The PPU for Halo has been designed with flexibility to meet the needs of LEO spacecraft. The PPU can throttle in flight, providing the flexibility to change the operating point as the mission requires. For instance, varying the anode voltage between 150 to 300 V allows mission planners to trade between thrust and specific impulse. This allows the satellite to operate at a higher thrust early in the mission to reach its operating orbit (and begin operations) faster. For stationkeeping, the thruster voltage can be increased, providing higher specific impulse to conserve propellant and extend mission lifetime.
The PPU communication interface can be an RS422, RS485, or CAN serial type. The unit accepts unregulated voltage from 22-36 V. The cards are rated to 30 kRad TID, with the option to upgrade radiation tolerance to 100 kRad TID. The PPU weighs 1.88 kg, and fits within a 21 x 5 x 18 cm volume.