Snapshot: The James Webb Space Telescope is fully focused

The James Webb Space Telescope is aligned and ready for instrument commissioning.
By | Published: May 6, 2022 | Last updated on May 18, 2023
Images in full focus from various JWST instruments

The James Webb Space Telescope has taken one more step toward full operations with the April 28 announcement that the observatory is now fully focused — and it has the images to prove it.

The engineering images above come from each of JWST’s instruments: NIRSpec, a near-infrared spectrometer; NIRCam, an imaging camera; NIRISS, a dual spectrometer and imaging camera; MIRI, a camera that observes at longer wavelengths; and the Fine Guidance Sensor, which helps the telescope point at targets precisely.

The seven-stage process of focusing the telescope involved aligning each of its 18 hexagonal mirror segments, which make up a collecting area with a diameter of 6.5 meters (21.3 feet). The JWST team says that the angular resolution of the fully-aligned ensemble is better than their predictions.

Crops of the images from NIRCam, the Fine Guidance Sensor, and MIRI.
Details of the fully-focused images from NIRCam, the Fine Guidance Sensor, and MIRI.

The next stage in bringing JWST online will be to commission each of its individual instruments, which entails studying their performance to better understand their characteristics and eventually calibrate the data they produce. In particular, the performance of JWST’s infrared instruments may be affected ever so slightly by thermal variations as the telescope changes its attitude, causing sunlight to fall on its sunshade at different angles. 

Instrument commissioning is expected to last two months and is the last major scheduled step before JWST begins science operations in earnest this summer.