Long March 3C successfully launches Chang’e-2, China’s second lunar probe

by Rui C. Barbosa

The second phase of China’s lunar exploration launched on Friday, the national day of China, at 10:59:57 UTC (6:59am Eastern) – with the lift-off of Chang’e-2, China second lunar probe. The spacecraft is being lofted by a CZ-3C Chang Zheng-3C (Y7) (Long March 3C) launch vehicle from the LC2 launch complex of the Xi Chang Satellite Launch Center.

China’s Lunar Launch:

The Long March-3C completed its mission 25 minutes after the launch, when the satellite was separated from the vehicle. Chang’e 2 then opened its solar wings and continue to fly, while adjusting its altitude and direction.

After 110 hours, Chang’e-2 will reach the near-moon area and begin to adjust its direction and speed for braking around 100 kilometers away from the moon. The lunar probe will brake three times more and enter an orbit located 100 kilometers from the moon at a speed of 117 minutes per orbit. This is the major circular orbit where the Chang’e-2 probe will begin its tasks.

Originally built as the back-up vehicle for the Chang’e-1 probe, China’s first lunar mission, which launched on October 24, 2007. Chang’e-2 is a more capable probe than is predecessor, undergoing numerous technical upgrades for its mission

The probe sports new lunar capture maneuvers, orbit control, an improved high-resolution stereo camera and a new CCD camera – with an increased higher resolution camera compared to Chang’e-1.

Chang’e-2, with a launch mass of 2,480 kg, will take five days to arrive in lunar orbit, instead of the 14 days it took for Chang’e-1 to reach the Moon.

To achieve this improvement, Chang’e-2 will be launched directly into an Earth-Moon transfer orbit with a perigee 200 km and an apogee of about 380,000 km. Later, Chang’e-2 will lower its orbit to 100 km and having a lower point of only 15 km.

Once in orbit, the new probe will be able to utilize an improved resolution of 10 meter at 100 km altitude and 1.5 meter at 15 km altitude. However, during testing, the camera onboard Chang’e-2 achieved a resolution of just 7 meters.

This is a notable improvement compared to the 120 meter resolution of the Chang’e-1 camera, which is capable of capturing tridimensional topographic images of the Moon surface, surveying possible landing areas.

The content of the lunar surface will also be studied using gamma-ray and x-ray spectroscopy, in order to detect the content and distribution of silicon, magnesium, aluminum, calcium, titanium, potassium, thorium and uranium. The instruments will permit a greater rate of precision and distribution of such elements on the lunar surface.

Other experiments will focus on the properties of the lunar surface, using microwave detection technologies for measuring the microwave radiation of the lunar surface at 3.0GHz, 7.8GHz, 19.35GHz and 37GHz. This will be used to estimate the thickness of the lunar soil and other properties.

Chang’e-2 will also study the effects of the solar energy particles from the CME (Coronal Mass Ejections) and solar wind on the lunar surface. In order to achieve such results, the probe is equipped with a solar particle detector and an ion detector, which will study the composition, energy spectrum and characteristics of the solar particles.

Chang’e-2 is also carrying an increased amount of experiments, carrying out deep space exploration and land camera pilot projects.

The “probe mission flight monitoring and control” will be the first validation of the new Chinese X-band deep-space monitoring system. Compared to the previous lunar mission which work with the S-band satellite-based monitoring network, the X-band high frequency radio transmission, remote monitoring and control communication for Chang’e-2 is better and is an important asset of deep space exploration for China.

The probe will also test a new camera, verifying a substantial increase in data transmission capacity. This capacity will be very important for the Chang’e-3 soft-landing mission planned for 2013. Chang’e-3 is planned to land on the Sinus Iridium region – which is one of the main sites that will be surveyed by Chang’e-2.

Chang’e-2 mission will be six months in duration, although this mission length can be prolonged if Chinese engineers deem the spacecraft to be in good working order.

This will be the fifth flight of the CZ-3C Chang Zheng-3C launch vehicle. The rocket was developed to fill the gap between the CZ-3A Chang Zheng-3A and the CZ-3B Chang Zheng-3B, sporting a payload capacity of 3,800 kg for GTO. This is a three stage launch vehicle, identical to the CZ-3B, but only the two strap-on boosters on its first stage.

The development of the CZ-3C started in February 1999. The rocket has a liftoff mass of 345,000 kg. The first two stages as well as the two strap on boosters use hypergolic (N2O4/UDMH) fuel while the third stage uses cryogenic (LOX/LH2) fuel. The total length of the CZ-3A is 54,838 meters, with a diameter of 3,35 meters on the core stage and 3,00 meters on the third stage.

The first launch of the CZ-3C Chang Zheng-3C launch vehicle took place on April 25, 2008 when it orbited the first TL-1 Tian Lian-1 tracking and data relay satellite.

This will be the 132nd successful Chinese orbital launch, the 131st launch of a Chang Zheng launch vehicle, the 10th orbital launch in 2010 and the fifth launch from Xi Chang in 2010.

The Xi Chang Satellite Launch Centre is situated in the Sichuan Province, south-western China and is the country’s launch site for geosynchronous orbital launches.

Equipped with two launch pads (LC2 and LC3), the centre has a dedicated railway and highway lead directly to the launch site. The Command and Control Centre is located seven kilometers south-west of the launch pad, providing flight and safety control during launch rehearsal and launch.

Down range Tracking and Control stations of the launch center are located in Xi Chang City and Yibin City of Sichuan Province, and Guiyang City of Guizhou Province. Each of them houses tracking and measurement equipment for the powered phase of a launch vehicle flight.

Other facilities on the Xi Chang Satellite Launch Centre are the Launch Control Centre, propellant fuelling systems, communications systems for launch command, telephone and data communications for users, and support equipment for meteorological monitoring and forecasting.

During 1993-1994 Xi Chang underwent extensive modernization and expansion, in part due to the requirements of the CZ-3 launcher family and in part to meet commercial customer needs.

The first launch from Xi Chang took place at 12:25UTC on January 29, 1984, when the CZ-3 Chang Zheng-3 (CZ3-1) was launched the Shiyan Weixing (14670 1984-008A) communications satellite into orbit. 

Chinese Space Flight Specific Articles: http://www.nasaspaceflight.com/news/chinese/

Before the end of the year China is planning for the launch of the FY-3B Feng Yun-3B meteorological satellite, the launch of the ST-1B Shen Tong-1B / ZX-20 (2) ZhongXing-20 (2) military communications satellite, the launch of two more BeiDou navigation satellites and the Shi Jian-6 Group 4 mission.

Next year will see the launch of the TG-1 TianGong-1 space module. TiangGong-1 is expected to accomplish the country’s first space docking and is regarded as an essential step toward building a space station.

Images from Sina News (China) and the 200 page Long March 3C user manual presentation (available on L2).

Related Articles