Posts Tagged ‘Chang’e 2’

Chang’e 2 is now “liberated” from earth and lunar gravity

September 11, 2011

China’s lunar probe Chang’e 2 completed its mission orbiting the moon three months ago and has now reached Lagrange (liberation) Point L2.

It has now reached a point in space where neither the moon nor the earth’s gravity will affect the probe. This point is called L2. It’s the farthest a Chinese spacecraft has ever been.

Chang’e 2’s primary mission was to orbit the moon at only 100 kilometers from the surface, taking high resolution photos. After completing this, scientists decided that there was enough fuel to continue with the second part of the mission. But sending the probe from the moon was unprecedented. Similar missions has previously left directly from Earth, so keeping the satellite on course was a technological challenge.

Zhou Jianliang, Deputy Chief Designer, Measure & Control System of Chang’e 2, said, “The satellite faced various disruptions on its journey, which could have led it off course. We had planned four readjustments to keep it on track. But we only need(ed) to do it once since the first adjustment proved so accurate.”

China’s ambitious three-stage moon mission is steadily advancing. The next phase will be the launch of Chang’e-3 in 2013. The probe’s mission is to land on the moon together with a moon rover. In the third phase, the rover should land on the moon and return to Earth with lunar soil and stones for scientists to study. The Chang’e program was named after the legendary Chinese goddess who flew to the moon. With the progress in technology and experience from the Chang’e mission, sending a Chinese astronaut to the moon is now clearly feasible.

On Lagrange Points:

The Italian-French mathematician Joseph-Louis Lagrange discovered five special points in the vicinity of two orbiting masses where a third, smaller mass can orbit at a fixed distance from the larger masses. More precisely, the Lagrange Points mark positions where the gravitational pull of the two large masses precisely equals the centripetal force required to rotate with them. Those with a mathematical flair can follow this link to a derivation of Lagrange’s result (168K PDF file, 8 pages).

Of the five Lagrange points, three are unstable and two are stable. The unstable Lagrange points – labeled L1, L2 and L3 – lie along the line connecting the two large masses. The stable Lagrange points – labeled L4 and L5 – form the apex of two equilateral triangles that have the large masses at their vertices.

Lagrange Points

Lagrange Points of the Earth-Sun system (not drawn to scale!): NASA

 The easiest way to see how Lagrange made his discovery is to adopt a frame of reference that rotates with the system. The forces exerted on a body at rest in this frame can be derived from an effective potential in much the same way that wind speeds can be inferred from a weather map. The forces are strongest when the contours of the effective potential are closest together and weakest when the contours are far apart. In the contour plot below we see that L4 and L5 correspond to hilltops and L1, L2 and L3 correspond to saddles (i.e. points where the potential is curving up in one direction and down in the other).

Effective Potential

A contour plot of the effective potential (not drawn to scale!): NASA


Chinese Premier Wen Jiabao unveils Chang’e-2 pictures

November 8, 2010

Xinhua reports the success of the Chang’e-2 mission.

Chinese Premier Wen Jiabao Monday unveiled the first pictures of the moon’s Sinus Iridum, or Bay of Rainbows, marking the success of China’s Chang’e-2 lunar probe mission.

Chinese Premier Wen Jiabao attends an unveiling ceremony for pictures of the moon's Sinus Iridum, or Bay of Rainbows, taken and sent back by the Chang'e-2, China's second lunar probe, in Beijing, capital of China, Nov. 8, 2010. (Xinhua/Huang Jingwen)

The pictures were taken and sent back by the Chang’e-2, China’s second lunar probe, which was launched on October 1.

Chang’e-2 entered into its final 118 min orbit and formally started its mission of mapping the moon and preparing the way for Chang’e-3 on October 9th.

Lunar activity: Chang’e-2 starts mission and Nasa revives 2 satellites

October 29, 2010

Xinhua reports

Scientists successfully activated four attitude control engines on Chang’e-2 and sent the satellite into the orbit with a perilune of just 15 kilometer above the moon, according to a flight control official in Beijing. It will photograph the Bay of Rainbows region with its CCD cameras from Wednesday, according to the center.

NASA has revived 2 satellites that were dying and sent them to the moon creating the ARTEMIS mission:

A pair of NASA spacecraft that were supposed to be dead a year ago are instead flying to the Moon for a breakthrough mission in lunar orbit. “Their real names are THEMIS P1 and P2, but I call them ‘dead spacecraft walking,'” says Vassilis Angelopoulos of UCLA, principal investigator of the THEMIS mission. “Not so long ago, we thought they were goners. Now they are beginning a whole new adventure.”

The story begins in 2007 when NASA launched a fleet of five spacecraft into Earth’s magnetosphere to study the physics of geomagnetic storms. Collectively, they were called THEMIS, short for “Time History of Events and Macroscale Interactions during Substorms.” P1 and P2 were the outermost members of the quintet. Working together, the probes quickly discovered a cornucopia of previously unknown phenomena such as colliding aurorasmagnetic spacequakes, and plasma bullets shooting up and down Earth’s magnetic tail. These findings allowed researchers to solve several longstanding mysteries of the Northern Lights.

The mission was going splendidly, except for one thing: Occasionally, P1 and P2 would pass through the shadow of Earth. The solar powered spacecraft were designed to go without sunlight for as much as three hours at a time, so a small amount of shadowing was no problem. But as the mission wore on, their orbits evolved and by 2009 the pair was spending as much as 8 hours a day in the dark. “The two spacecraft were running out of power and freezing to death,” says Angelopoulos. “We had to do something to save them.”

Because the mission had gone so well, the spacecraft still had an ample supply of fuel–enough to go to the Moon. “We could do some great science from lunar orbit,” he says. NASA approved the trip and in late 2009, P1 and P2 headed away from the shadows of Earth.

With a new destination, the mission needed a new name. The team selected ARTEMIS, the Greek goddess of the Moon. It also stands for “Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun.”

The first big events of the ARTEMIS mission are underway now. On August 25, 2010, ARTEMIS-P1 reached the L2 Lagrange point on the far side of the Moon. Following close behind, ARTEMIS-P2 entered the opposite L1 Lagrange point on Oct. 22nd. Lagrange points are places where the gravity of Earth and Moon balance, creating a sort of gravitational parking spot for spacecraft.


Artemis (Lagrange Points, 550px)

The ARTEMIS spacecraft are currently located at the L1 and L2 Earth-Moon Lagrange points: NASA


Flight accuracy gives Chang’e-2 new options

October 14, 2010


Chang'e flies to the moon.

Chang'e flies to the moon: Image via Wikipedia


After requiring only one course correction en route to the moon the fuel left on board Chang’e-2 keeps open all its future options after it completes its 6 month mission. Since Chang’e-1 was already crashed intentionally onto the moon, a return to earth or a flight into outer space are more likely than another descent to the moon’s surface. If the instruments remain in working order a continued flight past other targets in space could be more rewarding than a tame return to Earth.

Xinhua reports:

Chang’e-2 was carried into lunar orbit by a rocket, and only corrected once during the transfer from earth orbit to lunar orbit, so a large amount of fuel will be left after its mission, Zhou Jianliang, the vice chief-designer of BACC, said.

It is s expected to have enough fuel to fly back to earth, the vice chief-designer of the Beijing Aerospace Control Center (BACC) said Tuesday.

Zhou said there are three possible “fates” for Chang’e-2 after it finishes its six-month mission: landing on the moon; flying to outer space; or returning to earth. The fate of Chang’e-2 will be decided according to its condition when the mission is complete.

The Long March-3C carrier rocket took Chang’e-2 into space from southwest China on Oct. 1. The probe completed its final braking on Oct. 9 and is now orbiting the moon at a 100 km-high orbit.

Chang’e-2 enters final working orbit around the moon.

October 9, 2010

Chang’e-2 has now entered into its final 118 min orbit and formally starts its mission of mapping the moon and preparing the way for Chang’e-3.

Chang’e-2, following instructions from the Beijing Aerospace Control Center (BACC), started the third braking at 11:17 a.m. and entered the 118-minute, round working orbit 15 minutes later, changing the satellite’s apolune from 1,825 km to about 100 km, the BACC said. The satellite will begin scientific exploration activities soon.

Chang’e-2 lifted off from the Xichang Satellite Launch Center, in southwest China’s Sichuan Province, on Oct. 1. The moon probe completed its first braking on Wednesday and the second on Friday.



Chang’e-2 enters penultimate lunar orbit

October 8, 2010

China’s second unmanned lunar probe, Chang’e-2, has successfully completed its second braking at perilune on Friday, which decelerated the satellite and allowed it to enter a 3.5-hour orbit, according to the Beijing Aerospace Control Center (BACC).

Chang’e-2, following instructions from the center, started the second braking at 10:45 a.m. and entered the 3.5-hour elliptical moon orbit 17 minutes later, said Ma Yongping, vice-director of the BACC.

The second braking was to decelerate the satellite to prepare it for the final braking and its entering the designed 118-minute working orbit, Ma said.

Previous posts on Chang’e-2

Chang’e-2 starts transmitting data from lunar orbit

October 8, 2010


Chang'e-2 lunar probe: Credit: CNSA


Chang’e-2 remains on track and the scond orbit correction planned for Sunday may not be necessary.

From the Beijing Review:

All scientific exploration equipment has begun operation on China’s new lunar probe,Chang’e-2. The instruments that collect information about the space environment between the Earth and the Moon have sent back their first batch of data. The ground control center received the first readings from Chang’e-2 early Tuesday morning. The equipment on board detects a wide array of information such as gamma radiation levels.

The control center has confirmed that all instruments are working correctly.

The center announced that the second correction of Chang’e-2‘s orbit has been cancelled, as data proves the satellite is travelling strictly to plan following the first correction.

Experts said the satellite might change its orbit slightly due to the influence of the atmosphere and cosmic environment. Timely correction is therefore needed to prevent Chang’e-2 from deviating from its designed orbit.

The probe went through its first trajectory correction 17 hours after its successful launch. According to the original plan, the second correction would have been on Sunday. The control center is now watching closely for the timing of its next orbit correction. It’s the first time a Chinese lunar probe has directly entered an Earth-Moon transfer orbit without orbiting the Earth first.

Chang’e-2 satellite was launched just before 7 p.m. on October 1, inaugurating China’s second phase of a three-step moon mission, which will eventually culminate in a soft landing on the Moon.

From Spaceflight Now:

Chang’e 2 will map candidate landing sites for the next mission in China’s lunar program, which targets a robotic touchdown on the moon after launch in 2013. Another project in China’s long-term plans is a vehicle to return soil and rock from the moon back to Earth.

After its $134 million baseline mission at the moon is finished, Xinhua reports Chang’e 2 could enter an extended phase.

Officials are considering three scenarios for Chang’e 2’s overtime, including sending the spacecraft away from the moon and into deep space, giving Chinese engineers practice in operations further from Earth. The satellite’s propellant could also return Chang’e 2 to Earth orbit, according to Huang Jiangchuan, a chief designer quoted in Xinhua.

Chang’e 2 could also continue circling the moon, relaying more science data before attempting a landing or impact on the surface, officials said.

Chang’e 1 was deliberately crashed into the moon at the end of its mission in March 2009.

Chang’e-2 enters 12 hour lunar orbit

October 6, 2010

Chang’e-2 enters 12 hour lunar orbit

China’s second unmanned lunar probe  Chang’e-2, completed its first braking Wednesday, which decelerated the spacecraft and successfully allowed it to enter a 12-hour orbit, according to the Beijing Aerospace Control Center (BACC). Chang’e-2, following instructions from the center, started the first braking at 11:06 a.m. and entered the 12-hour elliptical moon orbit 32 minutes later. It was the first braking for Chang’e-2. The space- probe needs to brake another two times before it can enter the designed 118-minute working orbit. The braking “laid a solid foundation” for Chang’e-2 to carry out scientific explorations in its final orbit, BACC said in a press release.

Compared with Chang’e-1, it is more challenging for Chang’e-2 to brake as it must do so at a closer distance to the moon and at a higher speed. A Long-March-3C carrier rocket carried Chang’e-2 into space blasting off from the Xichang Satellite Launch Center, in southwest China’s Sichuan Province, at about 7 p.m. Friday.

To acquire more detailed moon data, Chang’e-2 will enter a lower lunar orbit about 100 km above the surface, compared with the 200-km altitude of Chang’e-1, according to the control center. Before its first braking, the lunar probe had traveled nearly 350,000 km.

Screen shows the virtual animation of the first braking of Chang'e II lunar probe in Beijing Aerospace Control Center in Beijing, capital of China, Oct. 6, 2010. China's second unmanned lunar probe, Chang'e II, completed its first braking Wednesday, which decelerated the satellite and successfully made it enter a 12-hour orbit, according to the Beijing Aerospace Control Center. (Xinhua/Tian Zhaoyun) (xzj)

Cheng'e - 2 enters 12 hour lunar borbit

Two satellites into orbit

In other news today a Long March 4B rocket carrying two satellites of the “Shijian VI-04” group lifted off from the launch pad in Taiyuan, capital of north China’s Shanxi Province, Oct. 6, 2010. The satellites which have entered their space orbits will carry out probes on space environment and radiation and conduct space science experiments, according to the Taiyuan Satellite Launch Center.

Chang’e-2 mission on track

October 3, 2010

Chang'e programme: Xinhua

On Saturday scientists successfully activated the attitude control engines on Chang’e-2 and trimmed the satellite for the first time on its journey, according to a flight control official in Beijing. “During Chang’e-2’s 380,000-km journey to the moon, we will conduct more orbit corrections if necessary to ensure that it enters a lunar orbit,” said Ma Yongping, vice director of the flight control center. Chang’e-2 blasted off on a Long-March-3C carrier rocket from the Xichang Satellite Launch Center, in southwest China’s Sichuan Province, at about 7 p.m. Friday. It is China’s first unmanned spacecraft to be boosted from the launch site directly to the earth-moon transfer orbit, greatly reducing the journey time from that of its predecessor Chang’e-1.

Chang’e-1 took about 13 days to travel to a lunar orbit after orbiting the earth in a geosynchronous orbit and then transferring to the earth-moon transfer orbit. Chang’e-2 is expected to travel for about 112 hours, or almost five days, to arrive in a lunar orbit. To acquire more detailed moon data, Chang’e-2 will enter a lower lunar orbit about 100 km above the surface, compared with the 200-km altitude of Chang’e-1, according to the control center.

Sinus Iridum - Bay of Rainbows

The satellite will eventually be maneuvered into an orbit just 15 kilometer above the moon. At that point, Chang’e-2 will take pictures of moon’s Bay of Rainbows (Sinus Iridum)  area, the proposed landing ground for Chang’e-3, with a resolution of 1.5 meters. The resolution on Chang’e-1’s camera was 120 meters, said Wu Weiren, chief designer of China’s lunar orbiter project.

China’s second moon probe Chang’e-2 to launch this weekend

September 30, 2010


On Thursday, workers will begin fueling the Long March rocket that will blast the unmanned Chang’e-2 probe into space from Xichang Satellite Launch Center in Sichuan province, Xinhua reported. Launch will occur “at an appropriate time” between Friday — China’s National Day, when the country marks 61 years of Communist rule — and Sunday (Oct. 3).


Chang'e-2 lunar probe


Chang’e-2 is the second step in China’s three-phase Chang’e moon exploration program, which is named after China’s mythical moon goddess. Chang’e-2 will test out technology and collect data on possible landing sites for the Chang’e-3 spacecraft, which is scheduled to land on the moon in 2013. According to the state news agency, Chang’e-2 should arrive at lunar orbit about five days after launch. It will eventually swoop down to an orbit just nine miles (15 km) above the lunar surface to take high-resolution pictures of landing areas for Chang’e-3. After snapping the photos, Chang’e-2 will retreat to an altitude of about 62 miles (100 km) to conduct a study of the lunar surface and dirt.

The Chang’e-1 probe  launched in October 2007 and conducted a 16-month moon observation mission, after which it crash-landed on the lunar surface by design, in March 2009.


The launch of Long March 3B Rocket, Xichang Sa...

Image via Wikipedia:Long March 3B Rocket launch


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