Moon over limb port measurements use for both the vertical and the horizontal direction the adjustment by the SFD. In horizontal direction, SCIAMACHY's sun follower device (SFD) is used to adjust the viewing direction. In sun over limb port observations, we utilise the vertical scans over the solar disk. sun and moon to detect possible mispointings. The basic principle is the same as used by the star tracker: We measure the viewing direction towards celestial objects, i.e. In this work, we present additional sources of attitude information from the SCIAMACHY measurements itself. These updates are implemented in version 9 of the SCIAMACHY Level 1b products and Level 2 version 7 (based on L1b version 9). The horizontal location of the tangent point is changed by about 5 km for all measurements. The altitudes assigned to SCIAMACHY's solar occultation measurements are changed in the range of −130 to −330 m, the lunar occultation measurements are changed in the range of 0 to +130 m and the limb measurements are changed in the range of −50 to +60 m (depending on season, altitude and azimuth angle). The geolocation of all retrieved products will benefit from this the tangent heights are especially improved. Using these three type of measurements, we fit improved mispointing parameters by minimising the pointing offsets in elevation and azimuth. In the horizontal direction the geometry of the port defines the viewing direction. Solar observations through SCIAMACHY's so-called sub-solar port (with a viewing direction closely to zenith) also use the SFD in the vertical direction. We use reference images from the USGS Robotic Lunar Observatory (ROLO) to take into account the inhomogeneous surface and the variations by lunar libration and phase to parameterise the location of the intensity centroid from the observation geometry. The viewing direction is steered towards the intensity centroid of the illuminated part of the lunar disk. sun and moon, to detect possible mispointings. The basic principle is the same as used by the star tracker: we measure the viewing direction towards celestial objects, i.e. The pointing information of the instrument is determined by the attitude information of the Envisat platform with its star trackers together with the encoder readouts of both the azimuth and the elevation scanner of SCIAMACHY. The SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on Envisat (2002–2012) performed nadir, limb, solar/lunar occultation and various monitoring measurements.
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