STScI is pleased to announce that the spectral resolution of the G130M 1055 and 1096 central wavelengths settings has been substantially increased above the values offered during previous cycles and, when combined with the 1222 setting first offered in Cycle 20, this now allows resolution of 8000 to 12,000 to be obtained at any wavelength between 900 and 1150 Å
(see Figure 5.5
). Users should note, however, that for each of these modes the focus values have been set to optimize the resolution over a limited part of their wavelength range, and it will be necessary to use multiple settings to get the maximum resolution over this full range.
The resolution values quoted here are based on ray-trace models and the actual resolution may be slightly different; however, preliminary comparison with on-orbit test data appears consistent with the predictions of these models. At the 1055 setting, these ray-trace models predict a resolution between 8000 and 10000 on Segment B
of the COS FUV detector between 900 and 970 Å. For the 1096 setting, resolutions between 8000 and 12000 can be obtained between 940 and 1080 Å
. These complement the G130M 1222 central wavelength setting that was first offered in Cycle 20, which provides resolution of 12000 to 15000 between 1067 and 1172 Å. At longer wavelengths, the resolution offered by any of these settings will be inferior to that available with the original complement of G130M central wavelength settings (1291, 1300, 1309, 1318, and 1327).