13.3 Gratings

For each COS grating, we present the resolving power, dispersion, plate scale, the wavelength range covered at each central wavelength setting and FP-POS position, sensitivities, effective areas, and a tool for estimating S/N. Advice on use is provided where appropriate.

Note that the quoted sensitivities are estimates for mid-Cycle 23 (April 2016). The COS ETC will be updated as the instrumental sensitivity evolves. Users should be aware that the BOA is not well calibrated below 1200 Å, and is an Available-but-Unsupported mode (See Section 5.13).

Wavelengths in this handbook, and in COS data products, are always measured in vacuum.