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Europe's first geostationary sounder satellite is launched

(www.eumetsat.int)
216 points diggan | 3 comments | 05 Jul 25 14:21 UTC | HN request time: 0.679s | source
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abra0 ◴[05 Jul 25 18:46 UTC] No.44474667[source]▶
> 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

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progbits ◴[05 Jul 25 19:49 UTC] No.44475054[source]▶
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...

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1. dmurray ◴[06 Jul 25 12:43 UTC] No.44480309[source]▶
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.

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2. slow_typist ◴[06 Jul 25 18:17 UTC] No.44482859[source]▶
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.
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3. dmurray ◴[06 Jul 25 20:10 UTC] No.44483641[source]▶
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.