More Updates As Webb Prepares For Consistent Science Operations
Since the James Webb Space Telescope was launched in late December of last year, it has stayed very busy in many different ways. From initial deployments, alignment milestones, and now final preparations, the journey has been packed full. This being said, now in early July, NASA and other agencies are getting excited as Webb is closer than ever to consistent science operations.
Up until this point, Webb has been completing different tests and getting ready for multiple future years of observations. Just over the last few days, NASA has provided a lot of additional information on the next-generation telescope’s progress. This includes a fascinating image thanks to Webb’s Fine Guidance Sensor and much more.
Not to mention the commissioning activities that are just about finished. Once complete, scientists around the world will have access to the most advanced telescope ever sent into space. A telescope that’s expected to change how we view the Universe we live in and more. Here I will go more in-depth into the recent progress Webb has made, the remaining tests, commissioning activities, and what to expect in the future.
Recent Image
Starting on July 6th, NASA tweeted saying, “Talk about an overachiever! Gaze at this test image, an unexpected & deep view of the universe, captured by Webb’s Fine Guidance Sensor (FGS) in May. Built by @csa_asc to point Webb precisely at targets, taking glamour shots isn’t even FGS’s main job.” This tweet included a test image that was acquired in parallel with NIRCam imaging of the star HD147980 over a period of eight days at the beginning of May. This engineering image represents a total of 32 hours of exposure time at several overlapping pointings of the Guider 2 channel. The observations were not optimized for detection of faint objects, but nevertheless the image captures extremely faint objects and is, for now, the deepest image of the infrared sky. The unfiltered wavelength response of the guider, from 0.6 to 5 micrometers, helps provide this extreme sensitivity. The image is mono-chromatic and is displayed in false color with white-yellow-orange-red representing the progression from brightest to dimmest. There are only a handful of stars in this image – distinguished by their diffraction spikes. The rest of the objects are thousands of faint galaxies, some in the nearby universe, but many, many more in the distant universe.
FGS has always been capable of capturing imagery, but its primary purpose is to enable accurate science measurements and imaging with precision pointing. When it does capture imagery, the imagery is typically not kept: Given the limited communications bandwidth between L2 and Earth, Webb only sends data from up to two science instruments at a time. But during a week-long stability test in May, it occurred to the team that they could keep the imagery that was being captured because there was available data transfer bandwidth. The resulting engineering test image has some rough-around-the-edges qualities to it. It was not optimized to be a science observation; rather, the data was taken to test how well the telescope could stay locked onto a target, but it does hint at the power of the telescope. It carries a few hallmarks of the views Webb has produced during its postlaunch preparations. Bright stars stand out with their six, long, sharply defined diffraction spikes – an effect due to Webb’s six-sided mirror segments. Beyond the stars, galaxies fill nearly the entire background. The result – using 72 exposures over 32 hours – is among the deepest images of the universe ever taken, according to Webb scientists. When FGS’ aperture is open, it is not using color filters like the other science instruments – meaning it is impossible to study the age of the galaxies in this image with the rigor needed for scientific analysis. But even when capturing unplanned imagery during a test, FGS is capable of producing stunning views of the cosmos.
“With the Webb telescope achieving better-than-expected image quality, early in commissioning we intentionally defocused the guiders by a small amount to help ensure they met their performance requirements. When this image was taken, I was thrilled to clearly see all the detailed structure in these faint galaxies. Given what we now know is possible with deep broad-band guider images, perhaps such images, taken in parallel with other observations where feasible, could prove scientifically useful in the future,” said Neil Rowlands, program scientist for Webb’s Fine Guidance Sensor, at Honeywell Aerospace. Because this image was not created with a science result in mind, there are a few features that are quite different than the full-resolution images that will be released July 12. Those images will include what will be – for a short time at least – the deepest image of the universe ever captured, as NASA Administrator Bill Nelson announced on June 29.
The FGS image is colored using the same reddish color scheme that has been applied to Webb’s other engineering images throughout commissioning. In addition, there was no “dithering” during these exposures. Dithering is when the telescope repositions slightly between each exposure. In addition, the centers of bright stars appear black because they saturate Webb’s detectors, and the pointing of the telescope didn’t change over the exposures to capture the center from different pixels within the camera’s detectors. The overlapping frames of the different exposures can also be seen at the image’s edges and corners. In this engineering test, the purpose was to lock onto one star and to test how well Webb could control its “roll” – literally, Webb’s ability to roll to one side like an aircraft in flight. That test was performed successfully – in addition to producing an image that sparks the imagination of scientists who will be analyzing Webb’s science data, said Jane Rigby, Webb’s operations scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The faintest blobs in this image are exactly the types of faint galaxies that Webb will study in its first year of science operations,” Rigby said.
While Webb’s four science instruments will ultimately reveal the telescope’s new view of the universe, the Fine Guidance Sensor is the one instrument that will be used in every single Webb observation over the course of the mission’s lifetime. FGS has already played a crucial role in aligning Webb’s optics. Now, during the first real science observations made in June and once science operations begin in mid-July, it will guide each Webb observation to its target and maintain the precision necessary for Webb to produce breakthrough discoveries about stars, exoplanets, galaxies, and even moving targets within our solar system.
Webb’s Future
In addition to the recent release of more test images, Webb has also been finishing up some of its commissioning activities. Each of Webb’s instruments has multiple modes of operation, which need to be tested, calibrated, and ultimately verified before they can begin to conduct science. The latest instrument to complete this process, the Near-Infrared Spectrograph, or NIRSpec, has four key modes the team officially confirmed as ready to go. “We made it: NIRSpec is ready for science! This is an amazing moment, the result of the hard work of so many JWST and NIRSpec people and teams over more than two decades. I am just so proud of everyone,” said Pierre Ferruit, Webb project scientist with ESA (European Space Agency) and principal investigator for NIRSpec. “Now is time for science, and I am eager to see the first scientific results coming from NIRSpec observations. I have no doubt they will be fantastic. Big thanks to all who made this possible across the years – great job!”
The final mode verified for NIRSpec was the multi-object spectroscopy mode, a key capability that allows Webb to capture spectra, or rainbows of infrared light, from hundreds of different cosmic targets at once. In multi-object spectroscopy mode, NIRSpec can individually open and close about 250,000 small shutters, all just the width of a human hair, to view some portions of the sky while blocking others. By controlling this “microshutter array,” Webb can observe multiple specific targets while reducing interference from others. The confirmation of NIRSpec’s multi-object spectroscopy mode marks the first time this capability has been verified for use from space. It will allow NIRSpec to characterize everything from the faintest objects in the universe to the formation of galaxies and star clusters. All of which leads up to the long awaited release of Webb’s first images in just a few days and the start of consistent science operations.
Conclusion
Many of us have kept track of Webb’s progress over the last few months as the telescope completed its starting tasks. Recently, the JWST has been especially busy as it finishes its commissioning activities and tests in other areas. Thanks to the telescope’s fast progress, we are not long from having access to unique and fascinating information about our universe. We will have to wait and see how it progresses and the impact it has on the space industry.
