Isro to launch PSLV's longest flight Scatsat-1 on 26 September for weather, ocean studies

Come Monday and PSLV will see its first mission where it will launch its payloads into two different orbits. Now, according to Nasa, the payloads of a rocket depend on its mission. For example, some of the earliest payloads on rockets were fireworks for celebrating the holidays. Isro is launching its continuity mission Scatsat-1 for ocean and weather-related studies, along with seven co-passenger satellites into polar Sun Synchronous Orbit (SSO) on 26 September. Scatsat-1 is a continuity mission for Oceansat-2 to provide vector data products to help with weather forecasting and cyclone detection. This is the 37th flight of the Polar Satellite Launch Vehicle (PSLV-C35) and it will launch the satellites at 9.12 am from the Satish Dhawan Space Centre in Sriharikota, according to Isro. [caption id=“attachment_3015586” align=“alignnone” width=“825”]  The Scatsat-1 spacecraft is being integrated with PSLV-C35. Also seen are two halves of the heat shield. Courtesy: Isro[/caption] Scatsat-1, which weighs 377 kg, will have satellites from Algeria, Canada and USA, along with two satellites from Indian universities as co-passenger. Scatsat-1 will be placed into a 720 km Polar SSO, while the two Indian universities satellites and the five foreign satellites will be placed into a 670 km polar orbit. This flight also marks another first for PSLV — it will be the longest ever, clocking at two hours and 15 minutes, according to The Hindu, whereas routine PSLV launches last about 20 minutes. The Hindu report further details that Scatsat-1 will drop at a marginally higher orbit (720 km Polar SSO) and will be out in the first 17 minutes. The other satellites, which are reportedly smaller, will get off at around 600 km, after two hours. Among the two universities set to participate in the launch, one is IIT-Bombay, which has designed and developed a satellite, Pratham, reports The Times of India. The other is by Bengaluru-based PES University, a student satellite named Pisat that carries an imaging camera as payload, reports The Hindu. The TeCake quotes the director of the Satish Dhawan Space Centre as saying that “the campaign is in full swing for the launch of the PSLV-C35 on September 26. We have planned to release its different payloads [or spacecraft] at two different orbits this time. This will be a first multiple orbit launch in a single PSLV mission using the PS4 restart method." What is the PS4 restart method? Isro explains. To achieve multiple orbits, there are two options available: either using a separate propulsion module or employing upper stage restart. PSLV has chosen to employ the latter, where it restarts PS4 engines twice in between a long coasting. The PS4 stage is powered by twin liquid engines and controlled by maintenance of certain critical parameters. The time usually taken during two restarts comes up to 7600 seconds that are between two widely spaced points in orbit. With inputs from PTI