[ethbr1]

Also, this is helium from the propulsion system.

>> Helium is used in the spacecraft’s thruster systems to allow the thrusters to fire without being combustible or toxic.

I'm assuming it's used to backfill tanks as they're emptied?

[CableNinja]

Theres 2 use cases:

1) To keep the fuel/oxidizer pressurized and liquid (by pressure) as the tanks content empties.

2) for RCS thrust, as a cold gas thruster.