# Payload Summary

ERS-1 carries instrumentation consisting of a core set of active microwave sensors supported by additional, complementary instruments (see figures):

- Active Microwave Instrument (AMI) combining the functions of a Synthetic Aperture Radar (SAR) and a Wind Scatterometer. The SAR operates in image mode for the acquisition of wide-swath, all weather images over the oceans, polar regions, coastal zones and land. In wave mode the SAR produces imagettes (about 5 km x 5 km) at regular intervals for the derivation of the length and direction of ocean waves. The Wind Scatterometer uses three antennae for the generation of sea surface wind speed and direction.
- Radar Altimeter (RA) provides accurate measurements of sea surface elevation, significant wave heights, various ice parameters and an estimate of sea surface wind speed.
- Along Track Scanning Radiometer (ATSR) combining an infra-red radiometer and a microwave sounder for the measurement of sea surface temperature, cloud top temperature, cloud cover and atmospheric water vapour content.
- Precise Range and Range-rate Equipment (PRARE) is included for the accurate determination of the satellite's position and orbit characteristics, and for precise position determination (geodetic fixing).
- Laser Retro-reflectors (LRR) allow measurement of the satellite's position and orbit via the use of ground-based laser ranging stations.

The ATSR and PRARE are jointly referred to as the Announcement of Opportunity package, which resulted from proposals for additional instrumentation from the scientific community. In summary, the total ERS-1 instrument package provides a complementary set of sensors to enable all-weather, day / night, high accuracy observations of the Earth.

## ERS-1 Overview

  Satellite Concept
  ERS-1 Orbit
  Payload Summary
  Operational Capabilities
  ERS-1 Specification Table

ESA Earth Observation