Entry: ENVISAT
URI: https://terra-vocabulary.org/ncl/FAIR-Incubator/earthscienceplatforms/c_f3c8d7f0
ENVISAT was successfully launched on March 1, 2002 from Kourou, French Guiana on Europe's Ariane 5 launcher. The ENVIronmental SATellite (ENVISAT) is an element of the European Space Agency (ESA) Columbus Programme. The ENVISAT satellite is part of the International Earth Observation System (IEOS). The ENVISAT is designed to study Earth's resources and to contribute to the study of land surface properties, atmospheric chemistry, aerosol distribution, ocean and ice processes, and marine biology. The ENVISAT spacecraft is based on the Polar Platform (PPF) concept and consists of a Service Module (SM) which provides main support functions, and a mission-specific Payload Module (PLM) which provides the instruments and payload support functions. The Payload Module consists of the Payload Equipment Bay (PEB) and the Payload Carrier (PLC). The Payload Data Management Subsystem performs instrument and support subsystems, data processing, telecommand and telemetry management, data-bus control, failure management, and instrument operations timeline management. Commonad and control is provided by the Payload Module Computer (PMC). Scientific data generated from the instruments will be processed by the High Speed Multiplexer (HSM) for recording or transmission to the ground. A set of four tape recorders provide a recording speed of 2 to 4 Mbps and a capacity of 25 Gbits. The communication subsystem uses an x-band link directly to the ground and a Ka-band bi-directional link via ESA's Data Relay Satellite (DRS). The Thermal Control Subsystem consists of a Heater Switching Unit (HSU), heaters, thermistors and thermostats. The Service Module (SM) consists of a carbon-fibre-reinforced plastic (CFRP) cone with a launcher interface at one end and a propulsion module at the other. The power subsystem consists of up to eight nickel-cadmium batteries (40 Ahr) and a modular solar array. The SM on-board data management is done by the Central Computer Unit (CCU). Command and contral are done via S-band communications direct to the ground or through the DRS. The Attitude and Orbit Control Subsystem (AOCS) provides three-axis stabilization. Altitude measurements will be provided by digital Sun sensors, Earth-horizon sensors and gyroscopes while altitude control will be provided by monopropellent thrusters. Fine pointing is accomplished through star sensors and gyroscopes, reaction wheels, and magneto-torquers. The ENVISAT consists of : (1) Advanced SAR (ASAR), (2) Global Ozone Monitoring by Occultation of Stars (GOMOS), (3) Medium Resolution Imaging Spectrometer (MERIS), (4) Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), (5) Radar Altimeter-2 (RA-2), (6) Advanced Along Track Scanning Radiometer (AATSR), (7) Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIMACHY), (8) Microwave Radiometer (MWR), (9) Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and (10) a Laser Retroreflector (LRR) for tracking. Just weeks after celebrating its tenth year in orbit, communication with the Envisat satellite was suddenly lost on 8 April. Following rigorous attempts to re-establish contact and the investigation of failure scenarios, the end of the mission is being declared.