terry@utastro.UUCP (Terry Hancock) (08/29/89)
In article <1615@agora.UUCP> rickc@agora.UUCP (Rick Coates) writes: > >Now, just a little while ago someone asked about putting a telescope in >orbit way out to study star parallax. Why not use images from Voyager? >It's not its primary mission, but they should work. I realize that the >craft is in no way set up to do whole sky surveys, but even a few images >might be helpful. The navigator also said that they could resolve images >to sub-pixel precision - would this be good enough? > NO. I was one one of the posters who suggested a project like you describe -- and in fact, my first impulse was to figure out how good Voyager could the job. It turns out that it's absolutely lousy for this -- you can do a lot better from Earth. Voyager's cameras were designed to take relatively close-up shots of planets. Even the 1500mm narrow angle camera really can't be called a telescope, certainly not for parallax purposes. A single pixel on a Voyager image is just too big to do it. Another poster mentions alignment problems with using Voyager as an astrometry platform. I'll just refer you to him on that subject. It's too bad really, I wish somebody could prove me wrong on this and figure out a way to do it with these instruments. Perhaps there's some way to set Voyager slowly rotating and use some part of the spacecraft to occult stars and watch it with the photopolarimeter. Is it possible to point the scan platform at one of the magnetometer booms, for example? Of course, you'd have to keep Voyager rotating at a very constant rate, or the data would be useless. And, of course, it could only be one end of the baseline (you could in principle just wait for it to move, but this causes a lot of problems that limit you to about what you can do on Earth anyway), although if it were to work, you could use both Voyagers. I can think of a lot of other problems too. Perhaps they are soluable, though. Anyone else have ideas? *********************** Terry Hancock terry@astro.as.utexas.edu *********************** ***********************