Mission and System

In May 2000, the European Space Agency will launch Envisat-1, an advanced polar-orbiting Earth observation satellite which will provide measurements of the atmosphere, ocean, land, and ice over a five year period.  The Envisat-1 satellite has an ambitious and innovative payload that will ensure the continuity of the data measurements of the ESA ERS satellites. The Envisat-1 data will support Earth science research and allow monitoring of the evolution of environmental and climatic changes. Furthermore, they will facilitate the development of operational and commercial applications.

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Mission Introduction

The overall Envisat-1 system includes several elements:

• the Envisat-1 Space Segment (the satellite itself) including the Polar Platform (PPF) and the payload
• the Envisat-1 Ground Segment consisting of the payload data segment (PDS) and the flight operation segment (FOS)

The Envisat-1 satellite works closely together with the Artemis data relay satellite (see the page on Artemis background information).

 

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Space Segment Introduction

Overall configuration

The major driver for the Polar Platform/Envisat-1 satellite configuration has been the need to maximise the payload instrument mounting area and to meet the viewing requirements within the constraints of the Ariane 5 fairing and interfaces. Additionally, the configuration also has been driven by the reuse of the SPOT Mk II service module concept and the ERS payload accommodation experience (concept of instrument electronics in an internal enclosure with externally mounted antennas).

 
The Envisat satellite in flight

In flight, the major spacecraft longitudinal axis (the Xs-axis) is normal to the orbit plane, the Ys-axis is closely aligned to the velocity vector and the Zs-axis is Earth pointing. This configuration concept provides a large, modular, Earth-facing mounting surface for payload instruments and an anti-sun face for radiative coolers, free of occultation by satellite subsystem equipment.

For more information:

• Ariane 5
• SPOT
• ERS

Satellite budgets

Launch configuration

Ground Segment

The Envisat-1 ground segment will provide the means and resources to manage and control the mission, to receive and process the data produced by the instruments, and to disseminate and archive the generated products. Furthermore, it will provide a single interface to the users to allow optimum utilization of the system resources in line with the user needs.

The ground segment can be split into two major elements:

• the flight operation segment (FOS), which is responsible for the command and control of the satellite;
• the payload data segment (PDS), which is responsible for the exploitation of the instrument data.

  
  Kiruna ground station

  The satellite-to-ground communication links will rely on various ground stations (Kiruna, Fucino, Svallbard, and Villafranca - the latter as TT&C back-up) and the ESA data relay satellite system Artemis which will provide direct communication between Envisat-1 and the ground even when the satellite is out of visibility of the ground stations. This will enable the use of high rate sensors which cannot be be stored on board, more optimally managed tape dumps, and enhanced visibility for command and control. Additional national and ESA ground stations will be involved.