Opnav Subprocess Integration

[sjz38]

We are planning to have opnav active as a subprocess only during normal mode, as it does not make sense for opnav to be running in any other flight mode. That is, the opnav subprocess will be spawned from normal mode whenever it is needed. Since the satellite will be in normal mode for the majority of the time, there should be enough time for opnav to run. If we need to switch to another flight mode (most of which are short in duration), we will pause the opnav subprocess. However, certain scheduling will need to be done such that opnav is not paused during the "critical period" of video recording (this is around 6 seconds) at the start of opnav. This is the current plan, however the design may change in the future.