Home Electromagnetic NASA’s James Webb Space Telescope passes halfway during final tests

NASA’s James Webb Space Telescope passes halfway during final tests


What is happening

The JWST team has completed 10 of 17 “modes,” or checkpoints, on the way to the telescope’s start-up.

why is it important

Successful testing means we are still on track to receive the first JWST images this summer.

It’s almost time.

NASA is preparing to publish its first-ever interstellar discoveries, thanks to the groundbreaking James Webb Space Telescope. Come July 12we can begin to see the universe through a much clearer lens.

And in preparation for the highly anticipated day, JWST researchers meticulously perfected each of the oscilloscope’s pioneering pieces of equipment – on that note, we have an update.

NASA scientists announced this week that they have successfully calibrated the eye of a JWST-mounted device called NIRSpec. This is quite a big step due to the streamlined way NASA has laid out the road to regular use of Webb. The agency basically has to go through 17 instrument “modes”, which you can think of as test checkpoints, through analysis and observation before fully starting JWST.

So, counting NIRSpec’s accomplishments now, the agency has officially passed halfway through the mode ledger, bringing the grand total to 10 out of a full 17.

“The recent confirmation of the acquisition of the NIRSpec target … prepares the NIRSpec team for our final commissioning activities,” the team said. “We can’t wait to see the first NIRSpec science observations arrive this summer!”

In fact, “the team has begun taking some of the first scientific data,” according to the agency’s statement.

A quick recap of James Webb’s specs

The JWST has four key elements, each contributing to these 17 modes described by the agency. It should be noted that almost all of these facets rely on some type of infrared light detection, which means that they can study a part of the electromagnetic spectrum invisible to the human eye.

“Studying the intensity or brightness of light across wavelengths can provide key diagnostic information about the nature of various objects across the universe,” the JWST team said. “From extrasolar planets around distant stars, to faint galaxies at the edge of the universe, and objects in our own solar system.”


A comparison of Hubble’s visible and infrared views of the Monkey Head Nebula. Although Hubble has infrared capabilities, it’s nothing compared to Webb.


You can learn more about the science of infrared in more detail here – but back to JWST’s tech army, here’s the breakdown.

Its alpha instrument is probably the Near Infrared Camera, or NIRCam. NIRCam will essentially lead the charge in sensing and imaging the cosmos as it was at the beginning of time. “If NIRCam doesn’t work, the telescope doesn’t work,” says Alison Nordt, director of space science and instrumentation at aerospace giant Lockheed Martin, who has been part of the JWST since its inception.


Alison Nordt, engineer at Lockheed Martin, working on Webb’s NIRCam.

Lockheed Martin

Then there’s the Mid-Infrared Instrument, or MIRI, which has both a camera and a spectrograph aimed at dissecting light-illuminated features in the environment-infrared electromagnetic region, and the Near Infrared Slitless Imaging Spectrograph, or NIRISS, which is essentially an exoplanet-hunting machine.

Also onboard JWST is a navigation system, aka the Fine Guidance Sensor, which helps the range, well, not get lost. And finally, the star of NASA’s latest update is the Near Infrared Spectrograph, or NIRSpec.


You can see an image of all of Webb’s major instruments in this collage.


What is the NIRSpec?

“The near-infrared spectrograph is the Webb Telescope instrument that observes the spectra of astrophysical and planetary objects at near-infrared wavelengths,” the JWST team said.

An image of stars taken by JWST's NIRSpec device.

A simulation of the NIRSpec MSA based target acquisition process, demonstrated on the NIRSpec sharpness check image. NIRSpec uses “reference stars” which you can see here, viewed through fixed slits in the device.

NASA, ESA and the NIRspec team

In other words, it works to examine spatial phenomena that emanate from light in the near-infrared region, but rather than just imaging these objects, it can study their chemical composition. This is the plot of spectrography. You get more than a picture of a planet, you get details of what it would be like to stand on it.


An optimized high resolution simulation of a star seen through a NIRSpec microshutter. For a correct estimation of the intensity of the NIRSpec scientific spectra, we need to know precisely the positioning of the targets within one tenth of the shutter width.

NASA, ESA and the NIRspec team

And in terms of target acquisition, the JWST team says NIRSpec has a significant mirror, which can place cosmic targets in their proper location while the telescope is exploring. This is crucial because this information helps NIRSpec’s spectrograph know where to look.

The mirror does this in two ways: wide-aperture target acquisition (WATA) and micro-shutter assembly-based target acquisition (MSATA). During testing, the team said WATA performed “excellent” and MSATA made solid progress, and luckily for us, both successes give us awesome cosmic images, like the one shown above.

Also, when it comes to MSATA, the JWST team claims that this method is quite difficult to master. This requires correct spectral intensity estimation from iNIRSpec science in one tenth of the shutter width of the camera. It’s incredibly accurate. For context, that’s “the approximate size of a bumblebee, 1.5 centimeters, seen from 150 kilometers away,” the team said.

Now that NASA has these successes, there are only seven modes left before we reach July 12 – the day we’ve all been waiting for.

To the stars, JWST.