During the afternoon of May 25th, the SX M2 adaptive secondary (ASM) was removed and the rigid secondary installed in its place. The coating on the SX ASM had been degrading, and it is being sent to Italy for recoating. Lab measurements indicated relative reflectivities of the SX ASM to the rigid secondary of 0.54, 0.66 and 0.72, at 4200, 5220 and 6500 angstroms, respectively.

After the secondary swap, spectrophotometric standard stars and a photometric imaging field were observed with MODS, and the zeropoints and signal-to-noise tracks are being updated.

The sensitivity of MODS1 shows an improvement consistent with the reflectivity measurements. In the blue channel, it was most dramatic and brings MODS1 almost up to its level at commissioning and to the level of MODS2. However, in the red channel there was less improvement and the sensitivity of MODS1 Red remains below its level at commissioning and that of MODS2 Red. The relative flux ratios of MODS1/MODS2 are now ~0.9-1 in the blue and ~0.5-0.6 in the red.