4.3 AOT 2

   

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.

 

Detector reset dwell stepsize Number of

Band time time LVDT up-down

sec sec 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.

 

Detector Detector Aperture Grating Band

Array material order start

1 InSb 1 4 2.38

1 InSb 1 3 2.60

1 InSb 2 3 3.02

1 InSb 2 2 3.52

2 Si:Ga 2 2

2 Si:Ga 2 1 5.30

2 Si:Ga 3 1 7.00

3 Si:As 1 2 12.0

3 Si:As 2 2 16.5

3 Si:As 2 1 19.5

3 Si:As 3 1 27.5

4 Ge:Be 3 1 29.0

 

1. Note that the band 2A start wavelength was changed from 4.05 to 4.08 in May 1996, and hence the band 1A end wavelength was moved accordingly.

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