Author Topic: Can a Telescope view GEO Satellites?  (Read 39786 times)

Offline Spiritual_Ghost

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Can a Telescope view GEO Satellites?
« on: 01/26/2010 12:40 am »
I have been wondering if we could see a Geostationary Satellites above us with a good Telescope or from Astronomical Observatory.
As everyone knows Geostationary Satellites will orbit fixed on the same coordinations. Is there anyone who have tried viewing the GEO satellites? Share some pictures if you guys have one.

Offline Lee Jay

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Re: Can a Telescope view GEO Satellites?
« Reply #1 on: 01/26/2010 12:43 am »
Yes.  Long exposures will yield a string of dots.

Offline Spiritual_Ghost

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Re: Can a Telescope view GEO Satellites?
« Reply #2 on: 01/26/2010 12:48 am »
What about from Astronomical Observatories?
Can their large Telescopes see the shape of it?


Offline Lee Jay

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Re: Can a Telescope view GEO Satellites?
« Reply #4 on: 01/26/2010 01:19 am »
What about from Astronomical Observatories?
Can their large Telescopes see the shape of it?

Not unless the object is huge.  At that distance (GEO), even the big stuff like Jim linked to doesn't have the resolution to see details.  On the other hand, even decent backyard scopes can see details of ISS.

Offline AlexInOklahoma

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Re: Can a Telescope view GEO Satellites?
« Reply #5 on: 01/26/2010 01:47 am »
Oh, the irony of Jim giving not one, but two(!) wiki links  ;-)

Most GEO sats are much too small for earth-based scopes to show much detail at all.  Atmosphere is what makes the details 'fuzzy'.  Adaptive-optics is the key for the finer points whenever peering through the atmosphere, of course. 

Alex

Re: Can a Telescope view GEO Satellites?
« Reply #6 on: 01/26/2010 05:18 am »
As shown in the article quoted by Ed, a fairly modest camera can collect enough light against the otherwise streaming star field to detect these objects. But imaging and detection are two different tasks. The detail that can actually be seen on a distant object depends on diffraction and scale in the optical system. For comparison, here is a very good article about what the Hubble Space Telescope can theoretically see on the Moon:

http://atomic-molecular-optical-physics.suite101.com/article.cfm/can_hubble_space_telescope_see_flag_on_the_moon

Since the Moon is roughly 10 times more distant than geostationary satellites, we can extrapolate that, at the geostationary distance of 22,236 miles above the earth (treating the Hubble's 353 mile high orbit as negligible), Hubble might be able to barely image something that is 1/10th of the noted 100m limit at the Moon's distance, or in other words, a 10m target.  I'm not sure that any of those satellites have that much spread, but it is just possible that the longest panels might image across 2 pixels in a Hubble photo. That would meet my criteria of "imaging" the satellite as opposed to just detecting it--two totally different takes on "seeing" a satellite.  ;)

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Online ugordan

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Re: Can a Telescope view GEO Satellites?
« Reply #7 on: 01/26/2010 10:17 am »
Hubble might be able to barely image something that is 1/10th of the noted 100m limit at the Moon's distance, or in other words, a 10m target.  I'm not sure that any of those satellites have that much spread, but it is just possible that the longest panels might image across 2 pixels in a Hubble photo.

Kind of a moot point since Hubble cannot track "fast" moving objects, even when it imaged the Moon IIRC it just stared at a point in the sky and let the moon drift in front of it. Apparent angular speeds of a GEO satellite as seen from Hubble would (WAG) most of the time be too high for it to track anyway.

Online kevin-rf

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Re: Can a Telescope view GEO Satellites?
« Reply #8 on: 01/26/2010 12:24 pm »

Kind of a moot point since Hubble cannot track "fast" moving objects, even when it imaged the Moon IIRC it just stared at a point in the sky and let the moon drift in front of it. Apparent angular speeds of a GEO satellite as seen from Hubble would (WAG) most of the time be too high for it to track anyway.

They should have a similar angular speed to the moon. But back to the point, Hubble is the wrong space telescope to look at GEO birds ;)
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Offline Nomadd

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Re: Can a Telescope view GEO Satellites?
« Reply #9 on: 01/26/2010 12:34 pm »
 I know Hubble locks onto a guide star to stay pointed but it must be able to pan some to get long planetary exposures. Of course, those would be a constant pan while lunar or Geo sats would be variable.
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Re: Can a Telescope view GEO Satellites?
« Reply #10 on: 01/26/2010 12:50 pm »
They should have a similar angular speed to the moon.

Not so sure about that. I'm thinking about parallax between the telescope and the GEO bird against the starfield vs. such parallax for the more distant Moon during one Hubble orbit.

Re: Can a Telescope view GEO Satellites?
« Reply #11 on: 01/26/2010 01:18 pm »
The original question was whether geosats could be photographed, and my point with the Hubble example was simply to set the theoretical limits for what can be expected, detail-wise. That exercise was interesting, but academic--these  birds are far too distant for any practicable imaging from here (or even near-earth-orbit). We can tell the OP, Yes, under the best of circumstances with something the size of Hubble, you could theoretically photograph it in enough detail to determine order of magnitude size.  Practically though, I'd just try to repeat the stationary, time-lapse detection examples, which can be done with prosumer-level skills and telescopes.

Here is another stunning example:
http://epod.usra.edu/blog/2007/09/geostationary-satellites.html
The feat can be done with scopes as small as 12", at least (the wider the aperture, the more photon scoop you have). The challenge is to gather satellite photons faster than the background sky glow can swamp those dots.

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Offline JohnFornaro

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Re: Can a Telescope view GEO Satellites?
« Reply #12 on: 01/26/2010 01:29 pm »
Ed's link was fascinating, as were the Wiki links.  So here's my question:

How close and how big would be the asteroid that one could theoretically photograph by this method, assuming that one knew the path of the asteroid, and could track it with one's telescope.
Sometimes I just flat out don't get it.

Offline toddbronco2

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Re: Can a Telescope view GEO Satellites?
« Reply #13 on: 01/26/2010 02:55 pm »
I have been wondering if we could see a Geostationary Satellites above us with a good Telescope or from Astronomical Observatory.
As everyone knows Geostationary Satellites will orbit fixed on the same coordinations. Is there anyone who have tried viewing the GEO satellites? Share some pictures if you guys have one.


There are examples out there.  Here's one.
http://www.noao.edu/outreach/press/pr01/pr0106.html

 - Ed Kyle

Ed, I just thought you should know that your link made my day.  I'm dying to try this out!  too cool


Offline Robotbeat

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Re: Can a Telescope view GEO Satellites?
« Reply #15 on: 01/26/2010 04:15 pm »
The equation for determining diffraction-limited resolution is this:

Angular resolution (in radians):
1.22*(wavelength)/(diameter of primary mirror or lens)

Spatial resolution:
(distance to target)*1.22*(wavelength)/(diameter of primary mirror or lens)

500nm is green light, so it's what I usually use for calculations like this (250nm for near-UV, and 1000nm for near-IR).

GSO is at an altitude of roughly 36,000km. So, for a Hubble-sized telescope (there are a few spy sats with roughly this performance or greater):

(3.6*10^7 m)*1.22*(5*10^-7 m)/(2.4 m) = 9.15 meters.

At near-UV:

(3.6*10^7 m)*1.22*(2.5*10^-7 m)/(2.4 m) = 4.575 meters.

For the Keck telescopes (separately, not combined):
(3.6*10^7 m)*1.22*(5*10^-7 m)/(10 m) = 2.2 meters.
However, the Keck telescopes cannot actually see at that resolution (I believe), because the Adaptive-Optics technique works at longer wavelengths. According to wikipedia, they have a limiting resolution of .04 arcseconds, which works out to about 7 meters in spatial resolution for a GSO object (but, I think the Kecks usually rely on the rotation of the Earth with respect to their target in order to cancel out the diffraction artifacts caused by their segmented mirrors, besides the fact that if your spatial resolution is smaller than your aperture, I think you need to "focus" closer than infinity in order to see the object properly...).

9 or 4.5 meters is not a bad resolution for spotting very large GSO satellites... The US supposedly has signals intelligence satellites 100 meters in diameter located at GSO.

EDIT: The easiest way to do these sorts of equations is to just plug them into Google. Google will take care of the units for you, so add your units of choice (if you want the answer in other units, just add " in feet" to get the answer in feet). For instance: http://www.google.com/search?q=(3.6*10^7 m)*1.22*(5*10^-7 m)/(2.4 m)
« Last Edit: 01/26/2010 04:21 pm by Robotbeat »
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Offline simonbp

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Re: Can a Telescope view GEO Satellites?
« Reply #16 on: 01/26/2010 05:20 pm »
The Navy Prototype Optical Interferometer can detect the glint of GEO sats, but not image them. Optical imaging interferometers are EXTREMELY difficult; you need to have positional tolerance in the nanometers over hundreds of meter baselines...

http://www.lowell.edu/npoi/index.php
« Last Edit: 01/26/2010 05:20 pm by simonbp »

Offline vt_hokie

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Re: Can a Telescope view GEO Satellites?
« Reply #17 on: 01/26/2010 09:49 pm »
There are examples out there.  Here's one.
http://www.noao.edu/outreach/press/pr01/pr0106.html

 - Ed Kyle

Ed, I just thought you should know that your link made my day.  I'm dying to try this out!  too cool

That is pretty cool!

Offline Paolo Astronomer

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Re: Can a Telescope view GEO Satellites?
« Reply #18 on: 02/08/2010 03:43 am »
I have been wondering if we could see a Geostationary Satellites above us with a good Telescope or from Astronomical Observatory.
As everyone knows Geostationary Satellites will orbit fixed on the same coordinations. Is there anyone who have tried viewing the GEO satellites? Share some pictures if you guys have one.


There are examples out there.  Here's one.
http://www.noao.edu/outreach/press/pr01/pr0106.html

 - Ed Kyle

Ed, I just thought you should know that your link made my day.  I'm dying to try this out!  too cool

Actually imaging is really hard at a place like NPOI, but is not as hard as interferometric astrometry which requires the hard metrology to get the fringes and phase closure etc.

Also depends on what bandpass telescope is looking at the GEO - optical, NIR, FIR, mm, radio etc... and how it might be illuminated  - which may produce specular relections and therefore some image information. Might look at a few of these at the top, remembering you can improve this proof of concept with more and shorter baselines.... In some ways NPOI in its regular configuration "zooms in" with too high a magnification/narrow FOV unless you made really short baselines:

http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?db_key=AST&db_key=PRE&qform=AST&arxiv_sel=astro-ph&arxiv_sel=cond-mat&arxiv_sel=cs&arxiv_sel=gr-qc&arxiv_sel=hep-ex&arxiv_sel=hep-lat&arxiv_sel=hep-ph&arxiv_sel=hep-th&arxiv_sel=math&arxiv_sel=math-ph&arxiv_sel=nlin&arxiv_sel=nucl-ex&arxiv_sel=nucl-th&arxiv_sel=physics&arxiv_sel=quant-ph&arxiv_sel=q-bio&sim_query=YES&ned_query=YES&adsobj_query=YES&aut_logic=OR&obj_logic=OR&author=&object=&start_mon=&start_year=&end_mon=&end_year=&ttl_logic=OR&title=&txt_logic=OR&text=NPOI+Glint+geo%0D%0A&nr_to_return=200&start_nr=1&jou_pick=ALL&ref_stems=&data_and=ALL&group_and=ALL&start_entry_day=&start_entry_mon=&start_entry_year=&end_entry_day=&end_entry_mon=&end_entry_year=&min_score=&sort=SCORE&data_type=SHORT&aut_syn=YES&ttl_syn=YES&txt_syn=YES&aut_wt=1.0&obj_wt=1.0&ttl_wt=0.3&txt_wt=3.0&aut_wgt=YES&obj_wgt=YES&ttl_wgt=YES&txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1




Offline ngc3314

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Re: Can a Telescope view GEO Satellites?
« Reply #19 on: 02/12/2010 02:25 am »
There was a report by Keith Hege and coworkers back in the 1980s, using speckle imaging in the days before adaptive optics. They used the original 6-mirror MMT (edge-to-edge span 6.9m) to resolve the solar arrays on FLTSATCOM 1, which span 13.2m according to Wikipedia. The project report abstract is here.

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