These spacecraft always have tons of instruments for measurings along loads of different axes. For example, a magnetometer specifically designed for testing a h

These spacecraft always have tons of instruments for measurings along loads of different axes. For example, a magnetometer specifically designed for testing a hypothesis about Europa's magnetosphere. Looking at the wikipedia page it seems like there are about a dozen of these. Perhaps worst case scenario they could determine which one was least critical relative to its weight and eliminate it to increase the mass budget.