS (like the Galileo system that the Europeans are launching)?

No. IRNSS is not compatible with GPS.

https://www.quora.com/Indian-Space-Research-Organisation-ISR...

Even if it doesn't become popular for civilian use because of the overwhelming popularity of GPS software and hardware, precise location fixes for military purposes is a no-brainer in 2014.

E.g., Imagine every solider fitted with a receiver/transmitter so that their location is known with a resolution of a few feet. Think that'll make it easier to save the wounded during operations?

It's supposed to cost $250 million (approx $25 million per year since it lasts 10 years). Cost seems wildy reasonable considering just the military benefits.

You don't have to imagine every soldier having that, there are already armed forces doing that now. The technologies have improved enough and the costs come down so low that it's affordable for even a mid-level country's armed forces to do it.

I've seen one of these systems demonstrated, which uses a cigarette-box sized unit with a GPS sensor, GSM modem, satellite transceiver, military radio connector and battery inside. Positions were encrypted and transmitted via least-cost routing to a centralised command and control system, showing the position of each soldier in real-time.

Of course, in real operations it becomes difficult to maintain line-of-sight radio communications over long distances, cellular service is spotty in combat zones and satellite communications are expensive even with small data packets. So the related infrastructure requires careful thinking too.

So I agree with you, this seems a worthwhile investment for the military benefits alone. It's one of the main reasons to have an indigenous space programme in the first place.

It will be useful after 2015 as it will cover entire India.

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