MOONS update – vibration tests successfully completed
07 May 2024



Instrument passes vital stage in Preliminary Acceptance Europe process.

The MOONS astronomy instrument, in the foreground is the display from the accelerometer which measures vibrations.



MOONS is a large blue astronomy instrument. In this picture it has been raised off the ground by a lifting bar.The Multi-Object Optical and Near-infrared Spectrograph (MOONS)​ has successfully passed the vibration tests carried out by the European Southern Observatory (ESO) in the Crawford Lab at UK ATC. An important stage of the Preliminary Acceptance Europe process, demonstrating to ESO that MOONS meets its specifications and requirements.

These tests were to ensure the instrument meets the required vibration thresholds before it can be shipped to Chile and integrated with the Very Large Telescope (VLT).

Vibration levels on the 8.5-tonne MOONS spectrograph, which houses all the cameras and detectors, were carefully evaluated to ensure any vibrations will not interfere with the sensitive VLT observations in Paranal.

The specification on how much vibration is permitted is incredibly stringent. ESO's designated acceptable level is at the threshold of what you can physically perceive with your hand.

To obtain an accurate measurement of the vibration within the spectrograph, MOONS was raised approximately one inch off the floor with a lifting bar. Therefore, a true measurement of the excitation can be determined without it being grounded by the floor of the lab.

To carry out these tests an accelerometer, that measures acceleration and vibration, is connected to MOONS close to where there is the most movement within the spectrograph and at the contact point between the instrument and the telescope.

Focusing on the three cold heads on MOONS, as each one contains a piston that is used to keep the instrument at subzero operating temperatures. The cold heads are isolated from the rest of the instrument to reduce the transfer of pulsation and therefore minimise the vibration levels at the contact points.

ESO also assessed vibrations from other components on the spectrograph, including the pumps and fans, which also passed.

Stephen Chittick, Project Manager on MOONS at UK ATC, said: “It is great to know that the MOONS spectrograph successfully passed ESO's rigorous vibration testing on the first attempt. It's extremely gratifying to know that the team's hard work and dedication to optimising the attenuation from the cold head mounting system has paid off."

Find out more about MOONS.