ISRO achieved another space milestone, launching multiple satellites from one rocket into two different orbits. Spread over two hours and fifteen minutes, the Polar Satellite Launch Vehicle (PSLV) had its longest flight on September 26, 2016, at 9:12 am which carried the cargo of 371 kg SCATSAT-1. The 320-tonne rocket, carrying eight satellites, took off from the launch pad at Sriharikota in Andhra Pradesh.
“SCATSAT-1 will be placed into a 730-km polar sun synchronous orbit (the satellite will travel from the North Pole to the South) whereas the two universities/academic institute satellites and the five foreign satellites will be placed into a 689-km polar orbit,” ISRO personnel said ahead of the launch.
The rocket includes two Indian satellites which include Pratham,(10kg) the first-ever satellite developed by the IIT-Bombay students, that will study the electron count in space, and another Indian satellite Pisat (5.25 kg) from PES University, Bengaluru, that will take pictures of the earth. Along with these are five foreign satellites from Algeria namely Alsat-1B 103kg, Alsat-2B 117kg, Alsat-1N 7kg, and one each from Canada (NLS-19, 8kg) and the US (Pathfinder-44kg).
In a statement, ISRO said, “The SCATSAT-1 is a continuity mission for Oceansat-2 scatterometer to provide wind vector data products for weather forecasting, cyclone detection and tracking services to the users. The satellite carries Ku-band scatterometer which is similar to the one put onboard the Oceansat-2. The mission life of the satellite is five years.”
These eight satellites will be placed in a 689-km polar orbit. This is the first mission of PSLV where it will be launching its payloads into two different orbits.
According to ISRO, SCATSAT-1 is a continuity mission for Oceansat-2 scatterometer to provide wind vector data products for weather forecasting, cyclone detection and tracking services to the users. The mission life of the satellite is five years.
The satellite carries Ku-band scatterometer similar to the one flown onboard Oceansat-2.
According to ISRO after putting into orbit SCATSAT-1, the rocket’s fourth stage or the engine will be shut down. After slinging SCATSAT-1 into its orbit the rocket’s fourth stage would be restarted after one hour 22 minutes into the flight and cut off around 20 seconds later.
Two hours and 11 minutes into the flight the fourth stage will again be restarted to be cut off one minute later. Following that, in three minutes all, the seven satellites would be ejected putting an end to PSLV’s longest mission till date.
The PSLV rocket is a four stage/engine rocket motorised by solid and liquid fuel alternatively. It has launched 39 remote-sensing satellites for ISRO, including the Mars mission of 2013-14.
Vikram Sarabhai Space Centre (VSSC) director K. Sivan told on September 25, 2016, that the long time gap between the cutting off of the engine and its restart is not an issue. The first time the multiple burn technology was first tested by ISRO while flying its PSLV rocket on December 16, 2015, and this June, the technology was again demonstrated, he added.
In May, India successfully tested its first reusable satellite launch vehicle that is being seen as the undisputed key towards attaining low-cost, steadfast and on-demand space access. Talking about the challenge to be faced, Sivan said: “After cutting off the engine, its condition should be brought to such a stage that it could be restarted again. The next challenge is controlling the engine and bringing it so as to eject the remaining satellites into a different orbit.”
He said the rocket has GPS-aided navigation system so that data generated by the rocket’s inertial navigation system and the one provided by the former will be blended so as to erase and errors and to generate a precise data.