Originally posted by Star_One
Why is there 1 Hubble ? Surely they could make a few more.
They made loads, except all bar one face downwards and are used to spy on people. This is the conspiracy theory wrt Hubble, that it was largely assembled from OTS spy satelite technology, and they fitted a downward looking lense, which is why it's focus was off.
But that speaks volumes, that world governments are far more willing to spend money spying on each other than on science.
Back onto the subject of fuzzy moon photos vs crisp spy satellite images. Spy satellites relied on returning film for development until the early 1980's, as until then, film resolution vastly outweighed the quality of data obtainable via CCD devices.
Which brings us nicely to CCDs. CCDs are a fixed array of light sensitive memory bits, each flipped by incoming photons, and have several limitations. Firstly, the resolution of each single CCD isn't that impressive wrt photographic film. They Do suffer from bleed over, in that each pixel isn't wholly discreet, and will have it's data changed by that of it's neighbour, if it's neighbour is registering a very bright source. So bright sources lose resolution, so without attenuation BEFORE the light hits the CCD, an image of the moon, would lose resolution. Get some astronauts to fit Ray Bans to Hubble, and you might get that hi-res picture of the moon, But as Hubble was designed to gather AS MUCH LIGHT AS POSSIBLE so it could look at faint objects, and therefore effectively peer back in time, at very distant objects, it currently is not configured for staring at the moon. Of course, with film, you want better resolution, you focus on a larger film plate, but you can't do that with CCDs, as large ones are hard (read, expensive) to make., so you end up using an array of CCDs, and mosaicing images back together,
Pictures from fly bys. Two issues. Firstly, film return wasn't really possible with many of these missions, so all that is available are the scanned images. Well, what was the resolution of the scanner on the satellite? For the Luna missions, I'm guessing not that good (what was the quality of terrestrial TV like back then? Size of Terrestrial TV cameras?). Also, what was the data sending capability? What was the data storage capability? Think when this took place!! It was hard to store data on earth back then, just think how big computer MEMORY was. So you have a choice, Take a med-res image, store to memory, and spend an age transmitting it back at the slow speed the onboard modem could handle, or take a series of lower res shots, and get more. Sending a probe all the way to the moon for a few med-res shots doesn't sound like too much of a bargain to me.
It seems obvious to me why the quality of the shots is low, but then I work in IT (and have done for a while) and used to work in aerospace, with guys thet designed and built space telescopes.
So guys, if you think the quality should be better, get a PhD, get funding, and build something that can live up to your own high expectations!