SEVIRI: a focused design
The overall SEVIRI layout
is based on a compact telescope and scan assembly, allowing the implementation of
a large passive cooler which improves IR detector performances by lowering their
operating temperature. It will provide the data quality, accuracy and flexibility
that the meteorological community needs from a geostationary system for many years
to come. Its fundamental components are as follows:
Telescope Scan Assembly:
The imaging SEVIRI radiometer is equipped with a patented three-mirror (3M)
telescope
of compact design which allows the insertion of a small black body for full-pupil
calibration. A refocusing mechanism will compensate for the telescope's long-term deformation
over the mission lifetime. The scan assembly is designed for continuous bi-dimensional
image scanning of the Earth.
Calibration Unit:
A mechanism
for the insertion/removal of a small black body in the optical path, allows the infrared
channels to be accurately calibrated.
Focal Plane and Cooler Assembly:
The twelve channel detectors are accommodated in the telescope's focal plane,
where the channel separation is mainly carried out.
The infrared detectors are passively cooled down by a system to optimise their radiometric performances.
State of the art technology is used in both devices. They are attached together in
the lower side of the base-plate interfacing the instrument and the spacecraft.
Detection Electronic Units:
The response by every detector to the target's radiation is converted into
an electronic signal by means of
pre-amplifiers and a main detection unit.
Functional Control Unit:
The instrument control and interfacing with the spacecraft are centralized in the
FCU, which is responsible for data flow handling, image control and housekeeping.
SEVIRI instrument characteristics compared
to Meteosat |