Envisat

Last updated

Envisat
Envisatmod.jpg
Model of Envisat
Mission type Earth observation
Operator ESA
COSPAR ID 2002-009A OOjs UI icon edit-ltr-progressive.svg
SATCAT no. 27386
Website envisat.esa.int
Mission durationPlanned: 5 years
Final: 10 years, 1 month, 6 days
Spacecraft properties
Manufacturer Astrium
Launch mass8,211 kg (18,102 lb)
Dimensions26 × 10 × 5 m (85 × 33 × 16 ft)
Power6,500 watts
Start of mission
Launch date1 March 2002, 01:07:59 (2002-03-01UTC01:07:59Z) UTC
Rocket Ariane 5G V-145
Launch site Kourou ELA-3
Contractor Arianespace
End of mission
DisposalNone
Declared9 May 2012 (2012-05-10)
Last contact8 April 2012 (2012-04-09)
(spacecraft failure)
Decay date~150 years
Orbital parameters
Reference system Geocentric
Regime Polar low Earth
Semi-major axis 7,144.9 km (4,439.6 mi)
Eccentricity 0.00042
Perigee altitude 772 km (480 mi)
Apogee altitude 774 km (481 mi)
Inclination 98.40 degrees
Period 100.16 minutes
Repeat interval35 days
Epoch 15 December 2013, 03:07:00 UTC [1]
Instruments

Envisat ("Environmental Satellite") is a large Earth-observing satellite which has been inactive since 2012. It is still in orbit and considered space debris. Operated by the European Space Agency (ESA), it was the world's largest civilian Earth observation satellite. [2]

Contents

It was launched on 1 March 2002 aboard an Ariane 5 from the Guyana Space Centre in Kourou, French Guiana, into a Sun synchronous polar orbit at an altitude of 790 ± 10 km. It orbits the Earth in about 101 minutes, with a repeat cycle of 35 days. After losing contact with the satellite on 8 April 2012, ESA formally announced the end of Envisat's mission on 9 May 2012. [3]

Envisat cost 2.3 billion Euro (including 300 million Euro for 5 years of operations) to develop and launch. [4] The mission has been replaced by the Sentinel series of satellites. The first of these, Sentinel 1, has taken over the radar duties of Envisat since its launch in 2014.

Mission

Envisat was launched as an Earth observation satellite. Its objective was to support the continuity of European Remote-Sensing Satellite missions, providing additional observations to improve environmental studies.

To accomplish the global and regional objectives of the mission, numerous scientific disciplines used the data acquired from the sensors on the satellite to study atmospheric chemistry, ozone depletion, biological oceanography, ocean temperature and colour, wind waves, hydrology (humidity, floods), agriculture and arboriculture, natural hazards, digital elevation modelling (using interferometry), monitoring of maritime traffic, atmospheric dispersion modelling (pollution), cartography and snow and ice.

Specifications

Dimensions

26 m (85 ft) × 10 m (33 ft) × 5 m (16 ft) in orbit with the solar array deployed. [5]

Mass

8,211 kg (18,102 lb), including 319 kg (703 lb) of fuel and a 2,118 kg (4,669 lb) instrument payload. [6]

Power

Solar array with a total load of 3560 W.

Instruments

Instruments carried by Envisat. Envisat instruments ESA194759.jpg
Instruments carried by Envisat.

Envisat carries an array of nine Earth-observation instruments that gathered information about the Earth (land, water, ice, and atmosphere) using a variety of measurement principles. A tenth instrument, DORIS, provided guidance and control. Several of the instruments were advanced versions of instruments that were flown on the earlier ERS-1 and ERS 2 missions and other satellites.

MWR

MWR (Microwave Radiometer) was designed for measuring water vapour in the atmosphere.

AATSR

AATSR (Advanced Along Track Scanning Radiometer) can measure the sea surface temperature in the visible and infrared spectra. It is the successor of ATSR1 and ATSR2, payloads of ERS 1 and ERS 2. AATSR can measure Earth's surface temperature to a precision of 0.3 K (0.54 °F), for climate research. Among the secondary objectives of AATSR is the observation of environmental parameters such as water content, biomass, and vegetal health and growth.

MIPAS

MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) is a Fourier transforming infrared spectrometer which provides pressure and temperature profiles, and profiles of trace gases nitrogen dioxide (NO
2
), nitrous oxide (N
2
O
), methane (CH
4
), nitric acid (HNO
3
), ozone (O
3
), and water (H
2
O
) in the stratosphere. The instrument functions with high spectral resolution in an extended spectral band, which allows coverage across the Earth in all seasons and at equal quality night and day. MIPAS has a vertical resolution of 3 to 5 km (2 to 3 mi) depending on altitude (the larger at the level of the upper stratosphere).

MERIS

MERIS (MEdium Resolution Imaging Spectrometer) measures the reflectance of the Earth (surface and atmosphere) in the solar spectral range (390 to 1040  nm) and transmits 15 spectral bands back to the ground segment. MERIS was built at the Cannes Mandelieu Space Center.

SCIAMACHY

SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) compares light coming from the sun to light reflected by the Earth, which provides information on the atmosphere through which the Earth-reflected light has passed.

SCIAMACHY is an image spectrometer with the principal objective of mapping the concentration of trace gases and aerosols in the troposphere and stratosphere. Rays of sunlight that are reflected transmitted, backscattered and reflected by the atmosphere are captured at a high spectral resolution (0.2 to 0.5 nm) for wavelengths between 240 and 1700 nm, and in certain spectra between 2,000 and 2,400 nm. Its high spectral resolution over a wide range of wavelengths can detect many trace gases even in tiny concentrations. The wavelengths captured also allow effective detection of aerosols and clouds. SCIAMACHY uses 3 different targeting modes: to the nadir (against the sun), to the limbus (through the atmospheric corona), and during solar or lunar eclipses. SCIAMACHY was built by Netherlands and Germany at TNO/TPD, SRON and Airbus Defence and Space Netherlands. [7]

RA-2

RA-2 (Radar Altimeter 2) is a dual-frequency Nadir pointing Radar operating in the Ku band and S bands, it is used to define ocean topography, map/monitor sea ice and measure land heights.

Mean sea level measurements from Envisat are continuously graphed at the Centre National d'Etudes Spatiales web site, on the Aviso page.

ASAR

ASAR (Advanced Synthetic Aperture Radar) operates in the C band in a wide variety of modes. It can detect changes in surface heights with sub-millimeter precision. It served as a data link for ERS 1 and ERS 2, providing numerous functions such as observations of different polarities of light or combining different polarities, angles of incidence and spatial resolutions.

ModeIdPolarisationIncidenceResolutionSwath
Alternating polarisationAPHH/VV, HH/HV, VV/VH15–45°30–150 m58–110 km
ImageIMHH, VV15–45°30–150 m58–110 km
WaveWVHH, VV400 m5 km × 5 km
Suivi global (ScanSAR)GMHH, VV1000 m405 km
Wide Swath (ScanSAR)WSHH, VV150 m405 km

These different types of raw data can be given several levels of treatment (suffixed to the ID of the acquisition mode: IMP, APS, and so on):

Data capture in WV mode is unusual in that they constitute a series of 5 km × 5 km spaced at 100 km.

DORIS

DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) determines the satellite's orbit to within 10 cm (4 in).

GOMOS

GOMOS (Global Ozone Monitoring by Occultation of Stars) looks at stars as they descend through the Earth's atmosphere and change colour, allowing measurement of gases such as ozone (O
3
), including their vertical distribution.

GOMOS uses the principle of occultation. Its sensors detect light from a star traversing the Earth's atmosphere and measures the depletion of that light by trace gases nitrogen dioxide (NO
2
), nitrogen trioxide, (NO
3
), OClO), ozone (O
3
) and aerosols present between about 20 to 80 km (12 to 50 mi) altitude. It has a resolution of 3 km (1.9 mi).

Loss of contact

ESA announced on 12 April 2012 that they lost contact with Envisat on Sunday, 8 April 2012, after 10 years of service, exceeding the initially planned life span by 5 years. The spacecraft was still in a stable orbit, but attempts to contact it were unsuccessful. [8] [9] Ground-based radar and the French Pleiades Earth probe were used to image the silent Envisat and look for damage. [10] ESA formally announced the end of Envisat's mission on 9 May 2012. [3]

Envisat was launched in 2002 and it operated five years beyond its planned mission lifetime, delivering over a petabyte of data. [3] ESA was expecting to turn off the spacecraft in 2014. [11]

Space safety

Space debris populations seen from outside geosynchronous orbit (GEO). Note the two primary debris fields, the ring of objects in GEO, and the cloud of objects in low Earth orbit (LEO). Debris-GEO1280.jpg
Space debris populations seen from outside geosynchronous orbit (GEO). Note the two primary debris fields, the ring of objects in GEO, and the cloud of objects in low Earth orbit (LEO).

Envisat poses a hazard because of the risk of collisions with space debris. Given its orbit and its area-to-mass ratio, it will take about 150 years for the satellite to be gradually pulled into the Earth's atmosphere. [12] Envisat is currently orbiting in an environment where two catalogued space debris objects can be expected to pass within about 200 m (660 ft) of it every year, which would likely trigger the need for a manoeuvre to avoid a possible collision. [13] A collision between a satellite the size of Envisat and an object as small as 10 kg could produce a very large cloud of debris, initiating a self-sustaining chain-reaction of collisions and fragmentation with production of new debris, a phenomenon known as the Kessler Syndrome. [13]

Envisat was a candidate for a mission to remove it from orbit, called e.Deorbit. The spacecraft sent to bring down Envisat would itself need to have a mass of approximately 1.6 tonnes. [14]

See also

Related Research Articles

<span class="mw-page-title-main">Earth observation satellite</span> Satellite specifically designed to observe Earth from orbit

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, meteorology, cartography and others. The most common type are Earth imaging satellites, that take satellite images, analogous to aerial photographs; some EO satellites may perform remote sensing without forming pictures, such as in GNSS radio occultation.

SCISAT-1 is a Canadian satellite designed to make observations of the Earth's atmosphere. Its main instruments are an optical Fourier transform infrared spectrometer, the ACE-FTS Instrument, and an ultraviolet spectrophotometer, MAESTRO. These devices record spectra of the Sun, as sunlight passes through the Earth's atmosphere, making analyses of the chemical elements of the atmosphere possible.

<span class="mw-page-title-main">Upper Atmosphere Research Satellite</span> NASA-operated orbital observatory (1991-2011)

The Upper Atmosphere Research Satellite (UARS) was a NASA-operated orbital observatory whose mission was to study the Earth's atmosphere, particularly the protective ozone layer. The 5,900-kilogram (13,000 lb) satellite was deployed from Space Shuttle Discovery during the STS-48 mission on 15 September 1991. It entered Earth orbit at an operational altitude of 600 kilometers (370 mi), with an orbital inclination of 57 degrees.

<i>Venus Express</i> European orbiter mission to Venus (2005–2015)

Venus Express (VEX) was the first Venus exploration mission of the European Space Agency (ESA). Launched in November 2005, it arrived at Venus in April 2006 and began continuously sending back science data from its polar orbit around Venus. Equipped with seven scientific instruments, the main objective of the mission was the long term observation of the Venusian atmosphere. The observation over such long periods of time had never been done in previous missions to Venus, and was key to a better understanding of the atmospheric dynamics. ESA concluded the mission in December 2014.

<span class="mw-page-title-main">European Remote-Sensing Satellite</span> European Space Agency Earth-observing satellite program

European Remote Sensing satellite (ERS) was the European Space Agency's first Earth-observing satellite programme using a polar orbit. It consisted of two satellites, ERS-1 and ERS-2, with ERS-1 being launched in 1991.

<span class="mw-page-title-main">Satellite imagery</span> Images taken from an artificial satellite

Satellite images are images of Earth collected by imaging satellites operated by governments and businesses around the world. Satellite imaging companies sell images by licensing them to governments and businesses such as Apple Maps and Google Maps.

<span class="mw-page-title-main">Space-based radar</span> Use of radar systems mounted on satellites

Space-based radar or spaceborne radar is a radar operating in outer space; orbiting radar is a radar in orbit and Earth orbiting radar is a radar in geocentric orbit. A number of Earth-observing satellites, such as RADARSAT, have employed synthetic aperture radar (SAR) to obtain terrain and land-cover information about the Earth.

Global Ozone Monitoring by Occultation of Stars (GOMOS), is an instrument on board the European satellite Envisat launched 1 March 2002. It is the first space instrument dedicated to the study of the atmosphere of the Earth by the technique of stellar occultation. The spectrum of stars in the ultraviolet, visible and the near infrared parts of the electromagnetic spectrum is observed. It is aimed to use GOMOS to build a climatology of ozone and related species in the middle atmosphere.

<span class="mw-page-title-main">MERIS</span>

MEdium Resolution Imaging Spectrometer (MERIS) was one of the main instruments on board the European Space Agency (ESA)'s Envisat platform. The sensor was in orbit from 2002 to 2012. ESA formally announced the end of Envisat's mission on 9 May 2012.

<span class="mw-page-title-main">SCIAMACHY</span>

SCIAMACHY was one of ten instruments aboard of ESA's ENVIronmental SATellite, ENVISAT. It was a satellite spectrometer designed to measure sunlight, transmitted, reflected and scattered by the Earth's atmosphere or surface in the ultraviolet, visible and near infrared wavelength region at moderate spectral resolution. SCIAMACHY was built by Netherlands and Germany at TNO/TPD, SRON and Dutch Space.

<span class="mw-page-title-main">Copernicus Programme</span> Programme of the European Commission

Copernicus is the Earth observation component of the European Union Space Programme, managed by the European Commission and implemented in partnership with the EU Member States, the European Space Agency (ESA), the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), the European Centre for Medium-Range Weather Forecasts (ECMWF), the Joint Research Centre (JRC), the European Environment Agency (EEA), the European Maritime Safety Agency (EMSA), Frontex, SatCen and Mercator Océan.

<span class="mw-page-title-main">MetOp</span> Series of European meteorological satellites

Metop 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 (EUMETSAT). The satellites form the space segment component of the overall EUMETSAT Polar System (EPS), which in turn is the European half of the EUMETSAT / NOAA Initial Joint Polar System (IJPS). The satellites carry a payload comprising 11 scientific instruments and two which support Cospas-Sarsat Search and Rescue services. In order to provide data continuity between Metop and NOAA Polar Operational Environmental Satellites (POES), several instruments are carried on both fleets of satellites.

<span class="mw-page-title-main">Ozone monitoring instrument</span>

The ozone monitoring instrument (OMI) is a nadir-viewing visual and ultraviolet spectrometer aboard the NASA Aura spacecraft. Aura flies in formation about 15 minutes behind Aqua, both of which orbit the Earth in a polar Sun-synchronous pattern. Aura was launched on July 15, 2004, and OMI has collected data since August 9, 2004. OMI can distinguish between aerosol types, such as smoke, dust, and sulfates, and can measure cloud pressure and coverage, which provide data to derive tropospheric ozone. OMI follows in the heritage of TOMS, SBUV, GOME, SCIAMACHY, and GOMOS. OMI measurements cover a spectral region of 264–504 nm (nanometers) with a spectral resolution between 0.42 nm and 0.63 nm and a nominal ground footprint of 13 × 24 km2 at nadir. The Aura satellite orbits at an altitude of 705 km in a sun-synchronous polar orbit with an exact 16-day repeat cycle and with a local equator crossing time of 13. 45 on the ascending node. The orbital inclination is 98.1 degrees, providing latitudinal coverage from 82° N to 82° S. It is a wide-field-imaging spectrometer with a 114° across-track viewing angle range that provides a 2600 km wide swath, enabling measurements with a daily global coverage. OMI is continuing the TOMS record for total ozone and other atmospheric parameters related to ozone chemistry and climate.

<span class="mw-page-title-main">Sentinel-3</span> Earth observation satellite series

Sentinel-3 is an Earth observation heavy satellite series developed by the European Space Agency as part of the Copernicus Programme. As of 2024, it consists of 2 satellites: Sentinel-3A and Sentinel-3B. After initial commissioning, each satellite was handed over to EUMETSAT for the routine operations phase of the mission. Two recurrent satellites, Sentinel-3C and Sentinel-3D, will follow in approximately 2025 and 2028 respectively to ensure continuity of the Sentinel-3 mission.

<span class="mw-page-title-main">EarthCARE</span> Joint European/Japanese Earth research satellite

EarthCARE, nicknamed Hakuryū, is a joint European/Japanese satellite, the sixth of ESA's Earth Explorer Programme. The main goal of the mission is the observation and characterization of clouds and aerosols as well as measuring the reflected solar radiation and the infrared radiation emitted from Earth's surface and atmosphere.

<span class="mw-page-title-main">ADEOS I</span> Derelict Japanese Earth observation satellite

ADEOS I was an Earth observation satellite launched by NASDA in 1996. The mission's Japanese name, Midori means "green". The mission ended in July 1997 after the satellite sustained structural damage to the solar panel. Its successor, ADEOS II, was launched in 2002. Like the first mission, it ended after less than a year, also following solar panel malfunctions.

GEOMS – Generic Earth Observation Metadata Standard is a metadata standard used for archiving data from groundbased networks, like the Network for the Detection of Atmospheric Composition Change (NDACC), and for using this kind of data for the validation of NASA and ESA satellite data.

<span class="mw-page-title-main">Suomi NPP</span> NASA/NOAA Earth weather satellite (2011–Present)

The Suomi National Polar-orbiting Partnership, previously known as the National Polar-orbiting Operational Environmental Satellite System Preparatory Project (NPP) and NPP-Bridge, is a weather satellite operated by the United States National Oceanic and Atmospheric Administration (NOAA). It was launched in 2011 and is currently in operation.

<span class="mw-page-title-main">Sentinel-5 Precursor</span> Earth observation satellite

Sentinel-5 Precursor (Sentinel-5P) is an Earth observation satellite developed by ESA as part of the Copernicus Programme to close the gap in continuity of observations between Envisat and Sentinel-5. It was launched in October 2017, and has a design life of 7 years. The TROPOspheric Monitoring Instrument (Tropomi) provides the most detailed methane emissions monitoring available.

<span class="mw-page-title-main">Sentinel-4</span> Earth observation satellite

Sentinel-4 is a European Earth observation mission under development to support the European Union Copernicus Programme. It will focus on monitoring of trace gas concentrations and aerosols in the atmosphere to support operational services covering air-quality near-real time applications, air-quality protocol monitoring, and climate protocol monitoring. The specific objective of Sentinel-4 is to support this with a high revisit time over Europe.

References

  1. "ENVISAT Satellite details 2002-009A NORAD 27386". N2YO. 15 December 2013. Retrieved 15 December 2013.
  2. EarthNet Online
  3. 1 2 3 "ESA declares end of mission for Envisat". ESA. 9 May 2012.
  4. European Space Agency web-site
  5. "EnviSat (Environmental Satellite)". eoPortal.
  6. Envisat – Overall configuration
  7. "I - Sciamachy".
  8. "Breaking News | Flagship Envisat satellite stops communicating". Spaceflight Now. Retrieved 21 April 2012.
  9. "ESA Portal – Envisat services interrupted". Esa.int. Retrieved 21 April 2012.
  10. Huge, Mysteriously Silent Satellite Spotted by Another Spacecraft Space.com article, 20 April 2012
  11. Contact lost with flagship Envisat spacecraft 12 April 2012.
  12. "Envisat To Pose Big Orbital Debris Threat for 150 Years, Experts Say." SpaceNews. Retrieved: 27 September 2015.
  13. 1 2 Gini, Andrea (25 April 2012). "Don Kessler on Envisat and the Kessler Syndrome". Space Safety Magazine. Retrieved 9 May 2012.
  14. "e.Deorbit Symposium". ESA. 6 May 2014. Archived from the original on 1 July 2015. Retrieved 2 June 2015.