Talk:Geostationary orbit

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[edit]

The two are not the same. A geosynchronous orbit can deviate from the equator, whereas a geostationary orbit cannot.

  • Either Geostationary orbit or Geosynchronous orbit should be turned into a redirection page to the other, as they are both the same thing. - Geostationary orbit seems to be the more commonly used (gets 65,000 results on google, versus 22000 for the other one). - And the information from the two should be merged into one as well...
    • Actually "geostationary orbit" gets around 30000 results on Google, not counting Wikipedia hits. "Geosynchronous" is the only one I've ever heard of. silsor 19:49, Mar 3, 2004 (UTC)
    • Assuming they actually mean the same, I've heard of geosynchronous, and vote that that title be the one kept. Anthony DiPierro 20:14, 3 Mar 2004 (UTC)
    • This is a redirect question, not a delete question. Let's move the discussion to one of the Talk pages. Rossami 20:18, 3 Mar 2004 (UTC)
    • "Geosynchronous" orbit is the more common term in my experience. I vote for a merge and redirect to Geosynchronous orbit. The highly technical distinction between the two is already well covered in the Geosynchronous orbit article.Rossami 20:22, 3 Mar 2004 (UTC)
    • Support redirect to "Geosynchronous" -- Decumanus 20:23, 3 Mar 2004 (UTC)
  • Actually it's not quite the same thing; a geostationary orbit is a special case of geosynchronous orbit. (That fact already is noted in the article.) Mkweise 20:34, 3 Mar 2004 (UTC)
It does not look like this discussion is very active nowadays (mid-May 2006), but my vote would be to keep both pages and cross-reference them. There is an infinity of geosynchronous orbits, but there is only one geostationary orbit. Most (if not all) of our meteorological, communication and TV satellites are on the same geostationary orbit, where they follow each other. --Michel M Verstraete 21:53, 21 May 2006 (UTC).

[edit] GSO

I was redircted here looking for GSO - a type of inorganic crystal used as a scintillator in nuclear medicine imaging (SPECT, PET, etc.) GSO is an abbreviation of cerium-doped gadolinium oxyorthosilicate.

I added an entry at GSO based on your description; thanks. Wmahan. 18:20, 14 September 2005 (UTC)

[edit] wrong

"Any point on the equator plane revolves about the Earth in the same direction and with the same period (speed) as the Earth's rotation." This is bogus. points do not revolve. The gravitational pull of the Earth provides the central force necessary for circular motion of objects in space with a specific velocity. This is independent of the motions of the Earth's surface. For a satellite of given [[mass], there is a specific height at which it could be geosynchronous if it is given the correct initial velocity. --MarSch 14:28, 8 September 2005 (UTC)


mass need not be given

[edit] Number of Satellites

How many geostationary satellites are up there? Do they stay there when they cease to function? Is it a stable orbit that could eventually cause other geostationary satellites to risk collosion from large numbers accumulating?

I don't know the numbers off the top of my head, but there are a number of satellite catalog pages that should be able to tell you. They do indeed stay up when they cease to function (it's only in low orbit that you have enough air resistance for orbits to decay). I seem to recall that organizations with satellites were encouraged to move them either into parking orbits or an earth-intersecting orbit when their useful life ended, but I don't think this happens for all satellites. As for collisions, the main risk isn't satellites themselves, but bits of metal and other debris that's kicked up as a result of micrometeorite impacts. This is discussed in more detail at space debris. --Christopher Thomas 20:08, 23 November 2005 (UTC)
There are several hundred "Active" geostationary satellites. The Inter-Agency Debris Coordination Committee (most international space orgs) develops guidelines for end-of-life procedures. In a nutshell, move it above GEO by at least 200 km (US govt moves up by +300km) and then remove all potential energy storage (e.g. drain batteries, vent fuel, etc). —Taka2007 14:12, 25 August 2006 (UTC)

[edit] Use of Newton's first law is completely bogus

Orbiting satellites are not under the influence of balanced forces, and one can *never* balance centripetal force with centrifugal force. The derivation is numerically correct, but conceptually flawed. The derivation should begin with Fc = FG, giving the source of the accelerating centripetal force.

Phillychuck 03:01, 2 February 2006 (UTC)phillychuck, Physicist

Indeed, this explanation is completely wrong: it appears to suggest that the satellite is subjected to two equal and opposite forces (which it is not, of course). If that were the case, the resultant force would be null and the satellite would pursue its trajectory in a straight line! --Michel M Verstraete 22:00, 21 May 2006 (UTC).
This appears to be a question of terminology. If you set up the problem using polar coordinates, you get equal and opposite radial forces, resulting in the second derivative of radius (radial acceleration) being zero. This is the way orbits are usually described in high school textbooks. In undergrad texts (in engineering, at least), the same type of coordinate system is used to derive Kepler's laws for elliptical orbits, as it's far easier to do that in polar coordinates than in Cartesian coordinates. --Christopher Thomas 06:02, 22 May 2006 (UTC)

The appropriate derivation is F=ma, using vectors, where F and a constantly point to the center of mass of the object being orbited. F is Newton's gravitational force = mMG/r^2. a can be simplified to a circular orbit, since that is what we are discussing with geostationary objects. a=vt^2/r. The only reason it remains in orbit is because there is an initial velocity tangent to the acceleration. There is a certain altitude where the angular velocity necessary for a circular orbit path coincides with the angular velocity of the earth and thus the object in orbit appears to be stationary over the same spot on earth for its entire orbit. This is a geostationary orbit. It must be directly over the equator for this to work. If it is off to the north or south, the object will still be geosynchronous, but its ground track will move north and south along a line centered on the equator. If the orbit is also slightly non-circular, its ground track will resemble a figure-8 centered on the equator. "Geostationary" is indeed a special case of a Geosynchronous Earth Orbit (GEO). I vote that the topics be merged under Geosynchronous Earth Orbit.--Someone

Even a circular inclined orbit has a figure-8 ground track, since the eastward component of the satellite's velocity varies with latitude. —wwoods 17:05, 4 July 2006 (UTC)

It's very easy to apply F=ma for a circular orbit, and less confusing than introducing the noninertial centrifugal force. I rewrote the section accordingly. Use of the first law is indeed bogus, but the second law is what we need. --Mike 18:03, 21 July 2006 (UTC)

[edit] GeoStationary & GeoSynchronus Orbits Merged

Geostationary and geosynchronus is not the same thing. It is two different things. This is an applied scientific fact.

The two articles should be merged and redirected to an article called Sattelite Orbit Types. This article should reassemble the different articles into Types of Orbits.

In fact, they are really types of orbit and mergance of article will just make things easier and clearer of access.


Here is a simple graphic explaning the basics of Geostationary and Geosynchronus with a fixed earth example. Just figure it out as if the earth was rotating, making Geostationary sattelites still in movement.

  • Sirius Sattelites : Geosynchronus
  • XM Satellites : Geostationary

[edit] GEO is sub-set of GSO

Geostationary orbits are a sub-set of GSO. It's a GSO orbit with zero inclination.

I've been involved in space operations for 9 years. I've operated a constellation of comm satellites for 3 plus years. As much as some people won't like it, we used geostationary 90% of the time to describe our orbits, even though they had a non-zero inclination (~1°). I would, however, have a problem with calling GSO orbits with significantly larger inclinations, GEO orbits. Not sure where I would draw the line though.

Possibly look at where the drop off in number of satellites at that altitude (i.e., if there is a significant decrease in the number of satellites below an inclination of i°, then that would be the switch over between GEO and GSO).

Of course, this reminds me of the whole debate about Pluto. I don't have much of a problem with the demotion of Pluto. My self-arguments were that there needed to be some scientific dividing line. That is completely the opposite of the fuzzy justification I gave above for dividing between GEO and GSO. —Taka2007 14:24, 25 August 2006 (UTC)

[edit] GEO is sub-set of GSO: I agree

I agree that the geostationary orbits are (merely) a subset of GSO, but they are a very important subset with unique and practically valuable properties for satellites, so a separate page seems to be merited. Martin 11:57, 7 September 2006 (UTC)

I agree. However, in my experience, "geostationary" is commonly used for a lot of satellites that are actually "geosynchronous". I'd be willing to bet that if I asked some of the operators I used to work with what the difference between geostationary and geosynchronous was, they'd be stumped. We very rarely used the term "geosynchronous" even though the satellites we were dealing with were not geostationary. However, the satellites we dealt with had an inclination less than 1°, thus the figure eight ground track was very small. Still we probably should be trying to get people to use the correct terminology. - Taka2007 17:17, 7 September 2006 (UTC)
The IADC is not consistent with their use of GEO. Their Protection Manual, the IADC defines GEO as geosynchronous orbit. In a Support Document they also define the Geosynchronous Region as Geostationary orbit ±200 km and ± 15°. - Taka2007 19:14, 7 September 2006 (UTC)

[edit] GEO is sub-set of GSO

There are articles on Wikipedia that have GEO as Geostationary and GSO as Geosynchronous and there are others with the opposite abreviations. Which is correct?

For what it's worth, I think these are foolish abbreviations to use. Just go with g-synch and g-stat.  :) Avraham 02:33, 15 December 2006 (UTC)

[edit] Non-Merging

OK, first of all, let me say I agree with basically what everyone has said so far. Yes, yes, yes, the two are not the same (although it's true that common usage is not really picky about their usages. Even physics students often used g-synch as a fancy name for g-stat. Compare naueous v. sick or infer v. imply) however that is not the issue. The issue with a merger is (1) is this article part of a broader category? and (2) if so, is it big enough to stand on its own? I think it's clear to everyone here that the answer to both those questions is yes. OK, fine, usage is sloppy, but we all know the two are seperate. However, we also all know that (a) g-stat (or near g-stat) is an extremely important case of g-synch and (b) (though this is more controversial) the Geostationary orbit article is beefy enough to stand on its own, and has potential for a lot more growth. Because everyone seems to agree with these points, and because the leaning from more recent posts seems to heavily favor my conclusion, I am removing the merge tags. Hope I don't get killed... Avraham 02:33, 15 December 2006 (UTC)

PS: The g-synch article DEFINITELY needs a section on g-stat. So if someone knowledgable, such as Taka, can write a good section there, I think that would be immensely helpful! Thanks, Avraham 02:37, 15 December 2006 (UTC)

There seems to be consensus that the two articles should not be merged; I am removing the merge tag. — Swpb talk contribs 00:07, 22 February 2007 (UTC)

[edit] Altitude vs. Mass

It should be clarified that, as a principal of physics, geostationary orbit altitude around Earth varies with the mass of the orbiting object, and that 35,786 km is only a practical reference figure that applies to objects of approximately the mass of current man-made satellites.

(If I'm not mistaken.) —The preceding unsigned comment was added by 75.6.224.142 (talk) 22:22, 30 January 2007 (UTC).

If you look through the equations, you'll see that the mass of the satelite ("msat") falls out of the equation really early on -- not through approximation, but through cancellation. It's counter-intuitive, but that's how the math goes. A similar result that surprised me when I first saw it: Suppose you set up a ramp to jump a creek, just like in the movies. You can calculate the speed you need to hit in order to make it across... and that speed is the same whether you're on a moped or in a fully-loaded dumptruck. Same result on the speed needed to complete a loopty loop (how do you spell it!? lol) . - grubber 23:20, 30 January 2007 (UTC)
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