Sriharikota: Majority of the satellite launches of ISRO are generally during the day. However, PSLV-C26/ IRNSS-1C was launched during the wee hours (1.32 am) of Thursday to enable the satellite reach the orbital slot (83 degrees East Longitude above equator in this case) spending minimum propellant (fuel).
The navigational satellites are placed at Geo Stationary Orbit that is located at 36,000 km above earth. International Tele-communications Union (ICU), a special organisation fun-ctioning under UN, allots the orbit slot. All countries under United Nations are members in ICU.
Interestingly, countries obtain permission for required slot at least six to seven years before scheduled launch. ICU allots the orbital slot to each satellite to prevent signal interference with other existing satellites in the same orbit. It will seek opinion of the countries having satellites in 10 degrees both sides of the proposed slot before giving its nod for requisite slot.
As many as 30 satellites belonging to different countries will be there within the 20 degrees unlike in the past where there used to one satellite for every 5 degrees.
When contacted the SHAR Director, Dr M.Y.S. Prasad, who is on his way to Master Control Facility of ISRO located in Hasan, 300 km away from Bengaluru to oversee the IRNSS-1C satellite operations from Thursday night, said that they give top priority to save fuel since it helps for orbit manoeuvring exercises, in case if it is placed in wrong orbit, apart from increasing the life of the satellite.
“Of the 1,425 kg weight of IRNSS, 825 kg is propellant and nearly 700 kg of fuel is spent for reaching the orbital slot and the balance will be used for orbit correction exercise, if necessary. Any saving would increase the life of the satellite. Thursday fuel consumption has worked out to very optimum,” Dr Prasad said.
Referring to 83 degrees geostationary orbit, at 83 degree east longitude earmarked to IRNSS-1C, the earlier two satellites IRNSS-1A and 1B were allotted 55 degree east longitude.
