On 6/6/19 2:17 PM, Michael Wouters wrote:
My radio astronomer colleagues tell me that there is about a 20 minute
limit to VLBI observing runs because of atmospheric instability so this
limits improvements to be had from better clocks. My recollection is that a
maser is still sufficient out to 100 GHz. There is a paper about this that
I will dig out later.
I would think it depends on the frequency of observation. The DSN does
>8 hour tracks on a regular basis for ranging and that's with a overall
measurement uncertainty on the order of 1E-15 at tau=10,000 seconds. The
station is much better. But that's at 8 or 32 GHz.
Cheers
Michael
On Thu, 6 Jun 2019 at 12:01 pm, Joseph B. Fitzgerald <
[email protected]> wrote:
Regarding Dana's remarks on VLBI, consider the recent black hole image
released by the Event Horizon Telescope. Measurements were taken at 230
GHz, and they would like to begin measurements at 345 GHz. Hydrogen
masers were used at each telescope. I am no expert, but I strongly
suspect that a better clock would result in longer/better observations.
The H maser only runs at 1.42 GHz ... the astrophysicist wizards are
proposing to do their measurements at about 250 times higher in frequency!
-Joe
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