Thrust Measurements of the Gaia Mission Flight-Model Cold Gas Thrusters

Thrust measurements are essential to qualify thrusters for space missions, especially for new technologies. In the framework of the Gaia mission, the 13 newly developed cold gas micronewton thrusters from Thales Alenia Space Italia (TAS-I) were subjected to acceptance tests on the micronewton thrust balance of ONERA in order to measure their thrust noise and specific impulse curve. The balance, based on the principle of a pendulum, has a high-thrust resolution (less than 0.1 mu N), with a thrust noise of 0.1 mu N/root Hz in the range of 0.02-1 Hz. The calibration of the balance is presented, and the postprocessing corrections leading to this performance are detailed. The specific impulse of the 13 cold gas micronewton thrusters flight models has been measured for thrust levels in the range of 0.1-1000 mu N, showing a slight increase of I-sp from around 50 to 63 s with thrust for all flight models.