Bright eyes

Webb Telescope: 4 instruments are vital to unlocking stunning views of the cosmos

Originally Published: 
NASA/Goddard Space Flight Center Scientific Visualization Studio


The iconic honeycomb-shaped mirror is likely the first thing you’ll notice when you see the James Webb Space Telescope.

But hidden behind the mirror are the “eyes” of the JWST, the Integrated Science Instrument Module (ISIM).


NASA, ESA, and G. Bacon (STScI)

Once the honeycomb mirror captures light from the universe, it reflects that light onto the instruments in the ISIM via secondary mirrors.

The ISIM makes it possible for the telescope to see, thanks to four separate instruments.


Over the past few months, the ISIM’s four instruments have been tested, aligned, and cooled to prepare for their much-anticipated survey of the cosmos.


Once they’re in full swing (very soon!) the instruments will capture never-before-seen views of the universe at wavelengths invisible to the human eye.


Here’s an inside look at JWST’s 4 science instruments:

4. Mid-Infrared Instrument (MIRI)

Containing both a camera and a spectrograph, MIRI can detect infrared light emitted by objects at frequencies far too low for our eyes to see.

NASA/Goddard Space Flight Center Scientific Visualization Studio


Its sensitivity to low wavelengths will allow MIRI to gather never-before-seen views of comets, newly forming stars, and some of the earliest galaxies in the universe.

But to do this, MIRI has to be extremely cold.

NASA/Goddard Space Flight Center/Chris Gunn

Earlier this month, the instrument reached 7 degrees Kelvin (negative 447 degrees Fahrenheit), and is the coldest instrument onboard the JWST.

3. Near-Infrared Camera (NIRCam)

NIRCam is the JWST’s primary imaging system. It will detect near-infrared wavelengths, which are at higher frequencies than the ones MIRI will see, but still invisible to the human eye.

NASA/Goddard Space Flight Center Scientific Visualization Studio


NIRCam will detect planets orbiting distant stars.

It has the ability to block out light from target stars, which will give us crisper, clearer views of planetary systems that would be otherwise obscured.

NIRCam also captured this selfie of the telescope during alignment, which was completed March 1.

2. Near-Infrared Spectrograph (NIRSpec)

NIRSpec will also detect light on the near-infrared spectrum, but will decode different information from objects than the cameras on board.

NASA/Goddard Space Flight Center Scientific Visualization Studio


As a spectrograph, NIRSpec will use incoming light to parse out the physical properties of distant objects such as their mass, chemical composition, and temperature.


It also has a tool called a microshutter array that will allow the instrument to survey several objects in the sky at once.

1. Near-Infrared Imager and Slitless Spectrograph/Fine Guidance Sensor (NIRISS/FGS)

A long name for a complicated instrument!

NASA/Goddard Space Flight Center Scientific Visualization Studio

The purpose of the FGS/NIRISS is twofold: to point the telescope precisely, and to investigate objects at near-infrared wavelengths.


The FGS does the guiding, while the NIRISS will detect the movements of exoplanets and try to find some of the oldest objects in the universe.

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