Dec 18, 2017

The spacecraft maintained its trajectory this last week as it continues on its outbound journey to Bennu. On Dec. 8, the spacecraft conducted a Sample Mass Measurement (SMM) pirouette activity as part of the ongoing outgassing campaign.

The SMM pirouette was originally designed to help the mission team measure the mass of the sample after it is collected from Bennu’s surface in 2020. Once the sample is in the TAGSAM head, OSIRIS-REx will back away from the asteroid surface and perform a spin maneuver. The ground team will then compare the spacecraft’s mass properties with those of a previous, sample-less spin in order to yield a basic estimate of the collected sample’s mass. For the outgassing campaign, however, the mission team employed this SMM spin maneuver to expose different parts of the spacecraft to the Sun in order to further remove water from the spacecraft. This exercise will prevent water from interfering with the spacecraft’s balance when it performs the maneuver after sampling. Preliminary reports indicate that the activity proceeded as expected.

The spacecraft has travelled 1.2 billion km since launch and will travel another 781.7 million km before it reaches Bennu.