A Long March 3B rocket blasted off from the mountains of southern China today, carrying with it the first spacecraft intended to land on the Moon since 1976 (the Soviet Union’s Luna 24). Nestled inside the Chang’e 3 spacecraft is a 260 pound rover named Yutu, China’s first land-mobile explorer. Chang’e 3 follows the country’s two previous lunar orbiters which flew in 2007 and 2010 as part of China’s ambitious long-term plan for the eventual human exploration of Earth’s companion.
Chang’e 3’s 185 foot tall Long March 3B carrier rocket blasted off at 12:30 p.m. EST (1:30 a.m. Beijing time) from the Xichang complex in Sichuan province. Powered by eight liquid fueled engines, the rocket quickly rose into the night sky. The launch appeared to be perfect. The four strap-on boosters and first stage completed their job and the hypergolic second stage continued powered flight before the third stage, fueled by liquid hydrogen and oxygen, fired to blast Chang’e 3 on a direct-insertion trajectory to the Moon.
Nineteen minutes after launch, Chang’e 3 separated to fly free on its journey to the Moon while cameras mounted on the third stage broadcast breathtaking views of the craft as it drifted away. The video, broadcast live on Chinese CCTV showed the lander flying free and plumes from its thrusters illuminated by the Sun as dawn was rising over Earth below.
Shortly after separating, the robotic lander deployed its legs and solar arrays to the cheers of ground controllers and viewers across China.
The stakes are high for Chang’e 3, the latest incarnation of China’s long-held ambitions to explore the Moon. It’s a high-profile project closely tied to China’s intense national pride.
“The Chang’e probe is on the way to the Moon. Of course, it’s a symbol of China’s national power and prowess,” said the head of the Xichang launch complex, Zhang Zhenzhong.
In the coming days, the spacecraft will execute three course-correction burns to set up for entry into lunar orbit on December 6. Landing is scheduled for December 14/15 in the Sinus Iridum, or Bay of Rainbows, region.
Chang’e 3 will descend to the lunar surface from an altitude of approximately 9 miles under full rocket power from its hypergolic descent engine. On its way down, instruments aboard the lander will analyze the terrain below and guide the craft to an area free of large rocks, craters and other terrain that could cause it to tip over on landing.
“(Using) special cameras, it will look for a flat place to land on. Then when it’s about 4 meters above ground, its engine will stop,” lunar exploration advisor Ouyang Ziyuan said. “The lander’s four legs are shockproof and will ensure a soft landing.”
The landing itself will be reminiscent of the Apollo LEM as the descent engine slows the lander to a relatively soft landing at less than 9 miles per hour, cushioned by the equivalent of shock absorbers on its legs.
After an initial checkout period, the lander will deploy a ramp and the rover will crawl down to the lunar surface. In an online poll, the public selected the name Yutu for the rover, which translates to Jade Rabbit and comes from a Chinese myth about a white rabbit that lives on the Moon.
The lander has a mass of 2,600 pounds and contains seven instruments and cameras. It is equipped with a radioisotope thermoelectric generator (RTG) in order to power its operations during the 90-day primary mission.
The lander is equipped with an astronomical telescope and camera that will observe in the extreme ultraviolet range. It’s the first lunar-based astronomical observatory and will make long-term continuous observations of important celestial bodies.
In addition to their lunar scientific roles, cameras will also acquire images of the Earth and other celestial bodies.
The solar-powered rover stands 4.9 feet tall and weighs approximately 260 pounds, including over 40 pounds of science payloads. The rover may transmit video in real time, and is able to dig and perform simple analysis of soil samples. While traversing the surface, it will be able to climb up and down inclines and has automatic sensors to prevent it from colliding with other objects.
The six-wheeled rover is designed to explore an area of 3 square kilometers during its 3-month mission, with a maximum travelling distance of 6.2 miles. The rover will carry a radar unit on its underside, allowing for the first direct measurement of the structure and depth of the lunar soil down to a depth of 98 feet, and investigation of the lunar crust more than 1000 feet below the surface. It will also carry an alpha particle X-ray spectrometer and an infrared spectrometer.
While it will become the first Chinese mission to the surface of the Moon, Chang’e 3 is China’s third mission to Earth’s largest natural satellite.
Chang’e 1 was launched from Xichang Satellite Launch Center on October 24, 2007 and entered lunar orbit on 5 November and operated for 14 months. It was intentionally impacted into the surface of the Moon on March 1, 2009. During its mission, Chang’e 1 was able to create a high-resolution 3-D map of the entire lunar surface, assisting site selection for the Chang’e 3 lander.
Launched on October 1, 2010, Chang’e 2 conducted research from a 60 mile high lunar orbit to prepare for Chang’e 3’s soft landing. It was equipped with improved instruments and provided higher-resolution imagery of the lunar surface to assist in the planning of the Chang’e 3 mission. When it completed its primary mission in 2012, Chang’e 2 was propelled out of lunar orbit for an extended mission to the asteroid 4179 Toutatis.
Meanwhile, NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) may feel the effects of Chang’e 3’s descent. Exhaust from the lander’s engines as well as dust kicked up on landing is expected to be dispersed into the Moon’s extremely tenuous atmosphere, possibly disrupting LADEE’s science observations. However, it might also present the opportunity for LADEE to observe how the dust and propellant residue disperses and settles back to the surface.
