China’s mission exploring the lunar far side has now entered into its seventh lunar day, with the Chang’3 lander and Yutu 2 rover resuming activities despite a recent communication problem with a relay satellite.
The lander and rover successfully awoke on June 27 after entering into hibernation mode back on June 9, reports the Chinese Academy of Sciences. The Chang’3 lander and Yutu 2 rover are both in “normal working condition,” according to the Lunar Exploration and Space Program Center of the China National Space Administration (CNSA).
The mission has now entered into its seventh lunar day, with one lunar day being roughly equivalent to 14.5 days on Earth (same for the lunar night). The devices are put to sleep during lunar nights due to the absence of available solar power and to protect their delicate components against the extreme cold. Temperatures on the surface at night can drop to -190 Celsius (-310 Fahrenheit).
With work commencing for a seventh lunar day, the mission continues to exceed expectations (it wasn’t planned to last past March 2019). The mission on the surface began on January 3, 2019, when Chang’e landed on the Von Karman Crater in a basin near the lunar south pole. To date, Yutu 2, or Jade Rabbit, has traversed 212 meters (696 feet), according to the CNSA. This is the first robotic mission to the Moon’s far side, which never faces the Earth.
As Andrew Jones reports in SpaceNews, however, the start to the seventh lunar day was not without incident:
According to a ‘Yutu-2 driving diary’ published June 27 (Chinese), the rover had suffered issues during lunar day six which caused interference with communications between the Yutu-2 rover and the Queqiao (“Magpie Bridge”) relay satellite, stationed around the second Earth-moon Lagrange point to facilitate communications between ground stations and the spacecraft on the far side of the moon, which never faces the Earth.
The issue meant a loss of telemetry and contact with Yutu-2. Analysis indicated an error caused by a cosmic ray striking a rover microchip and the issue was resolved successfully, according to the article, adding that the incident was a reminder that the space environment is complex and variable.
As Jones correctly pointed out, this is not the first time that cosmic rays—showers of fast-moving high-energy particles—have caused a headache during space missions. Cosmic rays also created problems during the Dawn mission to asteroids Ceres and Vesta.
Recent images captured by NASA’s Lunar Reconnaissance Orbiter (LRO) also point to the mission’s ongoing progress. This satellite passes over the Chang’e mission site about once a month, snapping photos as it zooms overhead. Using these images, Mark Robinson, the LROC principal investigator at Arizona State University, estimated that Yutu 2 has travelled 186 meters (610 feet) in total, which is about 26 meters shy of the reported Chinese total. This discrepancy is likely explained by work accomplished by the rover before it entered hibernation mode, six days after the photo was taken.
During its most recent pass on June 3, the LRO snapped a sweet picture (above) of the lunar surface and the lander itself, with its four solar panels reflecting quite brightly.
“Progress over the past two months has been slower than in previous months,” wrote Robinson at the LROC site. “Perhaps the rover has found some interesting geology and is lingering to collect a comprehensive set of measurements.”
Progress may be slower than before, but it’s still progress. This mission has already produced some useful science, including the discovery of mantle material on the lunar far side. For as long as the mission continues, Chang’e will continue to perform its mandated tasks, including low-frequency radio observations of the sky, surveys of the terrain, measurements of neutron radiation, and analyses of the mineral composition of the surface.