5.10	Wavelength Settings and Ranges

Table 5.4 and Table 5.5 show the wavelength ranges recorded on the detectors for each valid combination of grating and central-wavelength setting at the nominal FP-POS=3 position (Section 5.8.2). The wavelength ranges spanned at other FP-POS settings may be estimated using the FP-POS step values provided in Chapter 13. Note, however, that uncertainties in the positioning of the Optics Select Mechanisms (Section 3.1.3) correspond to about half of an FP-POS step. These wavelength ranges are subject to change as the instrumental calibration evolves. The most recent measurements are available from the COS Web site.

Table 5.4: Wavelength Ranges for FUV Gratings for FP-POS=3

Grating	Central wavelength setting (Å)1	Recorded wavelengths2
		Segment B	Segment A
G130M	1055	899 – 1040	1055 – 1196
	1096	940 – 1080	1096 – 1236
	1222	1067 – 1207	1223 – 1363
	1291	1134 – 1274	1291 – 1431
	1300	1144 – 1283	1300 – 1441
	1309	1154 – 1294	1309 – 1450
	1318	1163 – 1303	1319 – 1460
	1327	1172 – 1313	1328 – 1469
G160M	1577	1386 – 1559	1577 – 1751
	1589	1397 – 1571	1589 – 1762
	1600	1409 – 1581	1601 – 1774
	1611	1420 – 1594	1612 – 1786
	1623	1432 – 1606	1625 – 1798
G140L	1105	HV OFF	1118 – 22513
	1280	<900 – 1165	1280 – 23913

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1

The central wavelength is (approximately) the shortest wavelength recorded on segment A.

2

All wavelength ranges quoted here are approximate, due to uncertainties in the position of the OSM1 mechanism.

3

G140L spectra are flux calibrated up to 2150 Å. At longer wavelengths, second-order light may be present (Section 5.1.3).

Table 5.5: Wavelength Ranges for NUV Gratings for FP-POS=3

Grating	Central wavelength setting (Å)1	Recorded wavelengths
		Stripe A	Stripe B	Stripe C
G185M	1786	1670 – 1705	1769 – 1804	1868 – 1903
	1817	1701 – 1736	1800 – 1835	1899 – 1934
	1835	1719 – 1754	1818 – 1853	1916 – 1951
	1850	1734 – 1769	1833 – 1868	1931 – 1966
	1864	1748 – 1783	1847 – 1882	1945 – 1980
	1882	1766 – 1801	1865 – 1900	1964 – 1999
	1890	1774 – 1809	1872 – 1907	1971 – 2006
	1900	1783 – 1818	1882 – 1917	1981 – 2016
	1913	1796 – 1831	1895 – 1930	1993 – 2028
	1921	1804 – 1839	1903 – 1938	2002 – 2037
	1941	1825 – 1860	1924 – 1959	2023 – 2058
	1953	1837 – 1872	1936 – 1971	2034 – 2069
	1971	1854 – 1889	1953 – 1988	2052 – 2087
	1986	1870 – 1905	1969 – 2004	2068 – 2103
	2010	1894 – 1929	1993 – 2028	2092 – 2127
G225M	2186	2070 – 2105	2169 – 2204	2268 – 2303
	2217	2101 – 2136	2200 – 2235	2299 – 2334
	2233	2117 – 2152	2215 – 2250	2314 – 2349
	2250	2134 – 2169	2233 – 2268	2332 – 2367
	2268	2152 – 2187	2251 – 2286	2350 – 2385
	2283	2167 – 2202	2266 – 2301	2364 – 2399
	2306	2190 – 2225	2288 – 2323	2387 – 2422
	2325	2208 – 2243	2307 – 2342	2406 – 2441
	2339	2223 – 2258	2322 – 2357	2421 – 2456
	2357	2241 – 2276	2340 – 2375	2439 – 2474
	2373	2256 – 2291	2355 – 2390	2454 – 2489
	2390	2274 – 2309	2373 – 2408	2472 – 2507
	2410	2294 – 2329	2393 – 2428	2492 – 2527
G285M	2617	2480 – 2521	2596 – 2637	2711 – 2752
	2637	2500 – 2541	2616 – 2657	2731 – 2772
	2657	2520 – 2561	2636 – 2677	2751 – 2792
	2676	2539 – 2580	2655 – 2696	2770 – 2811
	2695	2558 – 2599	2674 – 2715	2789 – 2830
	2709	2572 – 2613	2688 – 2729	2803 – 2844
	2719	2582 – 2623	2698 – 2739	2813 – 2854
	2739	2602 – 2643	2718 – 2763	2837 – 2878
	2850	2714 – 2755	2829 – 2870	2945 – 2986
	2952	2815 – 2856	2931 – 2972	3046 – 3087
	2979	2842 – 2883	2958 – 2999	3073 – 3114
	2996	2859 – 2900	2975 – 3016	3090 – 3131
	3018	2881 – 2922	2997 – 3038	3112 – 3153
	3035	2898 – 2939	3014 – 3055	3129 – 3170
	3057	2920 – 2961	3036 – 3077	3151 – 3192
	3074	2937 – 2978	3053 – 3094	3168 – 3209
	3094	2957 – 2998	3073 – 3114	3188 – 3229
G230L	2635	1334 – 17332	2435 – 2834	1768 – 19673
	2950	1650 – 2050	2750 – 3150	1900 – 21003
	3000	1700 – 2100	2800 – 3200	1950 – 21503
	3360	2059 – 24584	3161 – 35605	2164 – 23613

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1

The central wavelength setting corresponds to the approximate midpoint of stripe B.

2

For central wavelength 2635 Å, the stripe A wavelengths are listed for completeness only (and in case a bright emission line falls onto the detector). The NUV detector’s sensitivity at these wavelengths is extremely low. To obtain a low-resolution spectrum at wavelengths below ~ 1700 Å, we recommend the FUV grating G140L.

3

The values in shaded cells are wavelength ranges observed in second order. Their dispersion is twice that of the first-order spectrum. First-order flux, from wavelengths twice those of the listed range, will be present at the ~ 5% level.

4

Lyman α may be present in second order.

5

Longward of 3200 Å, second-order light may be present. At these wavelengths, the flux calibration applied by calcos is unreliable (Section 5.1.3).