This is how it should be done! ISRO launched on 26th September 2016 from Satish Dhawan Space Centre, their PSLV rocket with number of satellites under the payload fairing. Fifth mission of PSLV in 2016 was completed successfully and eight satellites are on their correct designated orbits.
Launched conducted on 26th September was planned mainly for delivering to orbit SCATSAT-1 satellite. It is replacement for Oceansat-2 weather satellite (SCATSAT-1 was also known as Oceansat-3), which was launched in 2009 and finished its operational life. Oceansat-2 was operating on SSO orbit with perigee on 728 km, apogee on 731 km and inclination at 98.27°. SCATSAT-1 was designed to reach SSO orbit with altitude of 720 km and exactly same inclination. Just like its predecessor, it was design to gather data on sea surface, winds, chlorophyll level in sea water and perform various researches on natural environment. Observations performed by SCATSAT-1 and collected data will be utilized for predicting cyclones not only by Indian government agencies; they will be shared by NASA, EUMETSAT and NOAA. Satellite weighs 371 kg and it is equipped in deployable solar arrays to power its main onboard instrument: OSCAT-2 scatterometer operating on Ku band with frequency at 13.515 GHz. Device weight is 110 kg and spacecraft was built on standard IM-2 satellite bus.
ISRO decided to add to SCATSAT-1 additional smaller satellites and deploy them on lower orbit to offer best price per kg of payload for their customers. ISRO decided to launch with SCATSAT-1 seven satellites from different countries like Canada, Algeria and USA:
- Canadian satellite CanX-7 (NLS-19) is based on Cubesat platform research spacecraft designed and manufactured by Institute for Aerospace Studies from University of Toronto (UTIAS) for testing solar sail technology. It will deploy small solar sail and using it in various configurations, it will perform series of tests to gather data useful during designing system for deorbitation for small satellites in future. Satellite weight is 3.75 kg (with dimensions of 10 cm x 10 cm x 34 cm) and is powered by solar arrays.
- Three Algerian satellites Alsat-1B, Alsat-2B and Alsat-1N are operated by Agence Spatiale Algérienne (ASAL). Alsat-1B is result of cooperation of ASAL with SSTL and is earth observation satellite built on SSTL-100 bus with launch mass at 103 kg. Equipped with multispectral imager with resolution of 24 m and panchromatic imaging device with resolution of 12 m, it will monitor desert and water resources. Alsat-2B is based on EADS Astrium AstroSat-100 bus and weighs 110 kg. It is powered with two deployable solar arrays (just as Alsat-1B) observation satellite able to operate for at least five years and provide images with resolution up to 2.5 m in panchromatic mode and 10 m multispectral mode. Both satellites were assembled in Algeria. Alsat-1N is experimental satellite created by ASAL and UK Space Agency and manufactured by Surrey Space Centre. It was built in Cubesat standard and weighs 4 kg. Main objective of its mission is to test deploying long for 2 m boom, perform tests of C3D2 camera and new solar arrays known as Thin Film Solar Cells. All three innovative technologies will serve in developing small astronomical Cubesat satellites.
- BlackSky Pathfinder-1 is first from constellation of six high resolution (up to 1m) earth observation satellites designed for 3 year operational life and with mass of 44 kg. Satellite is manufactured by Spaceflight Services, while imaging device was provided by Exelis. Satellite will be operated by BlackSky Global Company.
- Additional payload, which was also delivered to space during PSLV-C35 mission, was two Indian satellites: Pratham and PISAT. First one is nanosatellite built by students at IIT Bombay. It weighs 10 kg (with dimensions of 26 cm x 26 cm x26 cm) and will measure total electron count in SSO orbit. PISAT is small imaging satellite designed and manufactured by Crucible of Research and Innovation Laboratory of PESIT (PES Institute of Technology) in Bangalore. With dimensions of 25.4 cm × 25.6 cm × 18.1 cm it weighs 5.25 kg and is equipped with experimental CMOS color camera designed by GomSpace Company able to provide color images with resolution up to 80 m. Both satellites are powered by solar arrays and onboard batteries.
Under payload fairing satellites were placed on special deploying device with SCATSAT-1 on atop. In the middle section next five satellites were placed: Pathfinder-1, Alsat-1B and Alsat-2B, Pratham and PISAT. On the bottom CanX-7 and Alsat-1N were installed.
Launch was performed according to plan. Weighing 295 t PSLV-G started to rise punctually on 26th September at 09:12 GMT after igniting core engine shortly before boosters. Core of the rocket (PS1 first stage, long for over 20 m with diameter at 2.8 m) powered with S138 engine supported by four strap on boosters (PS0M is long for 10 m with diameter at 1 m) equipped with engines S-9 (fueled with HTPB and providing thrust of 510 kN each) was working nominally. S138 engine was providing over 4383 kN of thrust (G version of PSLV is equipped in S138 engine providing 500 kN of thrust less than S139 engine, which is powering latest version of PSLV – CA). During first phase of flight, each booster burns 9 t of propellant, when first stage burns 138 t of HTPB. First pair of boosters separated at T+67″ and second at T+1’30”. First stage separated 21 seconds later and 0.02 s later second stage (L40) ignited its Viking 4 engine fueled with UDMH/N2O4. Second stage, long for 12.5 m with diameter at 2.8 m, burned 40 t of propellant after 4’28” of flight, when it was separated from third stage. Meanwhile at T+2’40” long for 8.3 m and wide for 3.2 m payload fairing was jettisoned. Third stage, long for 3.6 m with diameter of 2 m started to burn 7.6 t of HTPB to provide thrust of 330 kN with its S7 engine. At T+7’30” third stage cut off its engine and prepared for separation at T+9’48”. After stage was jettisoned, fourth stage started its first burn long for four and half minutes and starting at T+12’26”. At around T+17′ SCATSAT-1 was deployed on altitude of 730 km. Fourth stage (long for 2.9 m with diameter at 2.8 m) burned its L2 engine fueled with 2.5 t of MMH/N2O4 to provide 14 kN of thrust for the second time at T+1h 12′. Second burn took only 20′, but rocket managed to low its perigee; third burn, lasting for around 40 seconds pushed rocket into circular orbit (on altitude of 689 km) at T+2h 10″. One minute later last burn was performed and two minutes after, upper part of deploying device was separated. Satellites were deployed in following sequence: Alsat-1N, CanX-7 ten seconds later, Pratham after another 20 seconds; PISAT was deployed 10 seconds after Pratham. Alsat-1B was deployed 10 seconds later with Alsat-2B leaving deploying device fifteen seconds after. Finally BlackSky Pathfinder-1 was deployed as last one.