next up previous contents
Next: Calibration Lamp Up: Spectrometer Previous: Aperture Wheel Assembly

Diffraction Grating

The diffraction grating is fabricated out of stainless steel so that its radius of curvature will expand and contract at the same rate as the spectrometer housing and thus maintain proper focus. The grating characteristics are given in Table 1-1, and it is shown in cross section in Figure 2-4. It was ruled holographically on an optical master and then replicated onto the stainless steel blank. For Astro-2, the grating has been coated with silicon carbide and is about 80$\%$ more efficient than the osmium-coated grating used on Astro-1.