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Satellite-based instruments

The UV-Vis/DOAS group uses measurement from several satellite-based instruments to determine the concentration and distribution of some trace gases in the Earth's atmosphere. The intruments we use are all nadir-viewing, i.e. the look downward while orbitting the Earth. These instruments measure the sunlight scattered in the atmosphere and reflected by the surface of the Earth, as function of the wavelength of the light. In other words: the instruments measure earthshine spectra. Comparing such a spectrum with the spectrum of the sunlight itself provides information on the distribution and concentration of trace gases, such as ozone and NO2, because these gases absorb or scatter part of the incoming sunlight.

The following gives a very short description of the instruments used by the UV-Vis/DOAS group and the data products derived from their measurements:

 

TROPOMI

The TROPOsphere Monitoring Instrument (TROPOMI) is the only instrument onboard the Sentinel-5 Precursor (S-5P) satellite. This platform was launched on 13 October 2017 as the first mission for the monitoring of atmospheric composition in the series of Sentinel satellites within the EU Copernicus Earth Observation Programme. One of the most obvious improvements of TROPOMI in comparision with it predecessors is the enhanced spatial resolution. With ground pixels as small as 3.5x7 km2, the data allows the identification of trace gas pollution sources at city scale.

 

OMI

The Ozone Monitoring Instrument (OMI) is a Dutch/Finnish sensor flying on the EOS Aura satellite. Although one of its main objectives has been the monitoring of the ozone content in the atmosphere, it is well capable of measuring a whole range of trece gases in the UV an visible spectrum. Other than previous atmospheric chemistry instruments, OMI contains a so-called imaging sensor, a 2D sensor where one dimension is used for spectroscopy. Smallest ground pixel size is 13x24 km2.

 

GOME-2

The GOME-2 instrument is in a way the successor of the GOME instrument aboard ERS-2, mentioned above. The GOME-2 instrument flies aboard the MetOp series of satellites meant to monitor the Earth's atmosphere. The first in the series, MetOp-A, was launched by EUMETSAT on 19 October 2006. The satellite orbits the Earth at about 800 km in a sun-synchronus orbits that passes the Equator going north to south at about 09:30 a.m., and each orbit takes approximately 100 minutes. The full swath width of the scan GOME-2 makes is 1900 km, and the nominal of the ground pixels is about 80 by 40 km. Metop-B was launched on 17 September 2012). A third and final Metop platform, also containing a GOME-2 instrument, is foreseen to be launched in September 2018.

More information regarding GOME-2 can be found, for example, on the website of EUMETSAT and DLR

 

SCIAMACHY

The Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) instrument flies aboard the Environmental Satellite (ENVISAT), which was launched by ESA in March 2002 in an orbit at about 790 km. While orbitting SCIAMACHY scans the Earth with a full swath width of 960 km, with a nominal ground pixel size of about 60 by 40 km. The satellite orbits the Earth in a sun-synchronus orbits that passes the Equator going north to south at about 10:00 a.m. Along its orbit SCIAMACHY measures alternating in nadir and limb mode for 1 minute each.

More information regarding GOME can be found, for example, on the SCIAMACHY website or the websites of ESA, and DLR.

 

GOME

The (first) Global Ozone Monitoring Experiment (GOME) was launched aboard the second European Remote Sensing (ERS-2) satellite by the European Space Agency (ESA) on 21 April 1995. The satellite orbits the Earth at about 790 km in a sun-synchronus orbit, which means that it passes the equator always at the same local time (10:30 a.m., going north to south), and each orbit takes approximately 100 minutes. While orbitting, GOME scans the Earth with a full swath width of 960 km. The nominal size of the ground pixel, i.e. the area on the Earth's surface measured by the instrument, is 320 by 40 km.

More information regarding GOME can be found, for example, on the website of ESA, DLR and the University of Bremen.

 
Last update on 13 Jul 2018