which way do satillites traverse the globe

[osci]

This has always bugged me!

I've always thought that satillites always followed the same trajectory generally from west through to east or sw through to ne.

the other I saw two satellites traversing the sky frolm south to north? now I don't if this is out of the ordinary, but, can anyone giove a logical explaination?

[Fernbay]

I'm no rocket scientist, but heres a laymans explanation anyway

It depends on what way it is launched & put into orbit
A lot are geostationary & don't move at all

The secret is that all a satellite is doing is falling towards earth.
As it drops, while moving forward, the earth under it drops away - so it never hits the ground. It just keeps 'falling'

Theres lots of maths involved in calculating the orbit. After all, if you spend millions putting something into space, you don't want it to hit anything, do you

So it all depends on the direction it was 'pushed out' from

[OSIRUS]

Thanks Fernbay,

nicely put,

I bet someone else could put forward a lot of mathematical formula to explain it perfectly too,

& be very confusing !!

but I like your's

[SystemRat]

Geo stationary satellites sit in what is known as the Clarke belt 22 thousand mile above the equator where they sit effectively stationary in respect to a point on the earth. Small amount of fuel is used to maintain an exact position as the effect of the Sun, Moon and other object tends to make them drift in a figure eight pattern.

Non-geo synchronous satellites are satellites such as weather, gps, mapping etc operate at a variety of orbit heights with their orbital track set and maintained by the occasional use of onboard thrusters.

Most simply orbit in the same manner all the time with corrections being made to account for orbital decay and the effect of the moon etc if required. Some satellites are actively moved to new locations to allow imaging etc but that is very expensive as once the fuel in the satellite is exhausted its stuck in that orbit until it de orbits and burns up.

An object in motion tends to stay in motion barring outside influences in this case like atmospheric drag and gravity.

[osci]

thanks Fernbay & SystemRat for the explainations

I understand about the geostationary birds, but as for the non-geostat birds, I would have thought that when launched all of these birds would had to have been launched in the same direction as the earth is spinning due to the affects of gravity......well that was my assumption anyway.

cheers dudes

[beer4life]

Here's a link you may find interesting.
Heaps of junk floating around up there,

[trash]

Ok, the reason why you think they orbit west to east is that is just the easiest way into space. You use the velocity of the earth's rotation to assist the launch rather than trying to oppose it. It's ~1500kph velocity you get for free. If you launch against the Earth's rotation, then you have to pay double this price. Likewise launching at the poles is velocity neutral. The best launch economy is launching from near the equator in an easterly direction.

Once the satellite is in low Earth orbit, then you can change the orbit any way you like (with the appropriate amount of fuel).

Imagine our satellite is ideal. It is in orbit over the equator in a circular orbit.
We can put it into an inclined orbit by kicking it with the motors left or right.

The more thrust we apply, the more inclined the orbit will become.
Eventually if we apply enough thrust, the orbit will become a polar orbit.
(inclination = 90 degrees).
The satellite you saw was on in a polar orbit.
During one has of the orbit it goes from south to north and then over the pole and down the other side from north to south. The Earth rotates underneath this orbit. Every 90 minutes, the satellites path appears to move further west.

If we continue to kick the satellite to the left or right with our thrusters the orbit now becomes inclined >90 degrees or a negative inclination if we look at it from the other side <0 degrees.
So the satellite now appears to orbit east to west, and it appears to orbit quicker because of the earth's rotation.

To put a satellite into this kind of orbit obviously takes a bit of effort, so there has to be a good reason to do it. Fast moving spy satellites would be a reason, but not really for comms.

There is another way to make satellites appear to move backwards. Put them into a very high orbit. Place them higher and they appear to slow down until they reach geosynchronous orbit, where they appear to stop. Then as they are moved higher, they appear to move backwards (like the moon). It's orbiting west to east, but in the sky it always moves east to west.

A variation on this is the eccentric orbit. The satellite will appear to move both forward and backwards. Some of the amateur satellites have highly eccentric orbits.
As the satellite is low, it moves fast relative to the earth's surface. It moves from West to East very quickly. As it climbs back up to a higher orbit it appears to move slower and slower until the earth's surface is moving faster underneath. From the ground the satellite now appears to be moving slowly backwards. Finally the satellite decends back to the perigee of it's orbit. From the ground it appears to speed up and zip over the horizon from west to east.

Combine any of these qualities and you can get some bizzare orbits.

A good one would be a highly inclined and eccentrical westerly orbiting satellite.

Lets say the inclination is 70 degrees and the apogee is at +70 (north) and the perigee is -70 (south) and the eccentricity is ... out there ! The apogee like 50000km and the perigee 300.

From the equator, the satellite comes zooming over the horizon heading north west very quickly and as it gets further north is appears to slow down and disappears slowly in the north west. 12 hours later it appears in the north east and moves slowly along the northern horizon and sets again in the north west. Again it might rise slowly in the north east, but this time it races from the north east sky over the south western horizon.

From the north pole, the satellite rises from the horizon very quickly and then circles around overhead for a couple of days before dropping down very quickly below the horizon and 90 minutes later pops up very quickly form the almost opposite horizon.

From the south pole the satellite rises from one horizon shoots across the sky in 10 minutes and dissappears over the opposite horizon and isn't seen for 2 days.

Hows that for weird ?

[MrElectricity]

I was hoping trash would join in, always big on info there our trash is.

[osci]

Thank you Trash, an excellent description here!!

its cleared up virtually everything for me!

[bambbbam]

Well put trash.

I sometimes sit there looking at the tele thinking, "you know, it's amazing that a small uplink station is bouncing a signal of an object the size of a tennis court 37,000 kms away and I'm watching it within 3 seconds.."

[nathj]

KISS,

they travel anyway the launchers want

[porkop]

now all we need is some cheeky bugger to velcro a amateur sat onto a geostaionary sat and we dont have to have all the wiz bang high gain tracking antenna

[ol' boy]

Some say that he has no understanding of clouds, and that his ear wax tastes like Turkish delight... all we know is, he's called trash.

[Small Sad Sam]

This has always bugged me!

I've always thought that satillites always followed the same trajectory generally from west through to east or sw through to ne.

the other I saw two satellites traversing the sky frolm south to north? now I don't if this is out of the ordinary, but, can anyone giove a logical explaination?

Osci,

Here is something you will enjoy.

hxxp://science.nasa.gov/Realtime/jtrack/3d/JTrack3D.html

Hope that a link is allowed here. I have replaced the 'tt' in http with 'xx' so that it will not be a live link. You will have to insert the 'tt' to use it in your browser.

When you pull up the NASA home screen, click on Satellite Tracking, J-Track 3D on the left side of the screen, second line down.

It is really amazing to see how many sats are actually out there.

Small Sad Sam

[osci]

thanks heaps Sam for the link will check it out

cheers

[trash]

J-track is one of my favs Sam.
It's kind of like how I see satellite orbits in my head, but only one at a time, not all of them like that, which is very cool.

There are a couple of orbit or gravity simulators. I used to play with a very simple one under DOS many years ago. My favourate is a square orbit.
Yes, you can put a satellite into a square orbit !

A Tennis court Bambbbam ? They're not that big. The average geo-sync satellite is only about 4 metres accross. Their antennas aren't all that big either. The solar panels are what give them the impression of being big.
Still, ~6 tonnes of satellite isn't exactly small.

Some of the ham radio picosats are not much bigger than a shoebox. One of them was a shoebox. Suitsat was a recent hand launched satellite. They put a very cheap satellite into an old Russian space suit and tossed it overboard from the ISS.
It only worked for a short time before it failed. I think they are planing another one soon. It was basically a radio with a battery in the suit.

I can't help but wonder when we'll see an OSCAR on the moon. When the moon missions finally get going, I would be very supprised if ham radio didn't hitch a ride.

[nathj]

J-track is one of my favs Sam.
It's kind of like how I see satellite orbits in my head, but only one at a time, not all of them like that, which is very cool.

There are a couple of orbit or gravity simulators. I used to play with a very simple one under DOS many years ago. My favourate is a square orbit.
Yes, you can put a satellite into a square orbit !

A Tennis court Bambbbam ? They're not that big. The average geo-sync satellite is only about 4 metres accross. Their antennas aren't all that big either. The solar panels are what give them the impression of being big.
Still, ~6 tonnes of satellite isn't exactly small.

Some of the ham radio picosats are not much bigger than a shoebox. One of them was a shoebox. Suitsat was a recent hand launched satellite. They put a very cheap satellite into an old Russian space suit and tossed it overboard from the ISS.
It only worked for a short time before it failed. I think they are planing another one soon. It was basically a radio with a battery in the suit.

I can't help but wonder when we'll see an OSCAR on the moon. When the moon missions finally get going, I would be very supprised if ham radio didn't hitch a ride.

dude you need to get into rocketry!!

check out

wont be long till blokes like yourself have there own birds

and the brains behind it

this bloke even tells you how to build the things right down to the last bolt!!

[WhiteStarLine]

Suitsat was a recent hand launched satellite. They put a very cheap satellite into an old Russian space suit and tossed it overboard from the ISS.

Yes, Suitsat was just visible to the naked eye and seen by many enthusiasts. Amazing to think that you could see a spacesuit from earth. I got up at 4:30 am or so a few times and missed it, then a few days before it burned up I got up early and spotted it, presumably as the sun shone on the spacesuit visor, as it was 1200 km line of sight at the time.

The toolbag accidentally dropped from the current mission is currently visible and has seen by a few observers, usually with binoculars.

BTW, the standard orbital motion using the 500 m per sec free kick from the spinning earth is called 'prograde' and the rarely used opposite path is called 'retrograde'.

Cheers,

Bill

[trash]

dude you need to get into rocketry!!

Yep, been there done that. It's a lot of fun but it can be expensive and when you start to get into the big league it's very hard to get material in this country without various people assuming your some sort of terrorist. Try playing with nuclear physics as a hobby. I take it in my stride scaring the shit out of people with geiger counters.

I've been very tempted to get a hybrid NOX motor or build one. It remains a bit of a dream as I don't have much in the way of mechanical skills needed to set up the high flow gas valves etc.
I've built multiple and multi stage solid fuel rockets and make a few of my own solid fuel motors, but that's as much as I've done. 3000ft is probably as high as any of mine have gone.

My favourite rouge satellite was the tethered satellite that broke free from the shuttle. I saw it while they were conducting the experiment, you could see two stars one brighter than the other with a straight line between them.

When it broke and the shuttle returned to earth, you could still see the satellite with about 5km of tether floating free. It looked very weird.

[mate]

for those interested Optus C1 is one of the many orbiting the equator

i give thumbs up for Jtrack 3D it is an old fave.