The European Space Agency’s Hera Mission is designed to be failure-proof and radiation-hard. They are designed to operate at about 490 million kilometers from the earth and can withstand harsh radiation for up to four years.
The final stages of development of the mission are ongoing across Europe and the ready-to-build design would be presented before the space ministers of Europe in November at the Space19+ Ministerial Council. QinetiQ Space’s Peter Holsters drew an analogy of the satellite platform to a bus and said that the science-generated payloads are analogous to the passengers on the bus; the onboard computer is analogous to the bus driver and is the brain of the mission which operates and coordinates various onboard systems as well as payloads.
The main challenge is that the onboard computer is operating at a greater distance as compared to that of a typical mission. The spacecraft has to move deep into space, beyond the Mars orbit if it has to intercept the Didymos asteroids. Peter said that careful selection of components and software strategies are required as the spacecraft is moving into a different type of radiation environment as it goes deep into space. The space beyond the magnetic field of the earth contains charged particles and solar storms. These energy particles can pass through the shielding on the surface and can even corrupt the computer memory or cause latch-ups. These are permanent damages which are similar to small short circuits.
Peter said that flash memory is used in their systems which are similar to the ones found in smartphones or laptops and these have undergone thorough and careful radiation testing. He said that in case of earth orbit, computer entering into safe mode is not something to be worried about but in case of deep space, recovery from any failure must be done quickly and autonomously. This would require quick switch-over time and maximum redundancy.
In Hera all the functionalities are not performed by the single central computer. The image processing is handled by a dedicated unit which was developed in Romania by GMV. They use a LEON-3 dual-core processor. Their design has been developed from Advanced data and Power Management System(ADPMS).