The Gemini Near-infrared Integral Field Spectrograph (NIFS) was cooled down for the second time in late October 2002. The cool down began on Monday 28-OCT-02 and the cryostat was sufficiently cold to begin measurements by Thursday 31-OCT-02. Temperatures had stabilized by Monday 04-NOV-02.

The cryostat contained all of the NIFS spectrograph and OIWFS optics. The spectrograph occulting disks and Ronchi calibration mask were not installed. The J filter was not installed so that internal optical lamps could be viewed through the cryostat window. The camera lenses and collimator corrector lens were not anti-reflection coated. The spectrograph detector was the first engineering detector that has only two working quadrants. This device dissipates excessive heat during operation, so sensitive dark current and bias drift measurements were not possible. The OIWFS detector was not installed, so the OIWFS filter/aperture wheel was also not installed.

4 Initial Assessment

The spectrograph gave excellent initial results.

4.1 IFU Pattern

The IFU pattern occupies 2030 pixels (Table 1) in the spatial direction, as expected. The pattern is displaced by ~ 0.34 mm on the detector so there is a gap of ~ 28 pixels at the top of the detector instead of 9 pixels. This causes some of the bottom spectrum to be lost. The spectra are accurately aligned with detector rows, as is required. Flat field images for the Z, J, H, and K gratings, showing the IFU pattern, are shown in Figure 1 to Figure 4.

Table 1: Slitlet Positions in Flat Field Image

Grating	Bottom of Slitlet 1		Bottom of Slitlet 28		Height of Full Pattern	Vertical Decenter
Grating	Left	Right	Left	Right	Height of Full Pattern	Pixels	Microns
Z	1950	1951	61	62	2030	-18	-324
J	1949	1950	60	61	2030	-19	-342
H	1948	1948	57	58	2030	-21	-388
K	1953	1954	63	63	2030	-16	-296

Figure 1: Flat field image obtained with the Z grating.

Figure 2: Flat field image obtained with the J grating.

Figure 3: Flat field image obtained with the H grating.

Figure 4: Flat field image obtained with the K grating.

4.2 Spectral Resolution

The spectra are in reasonable focus with the spectrograph camera set to its nominal position. One purpose of the second cool down is to accurately determine the camera focus. Xenon arc lamp spectra obtained with each grating are shown in Figure 5 to Figure 8.

Figure 5: Dark-subtracted xenon arc lamp spectra obtained with the Z grating.

Figure 6: Dark-subtracted xenon arc lamp spectra obtained with the J grating.

Figure 7: Dark-subtracted xenon arc lamp spectra obtained with the H grating.

Figure 8: Dark-subtracted xenon arc lamp spectra obtained with the K grating.

Table 2 to Table 5 list positions, FWHM, and peak intensities for various Xenon lines over the detector area for each grating. The Gaussian FWHM are ~ 7-8 pixels, except for slitlet 29 (the bottom slitlet) that is significantly better at ~ 5-6 pixels. Xenon lines in the upper slitlets appear double while those in the lower slitlets appear single (Figure 9). This may indicate that one of the camera lenses is cracked (?). The narrower lines in slitlet 29 do not have greater peak intensities, so it is not simply that their light is more concentrated.

The undispersed "staircase" pattern produced by the mirror in the grating turret gives narrower lines with FWHM ~ 4.2 pixels in the lower region of the detector. This may indicate that the gratings are not flat (?). The lines are single in this lower region, but double in the upper region of the detector where the FWHM is ~ 6-7 pixels.

A new "staircase" image should be obtained.

Table 2: Xenon Arc Line Positions and FWHM for the Z grating.

Slitlet	Z Grating
	1.0251 μm			1.0707 μm			1.1085 μm
	Position (pixels	FWHM (pixels)	Peak (ADU)	Position (pixels)	FWHM (pixels)	Peak (ADU)	Position (pixels)	FWHM (pixels)	Peak (ADU)
1 (top)				1592.7	7.1	1261	1231.0	7.1	3421
2				1593.3	7.1	1328	1233.2	7.1	4119
3				1594.3	7.3	1372	1234.0	7.8	3605
4				1594.6	7.7	1441	1234.0	8.1	3486
5				1595.5	7.6	1382	1234.4	7.4	3760
6				1595.5	7.4	1522	1234.7	7.6	3556
7				-	-	-	1234.6	7.5	4085
8				1595.5	7.1	1636	1234.7	6.7	4381
9				1594.7	7.1	1563	1233.6	7.1	4395
10				1594.2	7.3	1624	1233.4	7.1	4546
11				1593.4	7.7	1495	1232.2	7.9	3871
12				1592.1	6.9	1539	1231.4	7.2	4828
13				1591.2	7.2	1515	1230.3	6.7	4833
14				1589.4	7.4	1488	1228.5	8.1	4009
15				1588.5	6.6	1663	1227.8	5.8	5501
16				1585.9	6.9	1860	1225.1	7.0	5163
17	2018.1	7.2	1295	1584.2	7.3	1688	1222.9	7.1	4462
18	2015.3	6.5	1328	1581.2	6.5	1902	1220.6	6.4	5323
19	2013.2	6.6	1338	1579.2	6.1	2066	1218.0	6.7	5047
20	2010.1	6.5	1361	1575.9	5.8	2032	1215.2	5.9	6147
21	2007.3	6.3	1445	1573.2	5.5	2272	1212.0	5.7	6318
22	2003.6	6.2	1337	1569.5	6.0	2146	1208.5	6.3	5933
23	2000.2	6.5	1325	1566.2	6.2	2086	1205.1	6.3	6002
24	1996.4	6.6	1369	1562.2	6.3	2083	1201.3	6.5	5733
25	1992.1	6.8	1165	1558.3	6.6	1866	1197.0	6.7	5714
26	1989.1	6.7	1264	1554.8	6.3	1935	1193.6	6.2	6565
27	1984.2	6.6	1235	1549.9	6.2	1860	1189.0	6.1	6369
28	1980.1	5.9	1303	1545.8	6.1	2194	1184.8	5.4	6667
29	1974.4	4.6	1145	1540.7	4.7	1980	1179.4	4.8	6130

Table 3: Xenon Arc Line Positions and FWHM for the J grating.

Slitlet	J Grating
	1.1742 μm			1.2235 μm			1.2623 μm
	Position (pixels	FWHM (pixels)	Peak (ADU)	Position (pixels)	FWHM (pixels)	Peak (ADU)	Position (pixels)	FWHM (pixels)	Peak (ADU)
1 (top)				1497.3	6.6	996	1125.3	7.0	10230
2				1499.3	7.2	1054	1126.9	7.5	10865
3				1499.9	7.3	1104	1128.6	7.2	12011
4				1501.1	7.5	1139	1128.9	7.5	9924
5				1501.5	7.6	1026	1129.7	7.2	11057
6				1502.4	7.0	1162	1130.4	6.6	12239
7				1502.5	7.1	1116	1130.2	7.1	11573
8				1502.7	6.1	1370	1130.3	7.0	11704
9				1502.2	5.5	1435	1129.6	6.7	12518
10				1502.2	6.2	1334	1129.6	7.2	11664
11				1501.3	5.3	1420	1129.3	5.3	14866
12				1500.0	6.2	1077	1127.5	6.2	13903
13				1498.9	7.0	1038	1126.9	5.9	13232
14				1498.2	5.5	1415	1125.3	6.7	12832
15	1967.5	6.5	3731	1496.8	4.3	1747	1124.2	4.3	18814
16	1965.3	6.7	3643	1494.4	5.0	1485	1121.9	6.7	13056
17	1963.3	6.9	3518	1491.9	6.8	1112	1119.9	5.5	15708
18	1961.2	6.3	4005	1489.8	5.9	1415	1117.4	6.2	14934
19	1958.3	6.3	3767	1486.9	6.4	1286	1114.4	6.1	15204
20	1955.5	6.7	3858	1484.1	6.4	1360	1111.6	6.1	15348
21	1952.2	6.8	3375	1480.6	7.0	1255	1108.5	6.0	18041
22	1948.9	7.0	3640	1477.2	6.7	1245	1104.8	6.3	15182
23	1945.1	6.9	3373	1473.9	6.4	1375	1101.2	6.9	14314
24	1941.0	7.1	3439	1469.9	6.5	1372	1097.2	6.5	16109
25	1936.8	7.6	3276	1465.7	6.7	1306	1092.8	6.4	15772
26	1933.4	6.6	3483	1462.0	6.3	1386	1089.4	6.0	16858
27	1928.3	6.8	3162	1456.9	6.4	1297	1084.1	6.4	15377
28	1923.7	6.1	3597	1452.2	5.8	1354	1079.3	5.7	15035
29	1917.4	5.2	2741	1445.6	4.9	1026	1073.0	4.9	11020

Table 4: Xenon Arc Line Positions and FWHM for the H grating.

Slitlet	H Grating
	1.5418 μm			1.6053 μm			1.67280 μm
	Position (pixels	FWHM (pixels)	Peak (ADU)	Position (pixels)	FWHM (pixels)	Peak (ADU)	Position (pixels)	FWHM (pixels)	Peak (ADU)
1 (top)				1683.2	8.6	10277	1253.3	8.1	16597
2				1683.1	8.5	11873	1253.6	8.2	16341
3				1683.6	8.4	11602	1254.3	8.1	16570
4				1684.6	9.0	10143	1254.9	9.2	15359
5				1684.8	9.0	10611	1255.2	8.5	16569
6				1685.7	8.5	11764	1255.7	8.6	14634
7				1685.2	8.8	11916	1255.8	8.4	16989
8				1684.8	8.0	13331	1255.8	8.1	17961
9				1684.0	8.0	12052	1254.8	8.2	17331
10				1683.7	7.8	12987	1254.7	8.1	17734
11				1682.7	8.2	12197	1253.4	8.5	16216
12				1681.7	7.7	12160	1252.3	8.3	16566
13				1680.3	8.1	12406	1251.3	7.7	19880
14				1678.8	8.1	12882	1250.2	8.0	17975
15				1678.0	7.8	14557	1248.4	8.2	17895
16	1990.3	7.7	873	1675.5	7.9	14303	1246.1	7.9	21907
17	1988.2	7.4	838	1673.6	7.9	14187	1244.4	7.6	20711
18	1985.7	7.8	815	1670.9	7.7	13713	1241.5	7.7	20779
19	1983.1	7.1	793	1668.0	7.2	15023	1239.1	6.9	24716
20	1980.4	6.8	953	1665.5	6.9	16261	1236.2	6.8	24237
21	1978.1	6.8	943	1662.6	7.4	15685	1233.1	7.2	22112
22	1973.5	6.5	908	1658.7	7.3	14945	1229.5	7.4	22504
23	1970.7	7.1	904	1655.7	7.3	16281	1226.0	7.2	24208
24	1966.6	7.2	915	1651.7	7.6	15838	1221.8	6.9	26200
25	1962.4	7.5	843	1647.5	7.6	15738	1218.0	7.5	24012
26	1959.4	6.5	977	1644.3	7.3	15882	1214.9	7.0	25147
27	1954.7	7.0	880	1639.5	7.1	15529	1210.0	6.9	24835
28	1950.4	6.2	892	1635.1	6.5	16575	1205.8	6.1	27153
29	1944.5	5.6	856	1629.7	5.3	15423	1200.3	5.2	24517

Table 5: Xenon Arc Line Positions and FWHM for the K grating.

Slitlet	K Grating