View Single Post
  #273  
Old October 10th 18, 08:56 AM posted to sci.astro.amateur
Martin Brown[_3_]
external usenet poster
 
Posts: 189
Default Neil DeGrasse Tyson headed down same loony road as Carl Sagan?

On 10/10/2018 07:29, Paul Schlyter wrote:
On Tue, 9 Oct 2018 14:36:12 +0100, Martin Brown
wrote:
It is the awkward gap where photon energy is too low for optical

devices
and frequency too high for microwave techniques to work adequately.


Which frequency range is that? And is thar radio waves or infrared?


Its in the crossover between mm microwaves and far far infrared. Roughly
1THz /* 5 or so depending on who you talk to is the tricky bit.

http://www.teraview.com/about/what-i...hertz-thz.html

It is all the rage for non-destructive testing with non-ionising
radiation now that bright emitters are available (for a price).

When I was a radio astronomer we could operate up to 31GHz limited by
baseline surveying and surface roughness as well as the availability of
LNB and down converters for the front end. VLA could go slightly higher
at up to 50GHz. It is a fair bit higher now.

Today there are some exotic devices capable of detecting signals almost
up to 1THz. ALMA in the Atacama desert is capable of observing at
frequencies from 31GHz up to 950GHz (although I expect it is pretty
ropey at the highest end). It is a nominal terahertz instrument (just).

There are a few precision single dishes about too. The surface has to be
a very good parabolic mirror finish for the system to form good images.
And coherent focal plane cameras to go with them with as many as 100
pixels (they are aiming for 1000)!

https://www.nrao.edu/meetings/isstt/...2011179000.pdf

--
Regards,
Martin Brown