SCIAMACHY

SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric CHartographY; Greek σκιαμαχή, fight, mutatis mutandis, against Shadow ) is one of ten instruments on the European environmental satellite Envisat and created global maps of various atmospheric trace gases (O3, NO2, O2, H2O, CH4, CO2, CO, BrO, OClO, SO2, IO) and other parameters. Spectral data were analyzed using the very much DOAS technique.

SCIAMACHY onboard Envisat was launched on an Ariane 5 rocket on 1 March 2002 from Kourou, French Guiana in a sun-synchronous polar orbit at an altitude of 799.8 kilometers with an inclination angle of 98.6 °. On 8 April 2012, the measurements transmitted by the loss of communication with Envisat. The direction of flight on the day side of the earth from north to south. Due to the Sonnensynchronizität are the local times overhead at a fixed local time zone via Central Europe by 10 clock in the morning. In polar latitudes, measurements at other times were possible. Measurements on the night side of the earth have been used among others for calibrations. For an orbit, the satellite takes about 100 minutes. In the course of a day just over 14 orbits are flown. SCIAMACHY thus appropriated for the Global Earth Observation.

Viewing geometries

SCIAMACHY is operated in different viewing geometries daily in a fixed order:

• Nadir observation: Here, the column of air is detected below the satellite. The visual field of the spectrometer in the amount of the earth's surface of about 750 kilometers, 25 x 0,6 km ², by the speed of the satellite of 7 km / s and the frequency of the scanning speed of 240 km / s, the resolution SCIAMACHYs in this observation geometry is approximately 30 km in the direction of flight and 240 km across the direction of flight. This observation geometry provides a relatively good spatial horizontal resolution. In the nadir geometry trace gas columns are mainly measured. With one exception, trace gas profiles can be measured, but the vertical resolution of the ozone profiles is lower than in the limb geometry.
• Limb- observation (English for edge ) or edge -sampling observation: The field of view is in this observation geometry 110 km across the flight direction and 2.6 km vertically in an approximately 4-fold greater distance of about 3000 km. With Limb- scattered light measurements, the Earth's atmosphere is tangentially sampled from the surface to 92 km tangent altitude in increments of 3 km. These measurements take a total of about 90 seconds During this time the satellite moves forward by about 630 km, resulting in a relatively poor spatial horizontal resolution of 960 x 630 km2, but a relatively good vertical resolution of the measurements of 3 km results.
• Sun and Moon Okkultationsbeobachtung: It is recorded as a direct background a spectrum with the sun or the moon. The field is located 30 km in the azimuthal and 2.5 km in the vertical direction. The high intensity of the sun and moon light allows very short integration times of about 62 ms. A complete vertical measurement therefore takes only 1 s and the field corresponding to this observation mode and the resolution of 30 km x 2.5 km horizontally vertically. Occultation measurements are among the most accurate measurements of high quality due to the large recorded intensities. Occultation measurements can be made only at certain times of day ( sunrise and sunset). Therefore, only a poor spatial coverage is given.

The eight-channel spectrometer measures light transmitted, scattered in the atmosphere, and reflected at the surface sunlight in the ultraviolet to near-infrared spectral range ( see Table 1). From the measurements, total column amounts and profiles of trace gases and aerosols, and cloud parameters can be derived depending on the observation geometry. Moreover, in six channels the polarization of the light is measured. A 5 -watt tungsten white light lamp, a NePtCr -cathode discharge lamp and the absorption of solar spectra at different viewing geometries are used for calibrations.