The November, 1992, ESA ministerial meeting reaffirmed the organization's
intention to follow the ERS
program with the ambitious Polar-Orbiting Earth Observation Mission
(POEM), which was separated into two distinct
projects: Envisat-1 and Metop1. The former, based on an 8-metric-ton
Polar Platform bus, will be launched in 1998-1999 into
an 800-km altitude, sun-synchronous orbit to understand and to monitor
better the Earth's environment and to continue the
SAR surveys of the ERS spacecraft. France and the UK will each fund
about one-fourth of the Envisat mission with other ESA
members pooling resources for the remaining half.
With a spacecraft bus measuring 2.75 m in diameter and 11 m long, Envisat-1
will carry a useful payload of about 2,000 kg,
including five ESA-funded instruments: an advanced synthetic aperture
radar, an advanced radar altimeter, a medium resolution
imaging spectrometer,a Michelson interferometer for passive atmospheric
sounding, and a global ozone monitor. National
sensors expected to be carried by Envisat-2 include a French radiometer
(SCARAB), a German imaging spectrometer
(SCIAMACHY), and a British-Australian radiometer (AATSR). A microwave
sounder, similar to the ones developed for
ERS, will also be installed. The spacecraft's orbit will be essentially
the same as used in the ERS program, and the 6.6 kW
electrical system will provide nearly 2 kW to the instrument suite.