Re: ISRO to launch GSLV-D5 in July
Could Isro not have waited for the GSLV to fly the mission since this would take the orbiter closer to Mars?
In August 2010, we formed a study group on what we should do, whether we should do a fly by or an orbiter. Fly by means we can carry large instruments but the observation time is very short but we can be successful because it will always pass somewhere near Mars. But we decided there is no point. We were clear we should do an orbiter. We then put up a team and they worked up to June 2011. They came out with a report with all the options. After looking at the vehicle that we have and what is required, a decision was taken.
There are two types of orbits — we have chosen a 365-by-80,000 km orbit which will require 855 kg of fuel. If I have to put it in a circular orbit of 1,000 km, we need 2,000 kg of propellant. That means the fuel itself is two tonnes — at present it is 850.8 kg. If you take the spacecraft, it is in the range of 500 kg to 600 kg. That means for a circular 1,000 km orbit, you are talking a 2,600-kg spacecraft. With a 1,350-kg satellite I am now getting a 350-by-80,000 km orbit.
Now if you are at 1,000 km orbit like Maven you need a couple of tanks, couple of liquid apogee motors, so you have to devise a different configuration for the orbiter spacecraft. Then there is the question of launcher. Even GSLV cannot lift it because its capacity is 2,200 kg. We are talking of 2,600 kg, plus the instrument. We decided to go for the elliptical orbit, 365-by-80,000.
There were launch opportunities for 2013, 2016 and 2018. Because of the geometries involved, 2016 would be costlier. You need a vehicle like GSLV at that time. In short, what we have done is that we have availed the best available opportunity — 2013 November.
How different would the Mars mission be if Isro were to wait for the GSLV?
If we had GSLV, two things would have happened, this transfer that we are talking of if you had the same mass of spacecraft, 1,350 kg, the initial orbit could have been bigger. Instead of 250 km-by-23,000 km, it could have been 36,000 km or 40,000 km. That means the number or orbit raisings could have been reduced. Secondly, we could have carried more payload. Now we are carrying 15 kg, it could have carried a few 100 kg — but where is the payload for it. There is no instrument, so there was no need. What we now have is a prudent strategy. GSLV would need more fuel for achieving the 1,000-km orbit around Mars (which is closer than the 350-by-80,000 km orbit for MOM) and it would need a different spacecraft. Though there is criticism there are clear parameters that have helped us decide.
Between the Mars mission and the GSLV development, which has suffered setbacks, which would you categorise as being the key to India's space programme?
Both are important. In the launch vehicle, GSLV is essential. If you look at GSLV, the first launch was aborted in 2001 because there was a problem. Within 22 days we corrected that and we had a flight. It injected a satellite but there was under-performance in the last cryogenic stage and the satellite did not last more than two months. Second and third were successful flights. The fourth flight was a failure and in the fifth, there was a problem in the control system. These were component problems. After nearly two-and-a-half years, we had a flight in April 2010 but last-stage cryo did not perform. It was the first flight for the indigenous cryo. In December 2010, the Russian cryogenic stage developed problems. The vehicle had to be destroyed. We went back to testing, reviews and we came back to launch earlier this year but there was a leak. GSLV is essential. We have been working on an indigenous cryo stage for the last 20 years, we have to stick with it. GSLV MK III is another advanced vehicle that we are developing. Now we are going to have the ground test of the cryogenic stage also. We had a small test last week that was successful. When you talk priorities you must understand these are two different areas. A Mars mission has no conflict with the development of GSLV.
'Mission not in conflict with GSLV development' - Financial Express