The Lunar-based Ultraviolet Telescope (LUT) – the first robotic telescope on the Moon – has just completed its first 18 months of observation, consolidating the notion that the Moon has the potential to be the base of operation for the next leap forward in astronomy. The first results will be published in the next issue of Astrophysics and Space Science. 

The telescope is on board Chang’e 3, the first Chinese lunar lander to include a rover, and it has shown an incredibly stable performance. The instrument was not affected by oxidation, which is a severe issue for the mirrors on Earth-bound telescopes, or by protons from solar winds that can cause over-excitation, thanks to the probe's shielding. Another possible limiting factor for lunar-based observations is the presence of charged dust that could affect the telescope by decreasing the efficiency of reflection or transparency. This was solved by moving the instrument inside a cabin, as the terminator (the line between night and day) approaches the lander.

The LUT is a robotic 15-centimeter (6-inch) Ritchey-Chrétien telescope, a telescope with two hyperbolic – U-shaped – mirrors. Its scientific mission is to observe galaxies and stars in the near ultraviolet range; the Earth’s atmosphere is not transparent to UV light. Between 97-99% of incoming UV radiation is blocked by the ozone layer. Not having the ozone would have severe consequences to life on Earth, though, as solar UV rays are highly damaging to biological substances. 

The Moon has a very tenuous atmosphere compared to Earth, making it a perfect location for astronomy. The lack of atmospheric perturbations and slow rotation of our natural satellite allow for prolonged and uninterrupted observation of targets. LUT is the first instrument carrying out this type of investigation; by gazing at a region of interest for an extended period of time, it allows for the generation of light variation maps that could lead to the formulation of more precise stellar models.

LUT is a precursor for several lunar projects. There are projects planned for very low radio astronomy that cannot be done on Earth, since the atmosphere is opaque at those frequencies, as well as studies of neutrinos and high-energy cosmic rays. The most interesting project is the creation of very long optical and infrared interferometers – instruments that combine data from several telescopes to create high-resolution pictures. It's hoped that these could produce detailed pictures of exoplanetary systems.

More details and images should be coming from the LUT in the upcoming months.

 ^{Chang’e 3 Lander’s LUT captured this photo of Galaxy M101 on Day 2 of operation. Chinese Academy of Science}