Talk:Geostationary orbit

From Wikipedia:Votes for deletion page

VfD discussion

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)
  • Agree. Geosynchronous Orbit is the broader term, so the other should redirect there. --Palapala 21:53, 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).

This discussion is both obsolete (because there is now a page for Geosynchronous orbit, and false, as the above comments show. I will delete it in a few days, if I get no adverse comments. Fpoto (talk) —Preceding comment was added at 10:27, 25 June 2008 (UTC)

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)

wrong

Superseded discussion

"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

This observation is partly obsolete — because the word "revolve" is no longer there — and partly wrong — because geosynchronicity is independent of the satellite mass (as the comment above this one suggests). For this reason, I will delete this paragraph in a few days, if no one objects. Fpoto (talk) 09:35, 24 June 2008 (UTC)

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)

A GEO must be maintained with somewhere in the ballpark of 50-63m/s of delta-v per year depending on how accurately you want your spacecraft to stay on station. If a GEO spacecraft dies on station (that is, without a deorbit maneuver to a graveyard orbit; to the best of my knowledge, no GEO spacecraft has ever deorbited to an Earth entry and I know it would be less delta-v to crash it into the Moon) it soon leaves GEO because of perturbations from the Moon and Sun. It will stay in the ballpark of GEO for at least several hundred years. If I remember correctly, lunar perturbation tends to raise GEO spacecraft orbits, so it will wind up in the standard graveyard area Taka2007 described within a couple of years. Also, modern spacecraft are engineered so that their solar panels degrade to a minimum payload power specification at about the same time they run out of orbit maintenance propellant. This isn't "dead" by anyone's definition, but without enough power to run the transponders and no ability to stay where the thousands of bolted-down rooftop satellite dishes are pointed at in the sky, it can't make money. Older (1965-73ish) spinners weren't totally useless in this condition, but a modern body-stabilized spacecraft with solar wings and high-gain dishes also loses attitude control when it runs out of propellant (not instantly, as its reaction wheels take a couple weeks to spin up to their limits), so it'll die pretty fast. Also, unlike in the 1960s when your typical satellite customer had a 20m steerable antenna and knew how to use it, the typical modern satellite customer might not even remember where on his roof the 16in dish has been bolted. So back in the day, a satellite designed to maintain GEO for three years was often still being used 20 years after it was launched. These days, the satellite is designed to maintain GEO for 20 years, but becomes quite useless once it can't (that's part of the reason why they've grown from 50kg to 6,000kg, but the big reason is that the receiving stations have shrunk even faster... you could probably throw a modern satellite receiver about the same distance as a 1960s station's diameter.) As for the collision hazard, "Space is Big" - Stardock Software, Galactic Civilizations 2, 2007. Low orbit has more spacecraft in a smaller space moving over twice as fast and over a far wider variety of inclinations; it's a bit like comparing the Indianapolis 500 to a demolition derby, except that you'd have to put the demolition beaters on the Indianapolis oval and the formula racers in the demolition ring to model the speed difference. I'd expect several dozen LEO collisions to occur before the first one near GEO was detected. Featherwinglove (talk) 18:36, 27 July 2013 (UTC)

Well...that's a seven-eight year old conversation, so I'm not sure anyone really reads them. On the other hand, you sound like you really know exactly what you're talking about, so maybe you could expand the corresponding section of this article. — Reatlas (talk) 04:56, 28 July 2013 (UTC)

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)

Not much of a physicist myself , but I also get the impression something is terribly wrong here, the text seems to accredit the notion that the centripetal force is distinct from the gravitational force, where two "distinct" forces pulling in the same direction would miraculously cancel out to allow for orbital motion . Isn't there a mistake here and centripetal acceleration here should be centrifugal ? — Preceding unsigned comment added by 88.190.24.84 (talk) 11:32, 23 June 2019 (UTC)

The centripetal force required to keep the object moving in a circle is provided by gravity. I don't see anywhere in the (2019) article saying they are "distinct"? Burninthruthesky (talk) 07:36, 24 June 2019 (UTC)

The centrifugal force is a fictitious force. It can be viewed as a reaction to the centripetal force caused by gravity. --Crystallizedcarbon (talk) 15:48, 7 July 2019 (UTC)

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

What exactly is the difference between geosynchronous and geostationary? Is geostationary a special case of geosynchronous...or vice versa?75.45.114.217 (talk) 05:46, 24 May 2010 (UTC)

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)

• I think these should be merged, leaving GSO as the final artilce. Bearian 15:03, 6 July 2007 (UTC)

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)

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)

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)

Altitude vs. Mass

Discussion resolved

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 ("m_sat") 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)

Grubber is right, at that point its more or less a matter of the amount of thrust required and the payload capacity of the launch vehicle that will determine wether or not a Geostationary orbit can be achived. That boils down to good old fasioned Aerospace engineering aka. rocket Science.M jurrens 19:59, 1 July 2007 (UTC)

Ooh, I think this one is tricky! For a 24-hour orbit around the Earth, the distance of the satellite from the barycenter of the two-body system (which is still a simplification) is invariant with the satellite's mass. But consider a satellite as massive as the Moon, but in a geostationary orbit: the barycenter would be above the surface of the Earth, and thus the altitude would be less than for a satellite with negligible mass! The given altitude is correct only if -- as in the case of anything launched by human endeavor to date -- the mass of the satellite is much (much!) less than the mass of the Earth. I don't think the article needs to cover the hypothetical case of a satellite of sufficient mass to make this a practical consideration.... (sdsds - talk) 04:12, 2 July 2007 (UTC)

This boils down to the fact that the equations in the article are valid in the approximation of satellite mass much less than the Earth's mass. I am going to write a note explaining that, after which this section could be deleted. Fpoto (talk) 09:41, 24 June 2008 (UTC)

Fpoto, you're quite right (I think), and your footnote is relatively well-written (I think) - however, it cites no authority at all, we generally dislike bald statements purporting to be fact - even when it's plain to some that the statement is a fact. Put another way, can you find a better way to state the relative mass assumption, using either a math equation in the article, or a reliable source in the footnote? Thanks! Franamax (talk) 11:07, 24 June 2008 (UTC)

In Geocentric_gravitational_constant#Small_body_orbiting_a_central_body the approximation is described, so the part of my note claiming that this is a standard approximation can have a foundation there. The fact that 10^-20 is negligible for any practical purposes could be justified, but that seems overkill to me. The fact that the error is in fact 10^-20 is based on the equation in Geocentric_gravitational_constant#Small_body_orbiting_a_central_body, by comparing the circular orbit equation in the cases of small body and general case. You see that the equations are the same, the only difference being the masses (the Earth's mass in the simple case, the sum of masses in the general case). In this article, the error is on the equation

$r={\sqrt[{3}]{\frac {GM}{\omega ^{2}}}}$.

If the satellite has weight eM, being M the Earth's mass given in the article, the relative error on M in the above equation is e and consequently the relative error on the resulting r is e/3. Supposing a satellite's weight of 2e5 kg, which is the weight of the ISS orbital station, e is 3e-20 and the error on r is 1e-20, which justifies my claim. Do you think that a concise version of this derivation should go into the note? Fpoto (talk) 08:44, 25 June 2008 (UTC)

Hmmm - I'm not sure how messy a <math> tag will make a footnote look, but that would be one option (and maybe change "independent of the mass of the satellite" to "independent of mass when the satellite mass is relatively small"?). The other way would be to work your derivation into the main text, something like "the calculation above has a small error, since the centre of orbit is not exactly at the centre of the Earth ...[succinct proof]". Your math looks reasonable, I'm not qualified to judge it - but if you can find a way to show it, all the better, I'm sure lots of other people will be happy to look it over :) Franamax (talk) 09:24, 25 June 2008 (UTC)

No, I did not mean to put the equation into the note, just to explain here (in the discussion page) how it was derived. The fact is, an error of 1e-20 is not only negligible for any practical purpose, which is what I wrote, and which I will correct, but it is negligible for any purpose whatsoever. On one side, such an error on the GEO altitude would be about one thousandth of a neutron's diameter; on the other side, it is 10 orders of magnitude less than the error on the geocentric gravitational constant, so in fact there is no error at all (which is the main point I should highlight in the note). And this is valid for a satellite the mass of the ISS, which is by far the bulkiest satellite ever. To get a significant error (say, 1e-10), you would need an object 10 billions times as bulky as the ISS. So it is like explaining why a mountain does not stir when you break an egg on it. Anyway, thank you for this discussion, which has helped me clarify in my mind what exactly is negligible: I will soon change the note to better explain that, after which I hope you will comment on my changes. Fpoto (talk) 10:08, 25 June 2008 (UTC)

Thanks Fpoto, I think you've done it quite well. For anyone with a casual question, you've given an explanation; for those of a more technical bent who might want to challenge the approximation, you've given all the clues for them to work it out for themselves. Looks good to me, we'll see if any other comments come up. Franamax (talk) 03:25, 26 June 2008 (UTC)

List of satellites in geostationary orbit

We need a list of satellites in geostationary orbit. Would it be copyvio to use this information? -- Petri Krohn 15:57, 30 June 2007 (UTC)

It would be great to find a second (and third and fourth) source of information, and for each entry in the table cite at least two. The obvious place to go is the NASA nssdc catalog. If you confirm the information in two sources before adding an entry to the table, there's little chance of someone claiming a copyright violation. On the other hand if you copy the entire table from a single source without cross-checking each entry, there might be some valid concerns raised! (sdsds - talk) 22:13, 12 July 2008 (UTC)

Don't overlook List of satellites in geosynchronous orbit. (sdsds - talk) 07:36, 13 July 2008 (UTC)

The best source of orbital data for the Earth's satellites (except US spy ones) is the Space Track web site. Alas, you should register (for free) to get access to the database. Makeyev (talk) 10:27, 12 August 2010 (UTC)

Property tax issues

I have removed the paragraph about LA County Tax Assessor wanting to assess tax on satellites. The issue came about because the company that manufactures the satellite was located in Los Angeles County, not because the satellite was supposedly flying over Los Angeles County. Nothing in the reference suggested that a geostationary orbit had any issue with the assessment of the property tax. --Mr. PIM 05:31, 1 September 2007 (UTC)

Clarke Orbit

According to this NY Times obit, the IAU "officially designated" this the Clarke Orbit. If true, probably worth a note here. William Pietri (talk) 14:51, 19 March 2008 (UTC)

going to class B

Reading the description for B-class, I think this is good for B class, and maybe even to ask revision for GA. However, I have no experience on that. Could anyone comment on this? Can I just change the status from Start to B myself? Fpoto (talk) 10:31, 25 June 2008 (UTC)

In several places the article currently makes assertions without providing reliable source citations. I would not support rating the article as B-class until reliable sources are cited for every major assertion. (sdsds - talk) 22:16, 12 July 2008 (UTC)

Usage

I put in a little more about the usage "geostationary" versus the older usage "geosynchronous." The "geostationary"-purists like to find and delete all usages of the word "geosynchronous" to mean "geostationary," but in fact, in the real world the two words are used entirely interchangably-- geosynch is a little older usage, and geostationary a little newer. Frankly, I far prefer "geosynchronous", but geostationary is beginning to be seen more and more. (Every time I hear it, though, I wince, because I know that it means I'm going to have to explain yet again to somebody that no, the orbit isn't really stationary, it's moving, and you can't be "geo" stationary over any point other than the equator. You can't park a satellite in "Geostationary" orbit over Antarctica, because "stationary" really means "synchronous," not "stationary".) Geoffrey.landis (talk) 21:59, 11 July 2008 (UTC)

I wish I had good source citations for this! I believe there is a major difference between these two terms. An orbit is only geostationary when it is circular and directly over the equator. On the other hand, any orbit -- even one with high inclination and eccentricity -- is geosyncrhonous if the orbiting object circles the earth in exactly the time required for one Earth rotation. (sdsds - talk) 05:32, 12 July 2008 (UTC)

"I believe there is a major difference between these two terms." Yes, you might think. In actual use, though, they have always been used interchangably. The term "geostationary" orbit (which is not actually stationary, of course) is begining to supplant "geosynchronous," but both terms are used. Geoffrey.landis (talk) 01:26, 13 July 2008 (UTC)

Please examine non-Wikipedia sources like the GOES project website. Does that leave any doubt about the use of "geostationary"? By the way you are of course correct: no object in orbit is stationary! And of course you are also correct: every object in "geostationary" orbit is also correctly described as being in "geosynchronous" orbit! But an object can be in an orbit which is properly called "geosynchronous" but which cannot properly be called "geostationary". Please, if inserting into the article the assertion that these terms "have always been used interchangably", be sure to cite a reliable source to support that! (sdsds - talk) 01:47, 13 July 2008 (UTC)

(e/c) The terms may be used interchangeably in the industry, but I imagine the industry is mostly concerned with geostationary orbits (which are also geosynchronous). In the case of a polar geosynchronous orbit (are there any such satellites?), someone who called it geostationary would probably get laughed out of the lunch room.

We should note that geostationary orbits are commonly referred to as geosynchronous (which they are), but we shouldn't give the public the impression that the two terms are synonymous.

The article already makes clear what the "stationary" part means:

Geostationary orbits are useful because they cause a satellite to appear stationary with respect to a fixed point on the rotating Earth. Franamax (talk) 01:56, 13 July 2008 (UTC)

Geoffrey, I've reverted your recent edit [1] on the following basis:

• Did you try to find the Potočnik reference before you deleted the text? It actually turned out to be pretty darn easy. Wait a few minutes while I figure out the {{cite book}} template and you'll be able to see it in the article.
• Why are you blanket changing geostationary to geosynchronous? This article is about the geostationary orbit, the circular equatorial-plane special case of the generalized geosynchronous orbit, which is elliptical and variously oriented and centred. It seems to me too that when you change the derivation of altitude to say it is for a geosynchronous orbit, you introduce a factual error, since a geosynchronous orbit is elliptical and thus continuously varies in altitude. Per the discussion above, I don't think you've gained consensus to change the wording in this article. Franamax (talk) 20:10, 31 August 2008 (UTC)

Thanks for adding the Potočnik citation.

As for changing geostationary to geosynchronous in the derivation, the mathematical section I edited in fact derives how high an orbit must be in order to be synchronous with the Earth's rotation, that is, it derives the altitude of geosynchronous orbit. I suppose we probably should just delete the section out of this article, add it to the geosynchronous orbit article, and put in a link saying "the derivation is in the geosynchronous orbit article" but that seemed too complicated. Geoffrey.landis (talk) 03:45, 1 September 2008 (UTC)

The section on altitude only makes sense for circular orbits, as the first four words make clear: "In any circular orbit, ...". A geostationary orbit is a circular equatorial geosynchronous orbit. But a geosynchronous orbit is generally elliptical, so no such a thing as the altitude of geosynchronous orbit exists, at least not as a single number. In this particular section, you could indeed replace geostationary with circular geosynchronous, but why? It is more complex and uselessly generic, as this article only speaks about geostationary orbits --Fpoto (talk) 13:45, 1 September 2008 (UTC)

"Geosynchronous," as Wikipedia uses it, means an orbit that is synchronous with the Earth's rotation. The "Derivation of geostationary altitude" section calculates "what orbital radius is needed to make an orbit with the same period as the Earth's rotation?" Therefore, prima facia, this section is calculating the radius of a geosynchronous orbit. Since Wikipedia has defined "geostationary" as a subset of geosynchronous, then obviously once you know this you know the altitude of a geostationary orbit, but the calculation is independent of inclination-- it is purely a calculation of altitude needed for the orbit to be synchronous with the Earth's rotation.

As I wrote above, you cannot compute, in general, the "radius of a geosynchronous orbit", so you cannot simply substitute geostationary with geosynchronous. Regarding what you write below, the semimajor axis of an elliptic orbit is not its radius; this is significant because this section is devoted to altitude, and subtracting the Earth's radius from the semimajor axis does not give you altitude. --Fpoto (talk) 22:16, 2 September 2008 (UTC)

In fact, the calculation is done for circular orbits, but trivially, by Kepler's law, the period is proportional to the semimajor axis and is independent of eccentricity, so once you know this result, you know the semimajor axis for a geosynchronous orbit of any eccentricity. Geoffrey.landis (talk) 23:10, 1 September 2008 (UTC)

So what? This article is about the geostationary orbit and only about the geostationary orbit. The consideration that the same equations can be used to solve the general case of any geosynchronous orbit is of no interest to us here. Do you realize that we also have an article on the geosynchronous orbit general case where you can concentrate your efforts? Franamax (talk) 23:50, 1 September 2008 (UTC)

This discussion has become tedious, so please pardon me if I do not continue. Geoffrey.landis (talk) 22:36, 2 September 2008 (UTC)

So if wikipedia were to use "geosynchronous" to mean circular and equatorial (just like geostationary), what term would we use for orbits with that exact same period but which are elliptical or inclined or both? One would want to call them "geosynchronous" too, since they are exactly in sync with the Earth's rotation. Is the assertion implicitly being made that these are not interesting cases? Or that for any interesting orbit in this class, there is some specific name, like tundra orbit? (sdsds - talk) 05:55, 1 September 2008 (UTC)

I think that wikipedia should simply not use "geosynchronous" to mean circular and equatorial. --Fpoto (talk) 13:45, 1 September 2008 (UTC)

Useless / confusing second image

The second image in the article, added about one year ago by User:Mike1024, is in my opinion out of scope and possibly confusing. If no one objects, I will remove it. --Pot (talk) 15:00, 23 December 2008 (UTC)

Orbit lenght

Which one of these?

• The Clarke Orbit is about 265,000 km (165,000 mi) long.
• The Clarke Orbit is about 265,000 km (165,000 mi) in circumference.

I am for the former, the old version.

An orbit is a path, a trajectory, and intuitively it has a length, as any path has. Sure, the second version is correct, but more complex, and uselessly so. --Pot (talk) 19:42, 16 October 2009 (UTC)

   The circumference seems to be calculated with the altitude substituted for the radius, thus
   giving a to short answer. Fabian85.228.229.105 (talk) 05:16, 24 November 2009 (UTC) I got my
   math wrong, disregard my previous comment. Fabian 85.228.229.105 (talk) 02:13, 25 November 2009 (UTC)

Actually, I'd argue that saying circumference is more precise. It reminds one what part of the circle is of interest.75.45.114.217 (talk) 05:44, 24 May 2010 (UTC)

Rumours

This is just about rumours:

Some people in the industry dislike the term "geostationary," because the orbit is not
actually stationary (in fact, the term stationary orbit would be an oxymoron), and
prefer to use  geosynchronous" because it emphasizes the key point that the orbit is not
actually stationary, but synchronized with the motion of the Earth surface.

This reasoning makes little sense for two reasons.

First the method: it can be argued that it is unimportant whether "geostationary" or "geosynchronous" can be significantly attributed to "orbit", because both are terms with a history and a dignity, not just pairs of words stuck together.

Second the merit: an orbit is a trajectory, and as such is "fixed" in the sky, so "geostationary orbit" is not an oxymoron. Orbits do not "move": it's the objects on them that move, so both "geostationary" and "geosynchronous" make perfect sense: one is about looking from the Earth's surface, the other is about looking from space.

I will delete the cited sentence if no one objects. --Pot (talk) 08:55, 7 November 2009 (UTC)

Yeah, this wording I think is the result of a discussion a year or so ago. I'd agree that at least "some people in the industry dislike" needs to go - which people, what industry, who what when? We should cover the fact that geostationary and geosynchronous have overlapping meanings though, and in the literature it's not uncommon to find this overlap. As I recall from last year, I'd seen some references presenting the geostationary equations but referring to them as geosynchronous orbital equations. We need to acknowledge this, but without the prejudical language. Franamax (talk) 10:02, 7 November 2009 (UTC)

It's not "geostationary" that is overlapping: in fact, some people simply do not use the word geostationary but use geosynchronous instead. I think this is not a problem to be covered here, but rather in the geosynchronous orbit page, where in fact it is. --Pot (talk) 12:24, 8 November 2009 (UTC)

I suppose no real-world orbit is ever precisely geostationary; everything is always wobbling a little relative to that. On the other hand some geosynchronous orbits are not remotely geostationary; and hence the problem.- Wolfkeeper 13:21, 8 November 2009 (UTC)

Well, I see no problem, in fact. Some people just do not like the term "geostationary", and they use the more generic term "geosynchronous" instead. I argue that geostationary orbit has nothing to say on this issue, because it is unambiguous. Some text is already present in geosynchronous orbit that mentions the issue, and that is enough, in my opinion. --Pot (talk) 17:53, 8 November 2009 (UTC)

Libration points

Could someone clarify exactly what "libration points" are? The phrase was linked in the section where they are named, but that just redirects to Lagrangian point, which is unhelpful at best; if not directly misleading, so I unlinked that. There is also a link to Libration in the Lagrangian article, but that does not seem to be relevant either. Is the same term used for these three different things, or is there some connection that I just can't see? (For what it's worth, that short paragraph explains what it means in this context well, it's just the terminology that seems confusing to me.) -- magetoo 20:46, 27 May 2010 (UTC)

User:Mikeo, could you explain why you deleted the part about libration points? --Pot (talk) 08:51, 30 September 2010 (UTC)

The first part of it was redundant in the article. In addition to that calling it "libration points" is unusual and misleading (see above comment by magetoo) - as this is normally only referring to the stationary solutions of the circular restricted three-body problem (the Lagrangian points). Someone had mixed things up. The thing which is causing the longitudal drift in GEO is (mainly) the second-order, second-degree component of Earth sperical harmonics (causing a slight periodic variation of the semimajor axis) - this is - in a little simlified version - explained in another part of the article). The second part was just plainly incorrect - there just are no 160 satellites gathered at these positions. Mikeo (talk) 16:05, 30 September 2010 (UTC)

Thank you. But what about this link where the same story is reported? Is it completely false? --Pot (talk) 16:58, 30 September 2010 (UTC)

Yes it is false (the gathering of the 160 satellites). Maybe the author of that article has misunderstood something. No reason for us to inherit that error. Mikeo (talk) 20:34, 30 September 2010 (UTC)

Other planets

Should mention what similar orbits around bodies other than the Earth are called. SharkD  Talk  07:26, 20 June 2010 (UTC)

Simplification?

I do not understand the simplicity of the section "Simplification", which is apparently only a redundant replica of the previous section (and has also internal redundancies). So, I will remove it, except perhaps the example of Mars, if nobody objects.--GianniG46 (talk) 20:50, 16 October 2010 (UTC)

Picture suggestion

Trackable objects including debris, note distinct ring of GEO satellites

Penyulap _talk 20:17, 6 June 2011 (UTC)

Conversion between units and precision

In the first line of the introductory paragraph is a precise conversion between kilometres and miles to one unit in each case. That's fine. But a few lines down, in reference to the "belt" containing the Clarke Orbit, the same very precise (to 1 km) metric measure is converted to a mileage seemingly specified to nothing more precise than the nearest thousand miles. 22000 miles (to the nearest mile) is 35406 km (to the nearest kilometre). Would it not be better from the point of view of a more appropriate level of precision to replace the latter distances by "35,400 km (22,000 mi)"?Jamjarface (talk) 16:04, 14 February 2012 (UTC)

Altitude

Doesn't the altitude of a stable orbit depend on the mass of the object? It's true of satellites, but anything much more massy than that would not be stable.Gymnophoria (talk) 17:57, 9 July 2012 (UTC)

No. Everything in free fall, falls at the same rate. That's what an orbit is. The difference for massive objects is how much energy it takes to put them in a particular orbit.

--67.162.165.126 (talk) 03:02, 23 May 2013 (UTC)

Mathematical symbols and equations error

Mathematical symbols and equations are not being properly displayed on the page. Anyone who can fix this please do so urgently. Ahmer Jamil Khan (talk) 14:11, 27 August 2012 (UTC)

Can you be more specific? A quick look shows everything appears to be displaying properly to me. siafu (talk) 17:01, 27 August 2012 (UTC)

poor gif animation

someone who knows how needs to replace the radial lines with' dotted ones, and reduce it to one satellite. It had it confused with spokes of a wheel at first. --67.162.165.126 (talk) 02:58, 23 May 2013 (UTC)

Cosine Rule

The cosine rule, as it is currently displayed, gives an estimation of the time needed for a signal to travel only from a ground station to a satellite but NOT back from the satellite to the station, as mentioned in the text. In order for the latter to be etsimated, I believe that the coefficient 1/c in the mathematical formula has to be changed to 2/c. I would recommend that an expert look into the matter. — Preceding unsigned comment added by Queen4thewin (talk • contribs) 22:37, 13 August 2013 (UTC)

Question

In the illustration "Comparison satellite navigation orbits", the orbits of different satellites appear to be at varying altitudes. Are they thus not precisely geosynchronous? How much variation in altitude and latitude is permissible? Does this eat up extra propellant? Thanks!

-Kortoso (talk) 23:37, 30 September 2014 (UTC)

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Radius

The radius of a geostationary orbit should appear explicitly in the Introduction. 94.30.84.71 (talk) 20:36, 1 October 2015 (UTC)

We have the altitude but not the orbital radius. At the distance that we are talking about, I can see how the radius might be more germane than the altitude. Kortoso (talk) 22:15, 1 October 2015 (UTC)

First gif does not appear at first glance to be geostationary

I'm no expert, but that first animation looks misleading to me. No matter how much I stare at it, I see the Earth rotating about the vertical axis, and therefore assume the satellite is oscillating above and below the equator.

For comparison, I think the red and yellow orbits shown here more clearly demonstrate the difference between a geosynchronous and geostationary orbit.

Assuming I am wrong, and the Earth *is* in fact tilted in that animation, there are two alternative ways it could be improved:

1. Rotate it to remove the tilt, thus emphasising that a geosynchronous orbit sits on the flat plane of the equator. (This would have the disadvantage of obscuring the fact that the Earth's is tilted relative to its orbit around the Sun.)
2. or simply add a little line above and below the poles of the Earth, to clearly show the axis of rotation. This will help to demonstrate that the Earth is tilted, and remove doubt from the viewer.

Is there a GIF expert who could work their magic to achieve the second suggestion? JoeyTwiddle (talk) 05:17, 27 December 2015 (UTC)

I have carefully studied the graphic, and found JoeyTwiddle is correct about the vertical axis of rotation. I have therefore removed File:Geosynchronous orbit.gif from this article. Thanks for pointing this out. Burninthruthesky (talk) 15:55, 10 February 2016 (UTC)

Technical flaw incorrect units

1) The units specified for the Gravitation Constant G should be kg-2 (exponent -2). The correct units are provided on the page specific to the Gravitation Constant. The same error is contained in the Geocentric Gravitation Constant page.

2) After fixing point 1, a further fix is needed to explain why the GGC does *not* have kg in it's units (which is correct). The reason for this is that the GGC is technically not just GMe. Rather it is GMe*(1kg). The 1kg is factored in presumably to simplify the calculation overall (since it would fall out in the end anyway). As I don't work in this area I don't know if there is already an appropriate term to describe this. It may be appropriate to describe this using the prefix "specific" as in "specific-GGC". This would be consistent with other uses of the prefix "specific" in the field of physics. — Preceding unsigned comment added by 23.29.213.104 (talk) 19:07, 20 December 2016 (UTC)

Hi, thanks for your comment. The units for G in the article (m³ kg⁻¹ s⁻²) correspond to the equation given in the text:

$|\mathbf {g} |={\frac {GM}{r^{2}}}$

These units can be equated to N m² kg^-2 via Newton's second law, F=ma (units: N=kg m s^-2). I hope this clarifies. Burninthruthesky (talk) 08:15, 21 December 2016 (UTC)

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File:Comparison satellite navigation orbits.svg scheduled for POTD

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View animation

This is an animation showing geocentric satellite orbits, to scale with the Earth, at 3,600 times actual speed. The second-outermost (shown in grey) is a geostationary orbit, 35,786 kilometres (22,236 miles) above Earth's equator and following the direction of Earth's rotation, with an orbital period matching the planet's rotation period (a geosynchronous orbit). An object in such an orbit will appear to occupy a fixed position in the sky. Some 300 kilometres (190 miles) farther away is the graveyard orbit (brown), used for satellites at the end of their operational lives. Nearer to the Earth are the orbits of navigational satellites, such as Galileo (turquoise), BeiDou (beige), GPS (blue) and GLONASS (red), in medium Earth orbits. Much closer to the planet, and within the inner Van Allen belt, are satellites in low Earth orbit, such as the Iridium satellite constellation (purple), the Hubble Space Telescope (green) and the International Space Station (magenta).

Animation credit: Cmglee

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