When ESA’s Juventas CubeSat lands on Dimorphos in 2026 to assess the effects of last year’s spectacular collisions with NASA’s DART spacecraft, the GRAvimeter for Small Solar System Bodies (GRASS) instrument will directly measure the asteroid’s one-millionth Earth gravity. . In September 2022, NASA’s Double Asteroid Orientation Test (DART) launched into Dimorphos, orbiting the larger asteroid Didymos, as part of an experiment to learn more about how to deflect potentially dangerous celestial bodies before they reach Earth. hit. That was only half the job, as ESA’s Hera robotic mission was tasked with assessing the effects of a cosmic collision.

Part of that effort includes the Juventas CubeSat, about the size of two loaves of bread, which will be deployed from the deep space probe Hera and land on Dimorphos. The small group of instruments includes the GRASS gravimeter, developed by the Royal Belgian Observatory (ROB) in collaboration with Spain’s EMXYS and currently completing pre-flight tests at the space agency’s Mechanical Systems Laboratory to determine its ability to withstand launch vibration. and aggressive environments. space

About the size of a pair of smartphones, GRASS was designed to measure Dimorphos’ gravity. This requires a high degree of precision, as the asteroid is only the size of the Great Pyramid of Giza in Egypt. It does this by means of two sets of thin plates fixed to continuously rotating stands. If the movement of these blades changes even slightly, it changes the electrical voltage in the blades and the walls surrounding them.

According to the ESA, this gives it the micrometer equivalent accuracy over the 20-hour battery life it will have after landing on GRASS, which will likely jam Junentas’ solar arrays. While on the asteroid’s surface, GRASS will be able to measure not only local gravity, but also any shift in the CubeSat’s position.

“It may be small, but GRASS is packed with complex mechanical parts and electronics,” said Jose Carrasco, responsible for instruments at EMXYS. “We are very pleased with its durability during the testing campaign. We will now perform a full integrity test to ensure it was not damaged during testing, and then it will be handed over to GomSpace in Luxembourg for integration on board Juventus”.