Editing Envisat (section)

== Instruments ==
[[File:Envisat instruments ESA194759.jpg|thumb|right|Instruments carried by Envisat.]]{{More citations needed section|date=August 2020|find=Envisat instruments}}
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, navigation, and control|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 [[Earth's atmosphere|atmosphere]].

=== AATSR ===
{{Main|AATSR}}
AATSR (Advanced Along Track Scanning [[Radiometer]]) can measure the [[sea]] surface temperature in the [[visible spectrum|visible]] and [[infrared spectrum|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 {{convert|0.3|K-change|sigfig=2}}, for [[climatology|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|Atmospheric Sounding]]) is a [[Fourier transform]]ing infrared spectrometer which provides pressure and temperature profiles, and profiles of trace gases nitrogen dioxide ({{chem|NO|2}}), [[nitrous oxide]] ({{chem|N|2|O}}), methane ({{chem|CH|4}}), nitric acid ({{chem|HNO|3}}), ozone ({{chem|O|3}}), and water ({{chem|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 {{convert|3|to|5|km|mi|abbr=on|sigfig=1}} depending on altitude (the larger at the level of the upper stratosphere).

=== MERIS ===
{{Main|MERIS}}

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

=== SCIAMACHY ===
{{Main|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&nbsp;nm) for wavelengths between 240 and 1700&nbsp;nm, and in certain spectra between 2,000 and 2,400&nbsp;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 [[Netherlands Organisation for Applied Scientific Research|TNO]]/TPD, [[SRON]] and [[Airbus Defence and Space]] Netherlands.<ref>{{Cite web|url=https://www.sron.nl/experimenten-50-jaar-ruimteonderzoek-2820/i-scimachy|title=I - Sciamachy}}</ref>

=== RA-2 ===
RA-2 ([[Radar]] [[Altimeter]] 2) is a dual-[[frequency]] [[Nadir]] pointing Radar operating in the [[Ku band|K<sub>u</sub> band]] and [[S band]]s, 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 (IEEE)|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 [[polarization (waves)|polarities of light]] or combining different polarities, angles of incidence and spatial resolutions.
{| class="wikitable"
|-
! Mode
! Id
! Polarisation
! Incidence
! Resolution
! Swath
|-
| Alternating polarisation
| AP
| HH/VV, HH/HV, VV/VH
| 15–45°
| 30–150&nbsp;m
| 58–110&nbsp;km
|- style="background:#efefef;"
| Image
| IM
| HH, VV
| 15–45°
| 30–150&nbsp;m
| 58–110&nbsp;km
|-
| Wave
| WV
| HH, VV
|
| {{0}}400 m
| 5&nbsp;km × 5&nbsp;km
|- style="background:#efefef;"
| Suivi global (ScanSAR)
| GM
| HH, VV
|
| 1000&nbsp;m
| 405&nbsp;km
|-
| Wide Swath (ScanSAR)
| WS
| HH, VV
|
| {{0}}150&nbsp;m
| 405&nbsp;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):
* RAW (raw data, or "Level 0"), which contains all the information necessary to create images.
* S (complex data, "Single Look Complex"), images in complex numeric form, the real and imaginary parts of the output of the compression algorithm
* P (precision image), amplified image with constant pixel width (12.5&nbsp;m for IMP)
* M (medium precision image), amplified radiometry image with a resolution greater than P
* G (geocoded image), amplified image to which simple geographical transforms have been applied to show relief.

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

=== DORIS ===
{{Main|DORIS (geodesy)}}

DORIS ([[Doppler effect|Doppler]] Orbitography and Radiopositioning Integrated by Satellite) determines the satellite's orbit to within {{convert|10|cm|in|abbr=on|sigfig=1}}.

=== GOMOS ===
{{Main|GOMOS}}

GOMOS (Global [[Ozone]] Monitoring by Occultation of [[Star]]s) looks at stars as they descend through the Earth's atmosphere and change colour, allowing measurement of [[gas]]es such as ozone ({{chem|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 ({{chem|NO|2}}), nitrogen trioxide, ({{chem|NO|3}}), {{chem|OClO}}), ozone ({{chem|O|3}}) and aerosols present between about {{convert|20|to|80|km|mi|abbr=on}} altitude. It has a resolution of {{convert|3|km|mi|abbr=on}}.