[irthomasthomas]

Did they know this was coming? Or how did they manage to have the satellite centred over the volcano at the right moment?

Edit: Found the answer, this was the second or third eruption from this volcano. So yeah they where already monitoring it. Amazing how they can manoeuvre these camera satellites now.

[perihelions]

It's a weather satellite 36,000 km from Earth; half of the planet is contained in its field of view. Here, see:

https://rammb.cira.colostate.edu/ramsdis/online/loop.asp?dat...

[irthomasthomas]

Is that the same as this though? https://mobile.twitter.com/US_Stormwatch/status/148222922041...

This looks to be zoomed way closer than your link, you can see small waves on the ocean etc. I did not think you could film the whole face of the earth at that resolution?

Edit: Or are those small waves actually large clouds?

[jcrawfordor]

The two GOES satellites use the ABI (advanced baseline imager) to image a large portion of the total planet at a spatial resolution of around 1km. The GOES ABI design is influential on the broader world of weather satellites and many weather satellites operated by other countries (e.g. Japan's Himawari) use derived or similar imagers. GOES and Himawari are the premier weather imaging satellites of the US-allied world, collectively the two systems image a very large percentage of the total planet surface except extreme latitudes. Data from GOES and Himawari are fused to produce the global satellite images provided by e.g. NWS.

The US Stormwatch image does seem to be cropped from Himawari. The size here may be deceptive, the spatial resolution is not as high as it looks because this cloud is so large.

Although the GOES ABI (and related Himawari AHI) are static designs that image the full planet from a fixed position (i.e. there is no aiming or steering as is sometimes the case in other remote sensing satellites), they do deal with practical limitations related to readout and downlink capacity. As a result they typically produce a full-disk image every 5 minutes but both are capable of producing more frequent images of selected regions (areas of interest) on command. This capability is mostly used for maintenance purposes (e.g. registration calibration) rather than for weather observations.

Incidentally NOAA is preparing to launch a new GOES satellite, GOES-T which will become GOES-18, in somewhat over a month. It is the same basic generation as GOES-16 and GOES-17 currently in primary use, including the same basic ABI, but has a minor "bugfix" to the ABI design that will avoid a problem GOES-16 and GOES-17 have that requires them to go into a reduced readout rate mode some of the time for thermal management reasons.

My basic meteorology knowledge is somewhat limited but I believe what appear to be waves are cirrus clouds. This is somewhat confirmed by their significantly increased prominence along the shockwave front, as large shockwaves in the atmosphere cause some additional formation of condensation clouds due to the increased pressure, and these tend to be cirrus up at high altitude (the condensation immediately freezes into small crystals).

[chasd00]

look like clouds to me but i'm not an expert in satellite imagery. the shockwave implies > the speed of sound so more of an explosion than eruption right?

[rpeden]

Many eruptions are explosive[1], like Mount St. Helens in 1980. Here's a small explosive eruption where you can see the shockwave and eventually hear it when it hits the ship the cameraperson is on: https://www.youtube.com/watch?v=BUREX8aFbMs

[1]https://en.wikipedia.org/wiki/Explosive_eruption

[vba616]

I remember seeing on a TV program about an eruption where some people were monitoring a volcano from some miles away at an airport where they thought it was probably safe.

And the comment was made that if the pyroclastic flow reached them, the first they would know about it, at night, was when the runway lights vanished.

Very different from magma gently flowing out.

[JshWright]

The satellite wasn't maneuvered, and it was not specifically monitoring this location. It is a weather satellite that looks at half the planet at a time. This is just a crop of a much wider field of view.

[pavelrub]

Satellites in general aren’t maneuverable. The camera angle can be changed to point at, and capture, a region of interest when the satellite passes over it, but the satellite’s orbit is determined on insertion and doesn’t change on demand.

[Symbiote]

Satellites can be moved, for example to avoid a collision with another satellite or debris, or to semi-permanently change the orbit. They have some sort of propulsion to allow this, and also counter atmospheric drag etc.

However, the lifetime of the satellite is generally limited by the amount of propellant (or whatever), after it's run out the satellite is useless. So it's not done on a whim.

[pavelrub]

They have a very limited amount of hydrazine, used for small course corrections for drag compensation and debris avoidance. It's not used, nor can be used, to "change orbit" in the sense of redirecting the satellite to look at some specific location on demand, outside of the satellite's original orbit.

[alangibson]

Parent post is correct. Raising and lowering the orbit is a matter of burning a reasonable amount of rather limited fuel. But making a left hand turn at 17.5 km/h is incredibly energy intensive.

Look at the SpaceX launch of DART. They needed a whole rocket to lift a tiny payload due to needing to turn roughly 45 degrees

[wrycoder]

https://blogs.nasa.gov/dart/2021/11/24/nasa-spacex-launch-da...

[numpad0]

You just put one in a polar orbit and tell them to look at coordinates next time it is to pass that area over. Earth rotates under it meanwhile.

[sva_]

Pretty sure these satellites from far away are all in geostationary orbit.

[numpad0]

GEO satellites never move. Only times they are moved out of its longitude is when they are decommissioned or relocated when absolutely necessary, which by the way takes months.

> ... when the satellite passes over it ...

GEO satellites don't "pass over" anything by definition. They permanently float in the air 35786km above a designated spot along equator(complicated). So GP is clearly not talking about GEO satellites.

[temp0826]

Exception of course being the X-37B spy "satellite"