AOT 6 was used to make observations over wavelength ranges, as opposed to observing individual lines. Up to 64 wavelength ranges could be chosen anywhere in the SWS grating range, i.e., between 2.38 and 45.2 $\mu m$ , under the restriction that each range falls within one of the AOT bands (see Table 3.2).

Table 4.9 shows the reset interval, dwell times, stepsize and number of up-down scans for AOT 6. The dwell time stops at 4 secs, and for higher sensitivity the scans repeat. This was not always the case. Earlier versions of the logic (prior to May 1996) had the dwell time increasing. After May 1996 the scanning strategy used to reach the desired S/N ratios was:

**Table 4.9:** AOT 6 parameters
Detector	reset	dwell	stepsize	Number of
band	interval	time	LVDT	up-down
	sec	sec		scans
1	1, 2, 4	$\ge$ reset	1, 2, 4	n
2, 3	1, 2	$\ge$ reset	1, 2, 4	n
4	1, 2	$\ge$ reset	1, 2, 3, 6	n

The wavelength coverage of AOT 6 is given in table 4.10. Note that there is a slight overlap between bands. Band 3E was introduced after PV because band 3D suffered from a light leak at the long wavelength end, rendering observations around 28-29 $\mu m$ problematical.

**Table 4.10:** AOT 6 wavelength ranges
Detector	Detector	Aperture	Grating	Band	Band	Band
Array	material		order		start	End
					$\mu m$	$\mu m$
1	InSb	1	4	1A	2.38	2.61
1	InSb	1	3	1B	2.60	3.03
1	InSb	2	3	1D	3.02	3.53
1	InSb	2	2	1E	3.52	4.08¹
2	Si:Ga	2	2	2A	4.05	5.31
2	Si:Ga	2	1	2B	5.30	7.01
2	Si:Ga	3	1	2C	7.00	12.1
3	Si:As	1	2	3A	12.0	16.6
3	Si:As	2	2	3C	16.5	19.6
3	Si:As	2	1	3D	19.5	27.6
3	Si:As	3	1	3E	27.5	29.0
4	Ge:Be	3	1	4	28.9	45.2

4.4.1 Example AOT 6 timeline

AOT SWS06 was executed by pointing the telescope to the target position, and then for each wavelength range (or pair of merged ranges):

As an example, an AOT 6 observation around 10, 12, 33 & 40 $\mu m$ would have the following timeline:

1. Acquisition - point aperture 1 to target
2. Dark current measurement (16 sec)
3. Scan up around 12 $\mu m$ (24 sec, fast)
4. Scan down around 12 $\mu m$ (24 sec, fast)
5. Dark current measurement (16 sec)
6. Switch to aperture 3 (10 sec)
7. Dark current measurement (16 sec)
8. Reference scans near 10 and 33 $\mu m$ (16 sec)
9. Scans around 10 and 33 $\mu m$ , up (360 sec)
10. Reference scans near 10 and 33 $\mu m$ (16 sec)
12. Scans around 10 and 33 $\mu m$ , up, continued (360 sec)
10. Reference scans near 10 and 33 $\mu m$ (16 sec)
14. Scans around 10 and 33 $\mu m$ , down (360 sec)
10. Reference scans near 10 and 33 $\mu m$ (16 sec)
16. Scans around 10 and 33 $\mu m$ , down, continued (360 sec)
10. Reference scans near 10 and 33 $\mu m$ (16 sec)
18. Dark current measurement (16 sec)
19. Dark current measurement (16 sec)
20. Reference scans near 10 and 40 $\mu m$ (16 sec)
21. Scans around 10 and 40 $\mu m$ , up (96 sec)
22. Scans around 10 and 40 $\mu m$ , down (96 sec)
20. Reference scans near 10 and 40 $\mu m$ (16 sec)
24. Dark current measurement (16 sec)
25. Internal photometric calibration (40 sec)

Only ICS 5's are used (after the instrument has been set up). The ICS starts with a dark current measurement (at the reference wavelength), then makes a reference scan. Then the grating(s) is commanded up to observe a wavelength region. Another reference scan occurs before the down scan of the up-down pair. A final reference scan and dark current measurement are then made. This operation is repeated until all wavelength regions have been scanned.

For short scans the reference scans are dropped, as they take too much time. Every approximately 3600 s there was a photometric check. If the entire observation takes less than 3600 s a photometric check was done at the end.

4.4.2 Example AOT 6 data

Figures 4.12 and 4.13 show ERD data from all bands taken during an AOT 6. Data for detectors 1, 13, 25 and 37 (bands 1, 2, 3 & 4) is shown in bit values against time (ITK). Only five samples are shown out of the 24 per second for clarity. The periods when apertures 1, 2 & 3 are used, times of dark current measurements and photometric checks are indicated.

Figures 4.14 and 4.15 show the wavelength as seen by the middle detector of each band, along with the SW and LW scanner position (LVDT) for the same period. Figures 4.16 and 4.17 show the SPD, in $\mu V/sec$ against time, and AAR, flux (in Jy) against wavelength, for the same observation. Figure 4.18 shows what can be achieved after further processing of such data in either ISAP or IA.

**Figure 4.12:** ERD data for detectors 1 and 13 during an AOT 6
$\begin{figure} \begin{tabular}{c} \centerline{\epsfig{file={sws06_erd1.eps},width=15.0cm}}\\ \end{tabular}\end{figure}$

**Figure 4.13:** ERD data for detectors 25 and 37 during an AOT 6
$\begin{figure} \begin{tabular}{c} \centerline{\epsfig{file={sws06_erd2.eps},width=15.0cm}}\\ \end{tabular}\end{figure}$

**Figure 4.14:** Scanner position and wavelength seen by detector 6 for bands 1 & 2 during an AOT 6
$\begin{figure} \begin{tabular}{c} \centerline{\epsfig{file={sws06_wave1.eps},width=15.0cm}}\\ \end{tabular}\end{figure}$

**Figure 4.15:** Scanner position and wavelength seen by detector 6 for bands 3 & 4 during an AOT 6
$\begin{figure} \begin{tabular}{c} \centerline{\epsfig{file={sws06_wave2.eps},width=15.0cm}}\\ \end{tabular}\end{figure}$

**Figure 4.16:** SPD data, in $\mu V/sec$ , for the first detector of each band during an AOT 6
$\begin{figure} \begin{tabular}{c} \centerline{\epsfig{file={sws06_spd.eps},width=15.0cm}}\\ \end{tabular}\end{figure}$

**Figure 4.17:** AAR data from all detectors for an AOT 6
$\begin{figure} \begin{tabular}{c} \centerline{\epsfig{file={sws06_aar.eps},width=15.0cm}}\\ \end{tabular}\end{figure}$

**Figure 4.18:** An example of what can be achieved by processing AOT 6 data further in either IA or ISAP
$\begin{figure} \begin{tabular}{c} \centerline{\epsfig{file={sws06_isap.eps},width=15.0cm}}\\ \end{tabular}\end{figure}$

4.4 AOT 6

4.4.1 Example AOT 6 timeline

4.4.2 Example AOT 6 data