james webb telescope

The Premier Observatory Of The Next Decade

The James Webb Space Telescope (sometimes called JWST or Webb) is a large infrared telescope with an approximately 6.5 meter primary mirror. Webb successfully launched from ESA's spaceport in French Guiana on December 25, 2021 07:20am EST ( 2021-12-25 12:20 GMT/UTC) .

Webb is the premier observatory of the next decade, serving thousands of astronomers worldwide. It will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System.

Webb was formerly known as the "Next Generation Space Telescope" (NGST); it was renamed in Sept. 2002 after a former NASA administrator, James Webb.

International Collaboration

Webb is an international collaboration between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA). The NASA Goddard Space Flight Center managed the development effort. The main industrial partner is Northrop Grumman; the Space Telescope Science Institute operates Webb after launch.

Innovative Technologies

Several innovative technologies have been developed for Webb. These include a primary mirror made of 18 separate segments that unfold and adjust to shape after launch. The mirrors are made of ultra-lightweight beryllium. Webb’s biggest feature is a tennis court sized five-layer sunshield that attenuates heat from the Sun more than a million times. The telescope’s four instruments - cameras and spectrometers - have detectors that are able to record extremely faint signals. One instrument (NIR Spec) has programmable micro shutters, which enable observation up to 100 objects simultaneously. Webb also has a cryocooler for cooling the mid-infrared detectors of another instrument (MIRI) to a very cold 7 K so they can work.

Launch Vehicle

The James Webb Space Telescope was launched on an Ariane 5 rocket. The launch vehicle and launch site are part of the European Space Agency's contribution to the mission. The Ariane 5 is one of the world's most reliable launch vehicles and was chosen for a combination of reliability (it was the only launch vehicle that met NASA's requirements for launching a mission like Webb) and for the value it brings via our international partnership. Read more about why the Ariane 5 was chosen.

Launch Location

Webb was launched from Arianespace's ELA-3 launch complex at Europe's Spaceport located near Kourou, French Guiana. It is beneficial for launch sites to be located near the equator - the spin of the Earth can help give an additional push. The surface of the Earth at the equator is moving at 1670 km/hr.

Webb Launch Configuration

For the telescope to fit into the rocket, it must fold up. These images show how it fits into the rocket fairing. Images courtesy of ArianeSpace.com.

A Solar Orbit

The James Webb Space Telescope will not be in orbit around the Earth, like the Hubble Space Telescope is - it will actually orbit the Sun, 1.5 million kilometers (1 million miles) away from the Earth at what is called the second Lagrange point or L2. What is special about this orbit is that it lets the telescope stay in line with the Earth as it moves around the Sun. This allows the satellite's large sunshield to protect the telescope from the light and heat of the Sun and Earth (and Moon).

Timeline Of Events After Launch:

In the first hour: The ride to space, solar array deployment, and “free flight.” The Ariane 5 launch vehicle will provide thrust for roughly 26 minutes after a morning liftoff from French Guiana. Moments after second stage engine cut-off, Webb will separate from the Ariane, which will trigger the solar array to deploy within minutes so that Webb can start making electricity from sunshine and stop draining its battery. Webb will quickly establish its ability to orient itself and “fly” in space.

In the first day: Mid-course correction to L2. Ariane will have sent Webb on a direct route to L2, without first orbiting Earth. During the first day, we will execute the first and most important trajectory correction maneuver using small rocket engines aboard Webb itself. We will also release and deploy the high gain antenna to enable the highest available rates of data communication as early as practical.

n the first week: Sunshield deployment. Shortly after we execute a second trajectory correction maneuver, we will start the sequence of major deployments, beginning with the fore and aft sunshield pallets. The next step is separation of the spacecraft bus and telescope by extending the telescoping tower between them. The tower will extend about 2 meters, and it is necessary at this point in the sequence so that the rest of the sunshield deployment can proceed. Next, the sunshield membranes will be unpinned and the telescoping sunshield midbooms will extend – first the port side and then the starboard side – pulling the membranes out with them. The last sunshield deployment step is tensioning of the membranes. In the meantime, other things like radiators will be released and deployed.

In the first month: Telescope deployment, cooldown, instrument turn-on, and insertion into orbit around L2. During the second week after launch we will finish deploying the telescope structures by unfolding and latching the secondary mirror tripod and rotating and latching the two primary mirror wings. Note that the telescope and scientific instruments will start to cool rapidly in the shade of the sunshield, but it will take several weeks for them to cool all the way down and reach stable temperatures. This cooldown will be carefully controlled with strategically-placed electric heater strips so that everything shrinks carefully and so that water trapped inside parts of the observatory can escape as gas to the vacuum of space and not freeze as ice onto mirrors or detectors, which would degrade scientific performance. We will unlock all the primary mirror segments and the secondary mirror and verify that we can move them. Near the end of the first month, we will execute the last mid-course maneuver to insert into the optimum orbit around L2. During this time we will also power-up the scientific instrument systems. The remaining five months of commissioning will be all about aligning the optics and calibrating the scientific instruments.

In the second, third and fourth months: Initial optics checkouts, and telescope alignment. Using the Fine Guidance Sensor, we will point Webb at a single bright star and demonstrate that the observatory can acquire and lock onto targets, and we will take data mainly with NIRCam. But because the primary mirror segments have yet to be aligned to work as a single mirror, there will be up to 18 distorted images of the same single target star. We will then embark on the long process of aligning all the telescope optics, beginning with identifying which primary mirror segment goes with which image by moving each segment one at a time and ending a few months later with all the segments aligned as one and the secondary mirror aligned optimally. Cooldown will effectively end and the cryocooler will start running at its lowest temperature and MIRI can start taking good data too.

In the fifth and sixth months: Calibration and completion of commissioning. We will meticulously calibrate all of the scientific instruments’ many modes of operation while observing representative targets, and we will demonstrate the ability to track “moving” targets, which are nearby objects like asteroids, comets, moons, and planets in our own solar system. We will make “Early Release Observations,” to be revealed right after commissioning is over, that will showcase the capabilities of the observatory.
After six months: “Science operations!” Webb will begin its science mission and start to conduct routine science operations.

Webb's Themes

Early universe :

After the Big Bang, the universe was like a hot soup of particles (i.e. protons, neutrons, and electrons). When the universe started cooling, the protons and neutrons began combining into ionized atoms of hydrogen (and eventually some helium). These ionized atoms of hydrogen and helium attracted electrons, turning them into neutral atoms - which allowed light to travel freely for the first time, since this light was no longer scattering off free electrons. The universe was no longer opaque! However, it would still be some time (perhaps up to a few hundred million years post-Big Bang!) before the first sources of light would start to form, ending the cosmic dark ages. Exactly what the universe's first light (ie. stars that fused the existing hydrogen atoms into more helium) looked like, and exactly when these first stars formed is not known.

Galaxies Over time:

Galaxies show us how the matter in the universe is organized on large scales. In order to understand the nature and history of the universe, scientists study how the matter is currently organized and how that organization has changed through out cosmic time. In fact, scientists examine how matter is distributed and behaves at multiple size scales in our quest for this understanding. From peering into the way matter is constructed at the subatomic particle level to the immense structures of galaxies and dark matter that span the cosmos, each scale gives us important clues as to how the universe is built and evolves.

To unravel the birth and early evolution of stars and planets, we need to be able to peer into the hearts of dense and dusty cloud cores where star formation begins. These regions cannot be observed at visible light wavelengths as the dust would make such regions opaque and must be observed at infrared wavelengths.

Stars, like our Sun, can be thought of as "basic particles" of the Universe, just as atoms are "basic particles" of matter. Groups of stars make up galaxies, while planets and ultimately life arise around stars. Although stars have been the main topic of astronomy for thousands of years, we have begun to understand them in detail only in recent times through the advent of powerful telescopes and computers.

A hundred years ago, scientists did not know that stars are powered by nuclear fusion, and 50 years ago they did not know that stars are continually forming in the Universe. Researchers still do not know the details of how clouds of gas and dust collapse to form stars, or why most stars form in groups, or exactly how planetary systems form. Young stars within a star-forming region interact with each other in complex ways. The details of how they evolve and release the heavy elements they produce back into space for recycling into new generations of stars and planets remains to be determined through a combination of observation and theory.