Re: Pulsars in place of GPS?

On May 29, 8:02 am, a...@xxxxxxxxxx (Andrew Robert Breen) wrote:
In article <KAPTl.229417$i%2.198...@xxxxxxxxxxxxx>,



Keith Willshaw <ke...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

"Andrew Robert Breen" <a...@xxxxxxxxxx> wrote in message
news:9rr4f6x38e.ln2@xxxxxxxxxxxxxxxxxx
In article <0YNTl.159597$3O6.48...@xxxxxxxxxxxxx>,
Keith Willshaw <ke...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

"Frogwatch" <dboh...@xxxxxxxxxxxxxx> wrote in message

Pulsars were originally detected with a fairly small radio telescope..


I confused the horn antenna used to originally ,measure the 3 deg
background radiation with the antenna used to find the first pulsars.
However, small ultra-low temp coolers have been recently developed
although costs are seriously high, roughly $100,000. If you do not
need liquid He temps, coolers going to liquid nitrogen temps are very
cheap, I use em all the time for small detectors.
I said cool the detector, not the reflector. The reflector emits
isotropically whereas your signal is focused onto the detector.
Cooling is a way to reduce noise in the detector itself and it is not
practical to cool large optical systems. Depending on the quality of
the optics, you can focus thru a very small cooled aperture onto a
detector thus rejecting a lot of the "noise" emitted from the large
reflector.
In space, one could use an inflatable sphere silvered on half as an
antenna thus covering as large an area as you like.
Such large silvered balloons in space are fairly easy as one can see
from the 1965 Echo satellite.
The "lock-in amp" idea will not work, it has been 25 years since I
used one and had forgotten how it was used for low level measurements.

Gawd help us, if you think the IPS was small, it initially covered 4 acres
and was extended to 9 , partly to enable the study of pulsars

To get an idea of just how big the IPS array was, go and take a look at
this picture:

http://radio.astro.gla.ac.uk/ips/array_annotated.jpg

To get a sense of scale, the white thing at top left is a 32m dish-type
radio telescope (yep, that's about 100' in merkin).

Small. Hardly. Sodding big, more like.

The switch-hut is fairly small, mind.

http://radio.astro.gla.ac.uk/ips/mugs.jpg

Looks like they bought it from the company selling garden
sheds just up the road in Barton :)

Could well have been - though in the 60s an old university like Cambridge
probably had its own garden-shed builders somewhere around the place...

I could ask, I guess.

--
Andy Breen ~    Not speaking on behalf of the University of Wales, Aberystwyth
                Feng Shui: an ancient oriental art for extracting
                 money from the gullible (Martin Sinclair)

.

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