Wired has a fascinating story that details how SpaceX’s cargo Dragon spacecraft have been contaminating the International Space Station during their stays there – and how NASA has tried to hide the fact.
The contamination was discovered by the Stratospheric Aerosol and Gas Experiment (SAGE) III Earth observing instrument, which was launched to the station aboard SpaceX’s CRS-10 resupply mission in February 2017. The instrument has crystals in it capable of detecting contamination at the space station.
The results are preliminary, but Dragon may have deposited, according to this presentation, up to 21 times the allowed amount of contamination on one sensor. The crystals also significantly changed in frequency when the next Dragon docked, and the report estimates that this mission may have left behind up to 32 times the rule-abiding amount of extra matter on one sensor….
During this thirteenth mission, one sensor may have been sprayed with up to 73 times more than what’s allowed during a sojourn. And for the month or so that Dragon was docked at the Station, two of the sensors individually detected more contamination than is allowed—total, from everything on the Station—in a whole year.
Among the space assets at risk from the capsule’s outgassing is the U.S. Laboratory Science Window, a porthole through which astronauts and instruments can gaze out on Earth. On the more scientific side, there’s CATS, an instrument that measures smoke, pollution, dust, and other particles in the planet’s atmosphere. In total, seven sensitive areas or instruments on the ISS, including SAGE, could be contaminated beyond the limit.
“NASA has communicated with the Station payload community its findings, and payload developers have responded either that their instruments have experienced no impact or they have taken precautions to mitigate impacts to their science,” says Space Environments in a statement. The SAGE III team closes the instrument’s “contamination door,” as a standard operating procedure, when any spacecraft visit to protect its optical instrument, although the resulting measurements aren’t as sensitive .
SpaceX said it is working with suppliers to develop low outgassing materials for use in future Dragon spacecraft. It said NASA pre-approved the materials used in the resupply ships. (The story, however, says that it’s possible materials such as paint are not being applied and cured properly.)
The information came from a presentation marked unclassified and unlimited public distribution that was posted on the NASA Technical Reports Server in September. A day after the Wired writer requested an interview about it with NASA officials, the document disappeared from the server. A NASA official said the report is “under review” and told Wired to submit a Freedom of Information Act request for it.