PSLV C-35: Longest Mission Ever- Its different!!

Sandarbha Desk
Sandarbha Desk

PSLV C-35: In News

  • On September 26, 2016 the PSLV (Polar Satellite Launch Vehicle) will for the first time place multiple satellites in two different orbits.
  • The PSLV rocket is a four stage/engine rocket powered by solid and liquid fuel alternatively.
  • The mission designation is PSLV C-35 and will be launched from the first launchpad at the Satish Dhawan Space Centre, Sriharikota.
  • A routine PSLV launch lasts for about 20 minutes but PSLV C-35 will be the longest ever launch till date lasting for about 2 hours and 15 minutes.
  • Three Indian and five foreign commercial spacecraft will ride together in it.
  • ISRO’s 370 Kg Scatsat-1 ocean and weather tracker, will get off first at a slightly higher polar sun synchronous orbit at around 700 Km. It will be out in the first 17 minutes, as is customary.
  • The two other Indian satellites are : Pratham (10 Kg) built by IIT (Bombay) and Pisat (5.25 Kg) from PES University, Bengaluru and its consortium.
  • Out of the five foreign satellites, three are from Algeria and one each from Canada and the USA.
  • The remaining smaller satellites, weighing between 5 kg and 110 kg will get off at around 600 Km after about two hours.
  • For this to happen, ISRO will use a new technology to shut down and restart the fourth and the last sage of the PSLV called PS-4 twice during the flight.

The New Technology

  • After putting Scatsat-1 into orbit, the rocket’s fourth stage or the engine will be shut down.
  • The fourth stage will be restarted and cutoff one hour 22 minutes after the blast off twice.
  • Two hours and 11 minutes into the flight the fourth stage will be restarted.
  • Four minutes later, all the seven satellites would be put in their intended orbit.
  • This switching on and off of the rocket’s fourth stage is known as multiple burn technology.
  • Restarting a rocket engine soon after it is shut off is a critical technology. Once a rocket engine is activated, then the heat generated is very high. The trick is to cool it down in space and to restart it at a short gap. This is entirely different from switching on and off the engine of a communication satellite in space. But in the case of restarting a rocket engine, the time gap will be in hours. The rocket engine has to be cooled down in a very short time.

    Benefits of the New Technology

  • This will help ISRO enhance its customer base.
  • It will help in cost reduction, as earlier, if two satellites were to be inserted into different orbits, ISRO had to launch them separately. Since the PSLV is an expendable launch vehicle, this also meant building two launch vehicles.
  • If the launch vehicle is able to move between orbits during a mission, it can deploy multiple satellites with greater control and lesser risk.

Earlier launches of the PSLV

  • The PSLV has so far launched 39 remote sensing satellites of ISRO, including the Chandrayaan-1 of 2008 and the Mars Orbiter Mission of 2013-14.
  • It has also orbited 74 foreign commercial and university satellites.

Special Features of the PSLV C-35 Mission

  • If successful, the launch will be the PSLVs 33rd consecutive success.
  • It will also be the 15th time the PSLV will launch in its XL configuration. The PSLV rocket has four stages: solid, liquid, solid, liquid. the first solid stage is one of the largest in use in the world, carrying 138 tonnes of hydroxyl-terminated polybutadiene urethane- bound propellant. It is augmented by six strap-on solid-fuel boosters. In the XL configuration, these boosters are larger than those on the standard configuration. All 15 XL launches have been successful.


  • According to ISRO, Scatsat-1 is a weather prediction satellite that will succeed the now defunct Oceansat-2
  • This satellite carries Ku-band scatterometer similar to the one flown onboard Oceansat-2. A scatterometer is an instrument used to study atmospheric diffusion.
  • It will better India’s ability to forecast cyclones.
  • The mission life of the satellite is five years.
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