Webb’s Fine Guidance Sensor Provides Preview Of Its Imaging Excellency

The first full-color photographs from NASA’s James Webb Space Telescope will be released in less than a week, but how does the observatory locate and look onto its targets?

This specific question was taken into consideration when the Canadian Space Agency created Webb’s Fine Guidance Sensor (FGS).

An intriguing preview of what the telescope’s science instruments can do may be disclosed in the upcoming weeks, months, and years after it captured a panorama of stars and galaxies.

Objective Of FGS

Although FGS has always been able to take pictures, its main objective is to make precise science measurements and capture pictures with almost as much accuracy as possible.

When it does capture imagery, it usually discards the image: Webb only has access to a small amount of the communications bandwidth between L2 and Earth.

However, the researchers realized they could retain the imagery being taken because there was available data transfer bandwidth during a week-long stability test in May.

How Will This Data Help Researchers?

The final engineering test image contains a few unsightly characteristics. The data was collected to test how well the telescope could stay locked onto a target rather than to be optimized as a science observation, but it does give some indication of the telescope’s power.

It exhibits certain characteristics of the viewpoints Webb has developed during its post launch planning. Due to Webb’s six-sided mirror segments, bright stars stand out with their six long, highly defined diffraction spikes. Beyond the stars, the backdrop is almost entirely made up of galaxies.

Related: Post 17 Modes Approval, Webb Will Start Its Instrument Commissioning Phase

How Does FGS Work?

FGS is capable of creating breathtaking views of the cosmos even while taking unintentional pictures while doing a test.

“Early in commissioning we purposefully defocused the guides by a modest amount to help guarantee they exceeded their performance requirements, with the Webb telescope delivering better-than-expected image quality. I was ecstatic to see all the intricate structure in these weak galaxies in this shot at the time it was captured.”

“Given what we currently understand to be possible with deep broadband guider images, perhaps such images, taken in parallel with other observations where practical, could prove scientifically useful in the future,” according to Neil Rowlands, programme scientist for Webb’s Fine Guidance Sensor at Honeywell Aerospace.

There are a few issues with this image because it wasn’t made with a scientific outcome in mind.

The Deepest Image Of The Universe

According to NASA Administrator Bill Nelson’s announcement on June 29, the photographs will contain what will at least temporarily be the deepest image of the universe ever taken.

The FGS image is coloured using the same reddish color scheme that has been used throughout commissioning on Webb’s other engineering photos.

Additionally, during these exposures, there was no “dithering.” The telescope moves somewhat between each exposure when it dithers.

The pointing of the telescope did not change across the exposures to catch the center from different pixels inside the camera’s detectors, hence the centers of brilliant stars look black because they saturate Webb’s detectors. The corners and margins of the image also exhibit overlapped frames from the many exposures.

How Will This Observation Help Scientists?

The goal of this engineering test was to lock onto one star while evaluating Webb’s ability to regulate its “roll,” or, more specifically, its capacity to roll to one side like an airplane in flight.

According to Jane Rigby, the operations scientist for Webb at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the test was carried out successfully and also resulted in an image that captures the imagination of scientists who will be evaluating the science data from Webb.

What Are These ‘Blobs’ In The Image?

The smallest blobs in this image exactly match the kind of weak galaxies that Webb will investigate during its first year of scientific activities, according to Rigby.

The Fine Guidance Sensor is the only instrument that will be used in every Webb observation over the duration of the mission’s lifespan, despite the fact that Webb’s four science instruments will ultimately unveil the telescope’s fresh perspective on the cosmos.


FGS has already been essential in bringing Webb’s optics into alignment. It will now direct every Webb observation to its intended target and maintain the accuracy required for Webb to generate ground-breaking discoveries about stars, exoplanets, galaxies, and even moving targets within our solar system once science operations start in mid-July.

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