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Tuesday, November 12, 2013

Mangalyaan ... ISRO's Mars exploration Probe

                      ( How will the Martian orbit be established?  Read  here  )

ISRO has launched a MARS ORBITER named as MANGALYAAN.

The satellite was launched on 5th Nov 2013 using PSLV rocket in its C25 flight.

The satellite is not directly launched towards Mars leading to a Martian Orbit, instead it was launched in about 383 Kms orbit which the capability of PSLV rocket. 

Afterwards the satellite was raised using several operations to raise the orbit as explained below. The figure shows how the orbit of ISRO’s Mars Probe is being raised step by step.  As on date 5 Orbit Raising Manouvers ( ORMs ) have been carried out. 

The s/c was launched in the orbit depicted as ‘Launch’. After first  ORM   is the shown as ORM-1 ..  etc. The orbit achieved after nth manouver is ORM-n.
Orbits are actually not in eqatorial plane ( shown in next figure ), but are inclined at about 19 deg with equator.

We know from our school physics that the orbit of Earth is inclined at 21deg w.r.t. its movement around Sun. In fact all the planets move around Sun in that plane called as Ecliptic. It follows that the Mars also resides in that plane so the satellite has to be released out of Earth's gravitational field in that plane.  That is the reason why the Mangalyan orbit is inclined at about 19 deg so the Mars orbiter is kept in such a position that when it encounters Mars orbit in the the last phase ( around Sept 2014 ) the s/c will enter into Mars’ gravitational field and become its satellite.

To release the s/c from Earth’s magnetic field we require a velocity of 32.7 km/s.  The s/c  orbit was to be raised through 6 planned ORMs. But due to a malfunction during 4th ORM now it may require more ORMs.  Every ORM raises the orbit Apogee which in turn increases its orbital velocity. Ultimately ( initially planned to achive after 6 th ORM but now may require some more ORMs ),  the s/c will achieve and cross escape velocity and will escape Earth’s gravitational force to become a ‘Temporary Manmade Planet ’ moving around Sun in an elliptical orbit. This elliptical nature of orbit makes it to go beyond Mars orbit but return again ( after reversing its direction near Apogee ) to cross Martian orbit again while returning towards Sun since it behaves like a planet moving around Sun.

The whole operation has been planned such that the Mars is nearby when Mangalyaan is near Mars' orbit, and the at an appropriate time one more maneuver is carried out such that the s/c enters Mars' gravity field and it becomes an artificial Satellite of Mars moving around it in about 363 X 80000 Km elliptical orbit.

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