8.5 Straylight

Off-axis responses were measured early in the PV phase on the bright source W Hya, out to a distance of 2$^\prime$. Later in the mission, specific straylight checks were performed, prompted by scientific needs for a better characterization of the influence of straylight from Saturn on planetary satellites such as Titan and Europa.

One measurement of straylight rejection was performed during observations of Titan on revolution 384. The spectral line due to C$_2$H$_4$ at 13.7$\mu$m was measured on Saturn and at a position Y $_{\mbox{off}} =$- $87^{\prime\prime}$, Z $_{\mbox{off}} =$- $163^{\prime\prime}$, corresponding to a total displacement of $3^\prime$. By comparing the spectral line at these positions a rejection factor of 10$^4$ was calculated (ref. Salama 1998, [32]).