How the James Webb Space Telescope exceeded all expectations

On December 25, 2021, the James Webb Space Telescope launched into space.

On December 25, 2021, the James Webb Space Telescope was successfully launched into orbit from an Ariane 5 rocket. Rocketry has been the only way we have successfully propelled spacecraft considerable distances through space.

(Credit: ESA-CNES-ArianeSpace/Optique Video du CSG/NASA TV)

The plan called for six months of implementation, cooling and calibration.

The secondary mirror deployment sequence is shown in this time-lapse image. It must be accurately located within 24 feet, or just over 7 meters, of the primary mirror. This was one of hundreds of steps that needed to happen as planned, without fail, to bring a fully functional JWST online.

(Credit: NASA/James Webb Space Telescope team)

Subsequently, scientific operations would begin, giving an anticipated useful life of 5 to 10 years.

James Webb Space Telescope

When all the optics are properly deployed and the telescope is fully calibrated, James Webb should be able to see any object beyond Earth’s orbit in the cosmos with unprecedented precision, with its primary and secondary mirrors focusing light on the instruments. , where the data can be taken, reduced and sent back to Earth.

(Credit: NASA/James Webb Space Telescope team)

However, on April 28, 2022, the alignment of each instrument was completed, and a useful life of ~20 years is expected.

This image shows the 18 individual segments that make up James Webb’s main mirror and the three independent sets of mirrors, labeled with letters A, B, and C and numbers 1-6, corresponding to the installed position of each mirror in the current mirror. unfolded telescope.

(Credit: NASA/James Webb Space Telescope team)

Both the telescope and the equipment performed brilliantly, generally exceeding expectations.

This multi-panel image shows the details returned by each of the JWST instruments at the same point/field of view. For the first time, all instruments across the entire field of view are properly and fully calibrated, bringing JWST one step closer to being ready to begin science operations.

(Credit: NASA/STScI)

First: the pristine launch underway conserved fuel intended for course correction.

When the solar array unfurled 29 minutes after launch, and about 4 minutes ahead of schedule, it was clear that NASA’s James Webb Space Telescope was operational and receiving power, and well on its way to its final destination. The launch was an unprecedented success.

(Credit: NASATV/YouTube)

JWST reached its destination, the L2 Lagrange point, ahead of schedule.

Each planet orbiting a star has five locations around it, Lagrange points, that co-orbit. An object located precisely at L1, L2, L3, L4, or L5 will continue to orbit the Sun with exactly the same period as the Earth, meaning that the distance between Earth and the spacecraft will be constant. L1, L2, and L3 are unstable balance points, requiring periodic course corrections to maintain a spacecraft’s position there, while L4 and L5 are stable. Webb was successfully inserted into orbit around L2 and must always face away from the Sun for cooling purposes.

(Credit: NASA)

Every component deployed correctly and cooled down as planned.

The current status of the JWST shows how far along it is in each of its implementation steps, including the calibration of various components and the temperature of each instrument. Science operations are almost ready to begin.

(Credit: NASA/JWST/STScI team)

In early February, the 7-step commissioning/alignment process began.

james webb hubble

A portion of the Hubble eXtreme Deep Field that has been imaged for 23 days in total, in contrast to the simulated view expected by JWST in the infrared. By judiciously choosing its targets, the James Webb Space Telescope should be able to reveal extraordinary details about the most distant objects in the Universe that no other observatory could hope to reveal. Once calibration is complete, this type of scientific work can begin.

(Credit: NASA/ESA and Hubble/HUDF team; JADES collaboration for NIRCam simulation)

First, the images produced by each segment of the mirror were identified.

james webb peaks

This image mosaic was created by pointing the telescope at a bright, isolated star in the Ursa Major constellation known as HD 84406. This star was specifically chosen because it is easily identifiable and is not crowded with other stars of similar brightness, which helps to reduce the background. confusion. Each point within the mosaic is labeled by the corresponding primary mirror segment that captured it. These initial results closely match expectations and simulations.

(Credit: NASA)

Second, the images were aligned, and third, they were stacked.

This three-panel animation shows the difference between 18 individual non-aligned images, those same images after each segment was better configured, and then the final image where the individual images from all 18 mirrors were stacked and added together. The pattern created by that star, known as the “nightmare snowflake,” can be enhanced with better calibration.

(Credits: NASA/STScI, compiled by E. Siegel)

Fourth, the thick phase synthesized 18 small telescopes into one large one.

After image stacking, where all the light is placed in one location on the detector, the segments still need to align with each other to a precision less than the wavelength of the light. The coarse phase measures and corrects for the vertical displacement (ie piston difference) of the mirror segments. Smaller piston errors create fewer “barber” streaks in this NASA simulation.

(Credit: NASA)

Fifth, the NIRCam fine phase was produced, creating the first fully focused image.

james webb peaks

The first fine-phase image released by NASA’s James Webb Space Telescope shows a single image of a star, complete with six prominent (and two less prominent) diffraction peaks, with background stars and revealed galaxies behind it. As remarkable as this image is, it’s likely to be the worst James Webb Space Telescope image you’ll see from here on out.

(Credit: NASA/STScI)

JWST’s unique set of peaks arises from the telescope’s optical design.

The point spread function for the James Webb Space Telescope, as predicted in a 2007 paper. The four factors of a hexagonal (non-circular) primary mirror, composed of a set of 18 tiled hexagons, each with spaces of ~4mm between them, and with three support struts to hold the secondary mirror in place, it all works to create the inevitable series of spikes that appear around bright point sources photographed with JWST.

(Credit: R.B. Makidon, S. Casertano, C. Cox, and R. van der Marel, STScI/NASA/AURA)

Sixth, alignment coverage was extended across the JWST instrument cluster and the entire field of view.

After fine phasing, the telescope is well aligned to only one place in NIRCam’s field of view. By making measurements at multiple field points on each of the instruments, intensity variations can be reduced until they are optimal, achieving a well-aligned telescope on all science instruments.

(Credit: NASA)

Seventh, the final iterative fixes finished the alignment.

Sharply focused star engineering images in each instrument’s field of view demonstrate that the telescope is fully aligned and in focus. For this test, Webb targeted part of the Large Magellanic Cloud, a small satellite galaxy of the Milky Way, which provides a dense field of hundreds of thousands of stars across all of the observatory’s sensors.

(Credit: NASA/STScI)

Now NIRCam,

Originally, when the first images of JWST’s spectacular bright “8-pointed” star were produced, that was an indication that the spacecraft’s onboard workhorse camera, NIRCam, was calibrated to one point. Now, that calibration is across the JWST field of view, across the NIRCam field, as well as the fields of all other instruments.

(Credit: NASA/STScI)

fine Guide Sensor,

The Fine-Gudance Sensor aboard JWST will track guide stars to pinpoint the observatory precisely and precisely, taking calibration images rather than images used to extract scientific data.

(Credit: NASA/STScI)


The near-infrared imager and slitless spectrograph, part of the same instrument as the fine guidance sensor, is designed to excel in exoplanet transit detection, characterization and spectroscopy. If there are biological clues around exoplanets, the NIRISS instrument should find them.

(Credit: NASA/STScI)


NIRSpec is a spectrograph rather than an imager, but it can take images, such as the 1.1-micron image shown here, for calibrations and target acquisition. The dark regions visible in parts of the NIRSpec data are due to the structures of its microshutter array, which has several hundred thousand controllable shutters that can be opened or closed to select which light is sent to the spectrograph.

(Credit: NASA/STScI)

and the MIRI instruments are all aligned.

Although the James Webb Space Telescope’s Mid-InfraRed Instrument (MIRI) achieves the lowest resolution due to the long wavelengths to which it is sensitive, it is also the most powerful instrument in many ways, capable of revealing the most distant features of the Earth. Universe of all .

(Credit: NASA/STScI)

Only the commissioning of the instrument and the final calibrations remain.

This is a simulated JWST/NIRCam mosaic that was generated using JAGUAR and the NIRCam Guitar image simulator, at the depth expected from the JADES Deep program. In his first year of science operations, James Webb will very likely break many records that Hubble set over the course of its 32-year (and counting) life, including the records for most distant galaxy and most distant star.

(Credit: C. Williams et al., ApJ, 2018)

With fuel savings and rapid alignment, ~20+ years of science operations will soon begin.

Mostly Mute Monday tells an astronomical story in pictures, visuals, and no more than 200 words. Talk less; smile more.

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