The goal of placing a rover on the Moon is to explore and examine multiple sites distant from each other. Additionally, the traverse between stations enables unique experiments, such as profiling the surface – the principal objective of the ground-penetrating radar on China’s rover. As the vehicle moves across the lunar surface, it emits radio waves of varying frequency into the surface. Reflections from subsurface layers or boundaries are then received by the rover’s antenna, thereby allowing scientists to infer subsurface structure. To get a subsurface profile, these measurements must be taken while the rover is moving. Thus, an immobile rover makes this experiment impossible. The rover’s other instruments operate during a stationary period. However, once a chemical measurement has been made or an image taken, there is little value in continually repeating it.
If the Yutu rover is immobile, its scientific mission is effectively over. News reports have stopped giving us data and information from the Chang’E 3 lander (which has a camera and an ultraviolet telescope) but assuming it is still operating, it may continue making observations. The lander spacecraft made a panorama of the landing site, so that objective was completed. Presumably, if the UV telescope is still operating, it can continue observing the sky but these observations are not significant to lunar science.
Thus, from the perspective of lunar science, it appears that the Chang’E 3’s Moon mission is over. So, how did Yutu do as a lunar explorer? For now, we really don’t know. Aside from a few color images and a chemical spectra that was released to the press, little scientific data has been revealed (a Google translate version of a Chinese web page describing the Chang’E 3 science to date can be read HERE). The data we have seen mostly show that the instruments were functioning. We do not know how many measurements were made, what they have told us, or the geological setting of the chemical analyses. The Chang’E 3 lander set down very near the rim of a crater 450 meters in diameter, a feature whose walls are littered with angular blocks clearly derived from the local bedrock. The fact that the Yutu did not make an immediate beeline over to those blocks for a detailed examination and chemical analysis tells me one of two things: either those planning the rover’s exploration traverse are not geologists or they didn’t get to it before the rover stopped working.
Yutu has led a famous existence in cyberspace, with numerous “tweets” to the world. A public eager to anthropomorphize machines has responded in kind, including offering several admonitions to the rover to “pay attention to his wake-up calls.” All this rhetorical cuteness hides the fact that China has been less than forthcoming about this mission, as they are about all of their space missions. We hear only what they want us to hear. Successes (of which they have had many) are widely trumpeted with blasts of publicity, while difficulties and failures are buried in silence. It’s true that a space program run by the military (in the case of China, the People’s Liberation Army) will tend toward such an ethic. But the WALL·E-like image promoted by China early in the mission is not the image conveyed by their current posture with the world press.
I find the Chinese attitude both interesting and dismaying. It is similar to one that I experienced with Indian Space Research Organization during the Chandrayaan-1 lunar orbiter mission. When the Chandrayaan spacecraft was running into difficulties after a few months in lunar orbit, the organizational instinct was to deny any problems and be less than forthcoming with the press about the status of the spacecraft. Spaceflight is inherently difficult and things break all the time. It is beyond ridiculous to cover up a problem by pretending that it doesn’t exist. Similar behavior patterns characterized the early Soviet space program, in which we never heard about mission failures, but successes were given widespread publicity. It seems that to date, China is adhering to that model.
There has been much in the media about the non-welcoming posture of some towards engagement and possible cooperation with China in space – admonishing Congress and NASA to be open to cooperating with China on future space missions. There may come a time when this is possible but for now, it seems that reality is far away.
Another lunar day has come and gone on the barren plains of Mare Imbrium. How fares its most famous terrestrial inhabitant, the Chang’E 3 spacecraft and Jade Rabbit, the little Yutu rover? The fact is, we really don’t know and those that presumably do aren’t talking about it much.
The Yutu rover of the Chang’E 3 mission has experienced some “mechanic control abnormality due to the complicated lunar surface,” is how the Chinese phrased the situation. Details on the nature of the problem are impossible to come by, but one clear result is that the Yutu cannot move. It apparently spent the last lunar day (which lasted from about 10 February until last weekend) sitting in one place. For some scientific investigations, that is not necessarily a problem, but for Yutu’s primary scientific mission, it is fatal.