Webb’s NIRCam Instrument Is Ready for Launch

In Kourou, Webb went through a thorough checkout called the Comprehensive Systems Test (#6). The test included turning on all of the room-temperature electronics and a test of the mirror actuators that will be used to align the mirror segments during commissioning. The tests went very well, and the next time we move the mirrors, they will be in space! The Near-Infrared Camera (NIRCam) plays a critical role in that process, and Marcia Rieke, scientific lead for the instrument at the University of Arizona, shares her look ahead for the next several months:

"The 20-year journey that has taken NIRCam, the near-infrared camera for the James Webb Space Telescope, from a concept to reality will culminate on December 18 with a ride on an Ariane 5 rocket. One of Webb's major science goals is the detection of the first galaxies to form after the big bang. NIRCam was built with this goal in mind, and the NIRCam team is using much of their observing time to achieve this goal. During the last few years the team has built on Hubble discoveries to simulate what Webb will see. The team can hardly wait to compare the real data to the simulation-which will tell us immediately what the real universe has produced.

"The launch will be scary, as rocket launches always are for those who have a delicate instrument atop the rocket, but confidence is very high that the telescope and instruments will reach orbit safely. And NIRCam is critical for what happens in the months after we get there. About 35 days after launch will be needed for NIRCam and the telescope to cool enough to first turn NIRCam on. The excitement will continue to build as NIRCam takes the data used to corral and align the 18 segments of the primary mirror. The segments will be higgledy-piggledy when they are lifted off the mounts used for safe stowage against the launch motions. Modeling the detailed motions of spacecraft parts during launch is essentially impossible, so the NIRCam data will show the engineers where the mirror segments are located. Careful measurement of the 18 star images, the same star seen reflected off each of the mirror segments, will provide the data needed to generate the commands for moving the mirrors into alignment. These data will not be valuable scientifically, but the NIRCam team will be jumping for joy to see them as they will be the first indications that the telescope and NIRCam can work together. After celebrating the first focused star data, the NIRCam team will have to wait several more months before the telescope and cameras are ready to make the observations showing the most distant galaxies. But after 20 years, waiting a few months when one knows that everything is working shouldn't be too bad."

-Marcia Rieke, principal investigator for the NIRCam instrument and professor of astronomy, University of Arizona

By Jonathan Gardner, Webb deputy senior project scientist, NASA's Goddard Space Flight Center

And Alexandra Lockwood, project scientist for Webb science communications, Space Telescope Science Institute