![ERS 2](https://upload.wikimedia.org/wikipedia/commons/f/fc/ERS_2.jpg)
European
Remote Sensing
Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring information about Earth ...
satellite (ERS) was the
European Space Agency
, owners =
, headquarters = Paris, Île-de-France, France
, coordinates =
, spaceport = Guiana Space Centre
, seal = File:ESA emblem seal.png
, seal_size = 130px
, image = Views in the Main Control Room (1205 ...
's first
Earth-observing satellite
An Earth observation satellite or Earth remote sensing satellite is a satellite used or designed for Earth observation (EO) from orbit, including spy satellites and similar ones intended for non-military uses such as environmental monitoring, me ...
programme using a
polar orbit
A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It has an inclination of about ...
. It consisted of 2 satellites, ERS-1 and ERS-2.
ERS-1
ERS-1 launched 17 July 1991 from
Guiana Space Centre
The Guiana Space Centre (french: links=no, Centre spatial guyanais; CSG), also called Europe's Spaceport, is a European spaceport to the northwest of Kourou in French Guiana, a region of France in South America. Kourou is located approximatel ...
aboard an
Ariane 4
The Ariane 4 was a European expendable space launch system, developed by the ''Centre national d'études spatiales'' (CNES), the French space agency, for the European Space Agency (ESA). It was manufactured by ArianeGroup and marketed by Arian ...
rocket.
The
satellite
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...
was put into a
Sun-synchronous polar orbit
A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It has an inclination of about ...
at an altitude of 782–785 km. ERS-1 failed on 10 March 2000 after nine years in orbit.
Instruments
ERS-1 carried an array of Earth-observation instruments that gathered information about the Earth (land, water, ice and atmosphere) using a variety of measurement principles. These included:
* RA (Radar Altimeter) is a single frequency
nadir
The nadir (, ; ar, نظير, naẓīr, counterpart) is the direction pointing directly ''below'' a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface.
The direc ...
-pointing
radar
Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
altimeter
An altimeter or an altitude meter is an instrument used to measure the altitude of an object above a fixed level. The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth under water. The m ...
operating in the
Ku band.
* ATSR-1 (
Along-Track Scanning Radiometer) is a 4 channel
infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
radiometer
A radiometer or roentgenometer is a device for measuring the radiant flux (power) of electromagnetic radiation. Generally, a radiometer is an infrared radiation detector or an ultraviolet detector. Microwave radiometers operate in the microwave w ...
and
microwave
Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ran ...
sounder for measuring temperatures at the sea-surface and the top of clouds.
* SAR (
synthetic-aperture radar
Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or three-dimensional reconstructions of objects, such as landscapes. SAR uses the motion of the radar antenna over a target region to provide fine ...
) operating in C band can detect changes in surface heights with sub-millimeter precision.
*
Wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...
Scatterometer
A scatterometer or diffusionmeter is a scientific instrument to measure the return of a beam of light or radar waves scattered by diffusion in a medium such as air. Diffusionmeters using visible light are found in airports or along roads to measur ...
used to calculate information on wind speed and direction.
* MWR is a
Microwave Radiometer
A microwave radiometer (MWR) is a radiometer that measures energy emitted at one millimeter-to-metre wavelengths (frequencies of 0.3–300 GHz) known as microwaves. Microwave radiometers are very sensitive receivers designed to measure thermally- ...
used in measuring atmospheric water, as well as providing a correction for the atmospheric water for the altimeter.
To accurately determine its orbit, the satellite included the PRARE (Precision Range and Range-Rate Equipment) and a
laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...
retroreflector
A retroreflector (sometimes called a retroflector or cataphote) is a device or surface that reflects radiation (usually light) back to its source with minimum scattering. This works at a wide range of angle of incidence, unlike a planar mirror, ...
. The PRARE became non-operational shortly after launch; later analysis concluded that the failure was due to a memory
latchup A latch-up is a type of short circuit which can occur in an integrated circuit (IC). More specifically it is the inadvertent creation of a low- impedance path between the power supply rails of a MOSFET circuit, triggering a parasitic structure which ...
caused by radiation.
The
retroreflector
A retroreflector (sometimes called a retroflector or cataphote) is a device or surface that reflects radiation (usually light) back to its source with minimum scattering. This works at a wide range of angle of incidence, unlike a planar mirror, ...
was used for calibrating the
Radar
Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
Altimeter
An altimeter or an altitude meter is an instrument used to measure the altitude of an object above a fixed level. The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth under water. The m ...
to within 10 cm.
Mission
ERS-1 had various mission phases using 3-day and 35-day repeat cycles. During the geodetic mission, ERS-1 was put in two long repeat cycles of 168 days, which is equivalent to a single 336-day cycle. The geodetic mission allowed for accurate mapping of the Earth's
bathymetry
Bathymetry (; ) is the study of underwater depth of ocean floors (''seabed topography''), lake floors, or river floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water de ...
and
geoid
The geoid () is the shape that the ocean surface would take under the influence of the gravity of Earth, including gravitational attraction and Earth's rotation, if other influences such as winds and tides were absent. This surface is extended ...
over the seas using the Radar Altimeter.
On 10 March 2000, ERS-1's
attitude control
Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc.
Controlling vehicle ...
system failed due to a
gyroscope
A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rota ...
malfunction and its mission was officially declared finished.
ERS-2
Its successor, ERS-2, was launched on 21 April 1995, on an
Ariane 4
The Ariane 4 was a European expendable space launch system, developed by the ''Centre national d'études spatiales'' (CNES), the French space agency, for the European Space Agency (ESA). It was manufactured by ArianeGroup and marketed by Arian ...
, from ESA's
Guiana Space Centre
The Guiana Space Centre (french: links=no, Centre spatial guyanais; CSG), also called Europe's Spaceport, is a European spaceport to the northwest of Kourou in French Guiana, a region of France in South America. Kourou is located approximatel ...
near
Kourou
Kourou () is a commune in French Guiana, an overseas region and department of France in South America. Kourou is famous for being the location of the Guiana Space Centre, the main spaceport of France and the European Space Agency (ESA). It i ...
,
French Guiana
French Guiana ( or ; french: link=no, Guyane ; gcr, label=French Guianese Creole, Lagwiyann ) is an overseas departments and regions of France, overseas department/region and single territorial collectivity of France on the northern Atlantic ...
. Largely identical to ERS-1, it added additional instruments and included improvements to existing instruments including:
* GOME (Global
Ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
Monitoring Experiment) is a
nadir
The nadir (, ; ar, نظير, naẓīr, counterpart) is the direction pointing directly ''below'' a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface.
The direc ...
scanning
ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
and visible
spectrometer
A spectrometer () is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where the ...
.
* ATSR-2 included 3 visible spectrum bands specialized for
chlorophyll
Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...
and
vegetation
Vegetation is an assemblage of plant species and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic character ...
When ERS-2 was launched, ERS-1 shared the same orbital plane. This allowed a
tandem
Tandem, or in tandem, is an arrangement in which a team of machines, animals or people are lined up one behind another, all facing in the same direction.
The original use of the term in English was in ''tandem harness'', which is used for two ...
mission, with ERS-2 passing the same point on the ground 1 day later than ERS-1. ERS-2 has a repeat cycle of 35 days.
ERS-2 has been operating without
gyroscope
A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rota ...
s since February 2001, resulting in some degradation of the data provided by the instruments. The tape drive aboard failed on 22 June 2003, leaving the instruments operating only within visibility of a ground station. Since the tape drive failure additional ground stations have been brought online to increase the data gathering abilities of the satellite. The Wind Scatterometer and GOME were the only instruments of their kind until the launches of
MetOp-A
Metop (Meteorological Operational satellite) is a series of three polar-orbiting meteorological satellites developed by the European Space Agency (ESA) and operated by the European Organisation for the Exploitation of Meteorological Satellites ...
and
Envisat
Envisat ("Environmental Satellite") is a large inactive Earth-observing satellite which is still in orbit and now considered space debris. Operated by the European Space Agency (ESA), it was the world's largest civilian Earth observation satell ...
, respectively.
The successor to ERS-2 was the
Envisat
Envisat ("Environmental Satellite") is a large inactive Earth-observing satellite which is still in orbit and now considered space debris. Operated by the European Space Agency (ESA), it was the world's largest civilian Earth observation satell ...
satellite, launched 1 March 2002. Envisat contained improved versions of many of the instruments onboard ERS-2. However, even after the launch of its successor, the operational life of ERS-2 was increased until 2011, when the decision was made to end the mission. Over a series of burns in July, August and September, ERS-2 was finally depleted of all fuel on 5 September 2011. At 13:16:38 the batteries were switched off and the satellite decommissioned. The spacecraft was left in an orbit where it will reenter the Earth's atmosphere and safely disintegrate within 25 years, in accordance with international standards.
In the final stages of emptying the fuel tanks, it was estimated that they would be empty after a 40-minute burn on 2 September 2011. However, the spacecraft survived both this maneuver and a second 40-minute burn on 3 September. On 5 September a third burn was initiated and the fuel tanks were finally drained.
See also
*
1991 in spaceflight
*
1995 in spaceflight
This article outlines notable events occurring in 1995 in spaceflight
Spaceflight (or space flight) is an application of astronautics to fly spacecraft into or through outer space, either with or without humans on board. Most spacefligh ...
Notes
*
References
External links
ERS homepage at ESANext ESA SAR Toolbox for viewing, calibrating and analyzing ERS 1 & 2 SAR Level 1 data and higher
{{ESA projects
Earth observation satellites of the European Space Agency
European Space Agency programmes
Space synthetic aperture radar
Earth satellite radar altimeters
Spacecraft launched in 1991
Spacecraft launched in 1995
Spacecraft launched by Ariane rockets