PARIS — Part of an instrument on the James Webb Space Telescope is temporarily out of service, although project officials are confident it won’t be a long-term problem.
NASA announced on September 20 that it was discontinuing the use of one of the four monitoring modes on the Mid-Infrared Instrument (MIRI) instrument on the JWST after a mechanism supporting that monitoring mode demonstrated “what appears to be an increase in friction” during monitoring preparations. The controllers first noticed the problem on August 24, and the project formed an offbeat team to study it on September 6.
The problem affects medium-resolution spectroscopy observations using the telescope. The other three monitoring modes—imaging, low-resolution spectroscopy, and coronagraph—were unaffected and observations using these modes from MIRI continue.
NASA officials downplayed the issue in presentations at the International Astronautical Conference (IAC) here on Sept. 21, “We’re taking a break and making sure it works well,” Thomas Zurbuchen, NASA associate director for science, said during a plenary session. . Power point.
Eric Smith, a JWST program scientist at NASA Headquarters, said during a newspaper article that the engineers “don’t expect that this will prevent this tool from being used in the future, but they wanted to understand why they saw this particular increase in friction.” Conference later in the day. He described the decision to discontinue the use of medium-resolution spectroscopy mode as a decision taken out of “a great deal of caution”.
The problem with MIRI is one of three challenges to JWST operations that Zurbuchen mentioned in his IAC presentation. Others are microwave strikes on telescope mirrors and access the Deep Space Network (DSN) communications during the upcoming Artemis 1 mission.
Smith said the project sees the expected number of micrometeorite impacts on the mirror, but that one of the effects, during the spacecraft’s operation, was larger than expected. “We might expect one hit of this magnitude every year,” he said. “So far, the evidence is that we’ve seen that happen early on, but we’ve got to check that over the course of the year.”
He said after the briefing that the demands related to the Artemis 1 mission may limit the amount of time the DSN can communicate with the JWST. “In nominal operations we have eight hours of contact a day,” he said. “We start to get anxious when it’s less than four hours a day.”
There may be a “handful” of days during the mission when the DSN time drops below the four-hour threshold, he said. In this case, the controllers will plan for observations that require less data to be stored on the spacecraft so that it can linger between DSN contacts. “Things get mixed up, but it doesn’t preclude science.”
JWST continues to perform at or above expectations otherwise. At the International Advisory Committee’s press conference, the mission released an infrared image of Neptune, its rings and moons, the most detailed look at the distant planet since the Voyager 2 spacecraft flew close to it in 1989.
The telescope has also observed galaxies in the distant universe, showing some as far back as only 400 million years after the Big Bang. Guido Roberts Borsani, a UCLA postdoctoral researcher involved in these notes, said in a press conference. “Let’s see what we can do in a year.”