Skip to main content

James Webb’s MIRI instrument has both a heater and a cooler

The long process of getting the James Webb Space Telescope ready for science operations continues, with the ongoing alignment of three of its instruments.

Webb recently reached the major milestone of aligning its mirrors with its NIRCam instrument, in a successful step that promises great results to come. “Webb’s alignment at the NIRCam field showed some spectacular diffraction-limited images, producing a tantalizing glimpse of the capabilities this observatory will carry for its science program,” wrote two Webb researchers, Michael McElwain, Webb observatory project scientist, and Charles Bowers, Webb deputy observatory project scientist, both at NASA Goddard, in a recent blog post. “This was a major milestone because it required nearly all of the observatory systems to be functioning as designed. It all worked as well as we dared to hope, and it was certainly a moment to celebrate.”

Related Videos

Now, the Webb team is working on aligning two more of the instruments — the Near-Infrared Slitless Spectrograph (NIRISS) and Near-Infrared Spectrometer (NIRSpec) — as well as the guider, called the Fine Guidance Sensor (FGS). This process is expected to take around six weeks and will ensure that all of the instruments can work together. Along with NIRCam, these comprise Webb’s near-infrared instruments.

While the three near-infrared instruments are passively cooled — meaning that heat is dispersed from the telescope and into space using design elements like heat sinks which require no power — the fourth instrument, MIRI, works in the mid-infrared wavelength and requires active cooling. Because MIRI uses a different type of detector than the other instruments, and these detectors need to be at an extremely low temperature of less than 7 kelvin to work properly, the instrument needs to be fitted with a cryocooler. This refrigeration system uses helium gas and includes pumps that require power but must produce very little vibration to avoid interfering with instrument readings.

In addition to this cooling system, MIRI is also fitted with heaters so that the cooldown process can be carefully managed to prevent ice from forming on the components. The heaters will shortly be turned off, allowing the cooling system to bring the instrument down to its operating temperature.

With the cooling of MIRI underway, it will take a few weeks until the final instrument gets cool enough to be ready for alignment. Then, with all four of the instruments aligned, the Webb team can move onto the next phase of commissioning — optical stability tests and instrument performance measurement — to get the telescope ready for science operations this summer.

Editors' Recommendations

James Webb Telescope catches a glimpse of young version of the Milky Way
This image shows an artist impression of our Milky Way galaxy in its youth. Five small satellite galaxies, of various types and sizes, are in the process of being accreted into the Milky Way. These satellite galaxies also contribute globular star clusters to the larger galaxy. The Sparkler galaxy provides a snap-shot of an infant Milky Way as it accretes mass over cosmic time.

Data from the James Webb Space Telescope has given a glimpse into what our galaxy was like in its formative years. Webb observed a galaxy called The Sparkler, which is analogous to what the Milky Way would have been like when it was young, when it had less mass and only a handful of globular clusters.

This image shows an artist impression of our Milky Way galaxy in its youth. Five small satellite galaxies, of various types and sizes, are in the process of being accreted into the Milky Way. These satellite galaxies also contribute globular star clusters to the larger galaxy. The Sparkler Galaxy provides a snapshot of an infant Milky Way as it accretes mass over cosmic time. James Josephides, Swinburne University.

Read more
A failed Webb telescope calibration leads to the discovery of this tiny asteroid
An asteroid roughly the size of Rome’s Colosseum — between 300 to 650 feet (100 to 200 meters) in length — has been detected by an international team of European astronomers using NASA's James Webb Space Telescope. They used data from the calibration of the MIRI instrument, in which the team serendipitously detected an interloping asteroid. The object is likely the smallest observed to date by Webb and may be an example of an object measuring under 1 kilometer in length within the main asteroid belt, located between Mars and Jupiter. More observations are needed to better characterize this object’s nature and properties.

With any new technology, there are bound to be failures -- and that's true of cutting-edge astronomy instruments like the James Webb Space Telescope as well. But failures can have a silver lining, as was demonstrated recently when an unsuccessful attempt to calibrate a Webb instrument to a well-known asteroid turned up a delightful surprise: the discovery of a new, different asteroid that is just a few hundred feet across.

An asteroid roughly the size of Rome’s Colosseum — between 300 to 650 feet in length — has been detected by a team of European astronomers using NASA's James Webb Space Telescope. They used data from the calibration of the MIRI instrument to serendipitously detect an interloping asteroid. The object is likely the smallest observed by Webb, and may be an example of an object measuring under 1 kilometer in length within the main asteroid belt, located between Mars and Jupiter.  ARTWORK: NASA, ESA, CSA, N. Bartmann (ESA/Webb), Martin Kornmesser (ESA), Serge Brunier (ESO), Nick Risinger (Photopic Sky Survey)

Read more
See a stunning field of galaxies captured by James Webb Space Telescope
A crowded field of galaxies throngs this Picture of the Month from the NASA/ESA/CSA James Webb Space Telescope, along with bright stars crowned with Webb’s signature six-pointed diffraction spikes. The large spiral galaxy at the base of this image is accompanied by a profusion of smaller, more distant galaxies which range from fully-fledged spirals to mere bright smudges. Named LEDA 2046648, it is situated a little over a billion light-years from Earth, in the constellation Hercules.

Stunning images from the James Webb Space Telescope continue to entrance, and recently the researchers using the telescope have shared a gorgeous image of a field of galaxies as part of the Webb Picture of the Month collection.

The image shows a spattering of different background galaxies, while the foreground shows bright individual stars and a bright spiral galaxy at the bottom called LEDA 2046648. Located around a billion light-years from Earth, this galaxy is relatively much closer to us than the far-off background galaxies which is why it is so prominent in the image.

Read more