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Geo3gh
2001-Oct-24, 03:10 AM
I just read today's Arizona Daily Star, our local paper. There's an article about the Optics dept. at the Uof A where they made this super-lightweight mirror that's only a millimeter thick. They're designing it for next-generation space telescopes. So far so good. But out of all that coolness, the following statement:

"An object in geosynchronous orbit remains in a fixed position with respect to the Earth."

Since I'm being charitable today, I'll just leave it at "that could have been said better."

the article is at: http://www.azstarnet.com/star/today/11023mirror.html

Kaptain K
2001-Oct-24, 11:07 AM
They were close, but no cigar /phpBB/images/smiles/icon_frown.gif Geostationary satelites are fixed WRT Earth over the equator.

ToSeek
2001-Oct-24, 12:33 PM
And there's a difference between "geostationary" and "geosynchronous," though the former is a subset of the latter.

GrapesOfWrath
2001-Oct-24, 04:30 PM
This was discussed on the old BABB. The term geosynchronous has more than one meaning, and must be interpreted in context.

www.dictionary.com (http://www.dictionary.com/cgi-bin/dict.pl?term=geosynchronous) lists "geostationary" has one of the meanings of geosynchronous, and my CD version of Ame.Her.Dic. says that geosynchronous has only one meaning, geostationary.

Back when, I even found some NASA sites that were using geosynchronous to mean geostationary--even though the distinction between the two would seem to be natural, once you think about it.

_________________
rocks
[changed "interpretted" to "interpreted"]

<font size=-1>[ This Message was edited by: GrapesOfWrath on 2001-10-24 15:45 ]</font>

CJSF
2001-Oct-24, 06:28 PM
So, could an object in geosynchronous, but NOT geostationary orbit appear to "bob up and down" in the sky, or dip below the horizon and then reappear along the same line in the sky?
CJSF

GrapesOfWrath
2001-Oct-24, 07:43 PM
Christopher

I think the answer to your question is yes. If you use a definition of geosynchronous such that the period of the satellite is 23 hours and 56 minutes, with any inclination. It would move up and down each day. I wonder how much it would precess...

Here is one of those NASA sites (http://www.ngdc.noaa.gov/stp/GLOSSARY/glossary.html#GEOSYNCHRONOUS) that say that geosynchronous is geostationary. Here is another page, the Standards Current Issues Group webpage (http://itp.colorado.edu/~scig/std_glossary.html#GEO), with the same point of view.

Mr. X
2001-Oct-24, 09:27 PM
Wait wait wait. Geosynchonous does NOT always equal Geostationary?

And if Geostationary = Geosynchrounous in the context, what else does Geosynchronous mean?

ToSeek
2001-Oct-24, 10:00 PM
On 2001-10-24 14:28, Christopher Ferro wrote:
So, could an object in geosynchronous, but NOT geostationary orbit appear to "bob up and down" in the sky, or dip below the horizon and then reappear along the same line in the sky?
CJSF


A geosynchronous satellite (and there are a few) would appear to form a figure-8 on a map of the Earth. This would be an orbit with a 24-hour period that's not always over the equator.

CJSF
2001-Oct-25, 10:40 AM
OK, the figure 8 makes sense - sort of a little analemma. Thanks!

CJSF

/phpBB/images/smiles/icon_cool.gif

GrapesOfWrath
2001-Oct-25, 11:04 AM
Hey, ToSeek, is this your website:
http://www.apl.jhu.edu/~parker/

By coincidence, the latest entry on the BA site (http://www.badastronomy.com/bad/news/index.html) is about satellite orbits, and in the last paragraph, BA refers to two satellite info websites. The first one (http://www.thetech.org/exhibits_events/online/satellite/4/4c/4c.1.html) says that geosynchronous means geostationary, and the second one (http://www.jpl.nasa.gov/basics/bsf5-1.html) says that geosynchronous does not mean geostationary. So you have to be careful.

Uh-oh. There seems to be another problem on that page. The BA is complaining about a Yahoo news story (http://dailynews.yahoo.com/h/nm/20011006/ts/attack_dc_310.html) that talks about satellites that can image a few inches from 360 km up in space, but will hover over Afganistan. BA points out that geostationary satellites are a lot more than 360 km up in space, more like 40000 km.

However, the news article is about the Keyhole class of satellites. These satellites typically use Molniya (http://www.geocities.com/CapeCanaveral/Hangar/1668/molniya.htm) orbits that are highly elliptical, and highly inclined. At their apogee, they can "hover" for hours over high latitudes, at distances typical of geostationary satellites, then zoom down to three or four hundred kilometers at perigee. Although they don't have the same image resolution at apogee as at perigee, the article does give it accurately apparently, in terms that the satellite is capable of.

_________________
rocks
[added words "at apogee as"]

<font size=-1>[ This Message was edited by: GrapesOfWrath on 2001-10-25 11:08 ]</font>

ToSeek
2001-Oct-25, 12:36 PM
On 2001-10-25 07:04, GrapesOfWrath wrote:
Hey, ToSeek, is this your website:
http://www.apl.jhu.edu/~parker/



No, that's not me. The site I originally used was one I did for a class, and they finally took it down (about three years after I finished the class). I've replaced it with a slightly less apt link for now, though it might be entertaining for some.

GrapesOfWrath
2001-Oct-25, 12:39 PM
I'd found the old one in your profile (http://www.badastronomy.com/phpBB/bb_profile.php?mode=view&user=25). It didn't work, so I took off the initial. Sorry about that.

ToSeek
2001-Oct-25, 04:32 PM
On 2001-10-25 08:39, GrapesOfWrath wrote:
I'd found the old one in your profile (http://www.badastronomy.com/phpBB/bb_profile.php?mode=view&user=25). It didn't work, so I took off the initial. Sorry about that.


I thought I changed that, but somehow it didn't take. It appears to be fixed now. Thanks for pointing it out.

GrapesOfWrath
2001-Nov-05, 12:42 AM
I got a form email reply from the BA. He received a lot of emails about the geosynchronous vs geostationary thing, and he seems to have fixed the page.

However, his main point is still in error. He says "So the Keyhole satellite (if that's what it was) launched by the U.S. to watch over Afghanistan is either in a low Earth orbit, and moves rapidly, or is in a much higher orbit, and appears stationary. But it cannot be both. Worse, Afghanistan is a bit too far north to get a geosynchronous satellite directly over it. While the country is still visible to a satellite in that orbit, it isn't optimally placed for viewing, and the satellite can never hover over it."

He doesn't seem to appreciate the characteristics of the Molniya orbit--which are highly elliptical, which move rapidly in a low earth orbit at times, and are designed to "hover" over higher latitudes--just not for 24 hours a day.

<font size=-1>[Change "which move rapidly" to "move rapidly"]</font>

<font size=-1>[ This Message was edited by: GrapesOfWrath on 2001-11-04 19:45 ]</font>

GrapesOfWrath
2001-Nov-30, 12:31 PM
Here is some more discussion on another board. (http://boards.straightdope.com/sdmb/showthread.php?threadid=101243#post1865389) No, I'm not being disloyal--check out who posted to that thread before me!

GrapesOfWrath
2001-Dec-03, 11:43 AM
The BA has added a correction (http://www.badastronomy.com/bad/news/index.html)

PS: The latest address of the page (http://www.badastronomy.com/bad/news/geosynch.html).

<font size=-1>[ Added PS (http://www.badastronomy.com/phpBB/viewtopic.php?topic=2546&forum=10&3) ]</font>

<font size=-1>[ This Message was edited by: GrapesOfWrath on 2002-10-26 12:11 ]</font>

David Hall
2001-Dec-03, 12:03 PM
On 2001-12-03 06:43, GrapesOfWrath wrote:
The BA has added a correction (http://www.badastronomy.com/bad/news/index.html)


I'm kind of confused about the practicality of a spy sattellite in a Molniya orbit. When it's at the nearly stationary apogee (apoapsis /phpBB/images/smiles/icon_smile.gif), it's too far away for very useful images. But when it's at perigee, It's moving too fast to be useful for very long. So what's the point? Wouldn't some other type of orbit be more practical overall?

GrapesOfWrath
2001-Dec-03, 02:57 PM
On 2001-12-03 07:03, David Hall wrote:
I'm kind of confused about the practicality of a spy sattellite in a Molniya orbit.

That's all you need to know.

Donnie B.
2001-Dec-03, 07:19 PM
On 2001-12-03 09:57, GrapesOfWrath wrote:


On 2001-12-03 07:03, David Hall wrote:
I'm kind of confused about the practicality of a spy sattellite in a Molniya orbit.

That's all you need to know.


If this was a joke, I'm laughing...

If not, I'm a bit ticked off. Does anybody think that the Russians (or the Enemy Of The Day) doesn't know all about the capabilities of those satellites? Why is it that the American public is the only group of people who aren't supposed to know?

[/rant]

Sorry, this is getting too far from Astronomy. I'll refrain from further digressions...

GrapesOfWrath
2001-Dec-04, 07:15 AM
You can blame it on "Need To Know". No fooling. That policy just shuts mouths. Otherwise, you'd have all sorts of coverstories to ferret through.

ToSeek
2001-Dec-04, 04:30 PM
On 2001-12-03 14:19, Donnie B. wrote:
If not, I'm a bit ticked off. Does anybody think that the Russians (or the Enemy Of The Day) doesn't know all about the capabilities of those satellites? Why is it that the American public is the only group of people who aren't supposed to know?


In nearly twenty years of having a secret clearance, the only information I've had access to that was actually marked secret was in an FBI briefing where they put up a slide showing the organization of the KGB. Does that make sense to anyone?

Garrette
2001-Dec-04, 06:34 PM
Sorry about being off-astronomy, but it's not often I can answer a question on this board.

Yes, it can make sense to classify the organizational chart of the KGB.

Do you remember if there were names associated with the positions, or was it a simple organizational chart? And if just a chart, did it include positions not known to be widely disseminated or acknowledged as existing? Either way, it could require classifying, and there are other reasons that would justify it.

Contrary to public opinion and to Hollywood's depiction, material is not for the most part classified based on the material itself; rather, it is based on the sensitivity of its source, with the object being not to compromise that source's safety or utility in the future.

For example, it is theoretically possible to have a report which merely says that Vladimir Putin wears pink-spotted underwear, nothing else, and for that report to be legitimately classified Top Secret/SCI/Codeword Codeword Codeword with the strictest conceivable dissemination.

Why should this be so? Well, if the only possible way to obtain the information about Putin's underwear is that Putin's washer-lady is in the pay of the CIA, and if Putin knows that this is the only possible way to obtain the information, then the information must be accorded the most severe protection. To protect it less, meaning to risk letting Putin know we have this information, would put the source (the washer-lady) at risk.

The underwear information might not be a big deal, and might even be worthy of some chuckles, but the subsequent loss of the washer-lady as a source would be a big deal indeed, because in future she might be able to pass legitimate information that does matter. Hence, the ultra-high classification of the information.

Make sense?

ToSeek
2001-Dec-04, 08:43 PM
On 2001-12-04 13:34, Garrette wrote:

Yes, it can make sense to classify the organizational chart of the KGB.

Do you remember if there were names associated with the positions, or was it a simple organizational chart? And if just a chart, did it include positions not known to be widely disseminated or acknowledged as existing? Either way, it could require classifying, and there are other reasons that would justify it.

Make sense?


I suppose you have a point, though the chart was fairly high-level, with no names on it. My attitude was "Do you think the KGB doesn't know we have this information?" I mean, this was part of a standard briefing given to anyone with a secret clearance, so there was certainly none of the usual "need to know" involved.

<font size=-1>[ This Message was edited by: ToSeek on 2001-12-04 15:43 ]</font>

GrapesOfWrath
2001-Dec-04, 08:44 PM
Maybe he was asking why it made sense to have a secret security clearance, when the only secret stuff he's seen in twenty years has been the organizational chart.

Clearances are expensive, and time consuming.

Garrette
2001-Dec-05, 09:30 AM
Then it requires more information to answer the question, but I'll give it one final guess.

Perhaps this information was obtained solely from the monitoring of signals, perhaps an intercepted phone conversation or fax transmission which would make it SIGINT (Signals Intelligence).

It is practice that any and all information obtained via SIGINT (and some related INT's, like ELINT) are classified at a minimum as SECRET, though usually with a codeword attached.

The reason is that the volume of SIGINT collected is massive and continuous with not enough analysts reviewing it, and it would be impractical to expect information that truly is not classifiable to be culled out. The practice is simply to err on the side of caution and classify it all. A few years down the road, someone will review it and it will be declassified, probably on a pre-designated date (about 7 years after collection).

I'll shut up now.

(Edited for grammar)

<font size=-1>[ This Message was edited by: Garrette on 2001-12-05 04:33 ]</font>

GrapesOfWrath
2001-Dec-05, 09:49 AM
OK, I was wrong. Nearly a simulpost too.

So, you had a secret clearance for twenty years, but the only secret thing you saw was during your briefing?

ToSeek
2001-Dec-05, 03:45 PM
On 2001-12-05 04:49, GrapesOfWrath wrote:
So, you had a secret clearance for twenty years, but the only secret thing you saw was during your briefing?


So far as I can remember. I have had access to facilities that required a secret clearance, though, so it wasn't a complete waste.

Azuth
2001-Dec-19, 01:17 AM
Quote

<font size="-2">I'm kind of confused about the practicality of a spy sattellite in a Molniya orbit. When it's at the nearly stationary apogee (apoapsis ), it's too far away for very useful images. But when it's at perigee, It's moving too fast to be useful for very long. So what's the point? Wouldn't some other type of orbit be more practical overall?</font>




Sorry to get away from the FBI posts, but I'd like to put forward a theory on this. Please bear in mind that I'm far from an expert in Satellites, so I'm asking for input not preaching gospel.

As I understand it a geostationary satellite is generally bound to the equator, thus a satellite of this nature with extremely powerful imaging equipment would be very limited in its field of view once zoomed in. Were it to zoom in on area's too far north or south the image would be very askew and it would have to look through more of the outer atmosphere, making for a less crisp image. So the compromise would be to have a powerful image satellite looking straight down on an area for as long as possible.


Assuming current military technology comes even close to that depicted in some movies this satellite would be very useful for tracking the movement of assets or even directing an attack on a moving target (i.e plotting an intercept point for a fast convoy). In certain circumstances I can see this being more useful than repeated snapshots from a satellite in low earth orbit which although providing better resolution for fixed targets may lose track of a moving target between passes. I look forward to hearing your idea's on this.

Mr. X
2001-Dec-19, 01:30 AM
On 2001-12-05 10:45, ToSeek wrote:


On 2001-12-05 04:49, GrapesOfWrath wrote:
So, you had a secret clearance for twenty years, but the only secret thing you saw was during your briefing?


So far as I can remember. I have had access to facilities that required a secret clearance, though, so it wasn't a complete waste.

ToSeek are you James Bond? /phpBB/images/smiles/icon_biggrin.gif

ToSeek
2001-Dec-19, 12:46 PM
On 2001-12-18 20:30, Mr. X wrote:
ToSeek are you James Bond? /phpBB/images/smiles/icon_biggrin.gif


If only. /phpBB/images/smiles/icon_wink.gif

GrapesOfWrath
2003-Jan-07, 04:21 PM
I just realized, as I type this, that I am in a geostationary orbit, not on the equator. Sometimes, atmospheric and lithospheric friction are good things.