I was confused for a minute on how it's both _geostationary_ and _over Europe_ -- you can't be geostationary if your orbit is not over the equator!
Turns out[1] the MTG-S1 satellite is in fact geostationary and parked at exactly 0°00'00"N 0°00'00"E (off the coast of Ghana), 42164 km up from the center of Earth, it's just pointing at Europe at an angle.
In other words, it is
> "The Infrared Sounder on MTG-S1 is the first hyperspectral sounding instrument in geostationary orbit."
https://www.esa.int/Applications/Observing_the_Earth/Meteoro...
Is there a more technical article describing this hyperspectral instrument somewhere? It sounds pretty novel.
edit: Also, I'm now confused about the ESA's claim to be "the first", because
> "In 2016, the Chinese Meteorological Agency (CMA) launched the Geostationary Interferometric Infrared Sounder (GIIRS), to be the first hyperspectral sounder in geostationary orbit"
https://www.aos.wisc.edu/aosjournal/Volume38/Loveless_PhD.pd... (PhD thesis of David M. Loveless (2021))
In fact, I have nothing but respect for any agency that makes free and public access to earth observation data a priority, regardless of how janky their API is.
Is there a way to list what's all in geostationary orbit (either stationary at the equator, or at which longitudes they commonly cross through the equator)? Edit: found https://en.wikipedia.org/wiki/List_of_satellites_in_geosynch... (geosynchronous is a superset of geostationary). The closest is H2Sat at 0.5°. Article notes: "Some of these satellites are separated from each other by as little as 0.1° longitude [or] approximately 73 km". Trickier than keeping them apart is apparently getting a narrow enough communications beam width. /edit.
How long until we can see this ring above the equator from the ground? Although I guess the thickness would rival Saturn's rings and we would probably not be able to make it out even if the sats were shoulder to shoulder. We do see satellites from the ground when the sun hits them right, but those are typically around 1000x closer
But you are right, [1] confirms "0° longitude".
[1] https://user.eumetsat.int/resources/user-guides/mtg-in-opera...
The IRS seems 4km and sentinel 4 8km if I read it correctly. The cool thing is that it is stationary unlike other sentinel satellites and can actually be used for now casting. No clue how infrared sounding performs with cloud cover.
I think you might have misread the title, "Europe’s first [...]"
> Is there a more technical article describing this hyperspectral instrument somewhere?
https://space.oscar.wmo.int/instruments/view/irs has an short overview
Then this document provides an introduction (+ details) about the MTG-IRS program in general: https://user.eumetsat.int/s3/eup-strapi-media/MTG_IRS_L2_ATB...
Are there any other standout national agencies you've dealt with?
And, have you seen any degradation recently with NOAA data? NGS has always impressed me, but I've been worried about their future lately.
Presumably it's an intentional choice to put it at such a round number, rather than any scientific benefit over it being, say, 10km west or east.
No; I'm quoting the esa.int article verbatim. The eumetsat.int article qualifies "...over Europe", but the esa.int does not. I suspect esa.int is just mistaken.
If that was not the question, can you provide more detail?
I think esa.int is probably one of the more popular .int domains on HN: https://news.ycombinator.com/from?site=esa.int
Perhaps earth's spherical shape gives an advantage to the satellites in both cases ?
Are you looking at sentinel 1 or sentinel 2
• World Health Organization - https://who.int
• NATO - https://nato.int
• Council of Europe - https://coe.int
• Mercosur - https://mercosur.int
• African Union - https://au.int
• EFTA - https://efta.int
But I guess this is what you get when these things get away from technologists.
for example, the US has stopped sharing weather data with canada.
[0] A few sites give 10km as a standard minimum separation for geostationary satellites. That theoretically allows a thousand of them in the 100km cube, but I am guessing a lattice of them every 10 km in all 3 dimensions would not be manageable.
(Not real affiliation but still: I added a domain to that page at some point)
(In Fortran 66, variables didn't have to be declared. They would be integer if they began with I, J, K, L, M, or N. Otherwise it would be floating point [REAL, in Fortran parlance]. To this day it's why for loops usually use "i". With the bonus joke that God is real unless declared integer.)
Citation needed. Most weather data from NWS is required by treaty to be disseminated through WMO compliant methods. The Metsat data is transmitted unencrypted from the GOES sats. I don’t believe they even have the capability to encrypt it. It’s only DoD weather data that’s not being widely disseminated, AFAIK.
But some geostationary satellites are close enough so that there can be failover without adjusting receiving antennas on the ground.
So you can of course keep them dense around the equator. Probably very close down to hundreds of meters (if not less) if you coordinate the station keeping. After all the forces that push or pull the satellites out of orbit (tidal forces and particle streams) should be very similar for close neighbours. Problem is that you have to share the bandwidth of the up- and downlink then because the dishes of the groundstations cannot focus so sharply.
Given that, and redundancy put aside, one bigger satellite with more payloads would usually be cheaper than two smaller ones without any disadvantages.
I don't know if that is still in effect. Google "Did the US stop sharing weather data with Canada?" or ask your favorite LLM that provides references for its answers for more information.
Extreme weather events like storms, flooding, and heatwaves have caused hundreds of billions of euros in damage and claimed tens of thousands of lives across Europe in the past decades. Launched on 1 July 2025, MTG-S1 will provide Europe’s national meteorological services with high-frequency data on temperature, humidity and trace gases throughout the atmosphere – enabling forecasters to detect the earliest signs of severe weather, extend the lead times of weather warnings, improve forecasting, and help protect lives and property.
Phil Evans, Director-General of EUMETSAT, said: “MTG-S1 will provide entirely new types of data products that will support specialists across EUMETSAT member states in detecting signs of atmospheric instability even before clouds begin to form. Combined with data from the MTG imaging satellites, it will, for the first time, offer a space-based view of the full lifecycle of convective storms. This will provide tremendous support to national meteorological services in carrying out their vital work, helping to save lives, reduce disruption, and strengthen resilience.
“The effects of the climate crisis are not distant threats: they are already being felt across Europe – through more frequent storms, longer heatwaves, and shifting climate patterns. MTG-S1 will support more timely warnings, safer travel decisions, more effective emergency response, and support informed action.
“My sincere thanks go to everyone who made MTG-S1 possible – our teams at EUMETSAT, our member states, the European Union, the European Space Agency, national meteorological services, and all our industrial and academic partners. This successful launch is a testament to the strength of European cooperation. We now look forward to moving to the next phases and preparing the satellite for full operations.”
MTG-S1 is the first geostationary meteorological sounder satellite to fly over Europe and carries two key missions: the Infrared Sounder and the European Union’s Copernicus Sentinel-4 Ultraviolet Visible Near-infrared spectrometer.
Applause broke out at EUMETSAT headquarters in Darmstadt, Germany, as staff, guests, and media watched a live stream of the satellite separating from its launcher and continuing its journey into orbit. Tension turned to celebration as confirmation arrived that the satellite had contacted ground control, deployed its solar panels, and was on course for geostationary orbit – some 36,000 km above the equator.
With power and communications established, MTG-S1 entered its Launch and Early Operations Phase, during which engineers are activating systems and guiding it to its geostationary orbital position. From this position, aligned with Earth’s rotation, MTG-S1 will maintain an uninterrupted view of Europe, Africa, and surrounding regions.
MTG-S1’s Infrared Sounder will scan nearly 2,000 thermal infrared wavelengths every 30 minutes to build vertical profiles of temperature, humidity, and trace gases. These data will be crucial for detecting fast-developing convective weather by revealing sudden shifts in instability, moisture, or wind – even before clouds begin to form.
Combined with imagery from MTG’s imager satellites, it will offer a continuous view of a storm’s full life cycle, from early instability through to lightning and dissipation. The observations made by MTG-S1 will also enhance very-short-range forecasts called nowcasts, daily forecasts, improve models linking weather, air quality, and climate, and support long-term climate monitoring.
The Copernicus Sentinel-4 mission is expected to provide hourly data on pollutants and aerosols – including from wildfires and volcanic eruptions – that will enable specialists to monitor emissions, enhance air quality forecasts, support public health and environmental policy. Copernicus is the Earth Observation component of the European Union Space Programme.
Simonetta Cheli, Director of Earth Observation Programmes at ESA, said: “These two groundbreaking missions are set to change the way we forecast both severe weather and the quality of air over Europe. It is thanks to the outstanding work our teams have done with EUMETSAT, the European Commission and dozens of European industry partners, that we are able to now look forward to more accurate and timely ways of predicting storm events and air pollution.”
Christoph Kautz, Director for Space Policy, Earth Observation and Satellite Navigation at the European Commission said: “I warmly congratulate everyone involved in the launch of MTG-S1 and Copernicus Sentinel-4, which will vastly enhance Europe’s ability to monitor the atmosphere from space. This achievement is a powerful example of how European cooperation can provide vital data in support of services such as the Copernicus Atmosphere Monitoring Service that protect public health, strengthen environmental monitoring, and improve lives across Europe.”
For further updates on MTG-S1, visit EUMETSAT’s launch hub, which features news, interviews, and insights into the satellite’s journey.
Find all relevant information, biographies of speakers, videos and testimonials on our dedicated press page.
Image credit: SpaceX
EUMETSAT, Europe’s meteorological satellite agency, monitors the weather and climate from space. Based in Darmstadt, Germany, EUMETSAT provides its 30 member states with meteorological imagery and data that are essential for keeping their communities safe and for the benefit of critical sectors of their economies.
EUMETSAT’s 30 member states are: Austria, Belgium, Bulgaria, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United Kingdom.