Sunday, July 17, 2011

PSLV notches up another success

The launch of PSLV-C17 Credit:ISRO

The PSLV has added another success in it's list after than the successful launch of the GSAT-12A on-board the PSLV-C17. This was the PSLV's 19th flight and it's 15th consecutive successful launch. The satellite was launched into a sub geostationary transfer orbit.

The 53 hour countdown started at 11:48 hours (IST) on July 13, 2011. ISRO has been generous enough to provide us with videos of launch vehicle integration which happened during the months and weeks leading upto the launch.

The integration of Solid rocket boosters with first stage.

Integration of the third and fourth stages.

Integration of the satellite and heat shield.

The GSAT-12A itself is a communications satellite of the INSAT-family, a replacement for the INSAT-3B. It was launched to address the ever-growing demand for transponders. This particular satellite carries 12 C-band transponders.

The launch window for this flight opened at 16:48 hours for 20 minutes. The weather was gloomy but there was no rain leading-up to the launch. The mission director gave the go-ahead for the launch at the scheduled launch time (16:48 hours IST). During the last 15 minutes, the onboard mission computer takes over the launch control. It is also important to mention that this particular flight was the first PSLV flight with the indigenous flight computer Vikram (which was previously used on the GSLV-D3 flight).

Due to this being a launch to sub-GTO orbit, the normal flight profile of the PSLV was altered slightly to obtain the large apogee. The configuration used here was the PSLV-XL
with 13.5 meter long strap on solid boosters that each carried nearly 12 tonnes of propellant instead of the standard version were they are 11.3 meters long and carry 9 tonnes of propellant. At liftoff the vehicle stood 44 meters tall and weighed about 320 tonnes.

The altered fight profile meant that
the fourth stage coasted for 2 minutes 25 seconds before ignition and fired for about 9 minutes. After about 20 minutes of the flight, the satellite was inserted into a sub-Geosynchronous Transfer Orbit (sub-GTO) with a perigee of 284 km and an apogee of 21,020 km with an orbital inclination of 17.9 deg. This was almost equal to the planned 284 km perigee and 21,000 km apogee orbit.

The satellite will be placed into Geostationary orbit by firing of it's onboard thrusters during the coming weeks.

Flight Brochure: Link
Image Gallery: Link


  1. Great collection of videos. Thanks!

  2. Hi Gopal,

    When I saw the vehicle progress screen, the vehicle is going out of predefined path on each stage. It's look the navigation and guidance system controls and corrects it's path all 4 stages. I remember most of the PSLV flights went on exact predefined path expect first PSLV launch on this year.

    I think the vehicle path changes frequently due to either high load or rocket under performance. But it happens on all stages. However earlier PSLV-XL version carries Chandrayaan-1 mission on exact path!

    Any idea on this?

  3. @Anon The path depends on many factors like wind speed for example. The wind might cause the rocket to veer off slightly from it's predefined trajectory. The mission computer then makes the necessary changes in the pitch, yaw and row controls to put vehicle back onto it's path. So, whether the actual path of rocket is same as the predefined depends on whether there is a significant change between the parameters like wind speed etc used to obtain the predefined path and the actual parameters at the time of launch.

  4. Gopal,

    I got you. I read an article on PSLV where the author ( mentioned the below info:

    "For launching SSPO satellites, the launcher flies south-east and then turns southwards in mid-flight to avoid dropping spent stages near Sri Lanka. The maneuver adversely affects the launcher's payload capability by 50 per cent"

    Any idea on this? Thanks.