Optical Performance
Retrieval Strategies
SCIAMACHY Main Page
SCIAMACHY measures in three viewing geometries: Nadir, Limb, and Occultation.
In Nadir mode the atmospheric volume directly under the instrument (i.e. the spacecraft) is observed. Each scan covers an area on the ground of up to 960 km across track with a maximum resolution of 26 km x 15 km.
In Limb mode the instrument looks at the edge of the atmosphere.
Scans at different tangent altitudes over a range of up to 960
km in horizontal direction are performed with a geometrical vertical
resolution of approximately 2.6 km.
Occultation measurements are performed using the same geometry
as in Limb mode, but with the sun or the moon in the instrument's
field of view. Atmospheric densities are obtained by comparing
measurements of the transmitted solar or lunar radiation with
the unattenuated source.
Solar occultation measurements are performed regularly during
sunrise (latitude range 90° N - 65° N).
Lunar occultation measurements during moonrise (between 30°S - 90°S) - which are possible for about one week per month - are used for process studies.
One of the most important features of SCIAMACHY is the possibility to observe the same atmospheric volume first in limb and then after about 7 minutes in nadir geometry.
By using this Limb/Nadir matching three-dimensional information about the atmosphere can be obtained.
With its orbital period of about 100 minutes, SCIAMACHY will be able to observe the whole Earth. Global coverage at the equator is achieved within 6 days when using the alternating Limb/Nadir scan option. Using only Nadir or Limb modes global coverage is achieved within 3 days (for 960 km swath width).
Because of the "dynamics scan mode" global coverage
goes in line with a rather "local" spatial resolution
for PMD measurements and special wavelength ranges. Therefore,
the vertical profiles of temperature and several long-lived trace
constituents will be measured at high spatial resolution.
| Geometrical FOV | Coverage | Typ. Spatial Resolution | ||
| Nadir | along track | 25 km | continuous | 30 km |
| across track | 0.6 km | +/- 480 km | 60 km | |
| Limb | azimuth | 110 km* | +/-460 km* | 250 km* |
| elevation | 2.5 km* | 0 - 200 km* | 3 km* | |
| Solar Occultation | azimuth | 40 km* | N.A. | 30 km* |
| elevation | 2.5 km* | 0 - 200 km* | 2,5 km* |
* at tangent point
© 1997-2000, page created by
Stefan Noël,
latest change 2000/11/16.
Optical Performance
Retrieval Strategies
SCIAMACHY Main Page