Lunar probe Chang'e-1, now operatig normally and smoothly, is expected to reach the moon orbit between 12:00 and 15:00 p.m. next Monday or on November 5, Pei Zhaoyu, the spokesman for the China National Space Administration (CNSA), told a press conference in Beijing Thursday.
Accurate orbital transfer
The probe was successfully shifted to the earth-moon transfer orbit at 5:28 p.m. last Wednesday, or October 31, with an apogee of about 380,000 km. So it has started to fly to the moon “in a real sense”.
Statistics from the Beijing Aerospace Control Center (BACC) indicate that the third orbital transfer was very successful, with a precision tolerance of less than 0.4 a thousand, far better than the tolerance norm set for the orbit designing. So there was no orbit correction on Thursday, or November 1st, which had originally been planned for the day.
It is learned that Chang'e-1 is operating normally at present. After entering the moon orbit around 11:25 a.m. next Monday, or Nov. 5, the satellite will perform its first braking at perilune to reduce its speed, so that it will be “captured” by lunar gravity and become a satellite of the moon.
International cooperation
Around 12:00 to 15:00 p.m. on Thursday, or November 1st (Beijing time), BACC is reported to have started for the first time to access the European Space Agency (ESA) ground station network, which was mobilized to provide direst support to the Chang'e-l moon mission. BACC collaborated with its network stations as New Norcia (Australia), Masapalomas (Spain) and Kourou (French Guiana) of ESA to observe and control Chang'e-1.
The New Norcial and Masapalomas stations started to perform the experimental tracking of Chang'e-1 satellite. BACC received telemetering data through the New Norcia station, and experimented with telemetering, telecontrol, and speed and range finding via Maspalomas station, which show all operations were normal.
Beginning 15:00 p.m. Thursday, the Kourow station formally began tracking Chang'e-1 and, with its assistance, BACC did the work of telemetering, telecontrol, and ranging and speed finding.
It is also learned that China has, as a matter of fact, conducted active cooperation on the mission of Chang'e-1 for telemetering and telecontrol and drawn support from international space telemetering and telecontrol resources and unfolded its professional cooperation with ESTRACK tracing station networks. Hence, the telemeting and telecontrol coverage rate of Chang'e-1 will be further increased.
Entering the “track of ‘flying to the Moon'”
An orbiting plan designed by China on its own is conducive for the success of the launch and for reduction of energy consumption.
Chang'e-1 has completed a seven-day “flying”encirclement around the earth and four orbital transfers. ... “Its orbit track design has been done on the basis of China's existing delivery technology and satellite conditions,” noted Sun Zezhou, deputy chief designer of Chang'e-1 satellite, “so an all-round consideration should be given to its launch conditions, carrying capacity as well as the capacity of its boosting system, and the amount of fuel it will carry, including a series of restrictive conditions for scientific probe.
The orbiting track plan designed by China itself also has a few special advantages, Sun acknowledged. First, phasing orbit maneuver is very essential and crucial for the lunar orbiter, which is relatively easier for the settlement of delaying the launch time, he said. Meanwhile, he added, orbital transfer can increase the precision of the “entrance” into the earth-moon transfer orbit so as to help ease project risks in a certain sense. Second, this track designing can effectively reduce satellite fuel consumption and enable Chang'e-1 to carry more viable loads to fulfill more missions.
Braking at perilune
Whether Chang'e-1 is able to perform its first braking at perilune represens the crux of matter to guarantee the success with its mission. A couple of options have been worked out with meticulous care to ensure the success of this vital pivotal link, Sun noted.
Chang'e-1 is anticipated to enter the moon orbit at 11:25 a.m. on Monday or Nov. 5, as disclosed by the China National Space Administration. To date, Sun said, it is operating normally, and its ground “flying” control is very accurate, while all facilities on the orbiter is at work and all remote-control parameters extremely precise, he said with satisfaction.
However, there are still about five days to go before Chang'e-1 to “fly into” the moon orbit, and the imminent earth-moon circumstance would not have a great impact on it, thanks to ample preparations done to the designing, Sun said.
By People's Daily Online and its author is senior PD reporter Liao Wengen
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