Chandrayaan-1 Mission Sequence


Chandrayan-1 spacecraft was launched from the Satish Dhawan Space Centre, SHAR, Sriharikota by PSLV-XL (PSLV-C11) on 22 October 2008 at 06:22 hrs IST in an highly 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, inclined at an angle of 17.9 deg to the equator. In this initial orbit, Chandrayaan orbited the Earth once in about six and a half hours.

• Subsequently, the spacecraft's Liquid Apogee Motor (LAM) firing was done on 23 October at 09:00 hrs IST, when the spacecraft was near perigee, to raise the apogee to 37,900 km while the perigee to 305 km. The spacecraft took eleven hours to go round the Earth once.

• The orbit was further raised to 336 km x 74,715 km on 25 October at 05:48 hrs IST. In this orbit, spacecraft took about twenty-five and a half hours to orbit the Earth once.

• The LAM was fired again on 26 October at 07:08 hrs IST to take the Chandrayaan-1 spacecraft to extremely high elliptical orbit with apogee 164,600 km and perigee at 348 km. Chandrayaan-1 took about 73 hours to go round the Earth once.

• On 29 October, orbit raising was carried out at 07:38 hrs IST to raise the apogee to 267,000 km and perigee to 465 km. Chandrayaan’s present orbit extends more than half the way to moon and takes about six days to orbit the Earth.

• On 4 November at 04:56 hrs IST, Chandrayaan entered the Lunar Transfer Trajectory with an apogee of 380,000 km.

• On 8 November at 16:51 hrs IST, the spacecraft’s Liquid engine was fired to reduce its velocity to insert the spacecraft in the lunar orbit (LOI) and enable lunar gravity to capture it. As a result, the spacecraft was in an elliptical orbit with periselene (nearest point to the moon) of 504 km and aposelene (farthest point from the moon) of 7,502 km.

• The first orbit reduction manoeuvre was carried out successfully on 9 November at 20:03 hrs IST. Thus the spacecraft was in lunar orbit with 200 km periselene. The aposelene remains unchanged (i.e 7,502 km).

• After careful and detailed observation, a series of three orbit reduction manoeuvres were successfully carried out and the spacecraft’s orbit was reduced to its intended operational 100 km circular polar orbit on November 12.

• On 14 November at 20:06 hrs IST, the Moon Impact Probe (MIP) was ejected from the Chandrayaan-1 spacecraft and hard landed on the lunar surface near the South Polar Region at 20:31 hrs IST after 25 minutes journey. It placed the Indian tricolour, which was pasted on the sides of MIP, on the Moon.

• Currently, the scientific instruments/payloads are being commissioned sequentially and exploration of Moon with the array of onboard instruments have begun.

K.Prabhu
CSE III year