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Friday, September 23, 2016

PSLV C35 flight on 26th Sept 2016

  PSLV-C35 will launch the Indian SCATSAT-1 for ocean and weather related studies and seven co-passenger satellites into polar  Orbit. It is scheduled to be launched on Monday morning at 9:12 hrs (IST) on September 26, 2016

The outstanding feature of this flight is that this is the first mission of PSLV in which it will be launching its payloads into two different orbits.

 The other satellites are from Algeria, Canada and USA as well as two satellites from Indian Universities/ Academic Institute.

SCATSAT-1 will be placed into a 730 km Polar Orbit. Others  will be placed into a 689 km polar orbit.
Dual Launch Adapter

PSLV is a 4 stage rocket and all the satellites are placed in the front noselike structure.
 This cone protects the satellites while the rocket is cruising through atmosphere. As the launch progresses the stages are ignited and after their function is over are discarded. While the 2nd stage is burning the rocket has attained 100+ kms and the atmosphere is almost nil. So at 115 Kms the nose covering the satellites  ( called Fairing in technical jargon ) is discarded exposing the Dual Launch Adapter ( DLA ) which contains all the satellites to be launched. This is called as DUAL because it has two chambers ..  front one has the main satellite SCATSAT and the rear part contains the remaining satellites.

 Next Figure shows the path that the PSLV will take from SHAR. The Blue line is the intended orbit of SCATSAT.
After lifting off the rocket rises and while rising it turns towards sea and in SE direction, In order to avoid flying over SriLankan landmass it turns around  it ( This  is called as Dog Leg  maneuver because of the typical shape ).
Then it turns further while rising in such a way that it rises to 730 Kms over equator with a speed of 7.5 kms.The SCATSAT is released at this stage into its intended orbit.

After launching SCATSAT  at 730 kms altitude and inclination of 98.1 deg,  the Launcher moves towards South pole. After about moving for half an orbit from backside of Globe appears over North Pole when the second ignition takes place ( using a station ranging and command station located at Svalbard ?? ). This is to reduce the altitude to  689 Kms in preparation for the release of other satellites. .Then when the DLA is near South pole remaining satellites are released.

 A detailed launch sequence for this launch is shown here:

In all viewes the s/c is moving from North to South in front of viewer.

Then after another half an orbit, when the launcher is over South pole at 689 kms altitude one more ignition is used ( to fine tune launch conditions ?? ).  After shutdown of this ignition the Dual Launch adapter is released.
After half a minute delaythe remaining satellites are released with an inclination of 98.21 deg ( Alsat-1N, NLS 19, Pratham, PiSAT, Alsat-1B, Alsat-2B and Pathfinder-1 .. in that order ) in about 2.5 minutes while the launcher is moving South to North behind the globe in graphic.

Notice that the Earth is rotating continuously from left to right.

SCATSAT-1 is a continuity mission for Oceansat-2 Scatterometer to provide wind vector data products for weather forecasting, cyclone detection and tracking services to the users. The satellite carries Ku-band scatterometer similar to the one flown onboard Oceansat-2. The spacecraft is built around standard IMS-2 Bus and the mass of the spacecraft is 377 kg. The spacecraft will be put in SSP orbit of 720 km altitude with an inclination of 98.1 deg by PSLV-C35. The mission life of the satellite is 5 years.

 PISat is a 5.7 kg Student satellite from PESIT, Bengaluru.

Pratham is a 10 kg satellite from IIT-Bombay's Dept of Aerospace Engg.

Other satellites are from International customers.


Update  27Sept 2016/1300 IST

Following graphic shows the position of launched satellites after one day  ( today ):

First figure shows the location where SCATSAT was inserted in the Red coloured orbit. Then it released other 7 satellites after two burns of 4th stage.

After about a day we can see all those satellites spread out in two orbits.

Officially the satellites have yet to be alloted with their respective names. Currebtly these have been identified alphabetically as objects A to K. Wait!  ..  How many are A to K?    ( There is no I to avoid confusion with 1 ) ..  TEN.

But we know that in all 8 satellites were launched then how come there are 10?

The extra two are .. 1. Dual Launch Adapter ( DLA ) which was ejected after first re-burn of 4th stage ..  and 2. the 4th stage itself .

Although the satellites are yet to be officially identified their positions imply to identifying at least a few :

Object H is clearly a lonely SCATSAT-1.

Objects J and A are clearly different from the other lot.  One is a DLA which was independently ejected and the other one is 4th stage.

Keep tuned in we will let you know as soon as it is officially declared

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