[net.astro] How good is the telescope aboard Voyager ?

gv@hou2e.UUCP (A.VANNUCCI) (01/27/86)

   Does anyone know how good the telescope aboard Voyager is ?

   Voyager 2 is now ~20 AU from the earth and, if I recall the
trajectory correctly, Voyager 1 is even farther away.  The imaging
hardware aboard the Voyagers is, undoubtedly, of excellent quality;
could it be used to take pictures of the stars ?

   A baseline of 20 AU is ten times larger than the baseline
for earth-based observations.   This would allow measurements
of stellar distances with the parallax method out to ten times
what is possible from earth, assuming that all the other limiting
factors are the same.

   Note that, being outside the earth's atmosphere, Voyager is not
subject to the degradation in resolution that plagues earthbound
telescopes.   Because of the atmosphere, the resolution of even
a large telescope such as Mt. Palomar's is no better than that
of your 10 inch backyard telescope  (however, the larger one
collects more light so it can see fainter objects).   This means that,
with a baseline ten times larger, Voyager needs optics with an
aperture of only 1 inch to match parallax measurements made from the
earth; furthermore, as its distance from the sun keeps increasing, its
advantage will become even greater.

   So, does Voyager have optics with an aperture greater than 1 inch ?
It's got to ! Your typical 50mm f2 camera lens has a diameter of 1
inch !   

   I'm sure that I am not the first one to think of this
possible application for Voyager, but I've never heard of any plans
for anything like this.  Are there difficulties that preclude such
measurements, such as inadequate sensitivity, field of view or
stability ?  Can anyone shed any light on this ?

      Thank you,

		Giovanni Vannucci
		AT&T Bell Laboratories      HOH R-207
		Holmdel, NJ 07733
		hou2e!gv

ivy@aicchi.UUCP (Iverson) (02/01/86)

> 
>    Does anyone know how good the telescope aboard Voyager is ?
> 
>    Voyager 2 is now ~20 AU from the earth and, if I recall the
> trajectory correctly, Voyager 1 is even farther away.  The imaging
> hardware aboard the Voyagers is, undoubtedly, of excellent quality;
> could it be used to take pictures of the stars ?

This was covered in Astronomy magazine about three years ago. The response
from a NASA representative (well, so the signature claimed) was that while
stars could be imaged by the Voyager telescopes, and had been for calibration
and navigation, the resolution of the imaging device limited the system.
Because of the size of a pixel (not an ideal point!) Voyager would have to
reach many times greater than the distance to Pluto (and still be in radio
contact) before parallax resolution could compete with Earth-orbit baselines
used by ground-based, high resolution telescopes.