ISOCAM Software Simulator

The ISOCAM Simulator was built to allow the estimation of observing times to the prospective ISOCAM user. The ISOCAM Simulator uses the photometry model of ISOCAM, noise characterization formulae, and detector stabilization data presented in this document. It furnishes the required integration time to achieve a given signal to noise ratio taking into account the stabilization time required to place the detectors in the apropriate operating range . The ISOCAM Simulator also estimates overheads incurred by the spacecraft when operating in raster mode or when performing the Beam Switching AOT. The ISOCAM Simulator has been designed to

• allow the astronomer to visualize how the Signal to Noise ratio varies as a function of the total observing time. This strategy was favoured over the approach that consists in computing the required time given the desired Signal to Noise. The reason for this choice is that it is not unusual for the Signal to Noise ratio to slowly tend to an asymptotic value; a small variation in plus or minus of the requested sensitivity will lead to much larger variations on the computed time. Such a behaviour is best comprehended by having the Signal to Noise variation plotted a function of , the observing time,
• thus guiding the astronomer towards the choice of the Astronomical Observing Template (AOT) more apt to achieve the desired Signal to Noise ratio with a minimum of observing time, overheads included.

Using the ISOCAM Simulator, the observer finds that there is an intricate interplay between readout noise, photon noise, and low frequency noise, on the one hand, and stabilization times and spacecraft overheads on the other. Only trial and error may lead to the choice of the best combination of parameters leading to the most efficient observing strategy.

Without this software and using the sample of performance figures to it is nevertheless possible to get an estimate of the observing time.

Note that for historical reasons, AOT2 does not exist.

  
Figure: S/N calculations, Point Source, SW, PFOV 3 arcsec

  
Figure: S/N calculations, Point Source, SW, PFOV 6 arcsec

  
Figure: S/N calculations, CVF, Point Source, SW, PFOV 3 arcsec

  
Figure: S/N calculations, CVF, Point Source, SW, PFOV 6 arcsec

  
Figure: S/N calculations, Extended Source, SW, PFOV 3 arcsec

  
Figure: S/N calculations, Extended Source, SW, PFOV 6 arcsec

  
Figure: S/N calculations, CVF, Extended Source, SW, PFOV 3 arcsec

  
Figure: S/N calculations, CVF, Extended Source, SW, PFOV 6 arcsec

  
Figure: S/N calculations, Point Source, LW, PFOV 3 arcsec

  
Figure: S/N calculations, Point Source, LW, PFOV 6 arcsec

  
Figure: S/N calculations, CVF, Point Source, LW, PFOV 3 arcsec

  
Figure: S/N calculations, CVF, Point Source, LW, PFOV 6 arcsec

  
Figure: S/N calculations, Extended Source, LW, PFOV 3 arcsec

  
Figure: S/N calculations, Extended Source, LW, PFOV 6 arcsec

  
Figure: S/N calculations, CVF, Extended Source, LW, PFOV 3 arcsec

  
Figure: S/N calculations, CVF, Extended Source, LW, PFOV 6 arcsec