China Readies Its First Lunar Rover, Chang'e-3, for Launch Tomorrow

China plans to launch its first lunar rover early tomorrow afternoon (Sunday) Eastern Standard Time (Monday, December 2, Beijing time).  Chang’e-3 is the country’s third lunar probe, but the first designed to make a survivable landing on the surface and it will deliver a 6-wheeled rover.

Launch on a Long March-3B rocket from the Xichang Satellite Launch Center is scheduled for 12:30 pm EST (1730 GMT, or 1:30 am Monday in Beijing).   Chang’e is China’s mythological goddess of the Moon.  The rover is named Yutu, or Jade Rabbit, after Chang’e’s pet white rabbit.  China says there are two narrow launch windows each day for three consecutive days.

The lander is equipped with cameras and a near-ultraviolet telescope.  The rover has a radar attached to its bottom that will “explore 100 to 200 meters beneath the moon’s surface” according to China’s press service Xinhua.

As its designation implies, this is China’s third robotic lunar mission. Chang’e-1 was launched in October 2007 and orbited the Moon until March 2009 when it was commanded to crash into the surface.  Chang’e-2, launched in October 2010, also orbited the Moon, taking 1.5 meter resolution images of Sinus Iridum, the site where Chang’e-3 will land.   When Chang’e-2’s primary mission was completed, the spacecraft was redirected to fly to the asteroid Toutatis where it collected 10-meter imagery.  That spacecraft is currently 60 million kilometers (km) from Earth and China expects to stay in contact with it until it reaches 300 million km.

The plan is for Chang’e-3 to land on the lunar surface at Sinus Iridum in mid-December.   It is powered by a plutonium-238 radioisotope thermal generator (RTG).  NASA has used RTGs for decades for spacecraft that journey too far from the Sun or spend long periods of “night” on the Moon or planetary surfaces to use solar power.   This is the first time China is using one, however.

The European Space Agency (ESA) will help China track Chang’e-3 and reports that the spacecraft will reach lunar orbit on December 6 and land on December 14.

Since the beginning of the Space Age in the late 1950s, many, many robotic spacecraft have been sent to fly by, impact, orbit or land on the Moon by a number of countries.  Only the United States, however, has landed people there.

The Soviet Union was the first country to send a probe to the Moon successfully, in 1959.  That began an intense robotic lunar program that lasted until 1976 and included three sample return missions (Luna 16, 20 and 24) and two rovers (Lunokhod 1 and 2).  Lunokhod 2, launched in 1973, still holds the record for the longest distance traveled by a robotic rover on the Moon or Mars.   Measurements using recent high resolution images taken by the U.S. Lunar Reconnaissance Orbiter (LRO) of Lunokhod-2’s tracks show that it traveled 42 km (26 miles).  NASA’s Opportunity rover on Mars is getting close — it has traveled about 38 km (24 miles).   The distance China expectes Yutu to traverse has not been made public.

The United States also successfully launched many robotic spacecraft to the Moon in the 1960s, including several landers in the Surveyor series, but they paled in comparison to the six landings of astronauts — Apollo 11, 12, 14, 15, 16 and 17 between 1969 and 1972. The last three crews (Apollo 15, 16, and 17) had rovers — “moon buggies” — to take them further from their landing sites than possible on foot.   In total, the Apollo crews returned over 380 kilograms of lunar material to Earth for study (by comparison, the three robotic Soviet sample return missions brought back a total of 330 grams).

The Soviet Union’s Luna 24 in 1976, the final sample return mission, was the last spacecraft to make a survivable lunar landing.    From that point until the mid-1990s, there was little interest in the Moon   Then, beginning with Clementine in 1994, the United States resumed robotic lunar exploration using orbiters.  Two are operating there today:  LRO, launched in 2009, and the Lunar Atmosphere and Dust Environment Explorer (LADEE), launched in September and quite recently placed into its operational lunar orbit.  

Others that have launched lunar orbiters are the European Space Agency (SMART-1,2004), Japan (Kaguya, 2007), and India (Chandrayaan-1, 2008).  None of those is operating any longer.  Nor are the U.S. Lunar Prospector or GRAIL missions, which were commanded to impact the lunar surface at the end of their missions (as did SMART-1, the LCROSS probe launched with LRO, and an impact probe launched with Chandrayaan-1).

China’s plans to send a series of robotic probes to the Moon are not new.  Almost a decade ago it announced a three-step plan for a spacecraft to orbit the Moon in 2007, a rover in 2010, and a sample return mission around 2020.   It achieved the first goal with Chang’e-1, but, based on that schedule, is three years late with its rover.