Open Access
Table 2
Optical properties of the flight model of the NISP grisms.
| Parameters | Red grisms | Blue grism BGS000 | |
|---|---|---|---|
| RGS000/180 | RGS270 | ||
| FWHM bandpass [nm] | 1206−1892 | 926−1366 | |
| Prism angle A | 2″.145±30″ | 1°.77 ± 30″ | |
| Mean groove height H [µm] | 3.16 ± 0.08 | 2.25 ± 0.1 | |
| Mean blaze angle β | 2°.49 | 2°.48 | 1°.94 |
| Mean pitch P of grooves [µm] | 72.55 | 72.96 | 66.22 |
| Groove density [grooves/mm] | 13.75 | 13.7 | 15.1 |
| Averaged 0st-order transmission | 2.4% | 2.3% | 2.0% |
| Averaged 1st-order transmission | 84.7% | 84.3% | 84.2% |
| Un-deflected wavelength [µm] | ≃1.2 | ≃ 0.9 | |
| Spectral resolution |dλ/dx|[nm/pix] | 1.372 | – | 1.239 |
| Resolving power R for 0″.5 diameter object | >480 | – | >400 |
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