Post by dwight on Oct 1, 2005 18:11:15 GMT -4
This is info that can be used in conjuction with the queries posed with regards to creating an artificial delay.
I just did a refresher course on satellite tracking...so I thought I better write this before the info vapourises:
All geo-stationary satellites are launched into an orbite which is always over the equator. This is why when you align a domestic dish, you get a reading in compass direction and degrees...it allows you to point the dish at the right spacecraft.
All geo-stationary satellites do fluctuate in their stationary orbits. This path generally resembles a figure 8 pattern, and can occur in the azimuth axis or elevation axis. The fluctuations are caused by the following: solar winds (minor, yet still measurable), the gravitaional effects of the moon (the same effects that causes tides here on earth), and several other things which I didnt bother to note down in the lecture (oops). The fluctuation of a geostat satellite is circa +/- 0,15 degrees (I am using the German/european decimal seperation convention).
Corrections for this fluctuation are made using acs type controls remotely steered from ground stations. As the "fuel" used for these corrections is finite, so too is the usuable life of the spacecraft.
Once the "fuel" ("" as it is not feul as in petrol or what have you) has been nearly depleted, the satellite is then moved into a graveyard orbit. This does not mean that it is completely useless. It is still possible to use it during a tracking station pass for short term uplinks/downlinks. (These can be done today for as little as $10 per minute!!!)
A beacon signal is used to allow a dish to track the orbiting spacecraft. A predicted model is then made of the orbital fluctuations, which allows the antenna (dish) to follow the spacecraft, and maintain a good signal dB ratio. Essentially the dish is steered slightly to the left, right, up and down over a given time window in order to develop this tracking model.
Theoretically, any satellite dish could be used to track a rocket powered spacecraft, although the approprite S-band recievers would need to be configured, and the dish would need to be fast enough to track a fast moving spacecraft, rather than one is geo-stationary orbit, or a slow moving elliptical orbit.
Attempting to fake an object to track would be very easily uncovered based on the tracking techniques detailed above. Furthermore, a dish the size of the one at Parkes is more sensiitive to orbit fluctuations, and the the tracking model needs to be extremely precise. The signal roll-off is steep, when the appropriate angles aren't continually kept in check.
Anyhow, hope that is useful. Given the recent radio signals thread, I thought I'd post it here rather than under the "realities" folder.
Cheers
Dwight
RTL TX
I just did a refresher course on satellite tracking...so I thought I better write this before the info vapourises:
All geo-stationary satellites are launched into an orbite which is always over the equator. This is why when you align a domestic dish, you get a reading in compass direction and degrees...it allows you to point the dish at the right spacecraft.
All geo-stationary satellites do fluctuate in their stationary orbits. This path generally resembles a figure 8 pattern, and can occur in the azimuth axis or elevation axis. The fluctuations are caused by the following: solar winds (minor, yet still measurable), the gravitaional effects of the moon (the same effects that causes tides here on earth), and several other things which I didnt bother to note down in the lecture (oops). The fluctuation of a geostat satellite is circa +/- 0,15 degrees (I am using the German/european decimal seperation convention).
Corrections for this fluctuation are made using acs type controls remotely steered from ground stations. As the "fuel" used for these corrections is finite, so too is the usuable life of the spacecraft.
Once the "fuel" ("" as it is not feul as in petrol or what have you) has been nearly depleted, the satellite is then moved into a graveyard orbit. This does not mean that it is completely useless. It is still possible to use it during a tracking station pass for short term uplinks/downlinks. (These can be done today for as little as $10 per minute!!!)
A beacon signal is used to allow a dish to track the orbiting spacecraft. A predicted model is then made of the orbital fluctuations, which allows the antenna (dish) to follow the spacecraft, and maintain a good signal dB ratio. Essentially the dish is steered slightly to the left, right, up and down over a given time window in order to develop this tracking model.
Theoretically, any satellite dish could be used to track a rocket powered spacecraft, although the approprite S-band recievers would need to be configured, and the dish would need to be fast enough to track a fast moving spacecraft, rather than one is geo-stationary orbit, or a slow moving elliptical orbit.
Attempting to fake an object to track would be very easily uncovered based on the tracking techniques detailed above. Furthermore, a dish the size of the one at Parkes is more sensiitive to orbit fluctuations, and the the tracking model needs to be extremely precise. The signal roll-off is steep, when the appropriate angles aren't continually kept in check.
Anyhow, hope that is useful. Given the recent radio signals thread, I thought I'd post it here rather than under the "realities" folder.
Cheers
Dwight
RTL TX