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Re:Large Eruption Near Tonga, Heard in NZ. Tsunami at Tonga ... by Symbiote on Saturday January 15, 2022 @09:29AM (#29946605)
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.

Re:Large Eruption Near Tonga, Heard in NZ. Tsunami at Tonga ... by pavelrub on Saturday January 15, 2022 @10:34AM (#29947095)
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.
Re:Large Eruption Near Tonga, Heard in NZ. Tsunami at Tonga ... by alangibson on Saturday January 15, 2022 @01:07PM (#29948675)
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

Re:Large Eruption Near Tonga, Heard in NZ. Tsunami at Tonga ... by wrycoder on Saturday January 15, 2022 @01:47PM (#29949055)
Re:Large Eruption Near Tonga, Heard in NZ. Tsunami at Tonga ... by numpad0 on Saturday January 15, 2022 @11:49AM (#29947879)
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.
Re:Large Eruption Near Tonga, Heard in NZ. Tsunami at Tonga ... by sva_ on Saturday January 15, 2022 @12:11PM (#29948091)
Pretty sure these satellites from far away are all in geostationary orbit.
Re:Large Eruption Near Tonga, Heard in NZ. Tsunami at Tonga ... by numpad0 on Sunday January 16, 2022 @09:15AM (#29956131)
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.