The months-long process of preparing NASA’s James Webb Space Telescope for science is now complete. All of the seventeen ways or ‘modes’ to operate Webb’s scientific instruments have now been checked out, which means that Webb has completed its commissioning activities and is ready to begin full scientific operations.
Each of Webb’s four scientific instruments has multiple modes of operation, utilizing customized lenses, filters, prisms, and specialized machinery that needed to be individually tested, calibrated, and ultimately verified in their operational configuration in space before beginning to capture precise scientific observations of the universe. The last of all seventeen instrument modes to be commissioned was NIRCam’s coronagraph capability, which works to mostly block incoming starlight by inserting a mask in front of a target star, suppressing the target star’s relatively bright light to increase contrast and enable detection of fainter nearby companions such as exoplanets. NIRCam, or the Near-Infrared Camera, is equipped with five coronagraphic masks — three round masks and two bar-shaped masks — that suppress starlight under different conditions of contrast and separation between the star and its companions.
In addition to capturing detailed imagery of the universe, NIRCam is the observatory’s main wavefront sensor that is used to fine-tune the telescope’s optics. It has this double duty by design due to having a comparatively wide field of view and possessing a suite of special internal optics that enable it to take out-of-focus images of stars and even take ‘selfie’ images of the primary mirror itself. The team was able to start aligning the telescope’s optics even while the observatory was still cooling down, because of NIRCam’s ability to safely operate at higher-than-normal, but still cryogenic, operating temperatures.
“From the moment we first took images with NIRCam to start the telescope alignment process to the checkout of coronagraphy at the end of commissioning, NIRCam has performed flawlessly. Observers are going to be very pleased with the data they receive, and I am extremely happy with how 20 years of work by my team are now realized in amazing performance,” said Marcia Rieke, principal investigator for the NIRCam instrument and regents professor of astronomy, University of Arizona.
Webb’s commissioning process culminates tomorrow on July 12, with the release of the telescope’s first full-color images and spectroscopic data, and the official beginning of its science mission.
-Thaddeus Cesari, NASA’s Goddard Space Flight Center
Three of the four science instruments on NASA’s James Webb Space Telescope have completed their commissioning activities and are ready for science.
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.
This commissioning test image is a subset of a NIRSpec multi-object spectroscopy exposure of a region close to the center of our Milky Way galaxy. NIRSpec’s two detectors and its microshutter arrays were used to pack more than 200 spectra in a single exposure. Each horizontal stripe is a spectrum that scientists will be able to analyze to better understand the composition and properties of the gas found between the stars in this region – for example, through the study of emission lines that show up at small, brighter, slightly tilted vertical lines in these spectra. Credit: NASA/ESA/CSA and the NIRSpec team
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.
NIRSpec was built for ESA by a consortium of European companies led by Airbus Defence and Space, with NASA’s Goddard Space Flight Center in Greenbelt, Maryland, providing its detector and microshutter subsystems.
Out of 17 total instrument modes across Webb’s four instruments, only one mode remains to be verified, for the Near-Infrared Camera (NIRCam). When the team confirms this remaining mode, the months-long process of preparing Webb for science will formally be complete.
Webb’s commissioning process culminates on July 12, with the release of the telescope’s first full-color images and spectroscopic data, and the official beginning of its science mission.
As the Webb team wraps up the final tests for commissioning this week, we are now only days away from the public release of the first images and spectra on July 12! This also means that Webb is moving into the phase of full science operations that includes a highly impressive suite of science programs from the solar system to the distant universe. The entire Webb team is ready to celebrate the long journey to this point and embark on the next few decades of groundbreaking infrared astronomy.
Eric Smith, Webb program scientist at NASA Headquarters in Washington, has been with Webb since its beginnings in the mid-1990s. We asked him to share his thoughts as we finalize commissioning and prepare for the first images release next week:
“Even after working on the program for many years, I’m as excited as everyone else who is anticipating the release of the first beautiful full-color images and data from NASA’s James Webb Space Telescope – an audacious endeavor in partnership with the European and Canadian space agencies. From a professional perspective, I’m thrilled with the mission and the realization that astronomers around the world will receive an amazing new tool to explore space. Webb joins existing Great Observatories, like NASA’s Hubble Space Telescope and Chandra X-ray Observatory, giving scientists ‘eyes’ from Webb’s infrared vision through the visible, ultraviolet part of the spectrum to X-rays. A fantastic new era is upon us as these powerful facilities complement one another to investigate the cosmos.
“Yet, as stunning as these capabilities are, NASA is always looking to the future. Even today, we are constructing the next great observatory that will come after Webb, the Nancy Grace Roman Space Telescope. Unlike the existing facilities, Roman is designed to capture images of huge portions of the sky all at once, allowing scientists to look for very rare and even time-variable phenomena. This impressive survey capability will come online in the latter half of the decade. As if that is not amazing enough, we’ve begun to think about how we might build a telescope specifically designed to image and study nearby exoplanets in ways impossible today even with Webb. All the facilities we currently have, and those in the planning stage, arose from questions ignited by astronomers seeking to answer age-old questions about our universe using previous observatories. What questions might Webb observations raise now that will turn our curiosity to things unimagined? We will soon begin to know how Webb will transform our understanding of the universe.
“On a personal level, my family was recently blessed with the arrival of our first grandchild. Watching her awaken to her surroundings rejuvenates the world for me. Anyone who has been a parent, aunt, uncle, grandparent, or had the fortune to spend time with infants and toddlers may have experienced this joy in seeing the curiosity and interest of someone experiencing fresh and novel sights and sounds. With each blink and head turn, they learn more about the place they live, constantly developing and improving their own conceptions about what different and initially strange things are and how they relate to them. With each blink and head turn, their new perspective recalls for us distant memories when all was new and exciting in the world. These joyful moments of seeing things for the first time through the eyes of a child are experienced at the individual level and in small family gatherings. Rarer are the moments when we can collectively experience this rush of discovery and wonder. The James Webb Space Telescope will give us a fresh and powerful set of eyes to examine our universe.
Blink
The world is about to be new again.”
Part of the Webb team in front of a full-scale model at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in 2005. Credit: NASA
– Eric Smith, Webb program scientist, NASA Headquarters
We are less than one week away from the release of the first full-color images from NASA’s James Webb Space Telescope, but how does the observatory find and lock onto its targets? Webb’s Fine Guidance Sensor (FGS) – developed by the Canadian Space Agency – was designed with this particular question in mind. Recently it captured a view of stars and galaxies that provides a tantalizing glimpse at what the telescope’s science instruments will reveal in the coming weeks, months, and years.
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.
This Fine Guidance Sensor test image 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. The bright star (at 9.3 magnitude) on the right hand edge is 2MASS 16235798+2826079. 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. Credit: NASA, CSA, and FGS team.
“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.
By Patrick Lynch, NASA’s Goddard Space Flight Center, Greenbelt, Md.
The public release of Webb’s first images and spectra is July 12 – now less than two weeks away! The Webb team has confirmed that that 15 out of 17 instrument modes are ready for science, with just two more still to go. As we near the end of commissioning, we wanted to let you know where you can see the first Webb science data and how to participate in the celebration of Webb science! Here are all the ways you can #UnfoldTheUniverse with Webb:
Watch: See the images revealed in real-time and hear from experts about the exciting results on NASA TV at 10:30am Eastern on July 12: https://www.nasa.gov/nasalive
Participate: Attend, virtually or in-person, one of hundreds of official Webb Space Telescope Community Events happening in the next few months! Find an event near you at: https://webbtelescope.org/news/first-images/events
Socialize: Follow along on Twitter, Facebook, and Instagram with @NASA and @NASAWebb using #UnfoldTheUniverse!
Ask: On July 13, ask your questions about these first images and spectra using #UnfoldtheUniverse, and you could see them answered on NASA Science Live at: https://www.nasa.gov/nasasciencelive
We look forward to celebrating the official kickoff of Webb science with you soon!
– Alexandra Lockwood, project scientist for Webb science communications, Space Telescope Science Institute
-Stefanie Milam, Webb deputy project scientist for planetary science, NASA’s Goddard Space Flight Center
-Jonathan Gardner, Webb deputy senior project scientist, NASA Goddard
The second of NASA’s James Webb Space Telescope’s four primary scientific instruments, known as the Mid-Infrared instrument (MIRI), has concluded its postlaunch preparations and is now ready for science.
The last MIRI mode to be checked off was its coronagraphic imaging capability, which uses two different styles of masks to intentionally block starlight from hitting its sensors when attempting to make observations of the star’s orbiting planets. These customized masks allow for scientists to directly detect exoplanets and study dust disks around their host stars in a way that’s never been done before.
Along with Webb’s three other instruments, MIRI initially cooled off in the shade of Webb’s tennis-court-size sunshield to about 90 kelvins (minus 298 degrees Fahrenheit, or minus 183 degrees Celsius). To perform its intended science meant dropping to less than 7 kelvins — just a few degrees above the lowest temperature matter can reach — by using an electrically powered cryocooler. These extreme operating temperatures allow for MIRI to deliver mid-infrared images and spectra with an unprecedented combination of sharpness and sensitivity.
“We are thrilled that MIRI is now a functioning, state-of-the-art instrument with performances across all its capabilities better than expected. Our multinational commissioning team has done a fantastic job getting MIRI ready in the space of just a few weeks. Now we celebrate all the people, scientists, engineers, managers, national agencies, ESA, and NASA, who have made this instrument a reality as MIRI begins to explore the infrared universe in ways and to depths never achieved before,” said Gillian Wright, MIRI European principal investigator at the UK Astronomy Technology Centre, and George Rieke, MIRI science lead at the University of Arizona. MIRI was developed as a partnership between NASA and ESA (European Space Agency), with NASA’s Jet Propulsion Laboratory leading the U.S. efforts and a multi-national consortium of European astronomical institutes contributing for ESA.
One of the James Webb Space Telescope’s four primary scientific instruments, known as the Near-Infrared Imager and Slitless Spectrograph instrument (NIRISS), has concluded its postlaunch preparations and is now ready for science.
The last NIRISS mode to be checked off before the instrument was declared ready to begin scientific operations was the Single Object Slitless Spectroscopy (SOSS) capability. The heart of the SOSS mode is a specialized prism assembly that disperses the light of a cosmic source to create three distinctive spectra (rainbows), revealing the hues of more than 2,000 infrared colors collected simultaneously in a single observation. This mode will be specifically used to probe the atmospheres of transiting exoplanets, i.e., planets that happen to eclipse their star periodically, momentarily dimming the star’s brightness for a period of time. By comparing the spectra collected during and before or after a transit event with great precision, one can determine not only whether or not the exoplanet has an atmosphere, but also what atoms and molecules are in it.
“I’m so excited and thrilled to think that we’ve finally reached the end of this two-decade-long journey of Canada’s contribution to the mission. All four NIRISS modes are not only ready, but the instrument as a whole is performing significantly better than we predicted. I am pinching myself at the thought that we are just days away from the start of science operations, and in particular from NIRISS probing its first exoplanet atmospheres,” said René Doyon, principal investigator for NIRISS, as well as Webb’s Fine Guidance Sensor, at the University of Montreal.
The Image Behind the Spectrum. This is a test detector image from the NIRISS instrument operated in its single-object slitless spectroscopy (SOSS) mode while pointing at a bright star. Each color seen in the image corresponds to a specific infrared wavelength between 0.6 and 2.8 microns. The black lines seen on the spectra are the telltale signature of hydrogen atoms present in the star. NIRISS is a contribution from the Canadian Space Agency (CSA) to the Webb project that provides unique observational capabilities that complement its other onboard instruments. Credit: NASA, CSA, and NIRISS team/Loic Albert, University of Montreal
The Webb team has now approved 10 out of 17 science instrument modes; since last week we added (14) MIRI imaging, (2) NIRCam wide-field slitless spectroscopy, and our final NIRISS mode, (10) single-object slitless spectroscopy. As we ramp down the final commissioning activities, some openings in the schedule have appeared. The team has started to take some of the first science data, getting it ready to release starting July 12, 2022, which will mark the official end of commissioning Webb and the start of routine science operations.
This week we asked Tracy Beck, Tony Keyes, and Charles Proffitt, all NIRSpec instrument scientists at the Space Telescope Science Institute (STScI), to tell us about how Webb gets the targets lined up for observation with the NIRSpec instrument.
“The Near-Infrared Spectrograph (NIRSpec) is the instrument on the Webb telescope that observes spectra of astrophysical and planetary objects at near infrared wavelengths. The NIRSpec Grating Wheel Assembly (GWA) uses diffraction gratings or a prism to separate the wavelengths of incoming light into a spectrum. Study of the intensity or brightness of light across the wavelengths can provide key diagnostic information about the nature of various objects across the universe – from extrasolar planets around distant stars, to faint galaxies at the edge of the universe, and objects in our own solar system. NIRSpec will observe them all.
“The WATA process takes an image of a single astrophysical target through the wide ‘S1600A1’ fixed slit to determine its position on the sky as seen through the instrument. The software on-board the Webb telescope autonomously calculates an offset to move the telescope and accurately position either this target or another nearby target at the optimal location in NIRSpec to spread the light into a spectrum. During instrument commissioning, the excellent performance of WATA has been demonstrated on the sky for all four of the NIRSpec observing modes: integral field unit imaging spectroscopy, fixed slit spectroscopy, bright object time series, and multi-object spectroscopy.
“NIRSpec includes the multi-object spectroscopy (MOS) mode, where spectra of dozens to hundreds of science targets will be observed at one time. This requires specialized apertures that can be configured by opening and closing specific tiny doorways (microshutters) of the 250,000 total that are arranged in a rectangular grid in the MSA, allowing individual targets to be observed with little contamination from nearby objects or background light.
A simulation of the NIRSpec MSA-based Target acquisition process, demonstrated on the NIRSpec Sharpness Check Image. NIRSpec uses “Reference Stars” observed through the fixed slits in the central area and the MSA to carefully correct the small x – y and position angle (rotation) offsets of the observatory so that the science targets will be aligned properly with their shutters across the entire NIRSpec MOS field of view. Credit: NASA, ESA, and the NIRSpec Team
“During MSATA, a set of target acquisition reference stars are imaged through open microshutters. The stellar positions are calculated autonomously by Webb’s on-board software and used to correct the initial spacecraft pointing and position angle (rotation). To allow accurate correction of the observed spectra for the centering of each source in its shutter, this process must place the MOS science targets across the full span of the NIRSpec field of view with an accuracy of 1/10th of a NIRSpec shutter width – or just 20 milli-arcseconds on the sky (the approximate size of a bumblebee, 1.5 cm, viewed from 150 km away!).
An optimized high-resolution simulation of a star at wavelength 2 microns seen through a NIRSpec microshutter (100×200 microns in size). For proper intensity estimation of NIRSpec science spectra, we need to accurately know the positioning of the targets to within 1/10th of the shutter width. Credit: NASA, ESA, and the NIRSpec Team
“The recent confirmation of NIRSpec target acquisition and additional work on the four science modes primes the NIRSpec team for our last activities of commissioning. We cannot wait to see the first NIRSpec science observations coming this summer!
“NIRSpec was built for the European Space Agency (ESA) by a consortium of European companies led by Airbus Defence and Space (ADS) with NASA’s Goddard Space Flight Center providing its detector and microshutter subsystems.”
–Tracy Beck, AURA Observatory and Webb NIRSpec Instrument Scientist, STScI; Tony Keyes AURA Scientist and Webb NIRSpec Instrument Scientist, STScI; and Charles Proffitt, AURA Observatory and Webb NIRSpec Instrument Scientist, STScI
Jonathan Gardner, Webb deputy senior project scientist, NASA Goddard
Stefanie Milam, Webb deputy project scientist for planetary science, NASA Goddard
This week we are featuring MIRI’s medium-resolution spectroscopy mode and sharing our first spectroscopic engineering data. We asked two of the MIRI commissioning team members – David Law, of the Space Telescope Science Institute (STScI), and Alvaro Labiano, of the Centro de Astrobiologίa (CAB) – to explain this mode to us:
“One of Webb’s most complex instrument modes is with the MIRI Medium Resolution Spectrometer (MRS). The MRS is an integral-field spectrograph, which provides spectral and spatial information simultaneously for the entire field of view. The spectrograph provides three-dimensional ‘data cubes’ in which every pixel in an image contains a unique spectrum. Such spectrographs are extremely powerful tools to study the composition and kinematics of astronomical objects, as they combine the benefits of both traditional imaging and spectroscopy.
“The MRS is designed to have a spectral resolving power (observed wavelength divided by the smallest detectable wavelength difference) of about 3,000. That is high enough to resolve key atomic and molecular features in a variety of environments. At the highest redshifts, the MRS will be able to study hydrogen emission from the first galaxies. At lower redshifts, it will probe molecular hydrocarbon features in dusty nearby galaxies and detect the bright spectral fingerprints of elements such as oxygen, argon, and neon that can tell us about the properties of ionized gas in the interstellar medium. Closer to home, the MRS will produce maps of spectral features due to water ice and simple organic molecules in giant planets in our own solar system and in planet-forming disks around other stars.
“In order to cover the wide 5 to 28 micron wavelength range as efficiently as possible, the MRS integral field units are broken up into twelve individual wavelength bands, each of which must be calibrated individually. Over the past few weeks, the MIRI team (a large international group of astronomers from the USA and Europe) has been focusing primarily on calibrating the imaging components of the MRS. They want to ensure that all twelve bands are spatially well aligned with each other and with the MIRI Imager, so that it can be used to place targets accurately into the smaller MRS field of view. We show some early test results from this alignment process, illustrating the image quality achieved in each of the twelve bands using observations of the bright K giant star HD 37122 (located in the southern sky near the Large Magellanic Cloud).
These are the first engineering data cubes for each of the twelve MRS spectral bands, illustrating the astrometric registration and image quality for observations of HD 37122. In each panel the dashed cyan circle shows a 1 arcsecond radius region around the expected location of the star in celestial coordinates. While the star is bright at short wavelengths it fades toward longer wavelengths, where the MRS also detects thermal emission from Webb’s primary mirror. Credit: NASA, ESA, and the MIRI Consortium.
“Once the spatial alignment and image quality of the several bands are well characterized, the MIRI team will prioritize calibrating the spectroscopic response of the instrument. This step will include determining the wavelength solution and spectral resolution throughout each of the twelve fields of view using observations of compact emission-line objects and diffuse planetary nebulae ejected by dying stars. We show the exceptional spectral resolving power of the MRS with a small segment of a spectrum obtained from recent engineering observations of the active galactic nucleus at the core of Seyfert galaxy NGC 6552. Once these basic instrument characteristics are established, it will be possible to calibrate MRS so that it is ready to support the wealth of Cycle 1 science programs due to start in a few short weeks.”
This portion of the MIRI MRS wavelength range shows engineering calibration data obtained of the Seyfert galaxy NGC 6552 (red line) in the constellation Draco. The strong emission feature is due to molecular hydrogen, with an additional weaker feature nearby. The blue line shows a lower spectral resolution Spitzer IRS spectrum of a similar galaxy for comparison. The Webb test observations were obtained to establish the wavelength calibration of the spectrograph. Credit: NASA, ESA, and the MIRI Consortium.
—David Law, AURA associate astronomer, STScI
—Alvaro Labiano Ortega, Telespazio UK for ESA, CAB (Consejo Superior de Investigaciones Cientificas – Instituto Nacional de Técnica Aeroespacial)
—Jonathan Gardner, Webb deputy senior project scientist, NASA Goddard
—Alexandra Lockwood, project scientist for Webb science communications, STScI
—Stefanie Milam, Webb deputy project scientist for planetary science, NASA Goddard
In the lead-up to the release of Webb’s first full-color images and spectroscopic data on July 12, the Webb team is now in the last phase of commissioning the science instruments. The first two instrument modes, NIRCam imaging and NIRISS imaging, have been declared ready for science; watch the “Where is Webb” page as the team works their way through the other 15 instrument modes.
After commissioning is finished, the fun – and discoveries – will start: implementing the hundreds of peer-reviewed science programs that have been selected for Webb’s first year. The area on the sky that Webb can see at any given time is called the field of regard. Deciding which observations to make on which day is a complicated process designed to optimize observational efficiency and manage the observatory’s resources. We asked Christine Chen, science policies group lead at the Space Telescope Science Institute (STScI), to tell us how Webb’s schedule comes together.
“Webb will soon transition from commissioning to regular operations when Webb’s time will be devoted to scientific observations.
“Webb’s first year of observations (Cycle 1) has already been selected. There are three types of scientific programs planned: General Observer (GO), Guaranteed Time Observer (GTO), and Director’s Discretionary Early Release Science (DD-ERS). The GO and DD-ERS programs include scientists from all over the world whose programs were selected in a dual anonymous peer review process. The GTO programs are led by scientists who made key contributions to the development of the observatory.
“All of the observations in approved Cycle 1 programs are available for scheduling at the beginning of regular operations. However, the DD-ERS observations have been given priority during the first five months because the DD-ERS programs are designed to help the scientific community understand Webb’s performance for typical scientific observations as soon as possible.
“Webb’s Long Range Planning Group (LRPG) has created a 12-month+ Observing Plan, including all of the approved observations, with the goal of creating the most efficient plan. Even though a Webb Observing Cycle is defined as a 12-month period, more than one year’s worth of observations have been approved for Cycle 1. This over-subscription will enable a smooth transition between cycles as well as provide a repository of flight-ready observations that can be moved earlier, if a window opens up. At the current time, before the start of Cycle 1, the Observing Plan is not yet completely filled. This allows the schedulers to accommodate late-breaking Targets of Opportunity (ToOs) and Director’s Discretionary (DD) programs. ToOs and DDs typically include ’unplanned for‘ events such as interstellar comets, gravitational wave sources, and supernovae.
“During regular operations, the Short Term Scheduling Group (STSG) will create detailed weekly schedules to be executed by the observatory during the following week. These Short Term Schedules will take into account several factors, including observing constraints, data volume limits for the onboard data recorder, momentum buildup on the observatory’s reaction wheels, etc. At the beginning of each week, the Flight Operations Team will uplink the week’s Short Term Schedule to Webb. At the end of each week, the LRPG will update the Observing Plan to reflect the actual programs that were executed, and to identify priorities for the following week. In this way, the LRPG and STSG work synergistically together throughout the observing cycle to maximize the scientific return from the observatory.”
— Christine Chen, Webb science policies group lead, STScI,
and David Adler, Long Range Planning Group lead, STScI
— Jonathan Gardner, Webb deputy senior project scientist, NASA’s Goddard Space Flight Center
