NASA is scheduled to release the first images taken by the James Webb Space Telescope on July 12, 2022. They will mark the beginning of the next astronomical era as Webb-the largest space telescope ever built-begins collecting scientific data to help. answer questions about the earliest moments of the universe and allow astronomers to study exoplanets in more detail than ever before. But it took nearly eight months of travel, setup, testing and calibration to make sure these most valuable of the telescopes were ready for prime time. Marcia Rieke, an astronomer at the University of Arizona and the scientist in charge of one of Webb’s four cameras, explains what he and his colleagues did to operate this telescope.
1. What has happened since the telescope was launched?
Following the successful launch of the James Webb Space Telescope on December 25, 2021, the team began the lengthy process of moving the telescope to its final orbital position, unfolding the telescope and – while everything was cooling – calibrating the cameras. and ship sensors.
The launch went as smoothly as a rocket launch. One of the first things my NASA colleagues noticed was that the telescope had more fuel left on the ship than predicted to make future changes to its orbit. This will allow Webb to operate and longer than the original 10 -year mission goal.
The first task of Webb’s full moon journey to its final location in orbit was to unfold the telescope. It went on without any obstacles, starting with white knuckle putting on the sun shield which helps to cool the telescope, followed by lining the mirrors and turning off the sensors.
Once the sun shield was opened, our team started monitoring the air temperature four cameras and a spectrometer on the shipwaiting for them to reach a temperature low enough so we can start testing each of the 17 different modes in which the instruments can operate.
2. What did you try first?
Webb’s cameras cooled as the engineers had predicted, and the first instrument the team operated was the Near Infrared Camera – or NIRCam. NIRCam was designed to study slow infrared light produced by the oldest stars or galaxies in the universe. But before that can be done, the NIRCam must help align the 18 individual parts of the Webb mirror.
When the NIRCam has cooled to minus 280 F, it is cold enough to begin detecting light reflecting off parts of the Webb mirror and making the first telescope images. The NIRCam team was delighted when the first light picture arrived. We are in business!
These images show the mirror parts all pointing to a relatively small area of heavenand the alignment was better than in the worst situations we had planned.
Webb’s Fine Guidance Sensor is also operational at this time. This sensor helps keep the telescope constantly focused on a target – such as image stabilization on consumers ’digital cameras. Using the star HD84800 as a reference point, my NIRCam teammates helped dial to align the mirror parts until it was perfect, better than the minimum required for a successful mission.
3. What sensors come to life next?
When the mirror alignment was completed on March 11, the Near Infrared Spectrograph – NIRSpec – and the Near Infrared Imager and Slitless Spectrograph – NIRISS – finished cooling off and joined the party.
NIRSpec is designed to measure intensity at different wavelengths of light from a target. This information can reveal the composition and temperature of distant stars and galaxies. NIRSpec does this by looking at the target object through a slit that blocks other light.
NIRSpec has many slits that allow this look at 100 items at a time. Team members started by testing the multiple targets mode, ordering the slits to open and close, and they confirmed that the slits responded correctly to the commands. Future steps will really measure where the slits are pointing and check that multiple targets can be observed simultaneously.
NIRISS is a slitless spectrograph that also breaks up light into its various wavelengths, but it is better at observing everything in a field, not just the slits. It has several modes, including two designed for studying exoplanets particularly close to their star parents.
So far, the inspections and calibration of the instrument are proceeding smoothly, and the results show that NIRSpec and NIRISS will provide better data than the engineers predicted before launch.
4. What was the last instrument to be turned on?
The last Webb boot instrument is the Mid-Infrared Instrument, or MIRI. MIRI is designed to take images of distant or newly formed galaxies as well as weak, small objects such as asteroids. This sensor detects the highest wavelength of Webb instruments and should be set to minus 449 F – 11 degrees F just above absolute zero. If it is hotter, the detectors will only draw heat from the instrument itself, not the interesting objects in space. MIRI has own cooling systemwhich requires additional time to become fully functional before the instrument is turned on.
Radio astronomers have found signs that there are full galaxies hidden in dust and unnoticed by telescopes like Hubble which captures wavelengths of light similar to those visible to the human eye. Extremely cold temperatures allow MIRI to be extremely sensitive to light in the mid-infrared range making it easier for dust to pass through. If this sensitivity is combined with Webb’s large mirror, it allows MIRI absorb these clouds of dust and reveal stars and structures in those galaxies for the first time.
5. What’s next for Webb?
On June 15, 2022, all Webb instruments were turned on and captured their first images. In addition, four imaging modes, three time series modes and three spectroscopic modes were tested and certified, leaving only three.
On July 12, NASA plans to release a set of teaser observations describing Webb’s capabilities. This will showcase the beauty of Webb imagery and will also give astronomers a real taste of the quality of the data they will receive.
After July 12, the James Webb Space Telescope will begin work throughout its scientific mission. The detailed schedule for next year has not yet been released, but astronomers around the world are eagerly waiting to get the first data from the most powerful space telescope ever made.