Four years after its first scientific observations, the James Webb Space Telescope continues to acquire new capabilities.
The MIRI instrument observes the mid-infrared, a form of light invisible to our eyes and associated in particular with cold objects and cosmic dust. It is the only James Webb instrument sensitive to wavelengths longer than 5 micrometres.
Front view of the James Webb Space Telescope, with its segmented primary mirror and multilayer sunshield.
Credit: NASA, ESA, CSA, Northrop Grumman
An international team details several improvements made to the use of this instrument in an article submitted to arXiv on August 14, 2026.
This is not a matter of sending new equipment into space: the changes concern how the instrument is operated, its detectors, and the data it produces. After several years of observations, the teams have gained a better understanding of its responses and can adapt procedures to obtain more information.
One area of focus concerns detector noise. This noise consists of unwanted variations superimposed on the faint signal coming from the sky, and better control makes it possible to distinguish fainter sources or obtain more precise measurements without physically modifying the detector.
Repeated observations of the same object also benefit from updates. They are particularly useful when a phenomenon changes over time. In astronomy, this type of monitoring can be used to measure regular variations or brief events, for which measurement stability matters as much as sensitivity.
Galaxies IC 2163 and NGC 2207 observed by MIRI, whose mid-infrared observations highlight dust and star-forming regions.
Credit: NASA, ESA, CSA, STScI
The team has also worked on coronagraphic imaging. A coronagraph blocks the very intense light from a star to better distinguish what lies immediately around it, and the new procedures should make these observations more flexible and effective. This type of imaging is used in particular to study the environments surrounding stars, such as exoplanets.
Another announced development is a slitless spectroscopy mode covering a wider field. Spectroscopy separates light according to its wavelengths; it provides information about the observed matter. The absence of a slit makes it possible to collect the spectra of several sources present in the same region of the sky simultaneously.
These procedural updates are especially important for MIRI because the mid-infrared is difficult to observe from the ground. Earth’s atmosphere absorbs a significant portion of this light and produces infrared radiation itself. From space, James Webb can therefore access wavelengths that are largely blocked from ground-based telescopes.
The improvements described apply to several uses, from the Solar System to distant galaxies. They also show that a space observatory can continue to evolve after its launch.