Abandon the ISS now and channel all its investiment to the next generation space shuttle.
If you don't want to kill the ISS completely, then focus on maintaining the ISS in orbit while developing the new generation vehicle (you could do this with a conventional booster). The use of the current shuttle should be restricted to non-ISS issue only.
Building something that cannot be used until the next generation space shuttle becomes available (for supply and emergency evacuation, etc) isn't exactly a smart thing to do.
I don't know if the artcile mentions it or not (DRFA), but a collision isn't a major issue in the short or long term.
But, in the long term, the ISS is now unable to push itself up to a higher orbit. Its orbit decays very slowly. So every so often when a space shuttle parked at it, the shuttle used its thruster to push the ISS to a higher orbit. It hasn't been able to do that, unfortunately.
Luck would have it, the solar maximum phase is behind us. At this point the atmosphere is fairly thin at the ISS's altitude. But in a few years when the Sun becomes active again, the perpetual mechanicam problem in a thruster like this would become a more serious problem.
Since you are a flight dynamics person, you probably wouldn't know but...
What do they use to flip a mirror in place(switch back from a calibration lamp)? These movable things are often used in other missions and it's good to know what type of hardware would malfunction like this.
The word "Terroism" became such a convenient word to use as a wild card in order to gain voters' attention toward a congress person.
Why would that work? It's not that the politicians forget what it means, I don't think. It is more likely that the voters are just becoming dumber and stupider when it comes to what "terrorism" means.
In this particular case, they may have used dithering (or drizzling). I surely would use a 1/2-pixel offset pattern, if I were them.
But to derive the characteristic Gaussian width of 1.5pixel, you don't need to. Because of the PSF at that waveband (435nm) with the HST is about 0.05" (arcseconds), or 2 ACS/HRC pixels. So the apparent size of the source would look like
sqrt((1.5)^2 + (2.0)^2) = 2.5 pixel wide
And that's fairly large enough to measure its size without a fancy method.
PS. your points are all valid! Not many people knew about the degrading sensitivity near the pixel gap.
Your idea would cost more than servicing the Hubble with a shuttle. Actually it might be cheaper to build another one, I'm afraid.
But fear not. The Hubble will be serviced, more than likely, and continue to be operated until a replacement (of sort) becomes available (i.e., JWST, though it ain't nothing like the HST).
If you read the article, you'll find that the size is only 1400km, though. The difference results from the fact that the measured size of 1.5 pixel includes the size of its point spread function for the HST/ACS/HRC (i.e., even a true point source show some finite size in optics...something we cannot beat).
So, how do you get half a pixel on a screen? I too was under the impression that an individual pixel was either all on or all off...
Do you guys know the concept of "resizing a ditital image"?
Subsampling of a pixel can be done by knowing the intensity values in the neighboring 8 pixels (or greater). In other words, you can derive the intensity value at the pixel boundary by taking the mean value of the intensity values detected in these two pixels.
In this case, the measured size is derived based on mathematical characterization of the apparent point source.
I ought to be able to say this in a simpler term, damn it...
A pixel is small, but nowhere near subatomic. It's measured only in microns.
When photons are distributed over the CCD surfrace, it has some measureable shape (e.g., Gaussian) which can be fitted as such to characterize the shape. The quoted size of 1.5 pixel is, I think, the FWHM of the fitted Gaussian function that characterize its source.
The instrument degradation isn't the key reason why the Hubble won't matter much on this mission.
The key instrument for a detetion of water is most probably a spectrograph (IR, UV, etc), which the Hubble has none at this point. Unless there is a servicing mission AND the NASA decides to repair the Space Telescope Imaging Spectrograph, the Hubble won't do us any good.
You cross your finger that there are other IR spectrograph in orbit. Or you could do this sort of things from 8m class ground telescopes, perhaps.
Slashdot Mirror
Abandon the ISS now and channel all its investiment to the next generation space shuttle.
If you don't want to kill the ISS completely, then focus on maintaining the ISS in orbit while developing the new generation vehicle (you could do this with a conventional booster). The use of the current shuttle should be restricted to non-ISS issue only.
Building something that cannot be used until the next generation space shuttle becomes available (for supply and emergency evacuation, etc) isn't exactly a smart thing to do.
Have courage and let go the ISS for now.
So it is both the size and density that make the difference.
Thanks, I hope someone mod you up.
Why do one chromosone have more genes than others?
I hope sailors and explorers remember how to use astrolabes and sextants.
Just looking at a face? You sure women didn't look down also?
I don't know if the artcile mentions it or not (DRFA), but a collision isn't a major issue in the short or long term.
But, in the long term, the ISS is now unable to push itself up to a higher orbit. Its orbit decays very slowly. So every so often when a space shuttle parked at it, the shuttle used its thruster to push the ISS to a higher orbit. It hasn't been able to do that, unfortunately.
Luck would have it, the solar maximum phase is behind us. At this point the atmosphere is fairly thin at the ISS's altitude. But in a few years when the Sun becomes active again, the perpetual mechanicam problem in a thruster like this would become a more serious problem.
There'd better not be a dupe for this! /Happy B-day, Rob.
Since you are a flight dynamics person, you probably wouldn't know but...
What do they use to flip a mirror in place(switch back from a calibration lamp)? These movable things are often used in other missions and it's good to know what type of hardware would malfunction like this.
Haha, FUNNY, guys and gals.
I went for funny and I got "insightful"...
Man, I suck at funny.
Yes, it was.
I dunno.
If I were the guy who built the original primary mirror, I wouldn't want the world to know...
Yes, indeed.
And M82 is truly a bad example of what the Hubble can really do.
Why?
Because you can get a picture of M82 from the ground just as well
as the Hubble does. See here for example.
The true advantage of the Hubble can be realized when you are looking at
a smaller object, like V838 Mon or the finer details of the Helix Nebula.
The word "Terroism" became such a convenient word to use as a wild card in order to gain voters' attention toward a congress person.
Why would that work? It's not that the politicians forget what it means, I don't think. It is more likely that the voters are just becoming dumber and stupider when it comes to what "terrorism" means.
So one cell gets split and then they merge back together again and again?
Just like Eminem and Kim?
In this particular case, they may have used dithering (or drizzling). I surely would use a 1/2-pixel offset pattern, if I were them.
But to derive the characteristic Gaussian width of 1.5pixel, you don't need to. Because of the PSF at that waveband (435nm) with the HST is about 0.05" (arcseconds), or 2 ACS/HRC pixels. So the apparent size of the source would look like
sqrt((1.5)^2 + (2.0)^2) = 2.5 pixel wide
And that's fairly large enough to measure its size without a fancy method.
PS. your points are all valid! Not many people knew about the degrading sensitivity near the pixel gap.
My head is finally clear of medication...
Now I'm re-reading some of my posts...and your post still doesn't make any sense. Are you taking some medicine with control substance, too?
Oh now I feel stupid. It must have been the medicine with Codeine I've been taking.
I wonder how dificult it
Your idea would cost more than servicing the Hubble with a shuttle. Actually it might be cheaper to build another one, I'm afraid.
But fear not. The Hubble will be serviced, more than likely, and continue to be operated until a replacement (of sort) becomes available (i.e., JWST, though it ain't nothing like the HST).
I'm talking about the physical size of a pixel on the ACS/HRC.
See my earlier post below:
0 &threshold=0&commentsort=0&mode=thread&pid=1511178 2#15111848
http://science.slashdot.org/comments.pl?sid=18284
It can be derived with trigonometry:
(angle)*distance_to_the_object == size_of_the_planet
which are
(1.5pixel*0.025"/pixel)/(60*60*57.3radian/") * 100AU * 1.5e8 km/AU ~ 2700km.
If you read the article, you'll find that the size is only 1400km, though.
The difference results from the fact that the measured size of 1.5 pixel
includes the size of its point spread function for the HST/ACS/HRC (i.e.,
even a true point source show some finite size in optics...something we
cannot beat).
So, how do you get half a pixel on a screen? I too was under the impression that an individual pixel was either all on or all off...
Do you guys know the concept of "resizing a ditital image"?
Subsampling of a pixel can be done by knowing the intensity values in the neighboring 8 pixels (or greater). In other words, you can derive the intensity value at the pixel boundary by taking the mean value of the intensity values detected in these two pixels.
In this case, the measured size is derived based on mathematical characterization of the apparent point source.
I ought to be able to say this in a simpler term, damn it...
A pixel is small, but nowhere near subatomic. It's measured only in microns.
When photons are distributed over the CCD surfrace, it has some measureable shape (e.g., Gaussian) which can be fitted as such to characterize the shape. The quoted size of 1.5 pixel is, I think, the FWHM of the fitted Gaussian function that characterize its source.
The instrument degradation isn't the key reason why the Hubble won't matter much on this mission.
The key instrument for a detetion of water is most probably a spectrograph (IR, UV, etc), which the Hubble has none at this point. Unless there is a servicing mission AND the NASA decides to repair the Space Telescope Imaging Spectrograph, the Hubble won't do us any good.
You cross your finger that there are other IR spectrograph in orbit. Or you could do this sort of things from 8m class ground telescopes, perhaps.