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StartScience NewsWebb Area Telescope’s Remaining Commissioning Actions

Webb Area Telescope’s Remaining Commissioning Actions


Webb Space Telescope Poster

NASA’s James Webb Area Telescope is a real technological marvel. The most important and most advanced area telescope ever constructed, Webb is ready to collect mild that has been touring for 13.5 billion years, virtually for the reason that starting of the universe. In impact, Webb is a time machine, permitting us to look on the first galaxies to kind after the Huge Bang. As a result of it gathers infrared mild, sees proper by way of the enormous clouds of mud that block the view of most different telescopes. Webb is 100 instances extra highly effective than the Hubble Area Telescope. Credit score: NASA/JPL-Caltech

With the telescope optics and devices aligned, the Webb group is now commissioning the observatory’s 4 highly effective science devices. There are 17 completely different instrument “modes” to take a look at on our option to preparing for the beginning of science this summer time. As soon as now we have accepted all 17 of those modes, NASA’s James Webb Space Telescope will be ready to begin scientific operations!

In this article we’ll describe the 17 modes, and readers are encouraged to follow along as the Webb team checks them off one by one on the Where is Webb tracker. Each mode has a set of observations and analysis that need to be verified, and it is important to note that the team does not plan to complete them in the order listed below. Some of the modes won’t be verified until the very end of commissioning.

For each mode we have also selected a representative example science target that will be observed in the first year of Webb science. These are just examples; each mode will be used for many targets, and most of Webb’s science targets will be observed with more than one instrument and/or mode. The detailed list of peer-reviewed observations planned for the first year of science with Webb ranges from our solar system to the most distant galaxies.

1. Close to-Infrared Digital camera (NIRCam) imaging. Close to-infrared imaging will take photos in a part of the seen to near-infrared mild, 0.6 to five.0 micrometers wavelength. This mode will likely be used for nearly all features of Webb science, from deep fields to galaxies, star-forming areas to planets in our personal photo voltaic system. An instance goal in a Webb cycle 1 program utilizing this mode: the Hubble Extremely-Deep Area.

2. NIRCam vast area slitless spectroscopy. Spectroscopy separates the detected mild into particular person colours. Slitless spectroscopy spreads out the sunshine in the entire instrument area of view so we see the colours of each object seen within the area. Slitless spectroscopy in NIRCam was initially an engineering mode to be used in aligning the telescope, however scientists realized that it may very well be used for science as effectively. Instance goal: distant quasars.

3. NIRCam coronagraphy. When a star has exoplanets or mud disks in orbit round it, the brightness from a star normally will outshine the sunshine that’s mirrored or emitted by the a lot fainter objects round it. Coronagraphy makes use of a black disk within the instrument to dam out the starlight in an effort to detect the sunshine from its planets. Instance goal: the fuel large exoplanet HIP 65426 b.

4. NIRCam time collection observations – imaging. Most astronomical objects change on timescales which can be giant in comparison with human lifetimes, however some issues change quick sufficient for us to see them. Time collection observations learn out the devices’ detectors quickly to look at for these modifications. Instance goal: a pulsing white dwarf star known as a magnetar.

5. NIRCam time collection observations – grism. When an exoplanet crosses the disk of its host star, light from the star can pass through the atmosphere of the planet, allowing scientists to determine the constituents of the atmosphere with this spectroscopic technique. Scientists can also study light that is reflected or emitted from an exoplanet, when an exoplanet passes behind its host star. Example target: lava rain on the super-Earth-size exoplanet 55 Cancri e.

NIRCam Sensor Array

A sensor array for the NIRCam instrument, designed and tested by Marcia Rieke’s research group at Steward Observatory. For the sensors to detect infrared light without too much noise in the data, Webb and its instruments must be kept as cool as possible. Credit: Marcia Rieke

6. Near-Infrared Spectrograph (NIRSpec) multi-object spectroscopy. Although slitless spectroscopy gets spectra of all the objects in the field of view, it also allows the spectra of multiple objects to overlap each other, and the background light reduces the sensitivity. NIRSpec has a microshutter device with a quarter of a million tiny controllable shutters. Opening a shutter where there is an interesting object and closing the shutters where there is not allows scientists to get clean spectra of up to 100 sources at once. Example target: the Extended Groth Strip deep field.

7. NIRSpec fixed slit spectroscopy. In addition to the microshutter array, NIRSpec also has a few fixed slits that provide the ultimate sensitivity for spectroscopy on individual targets. Example target: detecting light from a gravitational-wave source known as a kilonova.

8. NIRSpec integral field unit spectroscopy. Integral field unit spectroscopy produces a spectrum over every pixel in a small area, instead of a single point, for a total of 900 spatial/spectral elements. This mode gives the most complete data on an individual target. Example target: a distant galaxy boosted by gravitational lensing.

9. NIRSpec bright object time series. NIRSpec can obtain a time series spectroscopic observation of transiting exoplanets and other objects that change rapidly with time. Example target: following a hot super-Earth-size exoplanet for a full orbit to map the planet’s temperature.

10. Near-Infrared Imager and Slitless Spectrograph (NIRISS) single object slitless spectroscopy. To observe planets around some of the brightest nearby stars, NIRISS takes the star out of focus and spreads the light over lots of pixels to avoid saturating the detectors. Example target: small, potentially rocky exoplanets TRAPPIST-1b and 1c.

Webb MIRI Spectroscopy Animation

The beam of light coming from the telescope is then shown in deep blue entering the instrument through the pick-off mirror located at the top of the instrument and acting like a periscope.
Then, a series of mirrors redirect the light toward the bottom of the instruments where a set of 4 spectroscopic modules are located. Once there, the beam of light is divided by optical elements called dichroics in 4 beams corresponding to different parts of the mid-infrared region. Each beam enters its own integral field unit; these components split and reformat the light from the whole field of view, ready to be dispersed into spectra. This requires the light to be folded, bounced and split many times, making this probably one of Webb’s most complex light paths.
To finish this amazing voyage, the light of each beam is dispersed by gratings, creating spectra that then projects on 2 MIRI detectors (2 beams per detector). An amazing feat of engineering! Credit: ESA/ATG medialab

11. NIRISS wide field slitless spectroscopy. NIRISS includes a slitless spectroscopy mode optimized for finding and studying distant galaxies. This mode will be especially valuable for discovery, finding things that we didn’t already know were there. Example target: pure parallel search for active star-forming galaxies.

12. NIRISS aperture masking interferometry. NIRISS has a mask to block out the light from 11 of the 18 primary mirror segments in a process called aperture masking interferometry. This provides high-contrast imaging, where faint sources next to bright sources can be seen and resolved for images. Example target: a binary star with colliding stellar winds.

13. NIRISS imaging. Because of the importance of near-infrared imaging, NIRISS has an imaging capability that functions as a backup to NIRCam imaging. Scientifically, this is used mainly while other instruments are simultaneously conducting another investigation, so that the observations image a larger total area. Example target: a Hubble Frontier Field gravitational lensing galaxy cluster.

14. Mid-Infrared Instrument (MIRI) imaging. Just as near-infrared imaging with NIRCam will be used on almost all types of Webb targets, MIRI imaging will extend Webb’s pictures from 5 to 27 microns, the mid-infrared wavelengths. Mid-infrared imaging will show us, for example, the distributions of dust and cold gas in star-forming regions in our own Milky Way galaxy and in other galaxies. Example target: the nearby galaxy Messier 33.

15. MIRI low-resolution spectroscopy. At wavelengths between 5 and 12 microns, MIRI’s low-resolution spectroscopy can study fainter sources than its medium-resolution spectroscopy. Low resolution is often used for studying the surface of objects, for example, to determine the composition. Example target: Pluto’s moon Charon.

16. MIRI medium-resolution spectroscopy. MIRI can do integral field spectroscopy over its full mid-infrared wavelength range, 5 to 28.5 microns. This is where emission from molecules and dust display very strong spectral signatures. Example targets: molecules in planet-forming disks.

17. MIRI coronagraphic imaging. MIRI has two types of coronagraphy: a spot that blocks light and three four-quadrant phase mask coronagraphs. These will be used to directly detect exoplanets and study dust disks around their host stars. Example target: searching for planets around our nearest neighbor star Alpha Centauri A.

Written by Jonathan Gardner, Webb deputy senior project scientist, NASA’s Goddard Space Flight Center



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