M4L9: IRNSS

Now in the previous lecture, we discussed about PSLV and GSLV. But wait, IRNSS is a GPS system and uses communication satellites as follows. And I have just mentioned that communication satellites are mostly placed in Geo orbits and require GSLV launch vehicle. In case of IRNSS, we have used PSLV. Isn’t this conflicting?

In this case, what PSLV does is, it puts the satellite in Hohmann orbit also known GTO or Geo Transfer orbit. This orbit intersects Geo orbit at some point. This point is common to both the geo orbit and the medium orbit and therefore acts as a gateway to enter to the Geo orbit. PSLV had put all the satellites to Geo Transfer orbit. PSLV can carry payload up to 1,750 kg to Polar Orbits (max 600 km altitude) & 1425 kg to GTO. While GSLV MkIII is capable of placing payloads up to 5 tonnes in Low Earth Orbits & 2500 kgs to GTO