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Second orbital transfer

Moon trip on schedule as new phase succeeds

2007-10-27

CHINA'S lunar probe Chang'e 1 completed its second orbital transfer yesterday
 afternoon, one more crucial step forward in its journey to the moon.
 
 

The Beijing Aerospace Control Center issued the instruction for the orbital 
transfer about 4:50pm and it was completed at 5:44pm.

Chang'e 1 had traveled more than 389,000 kilometers after completing the 
second transfer.

"It still has about 1.19 million kilometers to go before it reaches the 
moon orbit as planned," said Zhang Bo, an engineer of the monitoring and 
controlling branch of the moon-probe program.

The probe is now moving on a 24-hour orbit with an apogee of 70,000km, 
up from the former 50,000km, according to data from the Yuanwang III 
space-tracking ship in the southern Pacific.

It will stay on the orbit for three days and then move further from the 
Earth to a 48-hour orbit on Monday, according to the BACC.

The lunar probe completed its first orbital transfer on Thursday night 
when it was transferred to a 16-hour orbit.

The first probe equipment on the orbiter began exploring the space 
environment between the Earth and moon on Thursday night. The high-energy 
solar-particle detector will collect information on the space expanse 
between 40,000km and 400,000km from Earth.

Chang'e 1, named after a mythical Chinese goddess who flew to the moon, 
blasted off on a Long March 3A carrier rocket at 6:05pm on Wednesday from 
the Xichang Satellite Launch Center in the southwest province of Sichuan.

The satellite is expected to enter the Earth-moon transfer orbit on 
Wednesday and arrive in the moon's orbit on November 5.

The 2,300-kilogram moon orbiter is carrying seven other sets of probe 
equipment - a stereo camera and interferometer, an imager and gamma/X-ray 
spectrometer, a laser altimeter, a microwave detector and a low-energy 
ion detector.

It has four scientific objectives:

A three-dimensional survey of the moon's surface;

Analysis of elements on the lunar surface.

An investigation of the characteristics of loose rocks and the powdery 
soil layer;

An exploration of the correlation between the Earth and the moon.

The satellite will relay the first picture of the moon in late November 
and will then continue scientific explorations for a year.

China's lunar-orbiter project has cost 1.4 billion yuan (US$187 million) 
since research and development was approved at the beginning of 2004.

The launch of the orbiter marks the first step of China's three-stage 
moon mission, which will lead to a landing and launch of a lunar rover 
in about 2012.

In the third phase, another rover will land on the moon and return to 
Earth with soil and stone samples in about 2017.

The launch of Chang'e 1 came after Japan launched its first lunar probe, 
Kaguya, in mid-September, while India is planning to send a lunar probe 
next April, sparking off concerns of a space race in Asia.

But Luan Enjie, chief commander of China's lunar-orbiter project, 
dismissed the speculation.

"China will, in the principle of pursuing a policy of peaceful use of 
airspace, share the achievements of the lunar exploration with the whole 
world," he said.

Chang'e I to turn on image sensors after 3rd transfer
(Xinhua)
2007-10-29 06:51

China's lunar probe Chang'e I is expected to arrive at the apogee of more than 120,000 kilometers from the earth on Monday afternoon after its third orbital transfer after launch, according to the moon probe team. [Full Coverage]

Ultraviolet image sensors installed on the satellite will begin to work  to collect information on the earth and the moon after it enters the 48-hour orbit, Wang Yejun, chief engineer with the Beijing Aerospace Control Center (BACC) told Xinhua.

The images it collects will be transmitted back to the earth when it enters the lunar orbit, Wang said.

The satellite will start its propeller when it begins the transfer to raise its apogee from 70,000 kilometers to 120,000 kilometers, according to Wang.

Wang said the working time of Chang'e-1 engine will be longer than that in the second transfer.

Since Saturday, surveillance posts, on land and sea, and four astronomical observatories have kept watching over Chang'e-1. According to the data received so far, all systems of the satellite have been working normally.

 

 Lunar probe completes last orbital transfer
(Xinhua)
Updated: 2007-10-31 19:39

BEIJING -- China's lunar probe Chang'e I completed its fourth orbital transfer on Wednesday afternoon, a critical move to push it to fly to the moon "in a real sense".

The engine on the probe was started at 5:15pm. Thirteen minutes later, the probe was successfully shifted to the earth-moon transfer orbit with an apogee of about 380,000 km.

The main engine of Chang'e I started operation and helped raise the speed of the probe to 10.916 km per second in a few minutes before the satellite reached the 'entrance' of the earth-moon transfer orbit, said Zhu Mincai, head of the Beijing Aerospace Control Center (BACC).

The probe will then start to fly to the moon "in a real sense", Zhu said.

"It's a success-or-failure point and we only have one shot as the fuel carried on the Chang'e I is limited," said Zhu. "If the orbiter misses the entrance and it will keep moving on the earth orbit instead of flying to the moon."

The probe is estimated to fly another 114 hours before it reaches the moon orbit on November 5.

The probe will brake for the first time on November 5 when it arrives at a position 200 km away from the moon, which is considered another crucial moment, since the satellite will crash into the moon if the braking is too late or it may float elsewhere in space if the braking is too early.

"Before it enters the moon orbit, the probe will be subject to two or three orbit corrections, which will help it adjust the moving direction and speed to ensure that it will approach the perilune as designed," said Sun Zezhou, deputy chief designer of the satellite.

In moon explorations of other countries, lunar probes often lost in space due to unprecise flying postures and speeds, Sun explained.

Chang'e I was previously moving on a 48-hour orbit with an apogee of more than 120,000 km, which was raised from the former 70,000 km through a third orbital transfer on October 29.

The probe completed its first orbital change on October 25, which transferred the satellite to a 16-hour orbit with its perigee up from 200km to 600 km.

It completed its second orbital transfer on October 26, which made it move on a 24-hour orbit with an apogee of 70,000 km, up from the former 50,000 km.

The ultraviolet image sensors installed on the orbiter began working on the morning of October 30 to collect information on the earth and the moon.

It's the first time that an ultraviolet image sensor is put into actual use on a satellite, though a few countries had tested them on the ground, said Wang Yejun, chief engineer with the BACC.

The images Chang'e I collects will be transmitted back to the earth when it enters the lunar orbit, Wang said.