It’s Done! JWST Successfully Deployed

It’s Done! JWST Successfully Deployed

Exactly two weeks after launch, deployment of the James Webb Space Telescope was completed today as the last wing of the 18-segment mirror swung into place. Several steps remain in the commissioning process before scientifically-usable data are obtained, but the telescope unfolded into its operational configuration with impressive precision.

JWST is the largest and most expensive space telescope ever built. At 6.5 meters (21.3 feet) in diameter, it is too big to fit into the Ariane 5 rocket that sent it on its journey so had to be folded and then unfolded once in space.

The final step was achieved today when the second of two wings of the gold-plated primary mirror locked into place. Twelve of the 18 hexagonal segments are on the main structure, then three each on two side wings. The port wing was released yesterday. Today, the starboard side.

Although there are no cameras on JWST to observe the deployment, NASA had an “Observatory Visualization Tool,” developed by Raytheon, that showed each step using real-time telemetry received from JWST.  If one could see it in person, this is how it looks now with the gold mirror bright against the black sunshade that shields it from the light of the Sun, Earth and Moon. One of the legs of the tripod structure supporting the secondary mirror crosses in front.

Front view of the James Webb Space Telescope from NASA’s real-time Observatory Visualization Tool following deployment of the final segment, the primary mirror’s starboard wing (with three of the 18 hexagonal segments), January 8, 2022.
Side view of the James Webb Space Telescope, fully deployed, as shown in the real-time Observatory Visualization Tool, showing the relative positions of the Sun and Earth behind the 5-layer sunshield that protects JWST’s instruments from their heat and light.

The telescope is a joint project among NASA, the European Space Agency, and the Canadian Space Agency. Collectively they spent approximately $10 billion on its development: NASA, $8.8 billion; ESA, 700 million Euros ($860 million); CSA, $200 million Canadian ($160 million U.S.). Operations costs will be on top of that.

Over the past two weeks JWST has travelled 74 percent of the distance to its destination, the Sun-Earth Lagrange Point-2 (SEL-2), 1.5 million kilometers (1 million miles) away.

Although deployment is complete, more work remains before scientists start getting the data they eagerly await.

JWST still has to reach SEL-2 and enter into a “halo orbit” around that point in space. That will occur on January 23, Day 29 after launch, ending the “29 Days on the Edge” NASA uses to describe this phase.

The nail-biting deployment sequence went so smoothly it is easy to forget how much could have gone wrong. JWST had 344 single points of failure when it left the Earth — pins that had to release, latches to lock into place, and a host of other mechanisms to perform as planned. The primary mirror had 178 release mechanisms itself. Mike Menzel, Mission Systems Engineer at NASA’s Goddard Space Flight Center, which manages the program, told reporters today that just 49 single point failures remain. They are common to most spacecraft, such as the propulsion system, and will remain throughout the lifetime of the telescope.

The primary and secondary mirrors need to be painstakingly adjusted to provide a single, sharp image instead of 18 fuzzy ones. Each of the primary mirror’s 18 gold-plated hexagons, 1.5 meters (5 feet) in diameter, has seven actuators on its back to change the shape. The secondary mirror also has actuators, a total of 132 all together on both. Lee Feinberg, Webb Optical Telescope Element Manager at NASA Goddard, estimates the process of aligning the mirrors will take three and a half months.

Infrared light is collected by the James Webb Space Telescope’s gold-plated primary mirror, reflected into the secondary mirror at the end of the tripod-structure (covered in black) and directed back into the four instruments in the center of the primary mirror. Credit: NASA

At the same time, the entire observatory and its four instruments must cool down to their operating temperatures. JWST will study the universe in infrared (heat) wavelengths, so the instruments must be very, very cold.

The Mid-Infrared Instrument (MIRI) provided jointly by NASA and the European Consortium (led by the U.K.) with ESA must be kept at 7 Kelvin (-447°F/-266°C). The Near-Infrared Camera (NIRCam) provided by the University of Arizona, the Near-Infrared Spectrograph (NIRSpec) provided by ESA, and Fine Guidance Sensor/Near InfraRed Imager and Slitless Spectrograph (FGS/NIRISS) provided by CSA operate at 40 K (-387°F/-233°C).

NASA estimates it will take six months before all of that commissioning is done and usable scientific data collected. The telescope will be looking at stars during that period of time, but NASA does not plan to release any of those fuzzy images. Jane Rigby, Webb Operations Project Scientist at NASA Goddard said at today’s media briefing they will wait until they have “wow” images that will “showcase what this telescope can do” as they begin science operations. They will show what “all four science instruments” can do and “really knock everybody’s socks off.”

Scientists from around the world can send in proposals to use JWST every year. The Space Telescope Science Institute (STScI) in Baltimore, MD operates JWST as well as the Hubble Space Telescope and oversees the selection process. Proposals are rated by panels of experts who do not know the identities of the applicants. They make their judgments based on the relative merit of the science to be achieved and whether JWST is the best instrument to collect the data.

NASA’s Hubble Space Telescope, which just passed the 1-billion second mark of operations after 31 years in orbit. Credit: NASA

Rigby said today that about 1,000 proposals were received for this first cycle and 300 were chosen. Although some scientists want to make observations using both JWST and Hubble none are in this first round, but could be next time. STScI is managed by the Association of Universities for Research in Astronony (AURA). AURA’s Vice President for Science Heidi Hammel said scientists using Hubble already have been preparing for the day when JWST was available by collecting complementary data.

Hubble just passed its 1-billion second mark of operations on January 1, 2022. JWST is often described as a successor or replacement for Hubble, but they are quite different. Hubble observes the universe mostly in the visible wavelengths and a little bit into the ultraviolet and near-infrared bands. JWST is all infrared. Hubble is in Earth orbit, JWST a million miles away. Hubble is 2.4 meters (8 feet) in diameter; JWST is 6.5 meters in diameter and 100 times more sensitive than Hubble. They are more like companions.

For now at least. Though it was launched 31 years ago, most of Hubble is younger than that because five space shuttle crews paid visits and replaced most of its parts and installed new instruments. Still, how much longer it will operate is an open question. The last servicing mission was in 2009 and the shuttle program ended in 2011 so cannot go back.

JWST is just beginning its life in space. Officially, the design lifetime is 5 years, but it was launched with sufficient fuel for 10 years and could last longer. Europe’s Ariane 5 rocket put it on such a precise trajectory that less fuel than planned was needed for the two mid-course corrections that already took place. The final course correction is on January 23 to get into the SEL-2 halo orbit. Menzel said today that is a minor engine burn and JWST will essentially fall into that orbit. He anticipates there might be enough fuel for “roughly” 20 years of operations, quickly adding that is “TBD.”

Other factors, such as how many micrometeorid hits the sunshield can withstand and how long MIRI’s coolant holds out will also determine the lifetime. But that bridge will not be crossed for many years.

Senator Barbara Mikulski, D-Maryland, retired. Credit: Johns Hopkins University

JWST’s journey to today began in 1995. It is years late and billions over budget. NASA Administrator and former U.S. Senator Bill Nelson paid tribute today to his retired Senate colleague Barbara Mikulski without whose steadfast support JWST might not have survived. He said he “called her personally to thank her” and “indeed, this is a proud day for her, too.”

A powerful member of the Senate Appropriations Committee from Maryland, home to NASA Goddard, Mikulski protected the program during difficult times, demanding an independent review in 2010 and then supporting its rebaselining by getting the money it needed. She told a Goddard auditorium full of JWST workers in 2014 that she “saved you from the Tea Party” that “was seeking quick fixes to cut the budget” and had its eye on JWST, then estimated to cost $8 billion.

She retired in 2016 and other members of Congress took up the mantle of defending JWST as costs rose even more. But the tough love meted out was aimed at NASA and prime contractor Northrop Grumman, not JWST itself. Bedazzled by the promise of breakthrough scientific discoveries, JWST was deemed “worth the wait.”

Those scientific discoveries will be some time in the making, but today’s exuberance suggests that memories of schedule delays and cost overruns will soon be forgotten.

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