JWST Sunshield Deployment Moving Quickly

JWST Sunshield Deployment Moving Quickly

After a short break for the team in charge of unfolding the James Webb Space Telescope, work began today on tensioning the sunshield that will protect the sensitive instruments from the heat and light of the Sun. By evening, three of the five layers were successfully in place, an “awesome” achievement.

The $10 billion space telescope continues its journey to the Sun-Earth Lagrange Point-2 (SEL-2) a million miles (1.5 million kilometers) from Earth as one after another piece falls into place. The 6.5-meter (21.3-foot) diameter telescope was too big to fit into the Ariane 5 rocket that lofted it into space, so it was folded and now must be unfolded into its operational configuration.

Everything has been going very well since launch on Christmas Day.

The team at the Space Telescope Science Institute (STScI) in Baltimore, MD that operates JWST took a well deserved break on New Year’s Day after five days commanding the telescope to unfurl step by step. They spent yesterday learning more about how the observatory behaves now that it is in space instead of in Earth-based laboratories and engineers made a few adjustments to the power system and made sure the motors needed for tensioning the sunshield were not overheating.

Amy Lo, the vehicle engineering lead at prime contractor Northrop Grumman, told reporters today that the telescope was reoriented in space so the motors were pointed away from the Sun after they got “a little bit high.” Now they are “nice and cool.”

The proof of the pudding was in the tensioning as three of the five layers were successfully stretched into shape over the next several hours. NASA JWST Project Manager Bill Ochs said at today’s media briefing that it would take two-three days for all five layers to be expanded, but by this evening three of the five were done.

The first layer, closest to the Sun, was pulled taut by 3:48 pm ET.  Work on the second layer began at 4:09 pm ET and took 74 minutes, followed by the third layer starting at 5:48 pm ET and lasting 71 minutes.

The 5-layer sunshield, the size of a tennis court, for the James Webb Space Telescope during testing at Northrop Grumman. Credit: NASA

Tensioning of the final two layers is planned tomorrow.

James Cooper, NASA’s sunshield manager, said tensioning was “the hardest part to test on the ground, so it feels awesome to have everything go so well today.”

JWST will study the universe in infrared (heat) wavelengths, looking back in time to the beginning of the universe more than 13.5 billion years ago. The instruments must be kept very cold. The Mid-InfraRed Instrument (MIRI) operates at 7°Kelvin  (-447°F/-266°C). The others, NIRSpec, NIRCam, and FGS/NIRSS, operate at 40°K (-387°F/-233°C). The sunshield’s job is protecting them from the heat of the Sun.

Illustration of the James Webb Space Telescope after all five sunshield layers are deployed. Credit: NASA

Once all five layers are expanded, the telescope will be ready for the next steps. JWST has 344 single points of failure and Ochs said 70-75 percent of that risk will be retired by the time the sunshield is fully tensioned. But the two wings of the 18-segment mirror still must be released along with several other major deployments. The timeline is flexible, but could be done by the end of this weekend.

Illustration of the James Webb Space Telescope in its fully deployed configuration. Credit: NASA

But it will still take another two weeks for JWST to reach its destination, a point in space where the gravitational effects of the Earth and Sun balance each other enough that the telescope can enter a “halo orbit” around that point using very little fuel.

JWST is a joint project among NASA, the Canadian Space Agency, and the European Space Agency.

ESA provided the launch at no cost to NASA and Europe’s Ariane 5 rocket placed it onto such a precise trajectory that less fuel than expected was needed for the first two mid-course corrections. NASA now anticipates there will be sufficient fuel for more than 10 years of operations, not just the 5 years in NASA’s design life estimate. NASA JWST program director Greg Robinson hesitated today to put a number on how many more than 10 years, noting they will not know until commissioing of the telescope is complete and a final mid-course correction is made.

But the scientists clearly are elated at the possibilities. It has taken more than 25 years to get to this point on a project that is billions over budget. They want as many years of observing time as possible. NASA estimates the first scientifically-usable umage will be obtained about 6 months after launch, once the observatory and its instruments cool down to operating temperatures and the mirror is fine-tuned.

NASA provided the spacecraft that houses all four instruments. The Near-Infrared Camera (NIRCam) was provided by the University of Arizona. The Mid-Infrared Instrument (MIRI) was provided jointly by NASA and the European Consortium (led by the U.K.) with ESA. ESA also provided the Near-Infrared Spectrograph (NIRSpec). Canada provided the Fine Guidance Sensor/Near InfraRed Imager and Slitless Spectrograph (FGS/NIRISS).

All in all, the development cost for JWST is about $10 billion. NASA spent $8.8 billion, Canada $200 million Canadian ($160 million U.S.), and ESA about 700 million Euros ($860 million), though ESA accounts for costs differently so that figure is not directly comparable to NASA’s (European scientists’ salaries are paid by their home institutions, for example, not by ESA). ESA also provided the launch.

NASA’s estimate for 5 years of operations is $900 million, for a total investment of $9.7 billion through that period of time. Additional funds will be needed for any extension beyond that, a bridge to be crossed in the future.

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