In order to assess the instrument performance under realistic conditions we used telescopic data kindly provided by Ann Sprague. We used the apparent emissivity they derived as input for our simulation. While using pure minerals is a best case assumption, using the telescopic data is a worst case assumption. The telescopic data is already noisy and is at least partly still contaminated by telluric absorption features.
We treated the telescopic data like the laboratory data, assuming again a surface tempera-ture of 590K typical for higher latitudes on the dayside. We added noise, both instrumental and background and calculated the simulated brightness temperatures as they will be ob-served by MERTIS.
The figure shows the resulting brightness temperature measurements. A visual inspection con-firms that the features are reproduced accordingly. Using the highest spectral resolution of 90nm and full spatial resolution we obtain an S/N ration of over 300 at 8µm. Using moderate 3*3 macro-pixel, as would be done in the mapping phase for medium to high latitudes, we obtain a S/N ratio of more than 1000 at 8µm.