The transponder detected the distress signals from a Chinese cargo vessel, MV Yujiya. Just after the rescue the ship sank.
According to ISRO officials, soon after the distress signals were detected the rescue authorities of the Indian Coast Guard were alerted by its Indian Mission Control Centre (INMCC) in Bangalore that is part of the international Cospas-Sarsat satellite-aided search-and-rescue programme.
Insat-3A, launched on 10 April 2003, carries a search-and-rescue transponder that keeps a constant vigil over the Indian Ocean region, complementing the Cospas-Sarsat satellites, for detecting distress signals from beacons carried by maritime, aviation and land users.
The satellites transmit the distress signals to the local user terminals established by ISRO in Bangalore and Lucknow. The alert signals are then passed on to the search and rescue coordination centres in Mumbai, Chennai, Kolkata and Delhi, along with location information, for rescue operations.
On 24 July 2003, a similar distress signal from a Panama cargo vessel, MV Jubilee, was picked up and all the 21-crew members were saved before the ship sank.