Touchdown for Chang’e 4! The ride to the Moon, and some pictures

Image taken after the soft landing, courtesy of CNSA.

China’s Chang’e 4 spacecraft made history when it successfully became the first spacecraft to perform a soft landing on the Moon’s far side on Thursday January 3rd.

As we reported last month, Chang’e 4 was launched on 7 December and entered lunar orbit on 12 December. It has spent most of the time since then making orbital corrections (the orbit was trimmed twice) and preparing for the delicate landing.

Due to the difficulty in communicating with the far side of the Moon, the Chinese National Space Agency (CNSA) has been making use of a relay satellite located at the L2 Earth-Moon LaGrange point. Engineers at CNSA have been extensively testing the communications link between Chang’e 4 and the comms satellite, named Queqiao, in the last few weeks. The communications link is a critical part of the mission architecture, so it’s worth making sure everything works. There are no second chances on a mission like this!

The probe entered a final elliptical orbit of 100km apoapsis and 15 km periapsis in the last days of 2018, as engineers and scientists prepared for the final touchdown in Von Kármán crater in the South Pole-Aitken Basin.

Apparently all went swimmingly, as Chinese news agencies have released the first photos captured by the spacecraft. You can see the first photo from the far side’s surface below.

Figure 1: First surface image from the far side (Image credit: CNSA)

In addition, the rover, named as Yutu 2 after its predecessor Yutu on the previous Chang’e mission, was successfully deployed some 12 hours after Chang’e 4 landed. And guess what? There are some cool images of that event too!

The first image below shows Yutu 2 rolling off the Chang’e 4 lander.

Figure 2: Yutu 2 rolls off the lander (Image credit: CNSA)

And in the last couple of days, we have seen history being made by the little rover, as it is the first vehicle to have left tracks on the far side of the Moon, as you can see in the next image.

Figure 3: The first tracks on the far side (Image credit: CNSA)

And here’s another image, this time, a close-up of Yutu’s wheel.

Figure 4: Checking the wheels (Image credit: CNSA)

Of course, there is more to the Chang’e 4 mission than just beaming back sweet pictures.

The mission is carrying a suite of instruments designed to monitor the environment on the Moon’s far side.

In addition, there is a small artificial biosphere onboard, which carries a variety of plant and animal life.In turn, the plants will provide oxygen for the silkworms. If all goes well, the experiment hopes to demonstrate a synergy between the plants and insects, which could provide valuable for growth of food and provision of oxygen on future manned space missions. The first flowers are expected to bloom in around 3 month’s time.

Once Yutu 2 has been fully tested and commissioned on the lunar surface, it will go about performing experiments from its own payload.

The instruments carries onboard Yutu 2 are:

  • Panoramic Camera (PCAM) is a panoramic camera that resembles a set of cute little eyes fitted on the rover’s mast. It can produce 3D images by use of its binocular cameras.
  • Visible and Near-Infrared Imaging Spectrometer (VNIS), used for the identification of surface materials and atmospheric trace gases (because contrary to popular belief, there is an atmosphere on the Moon…it’s just very small, extending an inch or two off the surface.)
  • Lunar penetrating radar (LPR), a ground penetrating radar. Like GPR on Earth, it is used to examine sub-surface structures and any changes in materials refractivity, which can potentially show any mineral deposits under the surface.
  • Advanced Small Analyzer for Neutrals (ASAN) is an energetic neutral atom analyzer and is designed to find out how solar wind interacts with the Moon’s surface.

If you cast your mind back to 2016, you may recall the original Yutu’s well-published fate on the Moon.

Yutu had its own “diary” on the Chinese state-run Xinhua media network, and the entire planet went on a feels trip as brave Yutu gave its final swansong before biting the lunar dust.

“If this journey must come to an early end, I am not afraid. Whether or not the repairs are successful, I believe even my malfunctions will provide my masters with valuable information and experience. Even so, I know I may not make it through this lunar night.”

The little rover’s social media accounts (some fan-made) were flooded with messages of sympathy and admiration.

Although the first Yutu was taken out by a malfunctioning solar panel, it did survive much longer than its planned operational lifetime of 3 months. In fact, Yutu became the longest ever operating lunar rover, clocking up an impressive 973 days of lunar operations.

Should we expect a longer mission this time?

Although Yutu 1 became immobile fairly early on in its mission, and the degradation to its systems over time meant that some of the science data became a little bit compromised, CNSA learned a great deal about the endurance of the electrical and mechanical systems. We should expect that these lessons have been implemented in Yutu 2.

Will Yutu 2 set another endurance record? Provided it beats the high infant mortality of the reliability bathtub curve, and provided there are no manufacturing defects, we can expect a longer mission this time. And hopefully we will be getting some more poetic musings from the Yutu 2 social media team.


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