In Message-ID:<hj0yj.24709$j7.452720@[EMAIL PROTECTED]
>,
Russell Wallace <russell.wallace.nospam@[EMAIL PROTECTED]
> wrote:
>Assume the targets being looked for are 10 m.
>
>Suppose diffraction limits the range to 1 million km.
>Then the fraction of the sky occulted is (1e1 / 1e9)^2 = 1e-16.
>
>Suppose there are 1 billion stars visible enough to be used for the
>purpose. (i.e. the target isn't careless or unlucky enough to wander in
>front of another galaxy, so we're using only the visible stars in our
>own galaxy.)
>Then the probability of occultation is 1e-16 * 1e9 = 1e-7.
>
>But the target is moving. So it has to travel 1e7 times its own length
>to have a reasonable chance of occultation.
>1e7 * 10 m = 100,000 km, which is less than the originally assumed
>range, so the concept looks workable, unless I'm making a mistake
somewhere?
IANAscientist. However, I have a couple of questions about
your assumptions.
First, are there really a billion visible stars in our
galaxy? For what value of "visible"?
Second, those stars are very non-randomly distributed. A
target out of the galactic plane has a much lower probability of
occulting than one in the plane. Similarly, one in the plane but
away from center has a lower probability than one in the plane but
towards the center.
--
Arthur T. - ar23hur "at" intergate "dot" com
Looking for a z/OS (IBM mainframe) systems programmer position
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