The copy-book launch of Indian Space Research Organization’s (ISRO) EMISAT satellite on Monday was a landmark achievement of the Indian space agency in many ways. The mission marked several firsts to the credit of the Indian space agency as it manoeuvred satellites in various orbits and also setup orbital experiments including on maritime satellite applications.
The satellite, intended for electro-magnetic spectrum measurement, was launched by PSLV-C45 from the Satish Dhawan Space Centre at Sriharikota, India’s premier space port. Besides the 436-kilogram EMISAT, twenty-eight smaller satellites from four international customers were also put into designated orbits at lower altitudes. Finally, after releasing all the satellites, the fourth stage of the rocket was not discarded but brought down to a still lower altitude to function as an orbiting science platform.
This success has once again demonstrated the high reliability of the PSLV rocket, which has become the workhorse of ISRO. Out of 47 launches till date, the rocket has encountered only two failures so far—its maiden developmental flight ended unsuccessful way back in 1993. In September 2017, the PSLV performed perfectly and the flight went off without any hitch, but the IRNSS-1H satellite could not be released into orbit after the PSLV-C39’s heat shield failed to open on reaching the orbit. The PSLV has also been used to launch Chandrayaan-1, India’s first mission to Moon.
However, this was the first time that ISRO used a new variant of the rocket PSLV-QL, equipped with four strap-on motors in the first stage. Other versions used till date used either none or two or six trap-on motors. Also, for the first time, ISRO has successfully performed space manoeuvres in three different orbits at different altitudes in a single launch. After launch, the main payload EMISAT was released into its designated orbit at an altitude of 749 kilometres. Thereafter, the fourth stage of the rocket carrying the 28 smaller satellites was re-ignited and brought down to an altitude of 504 kilometres, where all the smaller satellites were released sequentially. All the 28 satellites, which included 24 from the USA, two from Lithuania and one each from Spain and Switzerland, were launched under commercial arrangements.
Even after all the 29 satellites were placed in their designated orbits, the fourth stage was not discarded but again re-started and brought down to a lower orbit at a height of 485 kilometres where it will remain to serve as an orbital platform for carrying out carry out space-borne science experiments for the first time in ISRO’s history. This was also the first time that ISRO successfully re-ignited the fourth stage of the rocket thrice in a single mission.
Lasting almost three hours after lift-off, it was also the longest mission successfully completed by a PSLV.
In another first, the fourth stage of the rocket has been equipped with solar panels to provide power for three payloads for space-borne experiments. They include an automatic identification system from ISRO for Maritime satellite application capturing messages transmitted from ships; a system to assist amateur radio operators in tracking and monitoring position data; and the ARIS experiment from Indian Institute of Space Science and Technology for the structural and composition studies of the ionosphere. According to ISRO, this is the first time it has been envisaged to provide a micro-gravity environment for research organisations and academic institutes to perform experiments.
Yesterday’s success has proved once again the capability of our space scientists in not only launching satellites, but also in executing complex space manoeuvres like putting payloads in three different orbits in a single launch, which will be of great help in meeting the customer requirements for satellite launches in future. This success also sets the stage for Chandrayaan-2, India’s second mission to Moon, which is expected to take off in a few weeks.
Script: Biman Basu, Senior Science Commentator