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tony873004
2009-Nov-18, 05:55 PM
On Monday, I watched through a telescope and solar filter while the ISS transited the face of the sun. It was an impressive sight. Although I've seen the ISS plenty of times as a bright star in the twilight sky, the silhouette was very detailed. It was the first time in my life I felt I'd actually seen a spaceship!

But the ISS isn't the only satellite that transits the sun. They all do. And there are thousands of them. And TLE’s are available for most of them. But most are probably too small to see. Does anyone know where I can get a list of satellites by angular size? I'd like to compile a top 10 or so, so I can watch these transits more often.

astromark
2009-Nov-18, 06:39 PM
"But the ISS isn't the only satellite that transits the sun. They all do. And there are thousands of them. "

They all do, may not be correct. But I take your point and endorse that fact. They look great.
As for angular size, You want a list. It would start with the ISS...

jfribrg
2009-Nov-18, 07:42 PM
Here is a picture of the Shuttle as it transited the Sun. I find it amazing that the shuttle's "dorsal fin" is visible from 300 miles away.

eburacum45
2009-Nov-18, 07:48 PM
Do you mean this (http://spaceweather.com/swpod2009/14may09/Thierry-Legault2.jpg?PHPSESSID=qrjmo1c6broa6cfda7brkf1ru5&PHPSESSID=srhr9786q87omti810550h1l00)?

Swift
2009-Nov-18, 08:00 PM
Tony,

The closest I've found so far is this satellite database (http://www.ucsusa.org/nuclear_weapons_and_global_security/space_weapons/technical_issues/ucs-satellite-database.html) (links on that webpage) from the Union of Concerned Scientists.

The UCS Satellite Database is a listing of the approximately 900 operational satellites currently in orbit around Earth. Our intent in producing the database is to create a research tool for specialists and non-specialists alike by collecting open-source information on operational satellites and presenting it in a format that can be easily manipulated for research and analysis. It is available as both a downloadable Excel file and in a tab-delimited text format.
It doesn't seem to have info about angular size, but it does have information about mass, which would probably be a starting point (at least a first approximation).

Nick Theodorakis
2009-Nov-18, 08:09 PM
I would guess the KH-11 (http://en.wikipedia.org/wiki/KH-11_KENNAN) and successors (KH-12 (http://en.wikipedia.org/wiki/KH-12) and KH-13 (http://en.wikipedia.org/wiki/KH-13), aka "Keyhole") spy satellites are among the biggest, and not too distant in orbit, but good luck finding orbital data for them.

Nick

tony873004
2009-Nov-19, 02:54 AM
Thanks, Astromark, Nick and Swift.

...It doesn't seem to have info about angular size, but it does have information about mass, which would probably be a starting point (at least a first approximation).
Thanks for the link. I'm also looking at a list of the brightest satellites. Generally, brighter = bigger, just like more massive = bigger. There seems to be a big gap between the ISS and the next (largest, brightest, most massive).

Nick Theodorakis
2009-Nov-19, 05:48 AM
It wouldn't surprise me if they had taken some steps to minimize the brightness of spy satellites. OTOH, Iridiums flare up to incredible brightness without being particularly large.

As to size, I'm guessing that the reason for the size gap between the ISS and the next biggest satellite is because all the other ones went up in one piece, rather than being assembled from modules in orbit.

Nick

mugaliens
2009-Nov-19, 08:04 AM
They all do, may not be correct.

Actually, it is.


They look great.

I've only seen one satellite transit the sun, but it was on a video taken by someone else!

I need to get out more...

ngc3314
2009-Nov-19, 01:02 PM
"But the ISS isn't the only satellite that transits the sun. They all do. And there are thousands of them. "

They all do, may not be correct.

It depends on location (like the real-estate agents always say). Low latitudes are favored for number of possible transiting objects. For example, from my location, the large number of satellites in LEO at the popular 28.5-degree inclination can transit the Sun only in winter. They are never visible at all more than about 42 degrees from the equator. So areas close to the equator win not only by having opportunities to see everything in Earth orbit transit the Sun, but having opportunities to see them at all times of year.

chornedsnorkack
2009-Nov-19, 02:50 PM
Thanks, Astromark, Nick and Swift.

Thanks for the link. I'm also looking at a list of the brightest satellites. Generally, brighter = bigger, just like more massive = bigger. There seems to be a big gap between the ISS and the next (largest, brightest, most massive).

Not necessarily.

One of the early, 1960s US satellite was named Echo. It was low in mass but big. Basically, it was a big but lightweight aluminum foil balloon inflated with gas. Its goal was to reflect radio waves passively.

Are there any newer lightweight but big satellites?

mugaliens
2009-Nov-21, 03:47 PM
Are there any newer lightweight but big satellites?

Impractical, due to drag and orbital decay.

ngc3314
2009-Nov-22, 08:52 PM
It is widely rumored that there are quite large deployed dish structures in high-to-geosynchronous orbits, where orbital decay isn't a concern, but they are probably mostly mesh and don't have very large angular sizes. Their operators would prefer them to be as inconspicuous as possible.

Both Echo 1 and 2, the original balloon sats, wound up doing very interesting gyrations of orbital properties due to residual atmospheric drag and (IIRC) even sunlight pressure. (I am just old enough to remember my family pointing Echo 1 out to me on at least one evening.)

publiusr
2009-Nov-24, 01:32 AM
Envisat is pretty heavy at eight tons IIRC. Comsats are getting bigger, Lacross etc.