ISRO on Monday successfully launched PSLV-C35 from the Sriharikota launch pad in Andhra Pradesh. This is the longest PSLV launch mission spread over two hours and 15 minutes. Here's what makes this ISRO mission significant for India:
Eight satellites on board
The PSLV carries three satellites from India, three from Algeria and one each from Canada and the US.
Of the eight satellites on board the PSLV-C35, the Indian satellite ScatSat-1, weighing 377 kg, is probably the star of the mission. ScatSat-1, a weather satellite, will succeed the now defunct OceanSat-2, launched five years ago. The ScatSat gets its name from scatterometre, a device to track the speed and direction of ocean winds. Equipped with a scatterometre, the ScatSat-1 will improve India's capability to predict and track cyclones accurately. OceanSat-2 had played a pivotal role in prediction of cyclone Phailin on the Orissa coast in 2013, which helped reduce casualties. The satellite became defunct in February 2014. Since then, India has been depending on NASA’s ISS-RapidScat to monitor ocean winds and cyclones.
The other two Indian satellites on board the PSLV-C35 are Pratham and Pisat, developed by the students of IIT-Bombay and PES University, Bengaluru respectively. Pratham, a micro-satellite weighing 10 kg, will measure the electron count in the atmosphere, which is useful in generating tsunami warnings and reduce errors in GPS. Pisat, a nano-satellite, is equipped for remote sensing. ISRO has been encouraging student community to participate in its missions and learn space technology as a capacity building effort to prepare future space scientists and technologists.
While two of the Algerian satellites are for remote sensing, the third one is a technology demonstration satellite for the students of that country. The Canadian satellite looks at reducing space debris and the American one is a commercial earth imaging satellite.
Multiple orbits in the same launch
What makes this mission a challenge is that the PSLV will launch its payloads in two different orbits. Most countries launch satellites in a single orbit and even if multiple satellites are injected, it is in a sequence in the same orbit.
“This is a challenging two-in-one mission which puts India in a unique league of nations having the capability to achieve two different orbits in a single mission,” ISRO chairman A. S. Kiran Kumar had told media before the launch.
For this, the space agency used the multiple burn technology in which the PSLV engines shut down for a while and restart again. The challenge in the launch is igniting and shutting down the fourth-stage engine twice within a short span of time. The trickiest part, however, is cooling down the engine between two restarts, else the rocket and satellites will not be able to withstand the heat generated when the engine was running. By successfully mastering this technology, ISRO can accommodate satellites meant for different orbits in a single rocket thereby saving costs. Earlier, they had to build separate rockets to be flown to different orbits; building an average PSLV costs Rs 120 crore.
This technique also paves way for India to step into the field of commercial satellite launches, offering cheaper options for foreign satellite makers.