Bangalore, November 8
After more than two weeks of journey in the space, Chandrayaan-1, India’s first moon mission, successfully entered the lunar orbit today.

The unmanned satellite was launched in the space from Sriharikota in Andhra Pradesh on October 22 with the help of indigenously developed PSLV rocket. The launch had put the satellite in an elliptical initial orbit (IO) with perigee (nearest point to the earth) of 255 km and an apogee (farthest point from the earth) of 22,860 km.

The satellite’s orbit was gradually raised with the fifth and final orbit raising manoeuvre carried out on November 4. The spacecraft was put on the lunar transfer trajectory with an apogee of 380,000 km.

During its revolution around the earth in this orbit, the spacecraft was to approach moon’s “North Pole” at a distance of about a few hundred kilometres. Moon, at that time, arrived at a particular point in its journey round the earth.

The plan was to bring the satellite as close to moon as possible and then slow it down to enable it to be captured by the gravity of moon. Putting the spacecraft in the moon’s orbit was the trickiest part of the mission. There is history US and Soviet missions sometimes failed to successfully pull off this crucial operation.

But the Indian scientists did not make any mistake on this count in their maiden mission to moon. Marking the successful insertion of Chandrayaan in moon’s orbit, an ISRO statement said, “This historic event occurred following the firing of Chandrayaan-1 spacecraft’s liquid engine at 4:51 pm for a duration of 817 seconds.

“The highly complex lunar orbit insertion manoeuvre was performed from the Spacecraft Control Centre of ISRO Telemetry, Tracking and Command Network at Bangalore”.

The Indian Deep Space Network (IDSN) at Byalalu supported the crucial task of transmitting commands and continuously monitoring the vital event with the help of two dish antennas. One of these measured 18 m and the other 32 m.

The spacecraft’s liquid engine was fired when it was passing at a distance of about 500 km from the moon. Chandrayaan is now orbiting the moon in an elliptical orbit that passes over regions of moon that are believed to be its polar regions. The nearest point of this orbit (periselene) lies at a distance of about 504 km from the moon’s surface while the farthest point (aposelene) lies at about 7,502 km. Chandrayaan will take about 11 hours to do a whole round of the moon in this orbit.

The height of the spacecraft’s orbit around the moon will be brought down in steps to achieve a final polar orbit of about 100 km height from the moon’s surface. Following this, the Moon Impact Probe (MIP) of the spacecraft will be ejected to hit the lunar surface. Later, the other scientific instruments will be turned on sequentially.

Apart from the MIP, Chandrayaan has 11 other scientific payloads for sending data on topography and minerals of moon and on the moon’s evolution since it came into being. For long two years the spacecraft is expected to remain functional and send these data to ISRO.

With today’s successful manoeuvre, India becomes the fifth country in the world to send a spacecraft for scientific exploration of moon. Other countries, which have achieved this feat are, the US, former Soviet Union, Japan and China.

The European Space Agency (ESA), a consortium of 17 countries, has also sent a spacecraft for exploration of moon.