GMOS-N B480 unavailable from July 3 (HST) for ~3 weeks

The spring and bearings securing the GMOS-N B480 grating within its frame have not been functioning properly and need replacement. The net effects have been possible wavelength zeropoint shifts depending on the gravity vector. These shifts have not been a major concern for science quality, since they can typically be calibrated out via the on-sky arcs or via skylines, per these instructions. Although we had initially hoped to replace the B480 components during the fall shutdown, staffing considerations have caused us to move it earlier. After reviewing the current queue status (including ToO templates) and engOps, we’ve decided to proceed with the work during the upcoming bright time.