is significantly higher and the FWHM significantly smaller than during the rest of the orbit, due to the satellite stabilizing after re-entering the Earth shadow (Figure \[fig:state parameters\]). These lines are thus due to a different flux distribution compared to the rest of the orbit, and not to bad pixels. Typically, the first 20 images of each orbit are affected, plus [$\sim$]{}12 other images in each orbit of the 3[$^{\textrm{\scriptsize rd}}$ ]{}visit. In total, this represents 37% of the data. Since this fraction is large, we process these images similarly to the rest of the data, without considering those lines as bad pixels. The decorrelation from instrumental parameters will reduce the effects of such variations.

![Example of bad pixel masks at the beginning of an orbit (left), and after the instrument is stabilized (right). Lines at the location of the spectral traces appear at the beginning of orbits.[]{data-label="fig:bad pixels mask"}](fig6.png "fig:"){width="4cm"} ![Example of bad pixel masks at the beginning of an orbit (left), and after the instrument is stabilized (right). Lines at the location of the spectral traces appear at the beginning of orbits.[]{data-label="fig:bad pixels mask"}](fig7.png "fig:"){width="4cm"}

Flat-field correction
---------------------

Since the response of the pixels is wavelength dependent, a 