ESA’s NELIOTA Project, ‘The World’s Largest Eye On The Moon,’ Has Just Been Extended

So far, NELIOTA has detected 55 lunar impacts over the course of 90 hours of observations.

Telescope photograph of the surface of the moon.
Procy / Shutterstock

So far, NELIOTA has detected 55 lunar impacts over the course of 90 hours of observations.

In February, 2015, the European Space Agency (ESA) launched a project called NELIOTA, aimed at studying small near-Earth objects, such as meteoroids, asteroids, and comets. The goal of this endeavor was to track how many of these small celestial bodies come waltzing through our part of the galaxy by monitoring how often they slam into the moon.

Originally meant to last only three-and-a-half years, NELIOTA has just been granted a well-deserved extension and will continue to keep an eye on the moon until January, 2021, the ESA announced on Thursday.

Short for NEO Lunar Impacts and Optical TrAnsients, NELIOTA operates out of the Kryoneri Observatory in Greece, which ESA describes as “the world’s largest eye on the moon.” The project uses the 1.2-meter Kryoneri telescope of the National Observatory of Athens, equipped with two fast-frame cameras, to scour the lunar surface and to look for something known as impact flashes — dazzling flickers of light that occur whenever a small fragment of asteroid crashes into the moon.

“Most of this material ranges in size from dust particles to small pebbles, although larger objects can appear, unexpectedly, from time to time,” ESA explained in May, 2017, shortly after NELIOTA began its 22-month campaign of lunar observations.

The Kryoneri Observatory, the 'world's largest eye on the moon.'
The Kryoneri Observatory, the ‘world’s largest eye on the moon.’ Theofanis Matsopoulos / ESA

Also referred to as “transient lunar phenomena,” the impact flashes resulted from these minor collisions only last for just fractions of a second. These bright streaks of light are too small to be seen and too erratic to be predicted, which makes the NELIOTA sightings all the more valuable to science.

“By observing lunar impacts, NELIOTA aims to determine the size and distribution of near-Earth objects. With this information, the risk these space rocks pose to Earth can be better understood.”

The Road So Far

As ESA points out, NELIOTA is the first project to study the moon with the 1.2-meter Kryoneri telescope, the largest telescope on the entire planet to ever be used for lunar observations.

“As such, [it] is able to detect flashes two magnitudes fainter than other lunar monitoring programs, which typically use 0.5 meter-telescopes or smaller,” state ESA officials.

This sequence of 12 consecutive frames shows a bright flash detected on four frames during observations on 1 March, 2017.
This sequence of 12 consecutive frames shows a bright flash detected on four frames during observations on 1 March, 2017. NELIOTA / ESA

This comes in handy when looking for virtually invisible specks of light on the surface of the moon. Because these impact flashes are usually drowned in the sunlight reflected off the lunar surface, NELIOTA is searching for them on the dark side of the moon, where they are easier to spot.

Finding them requires a series of prerequisite conditions, such as scheduling observations only when the moon is above the horizon and solely in the periods between the new moon and first quarter moon or the last quarter moon and the new moon.

This has allowed for a total of 90 hours of observation so far, during which NELIOTA has detected 55 lunar impact events.

Locations of the lunar impact flashes detected by NELIOTA.
Locations of the lunar impact flashes detected by NELIOTA. NELIOTA / ESA

“Extrapolating from this data, scientists estimate that there are, on average, almost eight flashes per hour across the entire surface of the moon,” notes ESA. “With the extension of this observing campaign to 2021, further data should improve impact statistics.”