Planning for Change in Instrument FSW: Successes and Failures on MMS HPCA

Instrument Flight Software Developers face challenges when designing for operations. On the one hand, a highly flexible and reconfigurable system can permit adaptation on orbit without the need to develop, validate, and update software on orbit. On the other hand, projects are limited in budget and schedule, and predicting future needs for requirements that are not currently in scope may be untenable. For the Magnetospheric Multiscale Hot Plasma Composition Analyzer, we tried to anticipate future needs and build adaptable software. We had significant success, but some needs were difficult to predict. We discuss what we predicted correctly, what we missed, and interesting operational adaptions that allowed us to avoid flight software updates.