CCD-world: Re: Influence of meteorological radar system on CCDs

[Bruce Atwood]

The following was posted to CCD-world:

When NEXRAD was going to illuminate the 1.8-m at Anderson Mesa (Lowell
Observatory) we looked at what the increase in field strength might be
due to focusing by the dome.  Without doing a full diffraction
calculation we found field strengths in the dome that were 100 times the
indecent field strength.  If you are only 500 m from the source I would
be concerned about damage not just interference.

Tony Distasio wrote:
> 
> The following was posted to CCD-world:
> 
> On Tue, 21 Sep 1999, Byeong-Gon Park wrote:
> 
> > Thanks for the information,
> > The situation seems similar to ours. But what was the distance between
> > their installation site and observatories? And how strong is the radar power?
> 
> The radar systems we have here are the same NEXRAD (Next-Generation Radar)
> equipment installed all around the USA to monitor severe weather and
> rain conditions. Probably the same equipment as that described by
> Fred Harris at nofs.navy.mil, Naval Obs. Flagstaff.  Our radar sites
> are much farther away than yours will be, fortunately.  We were
> worried about influence of radar pulses from sites on other islands,
> perhaps 50 nautical miles or more away from us!
> >
> > The KMA (Korean Meteorological Administration)'s proposal to prevent
> > radar interference is the same idea. They say that they will turn off the
> > radar when the beam points to our telescope. Also, the radar will not
> operate on sunny days and clear nights - at least they promise during this
> time of negotiation phase, but who knows after installation? Any way, do
> you think  this will suffice with the frequency range and power at 500m
> distance?
> > I am also afraid of our solar telescope, the data of which is transported
> > via RG59 video cable - obviously weaker to the EMI than optical fiber
> > which carries CCD data.
> 
> You have every right to be concerned. 500m is terribly close to your
> astronomical installation. Spot blanking effectiveness will depend on
> the angular arc over which it is finally blanked. Plus, side lobes are
> a consideration. RG59 cable may be a problem.  The "shield" braid on
> that cable may not look like a "shield" anymore, but rather like an
> antenna.  It is hard to predict that.  RF-EMI problems are really
> a "black art" more than a science.
> >
> > Thanks,
> > Byeong-Gon
> 
> Hope your work with your government is successful.
> 
> Aloha,
> 
> Tony Distasio
> Institute for Astronomy
> Haleakala Observatories
> Maui, Hawaii
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-- 
Bruce Atwood
Director
Imaging Sciences Laboratory
Astronomy Department
The Ohio State University
174 W. 18th Ave.
Columbus, Ohio  43210-1106
(614) 292 6279 (V)
(614) 292 2928 (F)
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