The ESA HERA Mission and Its Planetary Altimeter—Learning to Deflect Asteroids

The ESA HERA mission (to be launched October 2024) provides an in-depth characterisation as follow-up from the impact of the moon of the Didymos asteroid system by NASA’s DART mission in September 2022. HERA, thanks to many scientific instruments, plans to characterize the Didymos binary asteroid system after impact to help our understanding for planetary defence. In specific, the Lidar instrument (PALT-Planetary Altimeter) is a time-of-flight ranging payload, operating at 1.535 µm, that will have dual use for both science and GNC (Guidance, Navigation and Control) purposes. PALT will assist in the shape determination of Didymos and its moon, Dimorphos, contribute to the mass determination of Dimorphos, and measure its orbital state and wobble. PALT will augment the datasets of HERA’s imaging payloads and radio science experiment. As a GNC sensor, PALT will support the autonomous navigation for very close asteroid flybys. PALT is a development from EFACEC (Portugal and Romania), Synopsis Planet (Portugal), Eventech (Latvia) and INOE(Romania). The HERA spacecraft is being built by OHB System AG in Bremen, Germany.