The Stretched Rohini Satellite Series (SROSS-C2), launched by ISRO on May 4,
1994 on board its Augmented Satellite Launch Vehicle (ASLV-D4) from
Sriharikota, re-entered the atmosphere this morning (July 12, 2001) after
successfully being in orbit for more than seven years. The satellite had far
outlived its design life of one year, sending valuable scientific data from
its two scientific instruments, namely, the Gamma Ray Burst (GRB) Detector
and Retarding Potential Analyser (RPA).

The GRB was to detect Gamma Ray Bursts that occur several million light years
away, which emit very high-energy electromagnetic radiations. These bursts,
which are the result of violent explosions, have been the subject of intense
research in the last few decades. Such Gamma-ray emissions last from a few
milliseconds to a few seconds. The primary focus of gamma-ray burst research
in the early 90’s has been to determine the sky distribution of these
emissions and to obtain as many independent gamma ray detections as possible
using widely spaced observation platforms in space. It is in this context
that the GRB on board SROSS-C2 assumed significance. SROSS-C2, during its
mission, detected around 60 Gamma Ray Burst events in the 20 KeV to 3000 KeV
range. The latest burst (GRB1267) detected was on April 27, 2001. The
information on such Gamma-ray bursts has been widely disseminated to the
world scientific community through the global coordination network.

The other instrument, Retarding Potential Analyser (RPA), has collected data
over the Indian subcontinent providing insight into the characteristics and
structure of the equatorial low latitude ionosphere. Scientists from eight
universities in the country are carrying out detailed analysis of the data.
It is significant to note that the data from RPA covers the solar activity
from its minimum in 1996 to its present maximum activity thus providing an
entire spectrum of data.

The life of SROSS-C2, which had almost come to an end in June 2000, was
extended by another year by raising its orbit using the residual fuel on
board. The last signals from SROSS-C2 were acquired at 7 am (IST) this
morning by the ISRO’s Telemetry, Tracking and Command Network station at
Mauritius when the satellite was in an orbit at a height of 139 km. It is
significant that all the satellite subsystems were working very well till
the 40,058th orbit, which was the last orbit to be tracked before its
re-entry. The ISTRAC network stations and the supporting station at Weilheim,
Germany, were able to track the satellite even when it was in the denser
part of the atmosphere with a fast orbital decay in its last moments. Thus,
SROSS-C2 well exceeded all the set goals in its seven years mission providing
valuable scientific data sets.