on 21 Oct, 2020
natural feature tracking ( NFT)
guardian 23 Oct:
stuffed with so much asteroid rubble from this week’s grab that the flap is jammed open and precious particles are drifting away in space, scientists said on Friday.
Scientists announced the news three days after the spacecraft named Osiris-Rex briefly touched asteroid Bennu 200m miles away.
The mission’s lead scientist, Dante Lauretta, said Tuesday’s operation collected far more material than expected for return to Earth – in the hundreds of grams. The sample container on the end of the robot arm penetrated so deeply into the asteroid and with such force, however, that rocks got sucked in and became wedged around the rim of the lid.
The team was scrambling to put the sample container into the return capsule as early as Tuesday – much sooner than originally planned – for the long trip home. Particles are continuing to escape, and scientists want to minimize the loss.
“Time is of the essence,” said Thomas Zurbuchen, chief of Nasa’s science missions.
A cloud of asteroid particles could be seen swirling around the spacecraft as it backed away from Bennu – at least one-half of an ounce (5 to 10 grams) at any one time. The situation appeared to stabilize, according to Lauretta, once the robot arm stopped moving and was locked into place.
The craft is believed to have collected some 400g (14oz) of fragments, he said.
The bulk of TAGSAM is made of aluminum alloy, and includes a stainless-steel screen mesh (38 micron openings), stainless-steel fasteners, and Mylar flap that assists in retaining the regolith after collection. These materials were selected because of their long use in curating lunar samples without introducing contamination.
They suspect bits of material are passing through small gaps where a mylar flap – the collector’s “lid” – is slightly wedged open by larger rocks.
The images also show that any movement to the spacecraft and the TAGSAM instrument may lead to further sample loss. To preserve the remaining material, the mission team decided to forego the Sample Mass Measurement activity originally scheduled for Saturday, Oct. 24, and canceled a braking burn scheduled for Friday to minimize any acceleration to the spacecraft.
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