The most recent public estimates of spy satellite resolution 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 to sci.astro copied 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 page 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.
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 mirrors are 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.
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.
Newsgroups: sci.astro, sci.physics, sci.geo.geology, alt.sci.planetary,
From: "Robert Clark" <rgregorycl>
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
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.
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
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
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
posted: 05 January 2006
02:11 pm ET
Mars Telecommunications Orbiter: Interplanetary Broadband.
By Bill Christensen
posted: 05 May 2005
06:41 am ET
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.