Mysterious sat-pic China desert markings - EXPLAINED The grids of white lines in China's Gobi desert that have got the world's conspiracy theorists in a lather for a week, are actually calibration targets used to help China's spy satellites, says a NASA researcher. Since the 65ft-wide white line patterns were spotted on Google Earth, it has been speculated that they were …
Granted, the day is young, but still -- the only way what you've said could even possibly make sense is if you were talking about an ICBM, and the idea of optical targeting on an ICBM-delivered warhead is risible to say the least.
Next time you're moved to comment, distract yourself with another bong hit or two instead. We'll all thank you for it.
Do a little reading. 'Fast' doesn't begin to describe the terminal profile of an ICBM-launched warhead, which is unguided -- hence "ballistic" -- anyway; even if someone were mad enough to build fins and optics into one, which they wouldn't because it'd be a waste of mass better used for payload or RV structure, it wouldn't have time to maneuver before fusing.
As for the rest, it is every sensible person's responsibility to shame arrant ignorance out of blithely opening its uninformed mouth in public.
Tricks could be done shifting the aerodynamic response of a fast-moving shell by shifting around the center of mass, for instance - no fins needed (or wanted at that speed). In fact, terminal evasiveness is supposed to be a characteristic of warheads from the superpowers nowadays.
Apparently the Indians can do it to.
from https://www.fas.org/irp/threat/missile/rumsfeld/pt2_tanks.htm
Agni. The 2500-kilometer Agni technology demonstrator uses the SLV-3
booster for its first stage and a liquid-fueled Prithvi for its second
stage. Three test shots were conducted before the U.S. successfully
pressured India into suspending testing (1994). Of particular
interest, the Agni tests demonstrated that India can develop a
maneuvering warhead that incorporates endo-atmospheric evasive
maneuvers and terminal guidance in the reentry vehicle.
errm... Aaron, m'lad, you don't seem to have heard of 'maneuverable re-entry vehicles'. Look 'em up, Google is your friend. There _are_ RVs which can, and do, modify their flight path from a purely ballistic path, and apparently at least one such type of RV uses an optical system, not for targeting guidance, but to help evade possible intercepting missiles. (Google is your friend with that one, too.) Note that you are the only one who mentioned 'fins', which almost certainly wouldn't work at RV velocities. Methods which would work include gyroscopes and reaction control thruster packages. (Yes, really.) (Google is your friend there, too.)
I leave as an exercise for the student the matter of exactly who should take a hit off his bong before ever again blithely opening its uninformed mouth in public.
Because a regular pattern would be 100% useless for orientation purposes. To fully orient a camera in 3 dimensions from a two-dimensional image, you need an image that appears unique however it is rotated in any of those three dimensions, If there are any two rotations that create the same (or roughly similar depending on the effective resolution) two-dimensional image, then the camera can't be sure how it's oriented.
It's also important that the image be unique in comparison to other subjects of the camera, so that, for example, a satellite camera doesn't mistakenly try to orient itself to the ridge patterns of a mountain range or the street patterns of a major city.
After all, you can sit home all day doing bong hits and babbling conspiracy-theory nonsense about something some red-eyed twat found on Google Earth when he had nothing better in mind to do at three in the morning last Wednesday.
Speaking as somebody who's been working his very testicles off for the last month without a break, I have to say the thought comes with a certain appeal, even if I would chop my own balls off with a cleaver in public before I'd sink so low as to haunt conspiracy theory forums.
Yes the UK uses a circular target with lines about the thickness of a road. For secrecy these are combined with the normal road network - the use of 1000s of them suggest a massive fleet of UK spy satelites.
however the Hanger Lane gyratory is still believed to be a message to aliens
Seeing as how there are also a number of interesting painted "airport shapes" nearby, and some large squares that appear to be covered in craters, could this be to do with developing a system that can target bombs or shells based on visual cues rather than GPS? The crazy-paving patterns could be the start of getting a system to be able to track location based on city streets.
https://maps.google.co.uk/maps?ll=40.491071,93.468995&spn=0.001611,0.003484&t=h&z=19&vpsrc=6
The whole area 14Km ENE (east north east) 40.490N 93.468E is fully of bomb craters and missile grazes. Looks like they had a whole load of whoosh bang blow things up fun there.
If I was to guess you got a bombing range with areas of ground marked out to simulate airfields and towns.
Calibrations targets??? Utter BUNK. Orient satellite? Hahahahahahahah. Ever heard of star sensors? Paint? If you check it out with Google Earth and drop back to 2005 historical imaging the "paint" is stored in a large pile near some buildings. If you followed the link to the LLM site Mr Hill also gives another "example" of a "satellite calibration target" located in Arizona. It's a Maltese cross near what is now a trap shooting range that appears to have a long disused helicopter runway. Yes, many helicopters use runways for safety reasons. The Maltese cross is a standard FAA symbol for a holding point for helicopters landing. If the runway is occupied they are directed to the cross to wait until the runway is clear.
It is clear that Mr. Hill either doesn't want to say what it is or just doesn't know and doesn't want to appear ignorant. I strongly suspect the latter.
I have no idea what it is but I do know what it isn't. It most certainly doesn't have anything to do with "calibrating" satellites. They don't require "calibration". Orientation is done by other means and has nothing to do with something on the ground passing by at 5 miles per second every 32nd orbit.
<A ground target is useless since it isn't visible most of the time.>
math illiterate yourself.
The star field is a 2-D map. One might thus figure out angles with respect to the ecliptic plane, but the field would look the same translated *very far* in Z perpendicular to the plane, since the stars are so far out.
A calibration only has to be done when doable, as for most instruments. Error accumulates due to the the limited precision of the calibration, over time, as one calculates positions using dynamics and the result of the last calibration.
In other words (and angles with respect to some other plane than the ecliptic can be used - you are possibly confused by the difference between that and what you get as an end result, that is, that the satellite lies on some *line* through the solar system which can be characterized by the angle it makes through some arbitrary plane. You cannot add information by specifying a different plane - it will be the same line described by different angles, which could have been calculated from math once you know the orientation of one plane with respect to the other. Thus, you get two degrees of freedom, regardless. The third degree has to come from elsewhere.
To be more precise (since I do have training in physics) : a perpendicular unit vector can describe the plane we use for observation. The observed orientation of the craft in the star field observed at that angle can also be described, since it is only a direction, as a unit vector. An observation in any other direction is related to the first by a unitary rotational transformation of the axis. The observed orientation of the spacecraft will be related by the corresponding contravariant transformation. Thus, there is no new information, and certainly nothing about an absolute position - you could translate many millions of miles in any direction and still see the same star field on any but Hubble-sized optics.
You *only* get orientation information from star observations. This has to be combined with other measurements to actually know where you are at.
There's are a couple of other interesting things in that area also
A similar grid...
http://maps.google.com/maps?q=40.452107,93.742118&hl=en&ll=40.455177,93.390999&spn=0.072494,0.10334&sll=37.0625,-95.677068&sspn=44.25371,67.412109&vpsrc=6&t=h&z=13
and other bombed buildings?. Hard to miss that shade of blue...
https://maps.google.co.uk/maps?ll=40.490896,93.510738&spn=0.002264,0.003229&t=h&vpsrc=6&z=18
Of a building nearby (where they monitored spy satellites) that was printed on the top of the buildings. It said "If you can read this, you are 10 years behind us". It was written in Cyrillic and was originally a few feet high. It was reduced each year. I have no idea if it is still there after the fall of the Soviet Union.
My guess is that the Chinese are just getting started.
It's fairly easy to detect lines and their cross sections. So if you wanted to build a satellite which automatically 'resets' its idea of its position, you can use such a pattern which can easily be precisely located even if visibility is low.
A simple grid or regular pattern is far harder to recognize as regular pattern can also occur by chance. That's less likely with such a pattern.
The great advantage of doing it this way is that there is no "calibration signal" which needs to be sent to the satellite for longer amounts of time. Instead you only need to send it the coordinates where it should take the picture and the coordinates where it should dump the data do. This could be done via many ways, even inconspicuously via RDS on FM-broadcast radio. Nobody would be any wiser where the control centre is.
You wouldn't even need to have a special monitoring station for that satellite since it will always report it's position. Normal monitoring (which everybody does) would be enough.
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[quote]math illiterate yourself.
The star field is a 2-D map. One might thus figure out angles with respect to the ecliptic plane, but the field would look the same translated *very far* in Z perpendicular to the plane, since the stars are so far out.
A calibration only has to be done when doable, as for most instruments. Error accumulates due to the the limited precision of the calibration, over time, as one calculates positions using dynamics and the result of the last calibration.[/quote]
I said "attitude fix", not positional fix. The description of attitude is independent of the description of position. It is also independent of the orbit. Further, once launched the satellite is not "calibrated", it is characterized. Calibration is placing a system in a preferred known state. Characterizing is discovering what state a system is in. A system is first calibrated and then characterized. The term "calibration" is one of the most often misused technical terms.
Calibration of the optical system once on orbit is no longer possible with the sole exception of focus. Once in orbit the satellite optical system must be characterized to discover how it deviates from the pre launch calibration. Also, the orbit must also be characterized since it directly affects the optical system image scale. That cannot be done with a single or a few ground targets.The Earth equipotential gravitational field isn't a globe or even a spheroid. It resembles a lumpy potato. Characterizing the orbit is done with numerous targets world wide which have been characterized by ground truth observations. A very large database of well characterized ground objects is used to constantly update satellite orbital parameters.
The attitudes fix provided by the star sensors is used together with the imaging data to characterize the pointing accuracy of the optical system. This permits the determination of boresight deviation from from the subzenithal point of the optical system to account for angular compression of apparent dimensions.
A single target tells you only what is correct for that target, hardly a very useful parameter. Since it isn't practical or even possible to go about painting targets all over the planet real world objects with well know dimensions are used instead.
As for what the strange hieroglyphs really are, the most like explanation has nothing to do with satellites. They are probably used as optical ground mapping test figures for cruise missile navigation systems.
No one has argued that one can't figure out the attitude of a spacecraft from the stars. The trick is to determine the exact position of what one is looking at in earth terms.
There is no distinction between characterization and calibration here. You characterize things so that your software will read "0" when it is at "0" here. That can be the same as calibration - - for instance, calibration you adjust a readout, maybe, so that the readout reads "0: when it should, when it is found by characterization that a certain voltage should read "0"
Lots more things are adjusted than the focus - I just read a paper that goes to the many steps that are needed for an accurate geolocation calibration. The idea is to establish known control points for accuracy (and darkness/lighness also) as well as focus so it is known how light/dark a target is, where it is, and to see it sharply.
<<As for what the strange hieroglyphs really are, the most like explanation has nothing to do with satellites. They are probably used as optical ground mapping test figures for cruise missile navigation systems.>>
Do you recognize that the same logic applies? Why draw test figures when the missile is already passing over known terrain? Could there be additional utility in characterizing all the different transfer functions [there are probably several measurements that they would like to make that I haven't even thought of, all with their own characterizations to be used to calibrate the software readout of measurements. [See, characterization is used *for* calibration - calibration is not misused as a word either by the scientists who wrote the paper I read or myself). Actually, I saw your comments elsewhere.
I fail to see your point. What I said is the star sensors provide a fix on **attitude** as you now seem to agree. Attitude is not position and position is not attitude. However, knowing absolute attitude relative to a "fixed" reference such as the "fixed stars" (astronomy term) is necessary in order to calculate the transformation matrix that describes the pointing of the optical system. That is why star sensors exist.
So what is your point?
BTW, data about gravitational anomalies, etc. would have been gathered from many other satellites, especially ones carrying atomic clocks like GPS satellites. Like I said, calculating orbits using differential equations taking into account the anomalies can be done to figure out position elsewhere. The anomalies do NOT have to be rediscovered anew. So orbital mechanics can still tell how the error propagates, and thus two measurements at different times of the same object will still tell you a lot.
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<<Characterizing the orbit is done with numerous targets world wide which have been characterized by ground truth observations. A very large database of well characterized ground objects is used to constantly update satellite orbital parameters>>
The paper you and I saw did calibration with 50k strips in the shape of a cross from an aerial survey, dense with control points. They *measured* targets around the world, but the main calibration was done rather locally (this is for a civilian satellite). This was for geolocation. The CCD calibration also seems to require several local points, in the paper. Image distortion and alignment seems to be something that one would want to check out with an entire small region of carefully surveyed points.
For a military satellite, let's just say that I have heard it said that they have pretty big station-keeping engines. Thus, for this, it may also be necessary to have a wealth of compact information for a quick recalibration.
I looked at the last paper more closely in an expanded version, and it was an image registration/alignment paper - it is useful to go over the same area multiple times. As far as alignment, it could probably be done at any of a number ot targets in the world. For a general characterization of the distortion of the imaging system, especially more nonlinear parts, it is probably best (as a picture in another paper of the same guys shows) to have many, many known points in the same image.
Yes, of course one can do a Green's function description of the gravitational anomalies. 1/r is harmonic except at r=0, so the gravitational field is harmonic outside of the surface. Once one fits a complete orthogonal set of harmonic functions to the description of the gravitational anomaly at the level of the GPS satellites, that set will continue to correctly describe the anomaly at other levels.
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