SATLASInfrared · Space
JWST
James Webb Space Telescope
OperatingOperating since 25 December 2021.
A 6.5 m gold-coated beryllium primary of 18 segments, passively cooled behind a five-layer sunshield, with MIRI cooled further to 7 K by a cryocooler. NIRCam, NIRSpec, NIRISS and MIRI provide imaging and multi-object, slitlessslitless spectroscopyPlacing a dispersing element (often a grism, a prism–grating combination) in the beam with no slit, so every source in the field gets a spectrum at once. Efficient for surveys; spectra of neighbours can overlap., integral-field and time-series spectroscopytransmission spectroscopyComparing a star's spectrum in and out of a planet's transit: wavelengths where the planet's atmosphere absorbs make the transit slightly deeper, revealing its molecules. from 0.6 to 28 µm: galaxies at z > 10, transmission and emission spectra of exoplanet atmospheres, and star and planet formation.
- Operator
- NASA, ESA, CSA
- Orbit
- Sun–Earth L2
- Aperture
- 6.5 m segmented mirror
- Passband
- 0.6 µm – 28 µm
- Launch
- 25 December 2021
Passband
Sky coverage
Pointed observationspointed observationObserving chosen targets, usually selected by peer review in annual proposal cycles, as opposed to surveying the sky systematically. Gives depth on few objects; the total area observed stays small. chosen in annual peer-reviewed cycles. The sunshield restricts pointing to solar elongations of 85°–135°, a band that sweeps the whole sky over a year; the continuous viewing zonescontinuous viewing zoneThe region of sky a spacecraft can observe without interruption through its whole orbit or year, usually around the ecliptic poles. Targets there accumulate the longest time series. lie within 5° of the ecliptic poleseclipticThe plane of Earth's orbit projected on the sky; the Sun, Moon and planets stay close to it. Solar-system bodies and zodiacal light concentrate there, and spacecraft that must keep the Sun at a fixed angle often observe in strips perpendicular to it, so the ecliptic poles get the deepest coverage.. Fields are arcminutes across, so the total area observed is small.
Data products
JWST's infrared detectors are read non-destructively many times during each integration. The jwst calibrationcalibrationRemoving instrument signatures and putting data in physical units: subtracting bias and dark current, dividing by the flat field (pixel-to-pixel sensitivity), correcting non-linearity and fitting the astrometric solution. Reference files hold these calibrations and are updated as the instrument is understood. pipeline fits these rampsup-the-ramp samplingReading an infrared detector repeatedly during one exposure without resetting it, so charge accumulates as a ramp. Fitting the slope gives a count rate and rejects cosmic-ray hits. to count-rate images (Stage 1), calibrates each exposure (Stage 2), then combines exposures into mosaicscoaddMany exposures of the same field resampled onto a common grid and combined, reaching deeper than any single exposure and rejecting artefacts. A mosaic stitches adjacent fields., cubesdata cubeA three-dimensional array with two sky axes and one spectral axis (wavelength, frequency or velocity), produced by integral field units and radio interferometers. and catalogues (Stage 3). MAST runs it automatically; any stage can be rerun locally with newer reference files.
Where to start
1Images and mosaics of an observation
2Deep extragalactic fields
3Spectra, including exoplanet time series
4Reprocessing with newer reference files or custom steps
From detector to catalogueAbout data levels
| 1RawUncalibrated ramps | 2CalibratedStage 1 and 2 | 3MeasuredStage 2 spectra | 4CombinedStage 3 | |
|---|---|---|---|---|
| Imaging | No product at this level | |||
| Spectroscopy |
Starting point, listed aboveContributed: made outside the mission pipelineSelect a product for its full entry
All products
RawUncalibrated ramps
uncal
*_uncal.fits
Public access: After the exclusive access period, usually 12 months; some programs have none
Every group of every integration, straight from the detector, in data numbers.
CalibratedStage 1 and 2
rate / rateints
*_rate.fits
Count rate per pixel after fitting the ramps (Stage 1, calwebb_detector1).
cal
*_cal.fits
Flux-calibrated, flat-fielded single exposures with world coordinatesworld coordinate systemHeader keywords in a FITS file that map pixel positions to sky coordinates (and wavelength or time), including projection and distortion. (Stage 2).
MeasuredStage 2 spectra
x1d / x1dints
*_x1d.fits
One-dimensional extracted spectra; x1dints keeps every integration for time-series work such as exoplanet transitstransitA planet passing in front of its star and blocking a fraction (R_p/R_*)² of its light, about 84 ppm for an Earth across the Sun. Repeated transits give period and radius; spectra taken during transit probe the planet's atmosphere..
CombinedStage 3
i2d
*_i2d.fits
Resampled, combined images or mosaics of all exposures in an observation.
s3d
*_s3d.fits
Three-dimensional IFUintegral field unitA spectrograph front end that slices a small field into many elements and takes a spectrum of each, giving a data cube with two spatial axes and one wavelength axis. cubes (two sky axes and wavelength).
Source catalogues
*_cat.ecsv
Positions and fluxes of sources detected in the combined images.
Community survey products
Image
Contributed product
Mosaics and catalogues from large programs such as JADES, CEERS and COSMOS-Web.
Archives
Quick start
astroquery's MAST module finds observations and downloads chosen products.
from astroquery.mast import Observations
obs = Observations.query_criteria(
obs_collection="JWST", target_name="NGC-3132", instrument_name="NIRCAM/IMAGE",
)
products = Observations.get_product_list(obs)
mosaics = Observations.filter_products(products, productSubGroupDescription="I2D")
Observations.download_products(mosaics)Key papers
Mission · 2023
The James Webb Space Telescope Mission (opens in a new tab)Gardner et al., PASP 135, 068001
The observatory, its history and science goals; the overview paper for the PASP instrument series.
Instrument · 2023
The Science Performance of JWST as Characterized in Commissioning (opens in a new tab)Rigby et al., PASP 135, 048001
Measured sensitivity, image quality, pointing stability and backgrounds for the observatory and each instrument.
Instrument · 2023
Performance of NIRCam on JWST in Flight (opens in a new tab)Rieke et al., PASP 135, 028001
Instrument · 2022
The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope. I. Overview of the instrument and its capabilities (opens in a new tab)Jakobsen et al., A&A 661, A80
The first of a series on NIRSpec's MOS, IFU, fixed-slit and bright-object modes.
Instrument · 2023
The Mid-infrared Instrument for JWST and Its In-flight Performance (opens in a new tab)Wright et al., PASP 135, 048003
Instrument · 2023
Result · 2023
Identification of carbon dioxide in an exoplanet atmosphere (opens in a new tab)JWST Transiting Exoplanet Community ERS Team, Nature 614, 649
CO₂ in WASP-39b's transmission spectrum with NIRSpec PRISM, from Early Release Science time-series data.
Result · 2023
Spectroscopic confirmation of four metal-poor galaxies at z = 10.3–13.2 (opens in a new tab)Curtis-Lake et al., Nat. Astron. 7, 622
JADES NIRSpec spectra confirming NIRCam photometric candidates beyond z = 10.
Sources
Verified 15 November 2026.