shuttler
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you are doing the same thing all the while on board! Now you are humbled a bit!
You guys' mistake here is in thinking that Medium Earth Orbit (MEO) is a fixed altitude. It is not. It has a range. Here is a more accurate illustration...
In terms of altitude, a geosynchronous orbit have the same altitude as a geostationary orbit.
Medium Earth Orbit (MEO) begins at 480km and stretches all the way up to 35,800km. No one with any bit of common sense and technical education is going to place a satellite at 500km altitude in the same category as one at 36,000km altitude even though technically speaking, both satellites are in MEO. To match that wide range of altitude, the orbital periods of MEO satellites ranges from 2 to 12 hrs. At the upper range of this scale, which is where GPS satellites are located (22,300km), satellites are moved into the classification of 'semi-'. You do know what the word 'semi-' imply, no?
But if you do want to get into the details, I will oblige and will dissect the relevant post...
That has nothing to do with the geostationary or geosynchronous orbit but about altitude, as if somehow the US back in the 1980s made a serious error in placing the GPS constellation at 22,300km altitude and as if somehow China gained the upper hand today by placing the Baidu navigation satellite at a higher altitude. You guys seems to do not know that the US have placed geostationary and geosynchronous satellites before China entered the space race. The first was Syncom 3 in 1964. Your error in logical thinking here is that if China does something different, it must be better.
You guys seems to believe that an anti-satellite weapon is a technically restricted constructed device when it is not. An anti-satellite satellite is just another satellite with a different purpose. We can reassign a weather satellite's mission from gathering cloud info into collision with another weather satellite if we wanted to. There -- we just made an ASAT satellite.
How we place an ASAT satellite in a geostat/geosync orbit is no different than how we would place a communication satellite in its geostat/geosync orbit.
If we can place Syncom 3 into a geostat orbit back in 1964, we can certainly place an ASAT satellite into the same altitude today. If anything, Baidu being in a geostat orbit make it easier to target because the satellite's location is constant. Not merely predictable. But actually constant. So look at the illustration above and see how Baidu can be targeted by an ASAT satellite. The Baidu satellite cannot maneuver, not because it cannot technically maneuver, but that if it maneuver to avoid the ASAT satellite, China will lose satellite assisted navigation coverage.
Here is Baidu's limited coverage...
File:Beidou-coverage.png - Wikipedia, the free encyclopedia
Do you guys know why Baidu 1 is geostationary? It have little to do with technical achievement. It is old news for US. Because a geostationary location is essentially fixed over an equatorial country, there is a tacit understanding among space-competent countries that a geostationary orbital location should be reserved for that country. That is understanding, not law.
CelesTrak: "Basics of the Geostationary Orbit"
Who Owns the Geostationary Orbit?
No country like to have another country's satellite in a geostationary orbit to observe 24/7/365. If an American spy satellite passes over Soviet territory, its passage is temporary and therefore tolerable. But if Russia is at the equator and the US had placed our own geostat spy satellite over Soviet territory, it would not exist for long. The Kremlin would have cancelled all kinds of projects and diverted those money to ensure the American spy satellite's destruction. On the other hand, if the US placed a geostationary spy satellite over Viet Nam, an equatorial country, there would be nothing the Viets could do but protest. It would be rude on the American behavior, but nothing the Viets could do. Even worse, what if that geostationary satellite is a nuclear weapon?
So there is nothing technically spectacular about Baidu's satellites being geostationary.
There are many technical and operational advantages to putting the GPS constellation where it is: at 22,300km altitude.
Foremost is overall system survivability and precision. If we are certain that satellites are perfectly constructed and that we do not have enemies, we would have placed the constellation at the geostat orbit over different geographical locations on Earth, providing 100% surface coverage with perfect signal integrity. But that is not possible. Satellites do fail. Signals do have propagation losses. So the US decided to place the GPS constellation where the combination of signal propagation losses and surface coverage is best: 22,300km altitude. You guys really thing we placed the GPS constellation at that altitude because our orbital science can reach only that high?
With a constellation, individual satellites produces diverse Doppler, range, and elevation angles and the receiver is forced to perform multiple calculations in order to ascertain position but multiple correlative factors are always desirable, especially if the receiver is mobile. Also because the constellation is at a semi geostat/geosync altitude where signal propagation losses are more tolerable, receiver antenna set can be made smaller, making the receiver more mobile and less costly to produce. This architecture worked so well that Baidu 2 essentially copied the American GPS. Baidu 1 satellites at geostat/geosync altitude uses directional transmit antennas. Baidu 2 satellites at the lower but semi geostat/geosync altitude will have omnidirectional transmit antennas, just like the American GPS design.
Its a long post Let us spend time reading it after our family gathering over the weekend It is not a top priority
You are just sad and stuboorn Never admit your own mistakes when confronted with blantant blunders!
