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Arxiv: On-orbit Degradation of the JWST/NIRSpec Micro-Shutter Array: Multiplexing and Target Acquisition Published: 5/7/2024 8:59:13 PM Updated: 5/7/2024 8:59:13 PM

Paper abstract: A statistical analysis of the impact of the diminishing number of operationalshutters experienced by the JWST/NIRSpec Micro Shutter Array sinceCommissioning is presented. It is shown that the number of high priorityscience targets that NIRSpec is able to observe simultaneously has so fardecreased by 3.1%. Of greater concern, however, is NIRSpec's diminished abilityto carry out autonomous MSATA target acquisition, which is more sensitive tothe loss of shutters than is the multiplexing. In the flagship case of MSAobservations of deep fields, the number of pointings at which it is notpossible to reach the required minimum number of 5 Valid Reference Stars hasincreased from 4.9% to 6.3% and is beginning to become noticeable. Similarly,the number of higher risk target acquisitions that need to be carried out withfewer than the maximum allowed number of 8 Reference Stars has grown from 27%to 31%.