## 2 EO Satellite and In Situ Observations for Earth Surface
### GOES, METEOSAT and Other Geostationary Satellites  
Geosynchronous satellites have the great advantage of orbiting with the Earth's rotation and therefore of providing observations of the same location at high temporal frequency. Such capability is particularly relevant for the estimation of variables rapidly changing with time over land and ocean surfaces. EUMETSAT currently operates four satellites of the Meteosat Second Generation (MSG) series over Europe and Africa (Meteosat-9, Meteosat-10 and Meteosat-11) and over the Indian Ocean (Meteosat-8). The redundancy over the former (nominal 0\({}^{\circ}\)E) disk allows a full disk service together with a rapid scan service over Europe, keeping one satellite as backup. MSG series observations are available for more than 14 years, since 2004. If combined with Meteosat First Generation satellites, these can be extended back in time to the early 1980s, despite the poorer spatial and temporal samplings, as well as lower spectral resolutions of that series. The National Oceanic and Atmospheric Administration, NOAA's operating strategy calls for two GOES satellites to be active at all times, one satellite to observe the Atlantic Ocean and the eastern half of the USA, and the other to observe the Pacific Ocean and the western part of the country. GOES-16 (or GOES-East) positioned at 75\({}^{\circ}\)W longitude and GOES-15 (or GOES-West) positioned at 135\({}^{\circ}\)W longitude are currently, the two operational meteorological satellites in geostationary orbit over the equator operated by NOAA. GOES-16 replaced GOES-13 on 8 January 2018 and GOES-15 replaced GOES-11 on 6 December 2011. Additionally, GOES-13 located at 60\({}^{\circ}\)W supports Central and South America to prevent data outages during the GOES-16 rapid scan operations, while GOES-14 is maintained as on-orbit spare to replace either, GOES-15 or GOES-16, in the event of failure. Russia's new-generation weather satellite Elektro-L No.1 (GOMS-2) operates at 76\({}^{\circ}\)E over the Indian Ocean. India also operates geostationary satellites called INSAT-3D which carry instruments for meteorology. China currently maintains three Fengyun geostationary satellites (FY-2E at 86.5\({}^{\circ}\)E, FY-2F at 112\({}^{\circ}\)E, and FY-2G at 105\({}^{\circ}\)E) in operations, while Japan maintains MTSAT-2 (very similar to GOES satellites prior to GOES-16) located over the mid Pacific at 145\({}^{\circ}\)E (although inactive since 10 March 2017) and the Himawari-8 (with instruments similar to GOES-16/17) at 140\({}^{\circ}\)E. Table 2 provides an overview of geostationary satellite series launched until this day and their main coverage area. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Geostationary Satellite** & **Agency** &
\begin{tabular}{l} **Operating** \\ **Longitude** \\ \end{tabular} & **Area Coverage** \\ \hline Meteosat First Generation series & \multicolumn{1}{c}{} & 0\({}^{\circ}\)E; & \\ (up to Meteosat-7) & EUMETSAT & 57\({}^{\circ}\)E–63\({}^{\circ}\)E; & Africa, Europe, partly South \\  & & 50\({}^{\circ}\)W & \\ \hline MSG series (Meteosat-8 to & \multicolumn{1}{c}{} & 0\({}^{\circ}\)E; 9.5\({}^{\circ}\)E; & Africa, Europe, partly South \\ Meteosat-11) & EUMETSAT & 45\({}^{\circ}\)E & America ; Indian Ocean Coverage \\ \hline GOES-East/West & NOAA & 75\({}^{\circ}\)W; 135\({}^{\circ}\)W & East Satellite: North and South America, \\  & & & America, Atlantic Ocean; West Satellite: North and South America, \\  & & & Pacific Ocean \\ \hline GOMS-2 & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \\ \hline INSAT-3D & \multicolumn{1}{c}{} & 82\({}^{\circ}\)E & Asia, Indian Ocean \\ \hline FY-2 & \multicolumn{1}{c}{} & 86.5\({}^{\circ}\)E; 105\({}^{\circ}\)E; & Asia, Indian Ocean, Australia \\  & & & \\ \hline MTSAT-2 & \multicolumn{1}{c}{} & 145\({}^{\circ}\)E & Asia, Indian and Western Pacific \\  & & & Ocean, Australia (inactive since \\  & & & 10 March 2017) \\ \hline Himawari & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \\ \hline \hline \end{tabular}
\end{table}