# ERS-1 Specifications

## Orbit

Type | Near-circular, polar, Sun-synchronous
Altitude | 782 to 785 km
Inclination | 98.52 deg.
Period | About 100 minutes
Orbits per day | 14.3
Repeat cycle | 3-day, 35-day and 176-day

## Instruments

Active Microwave Instrument (AMI) comprising a SAR (image and wave modes) and a Wind Scatterometer
Radar Altimeter
Along Track Scanning Radiometer (ATSR)
Precise Range and Range-rate Equipment (PRARE)
Laser Retro-relectors

## Mass

Total mass | 2157.4 kg
Total payload | 888.2 kg
Total platform | 1257.2 kg
Active Microwave Instrument | 325.8
Radar Altimeter | 96.0
IDHT | 74.0
ATSR | 55.3
PRARE | 12.0
Laser Retro-reflectors | 2.5

## Electrical Power

Payload peak power | <=2600 W
Payload permanent power | <=550 W
Power supply voltage | 23-37 V
On-board energy | 2650 WH max

## Attitude and Orbital Control

Type | 3 Axes stabilised earth pointed
Absolute rate errors | <=0.0015deg. sec (3 sigma)
Maximum errors | bias 0.11deg. (pitch/roll) 0.21deg. (yaw); harmonic and Random 0.03deg. (pitch/roll) 0.07deg. (yaw)
Prediction accuracy | 30 m (radial), 15 m (cross), 1000 m (along)
Orbit restitution | 5 m (radial), 15 m (cross) 60 m (along)

## Data Handling

On-board computer | word length: 16 bits
Payload memory capacity | 20 K words max
Payload data exchange | OBDH type bus
Number of payload users | redundant

## Communications

Transponder | coherent S-band (2 kbit/s)
Transmission power | 50 to 200 mW max
Telemetry rate | 2048 bit/s
Telecommand rate | 200 bit/s
Data down link | - X-band (105 Mbit/s high rate link for AMI image mode) - X-band (15 Mbit/s low rate link for real-time and playback of LBR data) - on-board recorders provide 6.5 Gbits storage - S-band telemetry links for housekeeping data - PRARE uses own ranging links for its telemetry data

## ERS-1 Overview

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

ESA Earth Observation