In-flight performance of the NIRSpec micro shutter array
Tim Rawle, Giovanna Giardino, David E. Franz, Robert Rapp, Maurice te Plate, C. Zincke, Yasin M. Abul-Huda, Catarina Alves de Oliveira, Katie Bechtold, Tracy L. Beck, Stephan M. Birkmann, Torsten Böker, Ralf Ehrenwinkler, Pierre Ferruit, Dennis Garland, P. Jakobsen, Diane Karakla, Hermann Karl, C. D. Keyes, Robert Koehler, Nimisha Kumari, Nora Lützgendorf, Elena Manjavacas, A. P. Marston, S. H. Moseley, Peter Mosner, James Muzerolle, P. Ogle, Charles Proffitt, Elena Sabbi, M. Sirianni, G. M. Wahlgren, Emily Wislowski, Raymond H. Wright, Chi Rai Wu, Peter Zeidler
Abstract
The NIRSpec instrument on the James Webb Space Telescope (JWST) brings the first multi-object spectrograph (MOS) into space, enabled by a programmable Micro Shutter Array (MSA) of ∼250,000 individual apertures. During the 6-month Commissioning period, the MSA performed admirably, completing ∼800 reconfigurations with an average success rate of ∼96% for commanding shutters open in science-like patterns. We show that 82.5% of the unvignetted shutter population is usable for science, with electrical short masking now the primary cause of inoperable apertures. In response, we propose a plan to recheck existing shorts during nominal operations, which is expected to reduce the number of affected shutters. We also present a full assessment of the Failed Open and Failed Closed shutter populations, which both show a marginal increase in line with predictions from ground testing. We suggest an amendment to the Failed Closed shutter flagging scheme to improve flexibility for MSA configuration planning. Overall, the NIRSpec MSA performed very well during Commissioning, and the MOS mode was declared ready for science operations on schedule.