Junk & Inclined Orbits

[martz]

Can somebody explain (Ihavesearched) about junk orbits, do the satellites just drift to outer space and keep going out or do they get a bit further out and become in a faster orbit no longer becoming geostationary. Also i've heard of the "wobbly bird" and it is inclined or bit, i understand that inclined orbits move a degree or so per year, eg if a satellite is at 27.2 one year and the next its at 28.2 wont it bump into other ones? also inclination angles, what does 2.5degrees or whatever mean? and do inclined orbit satellites become into junk orbit by themselves? sorry if this is a bit noob but i thought this is the best place to ask as i cant seem to find this kind of info elswhere and its a bit hard to get my head around (only 15) thanks

 

[Analoguesat]

Junk orbits are about 100km higher or lower than the geostationary orbits so drift faster or slower than the earth rotation. Satellites lowered will drift faster, satellites raised will drift slower.

Nowadays the operators try to leave a small reserve of fuel on board until the last few days of controlled operation so the satellites can be moved. The last dregs of fuel are used to move the satellite off the geostationary arc, then the final commands are uplinked to the satellite to "safe" it. The fuel valves are opened to drain the tanks (no accidental explosions wanted) and I think the batteries are shorted too on newer bird. The satellites will drift around the earth for thousands of years. Junk orbit is a much safer option than leaving the satellite in place on the orbital arc - gravitational effects would cause a satellite to eventually drift off station with the possibility of collisions in space. (There are a few dead satellites on the geostationary arc - normally those that have suffered a terminal breakdown in service - Intelsat 804 springs to mind.)

Incl;ined satellites dont drift around the arc - when the station keeping fuel runs low, noth south station keping is reduced to a minimum, so the satellite starts to wobble up and down off the main arc. Imagine the satellite describing a huge figure 8 in space with the middle node being its geostationary point. Inclined orbiting stretches the useful life of a satellite for another 4 or 5 years, although special dish tracking is required once the inclination gets above about 2 degrees.

In the next 5 years or so a company hopes to put a space tug into service which would extend the useful life of satellites - its almost always the case that the fuel runs out before the satellite fails, so if they could be "refueled" they could have several more years service.

Had the space tug:

http://www.orbitalrecovery.com/

been in service it may have saved Astra 1K when it was stranded in low earth orbit 3 years ago.

 

[martz]

thanks for answering my long question, so when the satellite is put into junk orbit it is not broken just run out of fuel. what happened to the intelsat 804? is it still on the arc?

 

[Analoguesat]

I-804 suffered an "electrical anomaly" probably triggered by an electrostatic dischargewhich killed it. As far as I know its still on the orbital arc.

You might find this site interesting:

h**p://www.sat-index.com/failures/

(not all broadcast sats)

Most of the satellites sent to junk orbit are indeed out of fuel, although there are a few damaged ones sent to graveyard orbit too. TV Sat 1 is up there somewhere with a stuck solar panel.