4.6 Overview of Instrument Observing Modes and AOTs

The ISO instruments had some 23 main observing modes, the so-called `Astronomical Observation Templates' or `AOTs'. A summary of them is given in Table 4.4.

For historical reasons the AOT numbers are not consecutive. The first column gives the AOT identifier, the second the AOT title and the third column gives the restriction for the AOT if applied to observations of solar system targets. `not applicable' means that this AOT could not be used for solar system observations, `single pointing' means that no raster maps could be performed, `staring' means that the chopper could not be used and `one entrance aperture' in the case for SWS AOTs means that a change of wavelength was not allowed when it involved an automatic change of the entrance aperture.

Table 4.4: Overview of the main ISO instrument observing modes, the so-called `Astronomical Observation Templates' or `AOTs'.

AOT	AOT Title	Solar System
CAM01	General Observation	single pointing
CAM03	Beam Switching	not applicable
CAM04	Spectral Observations	single pointing
CAM05	Polarisation	single pointing
LWS01	Grating Wavelength Range Spectrum	single pointing
LWS02	Grating Line Spectra	single pointing
LWS03	Fabry-Pérot Wavelength Range Spectrum	single pointing
LWS04	Fabry-Pérot Line Spectra	single pointing
PHT03	General Multi-filter Photometry with PHT-P	single pointing, staring
PHT04	General Multi-aperture Photometry with PHT-P	single pointing, staring
PHT05	Absolute Photometry with PHT-P	staring
PHT17	Sparse Map with PHT-P (start AOT)	not applicable
PHT18	Sparse Map with PHT-P (intermediate AOT(s))	not applicable
PHT19	Sparse Map with PHT-P (end AOT)	not applicable
PHT22	Multi-filter Photometry with PHT-C	staring
PHT25	Absolute Photometry with PHT-C	single pointing, staring
PHT32	Multi-filter Map / Linear Scan with PHT-C	not applicable
PHT37	Sparse Map with PHT-C (start AOT)	not applicable
PHT38	Sparse Map with PHT-C (intermediate AOTs)	not applicable
PHT39	Sparse Map with PHT-C (end AOT)	not applicable
PHT40	Spectrophotometry with PHT-S	single pointing, staring
PHT50	Single Filter Polarimetry with PHT-P	single pointing, staring
PHT51	Single Filter Polarimetry with PHT-C	single pointing, staring
SWS01	Low-Resolution Full Grating Scan	one entrance aperture
SWS02	Grating Line Profile Scan	one entrance aperture
SWS06	Grating Scan	one entrance aperture
SWS07	Combined Fabry-Pérot Line Scan and SW Grating Scan	one entrance aperture

Polarisation observations with ISOCAM and ISOPHOT were implemented in operations by a different route than that for the standard `AOT-based' observing modes.

Table 4.5 shows the relative usage of the four instruments in terms of time and number of observations performed.

Figure 4.9 shows the usage of the different instrument observing modes during the mission. It is interesting to note that 90% of the observations carried out come from around 50% of the modes.

Figure 4.9: Usage of the different observing modes of the four ISO instruments by time (green) and number of observations (red). For an explanation of the observing modes see Section 3.4.