The current R400 grating—one of GMOS-N’s most frequently used—is as old as the instrument itself, and the GMOS-N team has noted significant throughput degradation. A new R400 has been procured and is in the final stages of testing. We will publish a throughput comparison as soon as we had a chance to obtain the on-sky specphot data.

Our current plan is to switch over to the new R400 on August 1 (HST), coinciding with the start of the 2025B semester. This timing will help minimize the number of programs affected by the change.