[time-nuts] Result of Earth Quake speeds up earth?

Bob Camp lists at rtty.us
Sun Mar 20 22:55:47 UTC 2011


Hi

If the "signal" is actually 80 db below the noise, you will need a lot of cross correlation simply to find it at all. Your digitizers are going to have to be *very* good just to let you get that far in the first place. 

Bob

On Mar 20, 2011, at 6:36 PM, Magnus Danielson wrote:

> On 03/20/2011 08:26 PM, Bruce Griffiths wrote:
>> The beam from the interferometer/phased array can be swept over the sky
>> by varying the phase shift between the elements during the data
>> reduction process allowing high resolution imaging.
>> Compensating for Earth rotation and consequent changes in the
>> atmospheric delay are necessary. Differential phase shifts of a few tens
>> of picosec are significant in the imaging process.
>> The effect of atmospheric refraction has to be accounted for if accurate
>> positions of the source relative to the Earth's surface are required.
> 
> I would use cross-correlation between two (or more) antennas. The noise of the individual antenna assembly would cancel out for sufficient correlation length. That would help to boot-strap the direct correlation if not the FFTed correlation will do.
> 
> Long FFTs is cheap these days.
> 
> Then again, the real VLBI people would beat me up for such naive approaches.
> 
> Cheers,
> Magnus
> 
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