To elucidate: I'm visualizing two spacecraft, one with a movable mirror capable of adjusting the path of the light coming from the other by perhaps +- 1 meter. Rockets would be used to get the rate of change of the distance between the two spacecraft down to perhaps 1 cm/hr and then be shut off. You'd then start observing, using a laser to measure the spacecraft seperation and moving the mirror to compensate as it changes. This would give you a hundred hours or so of continuous observation before the mirror would reach the end of its track. You would then stop observing, move the mirror back, and start again. Wheels would be used to control attitude. No need to fire the rockets again until the separation gets too large.
However, with ion rockets good enough to run while observing the combined system of active optics and ion engines I described upthread would be preferable.
And "centimeters per hour" would be several orders of magnitude too big; especially when you can get very few photons per s.
I mean centimeters per hour before compensation: zero afterwards, until the compensator saturates and has to be reset. However, if the ion engines can be as good as you say they could be combined with a short-range movable mirror compensator ("active optics"). The ion engines would handle "gross" stationkeeping with perhaps a few millimeters of jitter which would then be compensated for by the active optics. An interesting control problem.
I would use a movable mirror to compensate for drift. If you could get the drift down to centimeters per hour you could still make fairly long continuous observations. You should also be able to combine multiple observations, each made after resetting the compensator. If you could get the drift rate low enough and/or tolerate short enough individual observing periods the compensator could be fairly small.
> Yeah, that's what the linked ESA mission was about...
The article makes it sound like they were planning on trying to station-keep to within a fraction of a wavelength rather than using active optics to compensate for drift which is what I had in mind (very precise station-keeping would still be needed, though).
Well, if the precision needed surpasses practical approaches possible to us, that's moderately close to fundamental, as far as seing it soon goes... Or perhaps, at the least, you'd probably need zero drag spacecraft; while doing it with a large part containing mirrors plus including all the "portholes" for incoming and outgoing (to the hub) light...fun.
My idea (which I assume others have already thought of) is to use two unconnected spacecraft. Don't try to rigidly control the separation: measure it and compensate for the rate of change. That eliminates the need for a gigantic rigid structure.
The problem of separation is what put on hold few recent plans for such missions, indefinitely (until it will be figured out, if practically possible)
I didn't mean to imply that the task was trivial: just that there is no fundamental barrier. It is not necessary to construct multi-kilometer sized structures in order to have multi-kilometer aperatures. You would use a laser interferometer to measure the separation and then use your adaptive optics technology to compensate for the changes in it (which should be fairly slow and predictable).
...but if I had a GSM phone (I have no cellphone at all, actually) I'd be a lot more interested in using this to set up my own cell and route my calls over the Net.
We're not going to construct one-hundred-kilometer size telescopes any time soon.
There's no particular barrier to the construction of interferometers of such aperature in space, especially at longer wavelengths. You don't actually need to control the separation precisely: just measure it.
The International Space Station has a significantly lower cosmic radiation environment due to the Earth's magnetic field.
The Earth's magnetic field shields it from solar "cosmic" rays and probably some secondary galactic ones. The primaries, however, are so energetic that they are merely deflected a bit. What does stop a lot of primaries is the field embedded in the solar wind. Since the heliosphere is asymmetric and poorly mapped this may very well account for the observed asymmetry.
I concede that the Earth's field may have more than negligible effect, but I still think that the researchers will have accounted for it.
> Seems to me, that the universe is in at least 3 Dimensions, and no matter > which direction we go, we are going to hit some "celestial" body.
Since all but a negligible fraction of all the celestial bodies in the universe are stars that would mean that the entire sky would glow at the surface temperature of the average star since no matter where you looked you would be looking directly at the surface of a star.
> FTA: whether it's due to the magnetic field surrounding us or to the effect > of a nearby supernova remnant, we don't know.
The cosmic rays will have travelled a long ways through interstellar space permeated by magnetic fields that, unlike that of the Earth, we don't have detailed maps of.
> I mean, it is what protects us from vasts amounts of cosmic rays...
No it isn't. The Earth's magnetic field has negligible effect on cosmic rays: they are far to energetic for it to influence them significantly. What protects us from cosmic rays is the atmosphere.
>...maybe those differences account for a vast majority of this patterns?
The physicists will have already taken the small (but known) effect of the magnetic field into account.
> And the various celestial bodies that surround us (constantly deflecting > this rays) account for the rest?
Celestial bodies do not surround us. The sun and the moon together cover less than 1/100,000th of the sky.
>...the devices are being designed to thwart the user's attempt to install > software without thwarting the manufacturer.
And the users are knowingly buying the devices.
> That is a strike against us and our rights, regardless of how you phrase it.
It has nothing to do with your rights. The fact is that 99+% of the users don't give a damn about installing software. They just want to use the things. If it doesn't do what you want don't buy it.
Slashdot Mirror
Not in the infrared.
> ...and probably 10 years behind spy sats on which it was based?
Astronomical telescopes and spysat cameras have little in common (not nothing, but little).
To elucidate: I'm visualizing two spacecraft, one with a movable mirror capable of adjusting the path of the light coming from the other by perhaps +- 1 meter. Rockets would be used to get the rate of change of the distance between the two spacecraft down to perhaps 1 cm/hr and then be shut off. You'd then start observing, using a laser to measure the spacecraft seperation and moving the mirror to compensate as it changes. This would give you a hundred hours or so of continuous observation before the mirror would reach the end of its track. You would then stop observing, move the mirror back, and start again. Wheels would be used to control attitude. No need to fire the rockets again until the separation gets too large.
However, with ion rockets good enough to run while observing the combined system of active optics and ion engines I described upthread would be preferable.
I mean centimeters per hour before compensation: zero afterwards, until the compensator saturates and has to be reset. However, if the ion engines can be as good as you say they could be combined with a short-range movable mirror compensator ("active optics"). The ion engines would handle "gross" stationkeeping with perhaps a few millimeters of jitter which would then be compensated for by the active optics. An interesting control problem.
I would use a movable mirror to compensate for drift. If you could get the drift down to centimeters per hour you could still make fairly long continuous observations. You should also be able to combine multiple observations, each made after resetting the compensator. If you could get the drift rate low enough and/or tolerate short enough individual observing periods the compensator could be fairly small.
> He disabled access from the WAN side...
Or so he says.
Of course not. They had permission.
Nonsense. If you changed it with his permission you would no more face "jail time" than he (or Verizon) would.
> Yeah, that's what the linked ESA mission was about...
The article makes it sound like they were planning on trying to station-keep to within a fraction of a wavelength rather than using active optics to compensate for drift which is what I had in mind (very precise station-keeping would still be needed, though).
My idea (which I assume others have already thought of) is to use two unconnected spacecraft. Don't try to rigidly control the separation: measure it and compensate for the rate of change. That eliminates the need for a gigantic rigid structure.
I didn't mean to imply that the task was trivial: just that there is no fundamental barrier. It is not necessary to construct multi-kilometer sized structures in order to have multi-kilometer aperatures. You would use a laser interferometer to measure the separation and then use your adaptive optics technology to compensate for the changes in it (which should be fairly slow and predictable).
...but if I had a GSM phone (I have no cellphone at all, actually) I'd be a lot more interested in using this to set up my own cell and route my calls over the Net.
There's no particular barrier to the construction of interferometers of such aperature in space, especially at longer wavelengths. You don't actually need to control the separation precisely: just measure it.
The Earth's magnetic field shields it from solar "cosmic" rays and probably some secondary galactic ones. The primaries, however, are so energetic that they are merely deflected a bit. What does stop a lot of primaries is the field embedded in the solar wind. Since the heliosphere is asymmetric and poorly mapped this may very well account for the observed asymmetry. I concede that the Earth's field may have more than negligible effect, but I still think that the researchers will have accounted for it.
> Seems to me, that the universe is in at least 3 Dimensions, and no matter
> which direction we go, we are going to hit some "celestial" body.
Since all but a negligible fraction of all the celestial bodies in the universe are stars that would mean that the entire sky would glow at the surface temperature of the average star since no matter where you looked you would be looking directly at the surface of a star.
> FTA: whether it's due to the magnetic field surrounding us or to the effect
> of a nearby supernova remnant, we don't know.
The cosmic rays will have travelled a long ways through interstellar space permeated by magnetic fields that, unlike that of the Earth, we don't have detailed maps of.
The Earth's magnetic field is well mapped. The physicists will already have taken it into consideration.
> I mean, it is what protects us from vasts amounts of cosmic rays...
No it isn't. The Earth's magnetic field has negligible effect on cosmic rays: they are far to energetic for it to influence them significantly. What protects us from cosmic rays is the atmosphere.
> ...maybe those differences account for a vast majority of this patterns?
The physicists will have already taken the small (but known) effect of the magnetic field into account.
> And the various celestial bodies that surround us (constantly deflecting
> this rays) account for the rest?
Celestial bodies do not surround us. The sun and the moon together cover less than 1/100,000th of the sky.
> ...the devices are being designed to thwart the user's attempt to install
> software without thwarting the manufacturer.
And the users are knowingly buying the devices.
> That is a strike against us and our rights, regardless of how you phrase it.
It has nothing to do with your rights. The fact is that 99+% of the users don't give a damn about installing software. They just want to use the things. If it doesn't do what you want don't buy it.
> What will define reputable?
Concensus.
> The battle rages on as users fight for the right to run their own software on their own hardware.
They have the right to run their own software on their own hardware. It's the knowledge of how to do so that they lacked. Now they have it.
> Blame Microsoft, their ruthless tactics led to that situation.
Yes. After all, how could one expect the tiny, helpless little British government to resist the power of the mighty Microsoft?
> Most people do know what a browser is.
Many don't even know what software is (though they will glibly assert that they know all about "technology" because they are adept with their 'pods).
> There are a few people around (like the elderly) who don't understand the concept.
Some of the elderly admit that they know little about computers. This puts them ahead of those who know a whole lot that isn't true.
> An ounce is a unit of weight, not mass.
A US ounce is 1/16th of a US pound, which is an SI unit equal to 0.45359237 kg.
And yet you continue to do business with them. It's pretty obvious why they don't have to do much.
> Oracle broke their contract.
No. The government alleges that Oracle broke their contract.