Flight Software Dictionary
We’re frequently finding new terms, acronyms, initialisms and more that confuse people trying to figure out the flight software world. Hopefully, this is a resource that will help in some small way. Please let us know if we’ve missed something.
Flight Software Dictionary
In cFS, it can also mean “Software Bus Service”. The Software Bus Service is one of the five core services hosted by the Core Flight Executive layer. The Core Flight Software system works by sending messages around. Apps and systems that care about these messages can subscribe to them. They can also send (publish) messages. The Software Bus manages this messaging traffic. It keeps track of which Apps want which message types, routes messages appropriately, reports errors if message transfer fails, manages the pipes (queues), and can report statistics.
It can also refer to things like a Raspberry Pi or an Arduino that put a lot of functionality onto a single board (E.g. a processor, memory, inputs/outputs, and so on.) It doesn’t have to mean your robot or spacecraft runs entirely on the Pi, it just means the Pi itself is a single board computer.
– The Ground Epoch is a date and time that everyone agrees to. It could be Midnight on Jan 1, 2001 or it could be the precise moment of your birth. It’s just a time that everyone on the program agrees is “Time Zero” and everything is calculated up from there.
– Mission Elapsed Time starts counting up the first time the computer is turned on for flight operations.
– And then the Spacecraft Time Correlation Factor is what you have to add to the Mission Elapsed Time to figure out the time since the Ground Epoch. In theory, it should never change once it’s calculated. So if the Ground Epoch is midnight of Jan 01 of this year and you launched at midnight of Jan 05 of this year then your STCF would be four days. You would store this number in your EEPROM so you could recalculate your Mission Elapsed Time if something bad happened to your system.