As they prepare to deploy the lander to the Comet 67P, Andrea Accomazzo, Rosetta flight director, and his team of 28 full-time engineers, will have to contend with a devious trio of forces acting on the spacecraft and signal delays, both of which are changing continuously.
The fact that Rosetta has traveled billions of miles to find and orbit a comet that is only 2.5 miles by 2.2 miles is extraordinary. As I understand, escape velocity from the comet is about 1 mph so if we walked on the surface, we'd "launch" off the surface, leave the comet's gravitational field, and be floating in space. It is hard to imagine the fine adjustments that must be made by Rosetta to remain in the vicinity.
@maxmaxfield :So if they'd had a larger budget, the operating system would have been allowed to access the other half of the RAM?"
I emailed Andrea Accomazzo of ESA to shed some light on your question and here is his answer:
"Yes, we could use part of the RAM extension but the CPU budget would decrease i.e. we would have the risk that the computer would not be able to run all the actions it has to run within the allocated time i.e. activities on-board would start being delayed which would be catastrophic for the mission.
Proper timing of orbital and attitude manoeuvres is essential for mission success. If the spacecraft can not execute them then we could not manoeuvre properly around the comet.
In reality the on-board computer has a protection against over-run but it would re-boot thus entering a safe status where all programmed activities would be de-scheduled i.e. the mission would be temporarily interrupted with an obvious disruption of science production and delays."
David Patterson, known for his pioneering research that led to RAID, clusters and more, is part of a team at UC Berkeley that recently made its RISC-V processor architecture an open source hardware offering. We talk with Patterson and one of his colleagues behind the effort about the opportunities they see, what new kinds of designs they hope to enable and what it means for today’s commercial processor giants such as Intel, ARM and Imagination Technologies.