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Europe's first geostationary sounder satellite is launched
  • abra0
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  • 3 weeks ago
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> MTG-S1 is the first geostationary meteorological sounder satellite to fly over Europe

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.

1 - https://space.oscar.wmo.int/satellites/view/mtg_s1

I had doubts about the "parked at exactly 0°00'00"N 0°00'00"E", thinking it was over Null Island just because the data wasn't updated yet and it was showing uninitialized values.

But you are right, [1] confirms "0° longitude".

[1] https://user.eumetsat.int/resources/user-guides/mtg-in-opera...

That specifies its position to about 30 metres of precision.

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.

Geostationary satellite are usually kept within in a cube of 100 km. That’s less than 1/10 degrees. For earth observation it shouldn’t matter much.
So there could reasonably be dozens [0] of satellites "parked at exactly 0°00'00"N 0°00'00"E". Definitely an unnecessary level of precision.

[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.

I don’t think that is a management problem but the mechanics will work against you and you would squander too much of the precious fuel if you stack’em in three dimensions.

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.

NOAA/NASA (USA), EUMETSAT (European organization), JMA (Japan), KMA (Korea), and CMA (China) all have a geostationary satellite (one or more actually). So, northern hemisphere countries, but the coverage is global thanks to the fact that you need to be, as you say, above the equator.
I am surprised they would pick 0 for the latitude, it seems that most of Europe, whether it's the land or the people is east of that. Maybe some important weather systems develop over the Atlantic and they want to track that?
It’s exactly that. In fact, information propagates along with the winds. If you don’t observe upstream, you instead propagate an information hole. Each new model run incorporates the output of the previous run to preserve sparse weather information. It’s not that there are few observations, it’s that Earth is really big.
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  • 3 weeks ago
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How the heck is 0,0 still available! Was nobody interested in this position before for any purpose?

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

0°00'00"N 0°00'00"E the country where all the scammer live
> "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."

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))

> edit: Also, I'm now confused about the ESA's claim to be the "first", because

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...

> "I think you might have misread the title,"

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.

Clearly, if it’s not European, it doesn’t count.
Here is a link that lists the sensors/data products roughly: https://webapps.itc.utwente.nl/sensor/getsat.aspx?Find=sat&N...

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.

The GIIRS on FY-4A was indeed first (2016), but MTG-S1's IRS has significantly higher spectral resolution (1960 vs 689 channels) and improved spatial coverage, making it the first "full" hyperspectral sounder in GEO.
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  • 3 weeks ago
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Imagine a world where America actually wanted to understand climate change.
Considering the emissions of the US and the outright rejection of climate action through the Paris accords, and the covering up of climate related research, it would seem fair to consider climate change as partly caused by outright American hostility. They say the most impacted will be people in developing nations, also, not in the US. Absolutely horrific actions.
Only tangentially related: I have nothing but respect for EUMETSAT and their public data store. For past work projects I've had to interface with a pretty broad sample of the world's space and/or meteorological agency's public data stores and APIs and EUMDAC (EUMETSAT's API client) was top tier. Well documented, modern, fast, and generally headache free.

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.

Shout-out to the NOAA GFS team, who publish the GFS analysis directly to AWS S3.

https://registry.opendata.aws/noaa-gfs-bdp-pds/

GFS outputs are also available for free from NOMADS. That was true long before AWS came up with the public dataset program.
I've worked with similar data in the past. As you say, nothing but respect for agencies that make such useful data publicly available.

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.

Copernicus browser allows to browser images of the earth in quite high resolution (I think up to 20x20m) refreshed every 3 days or so and it's absolutely cool to be able to use different views such as nir, swir...
I think the delay must be much longer than 3 days, since Iceland and Norway are still shown covered in their winter coats. Really interesting tool though.

https://browser.dataspace.copernicus.eu/

  • tacet
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  • 3 weeks ago
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Hmm, there is no delay. Iirc the full cycle (sattelites return to exactly same spot in relation to earth) is about 10 days and most paces get crossed in 1-3 days.

Are you looking at sentinel 1 or sentinel 2

I think this is the first time I have seen the .int tld used.
It isn't super popular, no. I think the requirements are pretty strict if I remember correctly (edit: https://www.iana.org/domains/int/policy).

I think esa.int is probably one of the more popular .int domains on HN: https://news.ycombinator.com/from?site=esa.int

Other notable .int domains:

• 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

List: https://en.wikipedia.org/wiki/List_of_organizations_with_.in...

(Not real affiliation but still: I added a domain to that page at some point)

[flagged]
In meteorology, you also have ecmwf.int (the European Center for Medium-Range Weather Forecasts).
It would have been better if the requirements also included the domain name had to start with a letter between I and N (inclusive).

But I guess this is what you get when these things get away from technologists.

Ah, a Fortran joke. That's not just "technologists". That's old farts.

(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.)

  • mkl
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  • 3 weeks ago
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Maths is the reason for loops use i. Fortran defines variables starting with those letters to be integers because maths has used those letters for iteration, counting, indexing, etc. for centuries. It was natural for a formula translating system to follow suit.
I think that's still the case, even in the latest FORTRAN standard. It's usually considered good practice to turn it off with IMPLICIT NONE.
  • r721
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  • 3 weeks ago
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interpol.int also comes to mind.
Probably the most appropriate one. The ESA is not quite part of the EU and has non-EU member states (including _Canada_), so .eu would be inappropriate (the EU is itself a member of ESA, but most EU member states are also members in their own right.)
  • petre
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  • 3 weeks ago
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The joke goes that thanx to Trump, Canada might actually join the EU.
Canada should be next.
Do you have more context? Naively, one would assume the geostationary satellites the US already has in orbit can see Canada just fine.
  • 8note
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  • 3 weeks ago
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access is however, gated behind the american government, and relying on american satelites is a national security risk to canada.

for example, the US has stopped sharing weather data with canada.

> for example, the US has stopped sharing weather data with canada.

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.

  • tzs
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  • 3 weeks ago
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The Trump administration in February temporarily ordered NOAA to stop communicating with foreign nationals, which included Canadians and included sharing data.

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.

Google says: no, the US did not stop sharing weather data. Communication isn’t automated weather data sharing. The data never stopped. Again, citation needed.
Meanwhile, NOAA and EUMETSAT are preparing to launch a joint satellite later this year.

https://www.eumetsat.int/sentinel-6

Naive question: what’s the benefit here to scan downward (from the satellite position) over upward, from the ground?
If the question is about satellite vs ground instrument: the geographic coverage from the satellite is much greater. Geostationary instruments over Europe cover the Atlantic Ocean, Europe, Africa, the Middle East.

If that was not the question, can you provide more detail?

Thanks, this is indeed the question. Thinking out loud: the coverage is probably somewhat conic therefore if you want to scan the ground or lower atmosphere an high altitude is optimal, while scanning the upper atmosphere could be done from the ground.

Perhaps earth's spherical shape gives an advantage to the satellites in both cases ?

Maybe, though a GEO satellite (or really any satellite) will always be much much farther from even the upper atmosphere than the ground will be, so satellites have a pretty dominant coverage advantage.
You can’t drive your sensor bank everywhere on the surface of the earth to point up.
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