[time-nuts] Pulsars make a GPS for the cosmos

[J. Forster]

A couple of points:

Pulsars are pretty faint and the only solution to that is antenna
aperture. We looked at that while doing SETI a ways back. Receivers are
now quite close to the theoretical limit as far as noise temperatuse.
There is very little room for improvement.

Pulsars are not infrinitely stable. They slowly decay, and, worse,
randomly undergto 'star quakes' which upset their timing. This was proven
in the 1960s.

Best,

-John

====================


> On 9/28/13 7:32 AM, Hal Murray wrote:
>>
>> jimlux at earthlink.net said:
>>> Scrolling down, it looks like they're getting a whopping 0.5 dB SNR on
>>> the Crab Nebula pulsar.
>>
>> How much of the noise comes from local sources vs thermal or galactic?
>>
>
> These are amateurs, so they're probably not using cryocooled receivers:
> a good part of the noise is kTB noise in the receiver.
>
>>
>> I'm missing the scale factor for the big picture.  How big a volume does
>> this
>> work over before I have to start counting fringes or something like
>> that?
>> Wiki says the longest one is 8.5 seconds.  That's small even on the
>> scale of
>> the Solar system.
>
> You also get direction, so for a "navigation" system, you can figure out
> where you are.
>
> Time wise, you'd have to count ticks.
>
>>
>> Is there some trick I'm missing?  Are there lots and lots of pulsars at
>> different frequencies so I can beat them against each other to make
>> larger
>> synthetic fringes?
>>
>> Are X-ray or gamma-ray pulsars (much) slower?
>>
>>
>
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