Stuff in Space

[Strange]

A pretty cool simulation of everything in orbit around the Earth: http://stuffin.space/?intldes=1983-001A

And an article about it here: https://www.universetoday.com/138981/this-is-the-coolest-everything-thats-orbiting-the-earth-right-now/

[Mordred]

pretty cool app lol

[michel123456]

7 hours ago, Strange said:

A pretty cool simulation of everything in orbit around the Earth: http://stuffin.space/?intldes=1983-001A

And an article about it here: https://www.universetoday.com/138981/this-is-the-coolest-everything-thats-orbiting-the-earth-right-now/

Nice!

When you look from far enough, there seems to have a large orbit with a lot of things, at approx 35800km. What is this zone?

 

Amazing, it is moving in real time!!

record_000002.avi

[dimreepr]

Who knew?

[Sensei]

21 minutes ago, michel123456 said:

 

When you look from far enough, there seems to have a large orbit with a lot of things, at approx 35800km. What is this zone?

Geostationary orbit..

https://en.wikipedia.org/wiki/Geostationary_orbit

 

[michel123456]

16 hours ago, Sensei said:

Geostationary orbit..

https://en.wikipedia.org/wiki/Geostationary_orbit

 

Thank you. I didn't know a Geostationary orbit was obligatory above the equator. I thought it could be anywhere.

From Wiki

Quote

A geostationary orbit, geostationary Earth orbit (often referred to as geosynchronous equatorial orbit)^[1] (GEO) is a circular geosynchronous orbit 35,786 kilometres (22,236 mi) above the Earth's equator and following the direction of the Earth's rotation.

 

I am fascinated. A good occasion to educate myself about Westford Needles and other stuff. 

[koti]

Nice one @Strange, I just looked up the furthest looking red dot satelite from earth and its a russian satelite launched in 1983 with a small 80cm, 160nm-350nm range telescope they did some physics experiments with. I was helping my Mom to que in lines to get toilet paper in 1983 and stuff like that was happening, wow. 

Edited April 11, 2018 by koti

[michel123456]

On 4/10/2018 at 7:27 PM, Sensei said:

Geostationary orbit..

https://en.wikipedia.org/wiki/Geostationary_orbit

 

Now I realize that GPS is not on geostationary orbit. I wonder why. I would have thought that a positioning system would have been based on unmovable reference points.

[StringJunky]

8 minutes ago, michel123456 said:

Now I realize that GPS is not on geostationary orbit. I wonder why. I would have thought that a positioning system would have been based on unmovable reference points.

It seems, as long as there's 4 satellites in view from any position on Earth, it works. I'm sure Swansont will elaborate.

Quote

he nominal GPS configuration consists of a network of 24 satellites in high orbits around the Earth, but up to 30 or so satellites may be on station at any given time. Each satellite in the GPS constellation orbits at an altitude of about 20,000 km from the ground, and has an orbital speed of about 14,000 km/hour (the orbital period is roughly 12 hours - contrary to popular belief, GPS satellites are not in geosynchronous or geostationary orbits). The satellite orbits are distributed so that at least 4 satellites are always visible from any point on the Earth at any given instant (with up to 12 visible at one time). Each satellite carries with it an atomic clock that "ticks" with a nominal accuracy of 1 nanosecond (1 billionth of a second). A GPS receiver in an airplane determines its current position and course by comparing the time signals it receives from the currently visible GPS satellites (usually 6 to 12) and trilaterating on the known positions of each satellite[1]. The precision achieved is remarkable: even a simple hand-held GPS receiver can determine your absolute position on the surface of the Earth to within 5 to 10 meters in only a few seconds. http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html

 

 

[Strange]

23 minutes ago, michel123456 said:

Now I realize that GPS is not on geostationary orbit. I wonder why.

Mainly because they would not be visible from high latitudes.

Quote

I would have thought that a positioning system would have been based on unmovable reference points.

The satellites tell the receiver their location and that can be used to work out the position of the receiver. (You can think of it as a position relative to the satellite that is then corrected for the position of the satellite.)

All the satellites share this information, every so often, so once you have found one you can quickly find any others that are in view. Finding the first satellite from a cold start can take some time because (a) you don't know the exact radio frequency to look for (because it will be Doppler shifted by a "random" amount because of the satellites relative speed) and (b) each satellite encodes its signal by mixing it with a different pseudo-random pattern. So you have to search (using a correlation) for each possible encoded signal while simultaneously sweeping across the range of possible frequencies. Once you have found one satellite, you can download the information about the other satellites, see which others that should be visible and their approximate speed, and hence find them. Once you have four (or more) you can do the location calculation. (Having ore than four can slightly increase accuracy and allows for temporarily losing satellites due to shadowing or reflection of signals.