Re: Pulsar Nav accuracy

KH.Ranitzsch@t-online.de wrote:
> 
> Indy schrieb:
> > > Thinking about it, I doubt that this accuracy could be
> > > achieved with distant objects alone.
> > >
> > > Problem is, we have to know the position of the objects
> > > in 3 dimensions and the measurement is unlikely to be very
precise.
> > >
> > Actually I think, given interstellar travel, we will be
> > able to nail the positions of other celestial objects
> > (pulsars, et al) down pretty darn accurately (okay, within
> > 1/10 ly ;-). Right now we are limited (see an earlier post
> > in this thread) to approx 100 parsecs for parallax
> > measurements.
> 
> I guess the 100 parsecs are the range at which measurements are
> possible, rather than the error in teh measures location ?

Affirmative. This is the current range of parallax measurements.
Technology will push this out later, but I don't think by a whole
lot. We need to increase the baseline to get much better results.

> > That's using a 2 AU baseline.
> 
> Going to Pluto to do parallax measurements would certainly help :-)
> Especially if you can do very-long baseline interferometry with
Neptune
> or Uranus as the other receiver.

:-)

> > Once we start heading out to other star systems (e.g., Alpha
> Centauri,
> > Sirius, even Vega), our baseline is going to grow massively and we
> ought
> > to be able to extend the parallax measurements out pretty far. And
> pretty
> > accurately.
> 
> You would have to know the distance between the sun and your other
star
> quite accurately. Anay error there gets multiplied massively in
> parallax measurements.

True. But it should not be difficult at all to determine this quite
precisely. We already know to 1/10 ly or better the distances to nearby
stars. Once we actually *travel* to them, all we have to do is turn a
sensitive receiver back toward Earth and pick up signals. From this we
can
determine *extremely* well the distance (you know when a given signal
was transmitted - such as, oh, a Weather Channel show which carries the
timestamp in the program - and with calibrated time instruments you can
determine to with lightseconds or tighter accuracy how long it took the
signal to reach your location, and from that, derive the distance to
some small number).

> > but hey, that's what will keep us astronomers in business
> > 200 years from now! ;-)
> 
> I certainly see an use for the GZG Clarke class survey ships.

More than K'V target practice, that is.  ;-)