Breaking with tradition, the Meteosat Third Generation (MTG) will be based on three axes stabilised platforms rather than the spin stabilised platforms of the first and second generation satellites. The advantage of having three axes stabilised platforms is that the instruments will be pointed at the Earth for 100% of their in orbit time, a prerequisite for the operation of sounding instruments.
The satellite series will comprise four imaging and two sounding satellites. The imaging satellites, MTG-I, will fly the Flexible Combined Imager (FCI) and the Lightning Imager (LI), an imaging lightning detection instrument. The sounding satellites, MTG-S, will include an interferometer, the Infra-red Sounder (IRS), with hyper-spectral resolution in the thermal spectral domain, and the Sentinel-4 instrument, the high resolution Ultraviolet Visible Near-infrared (UVN) spectrometer.
Flexible Combined Imager
The Flexible Combined Imager (FCI) on the MTG-I satellite will continue the very successful operation of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on Meteosat Second Generation (MSG). The satellite’s three axes stabilised platform will be capable of providing additional channels with better spatial, temporal and radiometric resolution, compared to the current MSG satellites.
Requirements for the FCI have been formulated by regional and global Numerical Weather Prediction (NWP) and Nowcasting communities. These requirements are reflected in the design which allows for Full Disk Scan (FDS), with a basic repeat cycle of 10 minutes, and a European Regional-Rapid-Scan (RRS) which covers of one-quarter of the full disk with a repeat cycle of 2.5 minutes. The FCI takes measurement in 16 channels of which eight are placed in the solar spectral domain between 0.4 µm to 2.1 µm, delivering data with a 1 km spatial resolution. The additional eight channels are in the thermal spectral domain between 3.8 µm to 13.3 µm, delivering data with a 2 km spatial resolution. In the RRS mode there will be two additional channels in the solar domain, with a spatial resolution of 0.5 km, and two in the thermal domain, with a spatial resolution of 1 km.
* The channels VIS 0.6, NIR 2.2, IR 3.8 and IR 10.5 are delivered in both FDS and RRS sampling configurations, the latter is indicated by * in the table.
With the FCI on-board the MTG-I satellites, Europe will continue to play the leading role in imaging radiometry from the geostationary orbit in the decades to come.
The Lightning Imager (LI) will offer improvements for Nowcasting by delivering information on total lightning (Inter Cloud – IC and Cloud to Ground - CG). The instrument will bring full hemispheric near real-time total lightning detection capabilities.
The benefit of the LI mission is that it will continuously and simultaneously observe total lightning over the hemisphere, providing the information to the users with an extremely high timeliness. One method of assessing the impact of climate change on thunderstorm activity is to globally monitor and long-term analyse the lightning characteristics, which would require a long-term stable and spatially homogeneous lightning observing system. Lightning is a major source of harmful nitrogen oxides (NOx) in the atmosphere. NOx plays a key role in the ozone conversion process and acid rain generation. A detailed knowledge of the global distribution of the total lightning (CG + IC) is a prerequisite for studying and monitoring the physical and chemical processes in the atmosphere regarding NOx. Lightning observations from the geostationary orbit, delivered with spatially homogenous and well-characterised quality, are specifically suited to support these climate and atmospheric chemistry applications.
The LI on MTG will compliment the two NOAA GLMs (Geostationary Lightning Mapper) on the GOES-R and the GOES-S satellites, thus contributing, in the long term, to near global coverage.
The Infrared Sounder (IRS) on MTG-S will be able to provide unprecedented information on horizontally, vertically, and temporally (4-dimensional) resolved water vapour and temperature structures of the atmosphere.
Retrieving highly resolved vertical structures of humidity (~2 km resolution with 10% accuracy) and temperature (~1 km with 0.5° - 1.5° accuracy) by remote sensing techniques does require measurements within the water vapour and CO2 absorption bands with extremely high spectral resolution and accuracy. The IRS is based on an imaging Fourier-interferometer with a hyperspectral resolution of 0.625 cm-1 wave-number, taking measurements in two bands, the Long-Wave InfraRed (LWIR) and the Mid-Wave InfraRed (MWIR), with a spatial resolution of 4 km. The IRS will deliver over the Full Disk in the LWIR (700 – 1210 cm-1 or 14.3 – 8.3 µm) 800 spectral channels and in the MWIR (1600 – 2175 cm-1 or 6.25 – 4.6 µm) 920 channels with a basic repeat cycle of 60 min.
The IRS includes the ozone band within LWIR and the carbon monoxide band within MWIR. This will allow measurement within the free troposphere, leading to information on enhanced levels of pollution in the boundary layer below. By providing operational measurements of carbon monoxide and ozone, IRS will also make a significant contribution to the space segment of the Global Monitoring for Environment and Security (GMES) initiative.
The Ultraviolet, Visible and Near-Infrared Sounding (UVN) instrument is a Global Monitoring for Environment and Security (GMES) Sentinel 4 instrument designed for geostationary chemistry applications. It will fly on board the MTG-S satellites. Funding for the UVN is provided by the European Commission in cooperation with European Space Agency (ESA).
The UVN is a spectrometer taking measurements in the ultraviolet (UV: 305 – 400 nm), the visible (VIS: 400 – 500 nm) and the near infrared (NIR: 755 – 775 nm) with a spatial resolution of better than 10 km. Its observations are restricted to Earth area coverage, from 30 to 65º N in latitude and 30º W to 45º E in longitude. The observation repeat cycle period will be shorter than or equal to one hour.
ESA is responsible for the definition of the Sentinel 4 mission and provision of the UVN Instrument, whereas EUMETSAT takes responsibility for the operational processing, delivery and management of the instrument data.