Lunar probe enters moon’s orbit

November 14th, 2007 - 8:35 am ICT by admin  
Chang’e I, following the instructions of the Beijing Aerospace Control Center (BACC), started braking at 11:15 a.m. at a position around 300 km away from the moon and entered the moon’s orbit at around 11:37 a.m. after completing the braking, according to the BACC.

Wang Yejun, chief engineer of BACC, considers the first braking just in time to decelerate the probe, enabling it to be captured by the lunar gravity.

“The first braking at perilune is a key moment in the long journey of Chang’e-1,” Xinhua quoted Wang, as saying.

After the braking, the probe’s speed was slowed down to 1.948 km per second and is now travelling along a 12-hour elliptical moon orbit, with a perilune of about 200 km and an apolune of about 8,600 km.

The probe is expected to brake for another two times in the following two days, which will slow down its speed first to 1.8 km per second to help it enter a 3.5-hour orbit and then to 1.59 km per second to make it enter a 127-minute round orbit, where it is supposed to start “working” formally.

Chang’e I will then stay a year in the round orbit, which is 200 km from the moon’s surface, for scientific explorations.

Chang’e I, named after a legendary Chinese goddess who flew to the moon, blasted off on a Long March 3A carrier rocket on October 24 from the Xichang Satellite Launch Center in south-western Sichuan Province.

The probe completed its fourth orbital transfer on October 31, which shifted it to the earth-moon transfer orbit and pushed it to fly to the moon “in a real sense”. Then, it flew another 114 hours to arrive at the perilune 200 km away from the moon.

It was previously moving around the earth and experienced three orbital transfers, which lifted it up first to a 16-hour orbit with an apogee of 50,000 km, then to a 24-hour orbit with an apogee of 70,000 km and next to a 48-hour orbit with an apogee of more than 120,000 km.

On November 2, BACC successfully carried out an orbital correction for Chang’e I to ensure that it travelled on the pre-set orbit. A second orbital correction scheduled for November 3 was called off because it was “unnecessary” — Chang’e I had been running accurately on the expected trajectory, a BACC scientist said.

The 2,350-kg satellite carried eight probing facilities, including a stereo camera and interferometer, an imager and gamma/x-ray spectrometer, a laser altimeter, a microwave detector, a high energy solar particle detector and a low energy ion detector.

Chang’e I is expected to relay the first picture of the moon in late November. (ANI)

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