Tycho Crater on the Moon in the most detailed image captured from Earth so far

Radar image of Tycho Crater on the Moon (Image NRAO/AUI/NSF)
Radar image of Tycho Crater on the Moon (Image NRAO/AUI/NSF)

A new image of Tycho’s crater on the Moon is the most detailed yet captured from Earth. A collaboration between Green Bank Observatory (GBO), National Radio Astronomy Observatory (NRAO), Raytheon Intelligence & Space (RI&S), and Green Bank Telescope (GBT) produced the image thanks to a new radar technology that greatly improved astronomical applications of radars. Images of the lunar surface are just the beginning because other objects can be examined to create far more detailed images than radars could before. This result can be achieved with low-power radar transmitters.

The use of radar in the astronomical field dates back to decades ago but technological progress made it possible to build much more powerful instruments, offering notable improvements in the results obtained in recent years. Much more sensitive radio telescopes allow far better detections of radar signals that become very weak. The techniques for constructing the images from the data collected also took advantage of technological advances: in this case, the new technique exploits the movement of the Earth and of the surveys’ targets to improve the resolution of the images.

The Green Bank Telescope (GBT) is the world’s largest fully steerable radio telescope. In 2020, it was equipped with a new system developed by the Green Bank Observatory (GBO) together with Raytheon Intelligence & Space (RI&S) to send radar signals into space. Various tests were also conducted using the antennas of the Very Long Baseline Array (VLBA), another NRAO radio telescope, to detect radar signals.

The tests conducted had the Moon as the target of the radar signals generated by the GBT transmitter, which has a power of about 700 Watts, comparable to that of a household appliance. The sophisticated technique used is applicable today thanks to the power of the computers used, which still take many hours to process an image. The image of the crater Tycho offers details that until now had only been captured by space probes, never from Earth.

The results obtained in these tests are promising and open prospects for a new generation of radar-based radio astronomy. The long-term project aims to build more powerful radars, up to 5,000 Watts, to be able to explore the solar system. If the hoped-for funding from the NRAO arrives, it will be possible to use the VLBA and in the future also the next-generation VLA (ngVLA), which is scheduled to be built during this decade, to examine invisible or nearly invisible objects such as asteroids. It would be an aid to monitor potentially dangerous asteroids.

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