James Webb Space Telescope

The James Webb Space Telescope (JWST or Webb; an early name was Next Generation Space Telescope, i.e., NGST) is a 6.5 meter (21 ft) NASA/European Space Agency/CSA space-based infrared telescope located at the Earth-Sun L2 Lagrangian point after a 2021 launch. Its lifetime will be limited by the fuel it carries for stationkeeping (maintaining its orbit). A five-and-a-half-year primary mission is targeted and a ten-year life or more is hoped for: it has fuel for about two decades. Infrared was chosen because it is necessary for viewing very distant, redshifted astronomical objects (distant galaxies and quasars) and Earth atmosphere limits infrared observation from the ground. Infrared is also useful for observation of nearer objects as well: it is virtually always present in thermal emission. Instruments:

• NIRCam - Near-infrared Camera.
• NIRSpec - Near Infrared Spectrometer.
• MIRI - Mid-infrared Instrument (imaging spectrometer and imager).
• FGS - Fine Guidance Sensor.
• NIRISS - Near Infrared Imager and Slitless Spectrograph.

One observation target is spectroscopy of extra-solar planets. NIRISS can operate in a mode termed SOSS, for single-object slitless spectroscopy, aimed at differential spectroscopy for observing the light curves of transiting exoplanets. MIRI includes an imager (MIRIM), coronagraphic imaging, and spectrography, including IFU spectroscopy. Its medium-resolution (MRS mode, offering resolutions of 1500-3500) can be carried out during direct imaging of exoplanets. NIRSpec offers several gratings, with grating labeled G395 offering a spectral resolution of as high as 2700. NIRCam offers WFSS (wide field slitless spectroscopy) mode. JWST also offers aperture masking interferometry (AMI). Established classes of JWST observing programs include:

• ERS (Early Release Science).
• GTO (Guaranteed Time Observations) - a program giving contributors to the instrumentation development some JWST time for research.

Among the GTO programs is NEAT (NIRISS Exploration of the Atmospheric diversity of Transiting exoplanets). Among the ERS programs is CEERS (Cosmic Evolution Early Release Science), GLASS (Grism Lens-Amplified Survey from Space), and ERS 1386 (high contrast imaging imaging of exoplanets), Among the surveys is JADES (JWST Advanced Deep Extragalactic Survey).