Orbital surveillance satellites now exceed 1 inch resolution.
Robert Clark
capabilities give them as about 10 centimeters, 4 inches. However, it
is widely known that the most advanced astronomical space
observatories lag what is currently available for military and
intelligence satellites. The Hubble Space Telescope for example was
derived from early technology surveillance satellites.
Then since the James Webb Space Telescope has a segmented 6.5
diameter mirror, very likely this at least is available now for
surveillance satellites.
I discussed the capabilities for such a mirror for space-borne
imaging in the post below. At 300 km altitude it would have better
than 3 cm resolution, about an inch. Spy satellites frequently have
elliptical orbits that can bring their altitude to half this at
closest approach, so their max resolution will be perhaps half this,
1.5 cm to 1 cm.
The James Webb Space Telescope is however an infrared telescope. The
question I had was whether the mirror smoothness tolerances required
at visible wavelengths were available using the beryllium material
used in the segmented mirror of the James Webb. From this web site we
may conclude that this is indeed possible:
ESO Press Photos 34a-b/97
12 December 1997.
First M2-Unit and Beryllium Mirror Delivered to ESO.
http://www.eso.org/outreach/press-rel/pr-1997/phot-34-97.html
The ESO's Very Large Telescope (VLT) uses 1.2 meter beryllium mirrors
for its secondaries. This requires visible wavelength smoothness since
the VLT will operate at both visible and infrared wavelengths. The
James Webb hexagonal mirror segments are each 1.3 meters in diameter.
So we may conclude beryllium mirrors of this size could be polished to
the smoothness required for visible light observations.
This question was raised by me in regards to astronomical planetary
imaging: how soon could this be adapted to space missions to the
planets? The James Webb telescope is a 4 billion dollar mission.
However, a large part of this cost probably has to do with the fact of
the high reliability required for this mission that has to operate far
away from the Earth and therefore can not be serviced by human
missions, and because of the fact the entire spacecraft's structure
has to be optimized to keep the cryogenic temperatures required for
the highly sensitive infrared observations.
Reductions in cost for similar sized planetary missions can be fueled
by commercial imaging interests. It is clear there there would be
commercial uses for Earth imaging at 1 inch resolution, though this
would raise clear privacy concerns. The technology for producing such
large foldable space mirrors has been patented so can now be licensed
by commercial imaging concerns:
Deployable space-based telescope.
Abstract
A large aperture light-weight space borne telescope is provided which
may be launched by a relatively small launch vehicle. A 6 to 8 meter
primary telescope composed of, e.g., 30 segments arranged in two
concentric rings is provided. Supplemental outer mirror segments are
stowed behind and substantially perpendicular to the main mirror which
is usable in the absence of supplemental mirror deployment. Deployment
of outer mirrors segments provides a large aperture telescope with a
large field of view. Other deployable components include a secondary
mirror, a bus, deployable with respect to the optics portion, and one
or more sun shade sheets or panels.
Patent number: 5898529
Filing date: Jun 20, 1997
Issue date: Apr 27, 1999
Inventors: Wallace W. Meyer, Robert A. Woodruff
Assignee: Ball Aerospace & Technologies, Inc.
http://www.google.com/patents?vid=USPAT5898529
Bob Clark
***********************************************************************
Newsgroups: sci.astro, sci.physics, sci.geo.geology,
alt.sci.planetary, sci.astro.amateur
From: "Robert Clark" <rgregorycl...@yahoo.com>
Date: 10 Jan 2007 09:12:09 -0800
Local: Wed, Jan 10 2007 1:12 pm
Subject: We will soon be able to resolve Mars microbes from orbit. ;-)
On another space oriented forum I noted:
"It took 20 years to increase the resolution by a factor or 10 over
Viking with the Mars Global Surveyor mission. But only 10 years to
increase the resolution over that of MGS by a factor of 10 with Mars
Reconnassance Orbiter.
Could we increase the resolution over MRO by another factor of 10 to,
gulp, 3 cm per pixel in only 5 years this time?"
Funny though, that rather off-the-cuff estimate of mine is close to
what is possible.
To resolve 3 cm in the optical from say a 300 km orbit would require
a
6 meter mirror. The James Webb Space Telescope will have a 6.5 meter
mirror and is scheduled for launch in 2013. But it was originally
scheduled for launch in 2011:
James Webb Space Telescope.
http://en.wikipedia.org/wiki/James_Webb_Space_Telescope
So going by this rate, it'll be 3mm/pixel 2.5 years after that, and
300 microns 1.25 years after that, and ...
Hmm, in less than a decade then we should be able to resolve
microbes
from space.
Admittedly though, the JWST is a 4 billion dollar mission. Also it
uses a beryllium metal mirror for infrared astronomy only. The
beryllium makes the mirror lightweight but it is unclear if you can
achieve the much more stringent smoothness requirements at optical
wavelengths with a metal mirror.
As for the data storage and transmission of the large files for such
high resolution images, data storage capacity and costs are doubling
and halving each year, respectively:
Bye-bye hard drive, hello flash.
By Michael Kanellos
Staff Writer, CNET News.com
Published: January 4, 2006, 10:00 AM PST
"Currently, NAND chips double in memory density every year. The
cutting-edge 4-gigabit chips of 2005, for example, will soon be
dethroned by 8-gigabit chips. (Memory chips are measured in gigabits,
or Gb, but consumer electronics manufacturers talk about how many
gigabytes, or GB, are in their products. Eight gigabits make a
gigabyte, so one 8Gb chip is the equivalent of 1GB.)
"Another driving factor in the uptake of the technology is cost: NAND
drops in price about 35 to 45 percent a year, due in part--again--to
Moore's Law and in part to the fact that many companies are bringing
on
new factories."
http://news.com.com/Bye-bye+hard+drive,+hello+flash/2100-1006_3-60058...
MRO uses the type of flash memory chips discussed here.
Also, interestingly NASA had planned a laser communication orbiter
for
Mars for launch in 2010 before it was canceled:
Record Set for Space Laser Communication.
By Ker Than
Staff Writer
posted: 05 January 2006
02:11 pm ET
http://www.space.com/missionlaunches/060104_laser_comm.html
Mars Telecommunications Orbiter: Interplanetary Broadband.
By Bill Christensen
posted: 05 May 2005
06:41 am ET
http://www.space.com/businesstechnology/technology/technovel_marstele...
This would have allowed data transmission rates of a hundred times
greater than what is currently available.
It was the great cost overruns overruns that led to cancelling of
the
Mars Telecommunications Orbiter, and great cost overruns also
threatened JWST as well.
That the costs for computer technology are dropping exponentially
with
capacity increasing exponentially is no doubt fueled by the free
market
in this sphere.
Conversely, that launch costs are staying static is no doubt because
the launches are controlled by large governments. When private
companies become the primary financer and purveyor of launches, the
launch costs will also drop dramatically.
Bob Clark
***********************************************************************
Randy Poe
> I discussed the capabilities for such a mirror for space-borne
> imaging in the post below. At 300 km altitude it would have better
> than 3 cm resolution, about an inch. Spy satellites frequently have
> elliptical orbits that can bring their altitude to half this at
> closest approach, so their max resolution will be perhaps half this,
> 1.5 cm to 1 cm.
Nah. Looking at this morning's imagery of your house, I can't
even make out for sure how many eggs you had. So don't be too
paranoid.
Cute dog you have. Some interesting titles in your library too.
- Randy
Peter Webb
"It may be possible for future orbital surveillance satellites to exceed 1
inch resolution", as this appears to be the claim you are actually making.
Orval Fairbairn
"Peter Webb" <webbf...@DIESPAMDIEoptusnet.com.au> wrote:
It would take one HELL of a focal length!
Chris L Peterson
<orfai...@earthlink.net> wrote:
>It would take one HELL of a focal length!
About 55 meters. But for a 6.5 meter aperture, that's just f/8.4, which
is pretty much the sweet spot for RC and Cassegrain designs.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
Shawn
It's not like you'd be limited for space!
Sylvia Else
> I discussed the capabilities for such a mirror for space-borne
> imaging in the post below. At 300 km altitude it would have better
> than 3 cm resolution, about an inch. Spy satellites frequently have
> elliptical orbits that can bring their altitude to half this at
> closest approach, so their max resolution will be perhaps half this,
> 1.5 cm to 1 cm.
A space-borne telescope used to look at the stars is not trying to look
down through a murky and shifting atmosphere. Ground based telescopes
are put on mountains to avoid having to look up through so much of the
same junk.
If you want your privacy, don't go to live atop a mountain.
Sylvia.
Pat Flannery
Orval Fairbairn wrote:
>
> It would take one HELL of a focal length!
>
Think of that hypothetical gizmo... you could pull it off looking at the
Moon, or another atmosphere-free body.
But peering down though sixty miles of turbulent atmosphere?
It would make more sense to use radar.
Pat
Chris.B
What next? We've had iris recognition, fingerprint recognition, facial
recognition, voice recognition... shall we now have scalp recognition?
(think about it)
If those who most interest the security forces all have arab headgear
will we now have headgear recognition?
Will Osama have to change his hat every day just to avoid detection?
Do adaptive optics now match raw resolution? If memory serves the big
astro telescopes use a laser to guide their adaptive optics.
If the surveillance satellites start pointing powerful lasers
downwards how will this affect global warming?
Will we be able to sue for loss of dark adaptation? Will cooking foil
hats avoid scalp irritation from all those lasers sweeping the
ground?
Will the Chinese start taking out US surveillance satellites and blame
the crazy North Koreans?
Only the paranoid need surveillance. Unless you deliberately make
enemies all over the world.
Blair gave us millions of street cameras to test out 1984 options.
Gates & Google offer constant surveillance of online behaviour.
Bush gave us the enemies we needed as the cover story for our
protection from extremists.
Will 24 x 7 webcams become compulsory on Vista 2 just to make it
work?
But now I'm being paranoid! ;-)
Len
Looking down is not the same as looking
up, Pat. It's not a mirror image (ugh :-( ).
Looking up through the atmosphere puts
atmospheric refraction errors at the beginning
of the optical path; looking down through the
atmospheres puts refraction errors at the
end of the optical path. Like looking at
your hand at a distance from a frosted
glass--or in contact with the glass.
I'm not sure how much of that sixty-mile
path you mention is really significant.
There are probably physical limitations.
However, I suspect that launch cost
llmitations may still be more important.
Hurrah for low-cost space access :-)
Len
> Pat
Craig Fink
A very long optical base of multiple satellites reduces the need for large
mirrors. Collecting vast amounts of light doesn't yield a better picture
for something bright and up close. A bunch of small mirrors with an
extremely large base (or base lengths) would allow you to read what he is
reading, over his shoulder so to speak. Probably correct for the first 60
miles of frosted glass too.
Craig Fink
If you want privacy, don't live above ground. ;-(
mme...@cars3.uchicago.edu
Only if you can combine the amplitudes (as opposed to the intensities)
of the images, else there is no improvement on resolution.
Mati Meron | "When you argue with a fool,
me...@cars.uchicago.edu | chances are he is doing just the same"
si...@situ.com
<mme...@cars3.uchicago.edu> wrote:
>Only if you can combine the amplitudes (as opposed to the intensities)
>of the images, else there is no improvement on resolution.
perhaps you meant: combine both the amplitude and phase information
from each detector, rather than just the intensities
or...
Jim Oberg
The advantage seems to be not in narrower and narrower area scans,
but in higher orbits that allow long dwell times over targets of interest --
eventually, you'd want an optical instrument in GEO that had tenth-meter
resolution -- or in Sun-Earth L1 so you have a continuously sunlit surface
to observe.
Chris L Peterson
wrote:
Good point. A theoretical ground resolution of one inch is all very
well, but doesn't do you much good if you can't aim your camera to that
precision. When Hubble imaged the Moon, it had to execute some tricky
attitude changes to reduce motion blur, and was only partly successful.
Various deep space probes have done the same when making close flybys of
moons.
One advantage of a large objective, besides resolution, is that you
collect a lot of photons and can make a shorter exposure. I'm sure this
is critical to getting high resolution ground images of the Earth, where
the atmosphere limits resolution (less of a problem looking down than
looking up, but still something that has to be dealt with).
Derek Lyons
Actually, Sun-Earth L1 isn't that good a position. You want some
shadows and some angle.
D.
--
Touch-twice life. Eat. Drink. Laugh.
-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL
Robert Clark
> Robert Clark wrote:
> > The most recent public estimates of spy satelliteresolution
> > capabilities give them as about 10 centimeters, 4 inches. However,
> > it is widely known that the most advanced astronomical space
> > observatories lag what is currently available for military and
> > intelligence satellites. The Hubble Space Telescope for example
> > was derived from early technology surveillance satellites.
>
> > Then since the James Webb Space Telescope has a segmented 6.5
> > diameter mirror, very likely this at least is available now for
> > surveillance satellites.
>
Not what I would count as definite proof, but I found this web
description of one of the newer "stealth" satellites, given the code
name Misty, describing it as one of the lightest satellites for its
physical dimensions:
USA 144: The Mystery Deepens - Flash Timings Needed.
"SRP Analysis Reveals Area to Mass Ratio.
SRP analysis has yielded an accurate estimate of the object's area to
mass ratio - more precisely, its kA/m value - area to mass ratio
multiplied by a constant which accounts for its shape and
reflectivity.
The value of k can be between 1 and 2,
A value of kA/m of about 0.135 m^2/kg appears to account for the
object's historical rates of orbital decay.
Assuming k = 1.5, then A/m = 0.09 m^2/kg - at least an order of
magnitude greater than that of most payloads and rocket bodies. For
comparison, consider:
Compton GRO 0.004 m^2/kg
Hubble ST 0.006 m^2/kg
UARS 0.007 m^s/kg"
http://www.satobs.org/seesat/Aug-2002/0045.html
This passage describes it as having a large surface area for the given
weight. But note this means it also has a very low weight for its
given surface area.
A key feature of the James Webb Space Telescope is also its low weight
for the size of its mirror. This is because of its beryllium mirror
which allows very thin mirror blanks.
So this low weight of the Misty satellites is consistent with
segmented beryllium mirrors.
Bob Clark
Jochem Huhmann
> This passage describes it as having a large surface area for the given
> weight. But note this means it also has a very low weight for its
> given surface area.
> A key feature of the James Webb Space Telescope is also its low weight
> for the size of its mirror. This is because of its beryllium mirror
> which allows very thin mirror blanks.
> So this low weight of the Misty satellites is consistent with
> segmented beryllium mirrors.
Or, if it has a very large surface for its mass it just may have a
large, lightweight, deployable structure... could be a radar spysat.
I was somewhat surprised to learn that SAR-Lupe 1 (a German radar
satellite) has a resolution of about 1 meter with a quite small antenna
(a few meters across). With a larger antenna (say 30 meters) you could
get to a nice resolution day and night with an added bonus of being able
to detect metal or water (even people).
Jochem
--
"A designer knows he has arrived at perfection not when there is no
longer anything to add, but when there is no longer anything to take away."
- Antoine de Saint-Exupery
laura halliday
> I was somewhat surprised to learn that SAR-Lupe 1 (a German radar
> satellite) has a resolution of about 1 meter with a quite small antenna
> (a few meters across). With a larger antenna (say 30 meters) you could
> get to a nice resolution day and night with an added bonus of being able
> to detect metal or water (even people).
The operative word here is SAR - Synthetic Aperture Radar.
It doesn't matter how big the antenna is if you can carry it
along a path, record data as you go, then synthesize an
image from those data with the resolution you would get
if you had an antenna as big as the path is long.
Radio astronomers have been doing aperture synthesis for
years: record data from antennas several kilometers apart,
then synthesize an image with the resolution of an antenna
several kilometers across. This is why facilities like VLA are
so exciting. And so big. :-)
The optical astronomers are starting to do this now, but it's
hard to get right...
Laura Halliday VE7LDH "Que les nuages soient notre
Grid: CN89mg pied a terre..."
ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte
Robert Clark
> Robert Clark <rgregorycl...@yahoo.com> writes:
> > This passage describes it as having a large surface area for the given
> > weight. But note this means it also has a very low weight for its
> > given surface area.
> > A key feature of the James Webb Space Telescope is also its low weight
> > for the size of its mirror. This is because of its beryllium mirror
> > which allows very thin mirror blanks.
> > So this low weight of the Misty satellites is consistent with
> > segmented beryllium mirrors.
>
> Or, if it has a very large surface for its mass it just may have a
> large, lightweight, deployable structure... could be a radar spysat.
>
Definitive proof one way or the other would be given by telescope
observations. This page shows images by a 1 meter scope of Mir and ISS
at around 400 km altitude:
Gallery - Artificial Satellites.
http://www.tsm.toyama.toyama.jp/curators/aroom/satellite/index.htm
These space stations are around 30 to 40 meters wide at their widest
dimensions. So at 2000 km altitude and 1/5th the size, the object in
question would appear 1/25th the size of the stations in these images.
You could probably resolve its shape. Of course a 2 meter scope could
do better.
The largest amateur scopes seem to be of size 1 meter. Two meter and
larger scopes are available at universities.
Some meter sized scopes available to amateurs:
The Searchers.
The World's Largest Amatuer Telescope Draws Scientists to the
Wilderness.
http://www.titanmag.com/2004/searchers/index.htm
Dan Bakken & Hercules.
http://www.runway.net/pilots/dan/welcome.html
The observatory of Puimichel.
http://www.groupeastronomiespa.be/pui.htm
And the Faulkes telescope project might be especially useful. It
provides access to two meter scopes for educational purposes:
Faulkes Telescope Web Site.
"The Faulkes Telescope Project is the education arm of Las Cumbres
Observatory Global Telescope Network (LCOGTN).
"Our aim is to provide free access to robotic telescopes and a fully
supported education programme to encourage teachers and students to
engage in research-based science education.
"Access to our resources and those of our partners is provided at no
charge to teachers and students."
http://faulkes-telescope.com/information/about_us
Bob Clark
Robert Clark
> On May 1, 5:28 pm, Jochem Huhmann <j...@gmx.net> wrote:
>
> > Robert Clark <rgregorycl...@yahoo.com> writes:
> > > This passage describes it as having a large surface area for the given
> > > weight. But note this means it also has a very low weight for its
> > > given surface area.
> > > A key feature of the James Webb Space Telescope is also its low weight
> > > for the size of its mirror. This is because of its beryllium mirror
> > > which allows very thin mirror blanks.
> > > So this low weight of the Misty satellites is consistent with
> > > segmented beryllium mirrors.
>
> > Or, if it has a very large surface for its mass it just may have a
> > large, lightweight, deployable structure... could be a radar spysat.
>
> > ...
>
> Definitive proof one way or the other would be given by telescope
> observations. This page shows images by a 1 meter scope of Mir and ISS
> at around 400 km altitude:
>
>
> These space stations are around 30 to 40 meters wide at their widest
> dimensions. So at 2000 km altitude and 1/5th the size, the object in
> question would appear 1/25th the size of the stations in these images.
> You could probably resolve its shape. Of course a 2 meter scope could
> do better.
> The largest amateur scopes seem to be of size 1 meter. Two meter and
> larger scopes are available at universities.
> Some meter sized scopes available to amateurs:
>
> The Searchers.
> The World's Largest Amatuer Telescope Draws Scientists to the
> Wilderness.http://www.titanmag.com/2004/searchers/index.htm
>
> Dan Bakken & Hercules.http://www.runway.net/pilots/dan/welcome.html
>
>
> And the Faulkes telescope project might be especially useful. It
> provides access to two meter scopes for educational purposes:
>
> Faulkes Telescope Web Site.
> "The Faulkes Telescope Project is the education arm of Las Cumbres
> Observatory Global Telescope Network (LCOGTN).
> "Our aim is to provide free access to robotic telescopes and a fully
> supported education programme to encourage teachers and students to
> engage in research-based science education.
> "Access to our resources and those of our partners is provided at no
> charge to teachers and students."http://faulkes-telescope.com/information/about_us
>
> Bob Clark
I've just been informed on the Bautforum.com list in a thread under
this same title that I didn't take into account the effects of
atmospheric distortion. This limits resolution to .5 arcseconds
regardless of the size of the scope if you don't have adaptive optics.
This means at 250 km altitude, your resolution could be at best 23
inches without adaptive optics. So at 2500 km, your resolution might
be only about 6 meters.
Then my hypothesized 6.5 meter mirror might not be resolvable without
adaptive optics if the satellite was above 2000 km.
(The object tracked by amateurs that had a high surface area to weight
ratio was above 2000 km altitude.)
In any case the actual purpose of this discussion was to promote the
producing of satellites with large multisegmented mirrors for
planetary imaging purposes. Publicly revealing secret military
satellites with this capability probably wouldn't be the best way of
achieving that.
It is already pretty certain anyway that we have the technical
capability for doing this in visible wavelengths. The question is of
the cost. I was arguing that commercial satellite interests investing
in this would lower the cost for the production of satellites for
planetary imaging. There are privacy concerns, but there would be some
beneficial societal effects as well.
We can imagine that such satellites are orbited in sufficient number
to provide world-wide round-the-clock coverage to be able to
distinguish faces and license plates. You could use "light
intensification" or infrared viewing devices for imaging at night.
This though raises the spectre of "Big Brother" in outer space.
However, an advantage which be the great reduction in crime this
would produce. For any crime committed you could trace back in the
images the houses that the perpetrators orginated from.
This would be preventive in the sense the perpetrators would know
they would soon be tracked and identified. However, in the case of
terrorists in many cases they wouldn't care that they would be caught
or identified. But this could be preventive if certain suspected
terrorists could be put under round-the-clock surveillance. Then
certain illegal activities or purchases could be identified beforehand
to stop the terrorist acts before they take place. You could also do
spectroscopy from space so that production and/or transport of
explosives would automatically set up a red flag to alert to the
possibility of terrorism.
The privacy concerns would be magnified even further by ongoing
research on imaging methods that can see through clothing and even
walls, if these methods were placed on satellites:
First Image from Revolutionary T-ray Camera; Sees through Fog,
Clothing and into Deep Space.
By Robert Roy Britt
Senior Science Writer
posted: 01:30 pm ET
11 February 2003
http://www.space.com/businesstechnology/technology/t-ray_camera_020613.html
Tuesday, February 20, 2007
T-Rays Advance Toward Airport Screening.
A new laser design helps create usable terahertz radiation, which
penetrates common materials but doesn't harm tissue.
By Neil Savage
"Zhang founded a company, Zomega Terahertz that makes a laptop-size T-
ray detector that can be attached to a flying drone for remote
detection of chemical and biological substances. While the trillionths
of a watt produced by the infrared laser in the device is fine for
spectroscopic analysis of air samples, it's not adequate for imaging,
and the laser technology is unlikely to improve enough to be used in
airport security, Zhang says. He believes that quantum cascade lasers
are the future of T-ray detection systems: "They will be the final
winner in the market."
http://www.technologyreview.com/Infotech/18203/page1/
The question: would you favor the use of such satellites if it would
virtually eliminate crime and terrorism?
How about if the imaging was only available to government agencies
and it required a court order to initiate preventive prior
surveillance or the tracing back in video of an individuals movements
in time?
Bob Clark
Robert Clark
> ...
>
> Tuesday, February 20, 2007
> T-Rays Advance Toward Airport Screening.
> A new laser design helps create usable terahertz radiation, which
> penetrates common materials but doesn't harm tissue.
> By Neil Savage
> "Zhang founded a company, Zomega Terahertz that makes a laptop-size T-
> ray detector that can be attached to a flying drone for remote
> detection of chemical and biological substances. While the trillionths
> of a watt produced by the infrared laser in the device is fine for
> spectroscopic analysis of air samples, it's not adequate for imaging,
> and the laser technology is unlikely to improve enough to be used in
> airport security, Zhang says. He believes that quantum cascade lasers
> are the future of T-ray detection systems: "They will be the final
> winner in the market."http://www.technologyreview.com/Infotech/18203/page1/
>
> The question: would you favor the use of such satellites if it would
> virtually eliminate crime and terrorism?
> How about if the imaging was only available to government agencies
> and it required a court order to initiate preventive prior
> surveillance or the tracing back in video of an individuals movements
> in time?
>
> Bob Clark
Could synthetic aperture techniques be used with terahertz imaging to
create high resolution images without requiring single antennas of
large size?
I'm thinking of how high resolution radio astronomy observations are
created using widely separated antennas. If so then the single
antennas on terahertz imaging satellites would not have to be very
large. You would get the resolution from combining the images from the
separate satellites.
Bob Clark
Randy Poe
Not until we're able to sample the optical signals above the
Nyquist rate (2*frequency). Signal processing hardware
isn't there yet.
However, something like what you're talking about has been
done to allow high-resolution interferometry with widely
separated optical telescopes. Delay lines are used to
achieve fine phase control.
Here's a French one:
http://www.obs-nice.fr/fresnel/gi2t/en/present_en.html
I believe I've seen plans to launch deep-space interferometers
also, to be used for planet-searching.
> I'm thinking of how high resolution radio astronomy observations are
> created using widely separated antennas. If so then the single
> antennas on terahertz imaging satellites would not have to be very
> large. You would get the resolution from combining the images from the
> separate satellites.
Not quite yet. I'd guess we're at least 10 years from that,
but I'll bet I'll live to see it.
- Randy
Robert Clark
> On May 8, 1:18 pm, Robert Clark <rgregorycl...@yahoo.com> wrote:
The terahertz waves are not in the optical range. Their wavelengths
are from millimeters to submillimeters.
The ALMA Observatory array will operate at these wavelengths which
suggests it is possible to do interferometry at these wavelengths:
Atacama Large Millimeter Array.
http://en.wikipedia.org/wiki/Atacama_Large_Millimeter_Array
Can this work with widely separated satellites as well? Also would
you get coherent images from this?
Bob Clark
Robert Clark
>
> Tuesday, February 20, 2007
> T-Rays Advance Toward Airport Screening.
> A new laser design helps create usable terahertz radiation, which
> penetrates common materials but doesn't harm tissue.
> By Neil Savage
> "Zhang founded a company, Zomega Terahertz that makes a laptop-size T-
> ray detector that can be attached to a flying drone for remote
> detection of chemical and biological substances. While the trillionths
> of a watt produced by the infrared laser in the device is fine for
> spectroscopic analysis of air samples, it's not adequate for imaging,
> and the laser technology is unlikely to improve enough to be used in
> airport security, Zhang says. He believes that quantum cascade lasers
> are the future of T-ray detection systems: "They will be the final
> winner in the market."http://www.technologyreview.com/Infotech/18203/page1/
>
> The question: would you favor the use of such satellites if it would
> virtually eliminate crime and terrorism?
> How about if the imaging was only available to government agencies
> and it required a court order to initiate preventive prior
> surveillance or the tracing back in video of an individuals movements
> in time?
>
> Bob Clark
>
Here's one possibile disadvantage of such a system in regards to
security concerns:
US intelligence wants ability to censor satellite images.
By Nate Anderson | Published: May 09, 2007 - 12:46PM CT
"The head of a US intelligence agency told the Associated Press that
commercial satellite services like Google Earth may need to be
censored in the future in order to protect American interests.
"Vice Admiral Robert Murrett, who heads the National Geospatial-
Intelligence Agency, spends his days helping the government map the
planet and studying imagery. Once the exclusive domain of the
government, commercial satellite imagery has attained high-enough
resolutions that the government is thinking about ways to restrict its
use in times of war or other emergency situations.
"If there was a situation where any imagery products were being used
by adversaries to kill Americans, I think we should act," he said in
the interview. "I think we may need to have some control over things
that are disseminated. I don't know if that means buying up all the
imagery or not. I think there are probably some other ways you can do
it."
http://arstechnica.com/news.ars/post/20070509-us-intelligence-wants-ability-to-censor-satellite-images.html
You could imagine governments that sponsor terrorism using it to
track politically or economically important individuals and using the
information to target them.
Also, even if the democratic governments required a court order for
such surveillance, you could imagine the political parties in power
using it to collect blackmail information on members of the opposing
parties. The information obtained could be just released to the press
anonymously without indicating how the information was obtained.
Bob Clark
Robert Clark
> The most recent public estimates of spy satelliteresolution
> capabilities give them as about 10 centimeters, 4 inches. However, it
> is widely known that the most advanced astronomical space
> observatories lag what is currently available for military and
> intelligence satellites. The Hubble Space Telescope for example was
> derived from early technology surveillance satellites.
> Then since the James Webb Space Telescope has a segmented 6.5
> diameter mirror, very likely this at least is available now for
> surveillance satellites.
> imaging in the post below. At 300 km altitude it would have better
> elliptical orbits that can bring their altitude to half this at
> 1.5 cm to 1 cm.
In regards to the question of whether there would be unknown U.S.
surveillance satellites currently in orbit this report suggests these
have been detected by French radar:
French Say 'Non' to U.S. Disclosure of Secret Satellites.
By PETER B. de SELDING
Space News Staff Writer
posted: 08 June 2007
09:58 am ET
"In a series of presentations here at the site of the French Graves
radar facility, French defense officials said they are gathering data
on classified satellites in low Earth orbit as part of a future
European space-surveillance program that European Space Agency
governments will be asked to approve in 2008. This program, with a
cost of some 300 million euros ($405 million), would feature higher-
performance radars to track space debris in low orbit and in
geostationary orbit."
...
"We have discussed the Graves results with our American colleagues and
highlighted the discrepancies between what we have found and what is
published by the U.S. Space Surveillance Network," said one French
defense official responsible for the Graves operation. "They told us,
'If we have not published it in our catalogue, then it does not
exist.' So I guess we have been tracking objects that do not exist. I
can tell you that some of these non-existent objects have solar
arrays."
http://www.space.com/news/060707_graves_web.html
Bob Clark
BradGuth
Of orbiting the moon with the same equipment should bring that
resolution down to roughly 8 mm, with a photoshop resampling worthy of
1 mm, and at least offering a 16 db worth of dynamic range.
Too bad our moon's rather unusual surface mascons, of otherwise so
much secondary/recoil IR/FIR, plus loads of gamma and hard-Xrays that
are more than most robotics can manage. In fact, we can't seem to
deploy and sustain a basic station keeping science platform within the
moon's L1.
-
"whoever controls the past, controls the future" / George Orwell
-
Brad Guth
Billzz
news:1181538591.6...@z28g2000prd.googlegroups.com...
I am not sure what this has to do with us.military.army, but you did make me
get out my slide rule to discover that 1 inch equals 25 mm (maybe, my
eyesight is not what it used to be.)
The remainder of the message seems pretty straightforward (for somebody -
and I even know what IR is - but not for me.)
"Whoever controls the future, controls the past." / Orwell George
Chris.B
their higher res European ground imagery onto a coarse cloth like
"screen" to kill fine detail. This is even more readily apparent in
direct comparison with (free online) European domestic ground imaging.
A shame really because Google Earth has a much more user-friendly
format than the domestic offerings. Presumably paying the providers
will buy higher res imagery from all of these ground imagery services.
This can't be doing the small aerial photography companies any good at
all.