Interplanetary 6U CubeSats Mature: Following MarCO and LICIACube, ESA’s Hera Carries Milani and Juventas Toward Didymos–Dimorphos
Building on NASA JPL’s MarCO-A/B at Mars and ASI’s 6U LICIACube during the DART kinetic impact, ESA’s Hera planetary defense mission carries two 6U XL CubeSats—Milani (hyperspectral dust/mineral mapper) and Juventas (low-frequency radar sounder).
Deep-space 6U CubeSats have transitioned from experimental technology demonstrators to baseline planetary science assets. After NASA JPL’s MarCO-A/B (2018) relayed InSight’s Mars landing and ASI’s LICIACube (2022) autonomously tracked and imaged the DART impact plume at Dimorphos from 55 km range, ESA launched the Hera spacecraft on 7 October 2024.
Stowed inside Hera’s Asteroid Deck are two 6U XL CubeSats: Milani (developed by Tyvak International), carrying the ASPECT visible/near-IR hyperspectral imager and VISTA thermogravimetric dust analyser; and Juventas (developed by GomSpace), carrying the JuRa 60 MHz monostatic radar to probe the internal rubble-pile structure of Dimorphos.
Unlike LEO CubeSats that dump reaction wheel momentum against Earth’s magnetosphere via magnetorquers, deep-space 6U buses rely on cold-gas micro-thrusters, inter-satellite S-band links, and radiation-tolerant avionics.