Restrictions

The SWS design and optimization of sensitivity and operational efficiency lead to a few general restrictions that apply to all SWS AOTs :

• There are minimum observing times   for all AOTs, even for very bright sources that could formally reach very high signal-to-noise ratio (SNR) quickly. First, there is a minimum detector reset time of 1 sec, leading to a minimum total integration time for each AOT, depending on the minimum number of grating or F-P settings. Second, fixed instrumental and satellite time overheads have to be added. Details are discussed with the individual AOTs (Chapter 6).
• The SWS will be used with fundamental integration times (detector reset times ) of 1, 2 and 4 sec. The fundamental integration time is however not selectable by the observer; it will be set by the AOT logic based on the flux and desired SNR provided by the observer as AOT input.
• The correspondence between wavelength range and aperture size (Tab. 2.1) is fixed and cannot be selected by the observer.
• The orientation of the SWS apertures on the sky is determined by the time of the observation. The observer cannot influence the position angle of the long axis of the apertures, but will be supplied with the actually achieved orientation.
• For observations of solar system objects, measurements in different entrance apertures have to be defined in separate AOT calls, i.e. as separate observation requests .