There are always going to be situations in which it makes sense to use hydrazine fuel," said Chris McLean, principal investigator for GPIM and staff consultant at Ball Aerospace and Technologies Corp. in Boulder, Colorado, prime contractor for the mission. "But after GPIM, when we're planning missions where this new green propellant has the potential for significant benefits, we'll be able to say, 'This has been demonstrated on orbit. Let's take advantage of these improvements for our mission.'"