Payload Instruments

A complex system like the Earth's environment with its atmosphere and oceans interacting on a wide range of temporal and spatial scales is realistically impossible to fully monitor or measure within practical constraints. In order to make a useful contribution, the Envisat mission's overall objectives have to be carefully defined and a specific set of multidisciplinary, complementary payload instruments selected by the Programme Board for Earth Observation, supported by scientific advisory groups (SAG).

The eventual payload complement was identified in a selection process which included available financial budget and physical system constraints. Its instruments have been selected to support synergism between their measurements and between scientific disciplines, thus making the total payload complement more than just the sum of the instruments.

The payload consists of a set of instruments for measuring the atmosphere and instruments for measuring the surface through the atmosphere. This set of instruments operates over a wide range of the electromagnetic spectrum, ranging from centimetre waves to the ultraviolet.

Payload instrument list

There are two radar instruments, three spectrometers of different types and measurement characteristics, two different radiometers (broad and narrow band), the first high-resolution spaceborne interferometer for long-term observation, and two instruments for range measurements:

• Michelson Interferometer for Passive Atmospheric Sounding (MIPAS);
• Global Ozone Monitoring by Occultation of Stars (GOMOS);
• Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY);
• Medium Resolution Imaging Spectrometer (MERIS);
• Advanced Along Track Scanning Radiometer (AATSR);
• Advanced Synthetic Aperture Radar (ASAR);
• Radar Altimeter 2 (RA-2);
• Microwave Radiometer (MWR);
• Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS);
• Laser Retro-Reflector (LRR).

Payload instrument responsibilities

The instruments fall into two categories reflecting the responsibilities for their development and procurement:

• EDIs - ESA development instruments, developed within the Envisat programme; and
• AOIs - Announcement of Opportunity instruments (AATSR, SCIAMACHY, and DORIS) provided by national or multinational institutions.

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry