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ISRO (Indian Space Research Organisation) so far never before used additional marine vessels to help track their launch vehicles, as an extension to the Indian Deep Space Network (IDSN). So why did it require additional tracking stations in the South Pacific for the launch of the PSLV C25 (Polar Satellite Launch Vehicle) on its Magalyaan / Mars Orbiter Mission (MOM)?

Wikipedia writes to say about the MOM tracking and command:

The Indian Space Research Organisation Telemetry, Tracking and Command Network performed navigation and tracking operations for the launch with ground stations at Sriharikota, Port Blair, Brunei and Biak in Indonesia, and after the spacecraft's apogee becomes more than 100,000 km, two large 18-metre and 32-metre diameter antennas of the Indian Deep Space Network will be utilised.

NASA's Deep Space Network will provide position data through its three stations located in Canberra, Madrid and Goldstone on the U.S. West Coast during the non-visible period of ISRO's network. Additional monitoring is provided by technicians on board two leased ships from Shipping Corporation of India, SCI Nalanda and SCI Yamuna which are currently in position in the South Pacific near Fiji.

How did they track their previous launchers, like e.g. Chandrayaan-1, without these additional tracking stations, and why was this extension to the IDSN necessary for Magalyaan, if they already used NASA's Deep Space Network with facilities in Canberra, Australia?

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   enter image description here                                                    ISRO's MOM lifting off (credit Universe Today).

What it comes down to is that this launch went over the ocean - thereby creating a need for man-made buoyant pieces of steel equipped with tracking devices to collect telemetry data. It's ground track looked like this:

   enter image description here                                                    MOM's ground track (credit SpaceFlight101).

As you can see, much of the track was over water, in places where ISRO didn't have access to tracking stations. I'm looking for the ground track of Chandrayaan-1, but so far haven't been able to find it. I'm willing to bet, though, that either:

  • The ground track was slightly different, perhaps going more directly over Australia, or
  • The launch vehicle was designed in such a way for that mission as to negate the need for continued tracking.

All in all, the extra ships were needed because of the way MOM's ground track was - right over an ocean.

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