Chandrayaan-1, the country’s first lunar satellite, is slated to be launched at 6.22 am. Heavy rain at the launch site in Sriharikota.

Chennai, October 21
It has been raining heavily in Sriharikota from where Chandrayaan -1, India’s first lunar satellite, is slated to be launched at 6.22 am tomorrow with the help of the indigenously developed polar satellite launch vehicle (PSLV).

“Even heavy shower is not a problem for the launch. But thunderstorm and lightening would definitely come as a hindrance”, an Indian Space Research Organisation (ISRO) official over the phone from the launching site, about 80 km from here.

The Met Department, while ruling out thundershower tomorrow, had predicted that the rain would continue. “We are hoping that everything would go on as planned”, the ISRO official said.

Work at the project site is going on in full swing to ensure Chandrayaan’s take off at the slated hour tomorrow. PSLV-C11, the launching vehicle, was today filled with 41.5 tonne of liquid propellant for the second stage of its flight.

The solid propellant needed for stage-1 and stage-3 of the flight and bi-prop needed for the stage-4 was earlier filled in the rocket.

On its historic journey, the lunar spacecraft would first reach a highly elliptical initial orbit (IO). In the IO, the perigee (nearest point to earth) will be about 250 km, while the apogee (farthest point from earth) will be about 23,000 km.

After circling the earth in its initial orbit for a while, the spacecraft will be taken into two more elliptical orbits whose apogees will be even more higher at 37,000 km and 73,000 km respectively. This will be done by firing the spacecraft’s liquid apogee motor (LAM), when it is near the perigee.

Subsequently, the LAM will be fired again to take the spacecraft to an extremely high elliptical orbit with an apogee of about 3,87,000 km. In this orbit, the spacecraft will make one complete revolution around the earth in about 11 days. During the second revolution around the earth in this orbit, Chandrayaan-1 will approach the moon’s North Pole at a distance of about a few hundred kilometers as the moon would arrive at a particular point on its journey round the earth.

Once the spacecraft will reach the vicinity of moon, it will be oriented in a certain way and will be slowed down so that it is attracted by the moon’s gravity and is put on an elliptical orbit round the moon.

Following this, the height of the spacecraft’s orbit around the moon will be reduced in steps. It is intended that the spacecraft finally orbits the moon at a height of around 100 km from the lunar surface.

Once the spacecraft settles down to the intended path, the moon impact probe (MIP) -consisting of C-band radar altimeter, a video imaging system and a mass spectrometer -will be ejected from it on the lunar surface. The MIP and 10 other scientific payloads of the spacecraft will be turned on at this phase, which will be known as the operational phase of the mission. The operational phase will last for two years.

A key focus of India’s maiden “Destination Moon” venture is to explore the possibility of finding water on the moon. A breakthrough in this direction will pave the way for retaining manned missions on the moon in future.

Two scientific instruments developed by the USA, namely, the mini synthetic aperture radar and the moon mineralogy mapper, have been included among the scientific payloads of Chandrayaan-1 to help collection of data toward this objective.

The Chandrayaan-1 also has three instruments from European Space Agency (one of which is developed jointly with India and another with the Indian contribution) and one instrument from Bulgaria. The remaining five scientific instruments for exploration are all indigenously developed.