A key James Webb tool on part-time work after an anomaly

NASA wants to be reassuring, but hopefully this minor malfunction doesn’t hide a deeper problem.

NASA has announced that the Mid-Infrared Instrument (MIRI), one of the James Webb Space Telescope’s main instruments, is currently out of service due to a technical problem. At the moment, there is no cause for alarm yet, and the agency considers that there is no risk to the device in the long term. But she still offered him some vacation time to get to the bottom of it.

The MIRI is one of the most important tools of the JWST. In fact, it is the only instrument at the observatory that operates in the mid-infrared, that is, it captures wavelengths between 5 and 28 micrometres. It offers four different observation modes. And one of them, labeled “medium resolution integral field spectroscopy”, or MRS, runs into some trouble.

In this observing mode, the telescope does not capture photos as such. Instead, record light spectra. Very briefly, they allow us to study the way in which different chemical species absorb light at certain very specific wavelengths; Astronomers can then deduce a lot of information about the objects that were in the path of the light rays.

the wheel of misfortune

To do this, the MIRI has a wheel equipped with different filters; simply turn it to select the corresponding filter and view the target object at the desired wavelength. This makes the instrument extremely versatile and allows researchers to study the spectra of many diverse and varied astronomical curiosities…at least, when this all-important piece is working properly.


Because it is this element that is at the origin of the problem identified by NASA. In late August, the agency detected shaft friction ; the structure did not turn as well as expected. On Earth, a little lubricant would certainly have sufficed. But the treatment is very different when we talk about a machine parked in orbit about 1.5 million kilometers from our planet.

The rest of the instruments are fine.

As a precautionary principle, the space agency has decided to dispense with medium resolution spectroscopy in the near future. Therefore, this mode of operation will remain in the bank time to identify the source of this friction. “Webb’s team has discontinued observations using this particular mode.”, announced the institution in a release. Time to analyze your behavior. ”It is currently developing a strategy to relaunch MRS observations as soon as possible.”, specifies.

However, she wants to be reassuring about the general condition of the telescope. “The observatory is healthy.”, explains NASA. It also indicates that there is no need to worry about the other three MIRI observation modes. “Imaging, low-resolution spectroscopy, and coronagraphy are operating as normal and will remain available for scientific observation.”, specifies the agency.

It only remains to wait for NASA to discover the origin of the problem. The agency has not yet communicated on this issue, but it could be the result of the impact of a micrometeorite.

These objects are tiny pieces of rock, often smaller than grains of sand, that travel at very high speeds and can therefore cause considerable damage. This is one of the main threats facing the telescope, and obviously the engineers took precautions. But the instrument is not entirely immune to these collisions. Last June, for example, the machine was hit by a meteorite that left a mark, admittedly small, but visible and irreparable on one of the 18 hexagonal mirrors (see our Article). Therefore, it is to be hoped that the MIRI has not suffered excessive damage, even if, of course, the most sensitive components are carefully hidden behind protective armor.

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