AOT 2 is used to observe up to 64 individual lines in an objects spectrum. It is carried out using chains of ICS 5. Each ICS 5 starts with a dark, then observes a line. ICS 6 is used to make a dark measurement when 1) the gain changes, 2) the reset interval changes, or 3) the aperture changes. Every approximately 3600 s there is a photometric check . If the entire observation takes less than 3600 s a photometric check is done at the end.
Table 4.3 shows the reset times, dwell times , stepsize and number of up-down scans for AOT 2. The dwell time may be higher for some merged scans.
|1||1, 2, 4||= reset||1||n|
|2,3||1, 2||= reset||1||n|
|4||1, 2||= reset||2||n|
The band start wavelengths for AOT 2 are given in table 4.7.
The length of the up and down scans in an AOT 2 may occasionally differ by small amounts. This is due to the runflag going down too early, signifying an early end to the observation.
Figure 4.7 shows the ERD and SPD from detector 25 as SWS scans across one particular line with an AOT 2. Figure 4.8 shows LW scanner positions, aperture information and wavelength seen by detector 25 during the same period, while 4.9 shows the SPD and AAR data from detector 25 during the same period.
Figure 4.7: ERD and SPD data for part of an AOT 2
Figure 4.8: Scanner position, apertures and wavelength seen by detector 25 during an AOT 2
Figure 4.9: SPD and AAR data from band 3 for AOT 2