This animation shows how the path light follows as it hits the primary mirror of the James Webb Space Telescope (JWST) and is reflected to the secondary mirror and then through the rear optics assembly where the tertiary mirror and fine steering mirror are located. The light is then reflected and split and passed through pick-off mirrors to the scientific instruments. JWST is a three-mirror Anastigmat telescope. Image credits: NASA, ESA and G. Bacon (STScI)
One of[{” attribute=””>James Webb Space Telescope’s four primary scientific instruments, known as NIRISS, has concluded its postlaunch preparations and is now ready for science. NIRISS, which stands for Near-Infrared Imager and Slitless Spectrograph instrument, provides observing modes for slitless spectroscopy, high-contrast interferometric imaging, and imaging, at wavelengths between 0.6 and 5.0 μm over a 2.2′ x 2.2′ FOV. It will be used to investigate the following science objectives: first light detection,
This mode will be specifically used to probe the atmospheres of transiting exoplanets, i.e., planets that happen to eclipse their star periodically, momentarily dimming the star’s brightness for a period of time. By comparing the spectra collected during and before or after a transit event with great precision, one can determine not only whether or not the exoplanet has an atmosphere, but also what atoms and molecules are in it.
The Image Behind the Spectrum. This is a test detector image from the NIRISS instrument operated in its single-object slitless spectroscopy (SOSS) mode while pointing at a bright star. Each color seen in the image corresponds to a specific infrared wavelength between 0.6 and 2.8 microns. The black lines seen on the spectra are the telltale signature of hydrogen atoms present in the star. NIRISS is a contribution from the Canadian Space Agency (CSA) to the Webb project that provides unique observational capabilities that complement its other onboard instruments. Credit: NASA, CSA, and NIRISS team/Loic Albert, University of Montreal
“I’m so excited and thrilled to think that we’ve finally reached the end of this two-decade-long journey of Canada’s contribution to the mission. All four NIRISS modes are not only ready, but the instrument as a whole is performing significantly better than we predicted. I am pinching myself at the thought that we are just days away from the start of science operations, and in particular from NIRISS probing its first exoplanet atmospheres,” said René Doyon, principal investigator for NIRISS, as well as Webb’s Fine Guidance Sensor, at the University of Montreal.
With NIRISS postlaunch commissioning activities concluded, the Webb team will continue to focus on checking off the remaining five modes on its other instruments.