PSLV-C35 Successfully Launches Eight Satellites into Two Different Orbits in a Single Flight

In its thirty seventh flight (PSLV-C35), ISRO's Polar Satellite Launch Vehicle successfully launched the 371 kg SCATSAT-1 Satellite along with seven co-passenger satellites today morning (September 26, 2016) from Satish Dhawan Space Centre SHAR, Sriharikota. This is the thirty sixth consecutively successful mission of PSLV. The total weight of all the eight satellites carried on-board PSLV-C35 was 675 kg. PSLV-C35 is the first PSLV mission to launch satellites carried onboard into two different orbits. This PSLV mission was the longest of the PSLV missions conducted till date and was completed in 2 hours 15 minutes and 33 seconds after lift-off.

After PSLV-C35 lift-off at 0912 hrs (9:12 am) IST from the First Launch Pad with the ignition of the first stage, the subsequent important flight events, namely, strap-on ignitions and separations, first stage separation, second stage ignition, payload fairing separation, second stage separation, third stage ignition and separation, fourth stage ignition and cut-off, took place as planned. After a flight of 16 minutes 56 seconds, the vehicle achieved a polar Sun Synchronous Orbit of 724 km inclined at an angle of 98.1 degree to the equator (very close to the intended orbit) and 37 seconds later the primary satellite SCATSAT-1 was separated from the PSLV fourth stage.

After separation, the two solar arrays of SCATSAT-1 satellite were deployed automatically and ISRO's Telemetry, Tracking and Command Network (ISTRAC) at Bangalore took over the control of the satellite. In the coming days, the satellite will be brought to its final operational configuration following which it will begin to provide weather related services using its scatterometer payload. The data sent by SCATSAT-1 satellite will help provide weather forecasting services to user communities through the generation of wind vector products as well as cyclone detection and tracking.

After the successful separation of SCATSAT-1, the PSLV-C35 mission continued. Still carrying the seven co-passenger satellites, the fourth stage of PSLV coasted over the South polar region and then started ascending towards the Northern hemisphere. A safe distance between the orbiting SCATSAT-1 and PSLV-C35 fourth stage was maintained by suitably manoeuvring the stage.

At 1 hour 22 minutes and 38 seconds after lift-off as the fourth stage was in the North polar region, the two engines of PSLV fourth stage were reignited and fired for 20 seconds. As a result of this, it entered into an elliptical orbit measuring 725 km on one side of the Earth and 670 km on the other.

And 50 minutes later, as the PSLV fourth stage was again coasting near the south pole, its engines were fired for another 20 seconds. This second firing made the fourth stage to enter into a circular orbit of 669 km height inclined at an angle of 98.2 degree to the equator.

37 seconds later, the Dual Launch Adapter was successfully separated from the PSLV-C35 fourth stage. 30 seconds after this event, ALSAT-1 was the first co-passenger satellite to be separated successfully. Following this, the NLS-19, PRATHAM, PISAT, ALSAT-1B, ALSAT-2B, and Pathfinder-1 were separated from the PSLV fourth stage in a predetermined sequence thereby successfully completing PSLV-C35 mission.

Of the seven co-passenger satellites carried by PSLV-C35, two – PRATHAM weighing 10 kg and PISAT weighing 5.25 kg – are University/Academic institute satellites and were built with the involvement of students from IIT-Bombay and PES University, Bangalore and its consortium, respectively.

The remaining five co-passenger satellites were international customer satellites from Algeria (three – ALSAT-1B, ALSAT-2B and ALSAT-1N), Canada (one- NLS-19) and the United States (one – Pathfinder-1).

With today’s launch, the PSLV’s capability to launch satellites into two different orbits has been successfully demonstrated. The total number of satellites launched by India’s workhorse launch vehicle PSLV has now reached 121, of which 42 are Indian and the remaining 79 are from abroad.

Five things to know about Isro’s PSLV C-35 launch
Isro successfully launched PSLV C-35, from Satish Dhawan Space Centre in Sriharikota
The Indian Space Research Organisation (Isro) successfully launched PSLV C-35, carrying eight satellites including India’s ocean and weather satellite SCATSAT-1, from Satish Dhawan Space Centre in Sriharikota, Andhra Pradesh, on Monday morning.

Here are five things to know about PSLV C-35 and the eight satellites.

1. The Monday’s launch used India’s Polar Satellite Launch Vehicle (PSLV), making its 37th flight. Introduced in 1993, the PSLV has a record of 34 successful launches, one partial failure and one outright failure, which occurred on its first launch. The PSLV has made 32 consecutive launches successfully over a period of almost 19 years since placing the IRS-1D satellite into a lower-than-planned orbit during its fourth flight in September 1997. PSLV is a four-stage rocket, with a mixture of solid and liquid-fuelled stages.

2. The 44.4 metre tall PSLV will carry a total weight of 675kg of all the eight satellites on board. This will be PSLV’s longest mission spread over two hours and it is the first time that the rocket is putting its payloads in two different orbits, demonstrating the restart capability of Isro on a complete mission.

3. It places the primary satellite SCATSAT-1 meant for weather forecasting, cyclone detection and tracking the polar sun-synchronous orbit (SSO) at 730 km, while the seven others will be injected in a 689 km lower orbit after over two hours.

4. The 371kg primary satellite, Scatterometer Satellite 1 or or SCATSAT-1, is designed to serve as a stopgap to help measure ocean winds following the failure of the OSCAT instrument aboard the OceanSat-2 satellite in February 2014. SCATSAT-1 is designed for five years of service, providing an overlap with the OceanSat-3 spacecraft currently scheduled for launch in 2018. The mission objectives of SCATSAT-1 are to help provide weather forecasting services, cyclone detection and tracking.

5. Besides SCATSAT-1, the PSLV rocket is carrying two Indian university satellites, three from Algeria and one each from the US and Canada. The two academic satellites are PRATHAM from IIT Bombay, and PISAT from BES University, Bengaluru, and its consortium. While PRATHAM’s objective is to estimate Total Electron Count, PISAT’s mission is to design and develop a nano-satellite for remote sensing applications.The foreign satellites on board the PSLV are ALSAT-1B, ALSAT-2B and ALSAT-1N (all from Algeria) and Pathfinder-1 and NLS-19, from the US and Canada, respectively.

In its longest-ever flight, the PSLV C-35, carrying India’s SCATSAT-1 meant for ocean and weather studies and seven other satellites including from the US and Canada, on Monday lifted off from the spaceport in Sriharikota.

The launch marked PSLV’s longest mission spread over two hours and it is the first time that the rocket is putting its payloads in two different orbits. The 44.4 metre tall PSLV rocket blasted off at 9.12am and 17 minutes later injected SCATSAT-1 in orbit.

“SCATSAT-1 has been successfully injected in orbit,” the Indian Space Research Organization said. The 371kg SCATSAT, the primary satellite meant for weather forecasting, cyclone detection and tracking, was first injected in a Polar Sunsynchronous Orbit (SSO) orbit while the seven others will be injected in a lower orbit after over two hours, the first time the rocket is putting its payloads in two different orbits.

The total weight of all the eight satellites onboard is about 675kg. Besides SCATSAT-1, the PSLV rocket is carrying two Indian university satellites, three from Algeria and one each from the US and Canada. SCATSAT-1 is a “continuity” mission for the Ku-band scatterometer payload carried by SCATSAT-1, which has enhanced features compared to a similar one carried by Oceansat-2 satellite in 2009.

The two academic satellites are PRATHAM, from IIT-Bombay, and PISAT, from BES University, Bengaluru and its consortium. While PRATHAM’s objective is to estimate Total Electron Count, PISAT’s mission is to design and develop a nanosatellite for remote sensing applications.

The foreign satellites onboard the PSLV are ALSAT-1B, ALSAT-2B and ALSAT-1N (all from Algeria) and Pathfinder-1 and NLS-19, from USA and Canada, respectively