India’s Polar Satellite Launch Vehicle (PSLV) has once again done its job perfectly, placing the country’s Oceansat-2 satellite as well as six European nano-satellites in orbit around the earth. Originally conceived as a rocket to carry India’s earth-viewing satellites, the PSLV has evolved into a versatile and reliable launch vehicle. Apart from successfully launching a dozen remote-sensing satellites, it has taken the Kalpana weather satellite and the Chandrayaan-1 lunar probe into space. The PSLV has also shown it can put multiple satellites in orbit. For a polar launch from Sriharikota, such as the one carried out on Wednesday, the PSLV first travels in a south-easterly direction in order to avoid dropping its spent stages on Sri Lanka. Only after the rocket is well clear of the island does it turn south. If the PSLV flew a southward trajectory right from lift-off, the rocket would be able to carry a heavier payload. But since India is liable under international law for any damage caused by spent stages falling on another country, the Indian Space Research Organisation took the decision early on not to overfly Sri Lanka. In the course of 15 consecutive successful flights in as many years, the PSLV has launched a total of 39 spacecraft.
The Oceansat-1 satellite, launched 10 years ago, was the first Indian earth-viewing satellite configured for watching over the oceans. Data from the satellite have allowed the Indian National Centre for Ocean Information Services based in Hyderabad to produce advisories for fishermen on where they are most likely to find large shoals of fish. Studies show that such advisories have proved most beneficial. Instruments on the spacecraft have also aided studies on coastal water pollution and sedimentation. The Ocean Colour Monitor on Oceansat-2 will allow such work to continue. In addition, Oceansat-2’s scatterometer, which sends out a radio signal in a narrow beam and detects the echo that comes back, can measure the speed and direction of surface winds over the ocean. Such information can help weather models generate more accurate forecasts. The scatterometer will aid the long-term monitoring of polar sea ice; the melting of the ice as a result of global warming will raise sea levels and inundate low-lying coastal areas. In addition, Oceansat-2 is carrying a GPS-based instrument supplied by the Italian Space Agency, which can provide temperature and humidity profiles of the atmosphere. This information will be invaluable for weather forecasters and atmospheric scientists. At a time of growing concern over climate change, ISRO’s ability to develop advanced satellites to monitor our imperilled planet must be put to good use.