Transient correction of the LW-ISOCAM data for low contrasted illumination

The detector of the Long Wavelength channel of the ISOCAM came:ca on-board the Infrared Space Observatory (ISO) presents systematic memory effects of the response which can bias the photometry by a factor as high as 40%. We show that, for uniform illumination; the non li near model developed by Fouks and Schubert (1995) for the detector of PHT-S channel of the ISOPHOT instrument allows us to describe the LW-ISOCAM response to upward and downward steps of flux with an accuracy better than Ire. For each pixel of the detector, only two parameters have to be used. These parameters are con stent over the whole life of ISO. On the other hand, spatial variations fi om pixel to pixel are significant. We present an inversion method of the Fouks-Schubert model. Without any fitting and for low contrasted illumination, data are corrected with a photometric accuracy of similar to 1%, which is typically ten times better than previous methods. We suggest that the same approach could be used for others ISO detectors. and in the future for other experiments.