Lunar probe enters moon's orbit
————China Daily
China's first lunar probe, Chang'e I, successfully completed its first braking at perilune and entered the moon's orbit Monday morning, becoming China's first circumlunar satellite.
Chang'e I, following the instructions of the Beijing Aerospace Control Center (BACC), started braking at 11:15 am at a position around 300 km away from the moon and entered the moon's orbit at around 11:37 am after completing the braking, according to the BACC.
The speed of Chang'e I reached about 2.3 km per second when it started braking. It would likely fly away from the moon if the braking was too early, or it would crash into the moon if the braking was too late, scientists explained.
After the braking, the probe's speed was slowed down to 1.948 km per second and is now traveling along a 12-hour elliptical moon orbit, with a perilune of about 200 km and an apolune of about 8,600 km.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 southwestern 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 flied 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 traveled 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.
The ultraviolet image sensors, put into actual use on a satellite for the first time, has begun working since October 30 to collect information on both the earth and the moon.
Chang'e I is expected to relay the first picture of the moon in late November.
It will fulfil four scientific objectives, including a three-dimensional survey of the Moon's surface, analysis of the abundance and distribution of elements on lunar surface, an investigation of the characteristics of lunar regolith and the powdery soil layer on the surface, and an exploration of the circumstance between the earth and the moon.
China's lunar orbiter project has cost 1.4 billion yuan (US$187 million) since research and development of the project was approved at the beginning of 2004.
The launch of the orbiter kicks off the first step of China's three-stage moon mission, which will lead to a moon landing and launch of a moon rover at around 2012. In the third phase, another rover will land on the moon and return to earth with lunar soil and stone samples for scientific research at around 2017.
[ 此贴被g.c.dr.在2007-11-05 16:21重新编辑 ]