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Proposed Alternate OpComms Test Sites and Fog: Difference between pages

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Created page with "Now that the OpComms team has successfully accomplished a 10km test, the group intends to scale up. The next set of testing locations has not yet been determined, but many si..."
 
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Now that the OpComms team has successfully accomplished a 10km test, the group intends to scale up.  The next set of testing locations has not yet been determined, but many sites were brought up in the initial search for a long-range test site pair. These are listed below:
SSI's [[Optical Communications]] team has had many encounters with fog.  Rain makes optical communication links difficult, due to the scattering properties of drops of water in the optical path. Fog tends to cause even more problems than rain, due to the large number of very fine water droplets.  


:'''Goat Mountain/Mendocino National Forest (10km)'''
On a typical night, fog forms where the coast meets the Pacific Ocean and is blown inland and over the top of the Santa Cruz mountains. The [[Skyline Boulevard]] test site is in the Santa Cruz mountains, and is quite often host to very dense fog as the temperature drops below the dew point with nightfall. To date, this phenomenon has severely interfered with three 10 km OpComms tests.
::Lat: 39.260165, Long: -122.714713 / Lat: 39.244135, Long: -122.835233
:'''Cowell Ranch Beach Access/San Gregorio State Beach (11.1 km)'''
::Lat: 37.421368, Long: -122.434249 / Lat: 37.322547, Long: -122.402297


:'''Santa Cruz Surfing Museum/Moss Landing (27.5km)'''
The OpComms team has gained some very basic weather prediction knowledge from studying this area.  Real-time weather information can be viewed at an Amateur Radio operator’s home weather station [http://aprs.fi/weather/a/KG6UWN], as well as many other locations in the area. Typical fog forming conditions involve a temperature and dew point within 4-5 degrees Fahrenheit. It is also important to look for unfavorable wind conditions (those that blow wet air from the ocean into the mountains) and dropping barometric pressure, which tends to herald cloudy weather.
::Lat: 36.95145, Long: -122.026718 / Lat: 36.8044, Long: -121.786895


:'''Santa Cruz Surfing Museum/Point Pinos Lighthouse (36.2 km)'''
For the most recent test, this problem was addressed by moving the time window earlier in the day, setting up in daylight, and completing the test before the fog rolled in. This time frame seems to be a successful compromise between fog formation and the optical need for darkness, but is still not immune to inclement weather.
::Lat: 36.95145, Long: -122.026718 / Lat: 36.633372, Long: -121.933698


The primary elements that determine a good test site pair are accessibility by car (due to equipment transportation requirements), access at night, and a clear line of sightNight access can be difficult in public locations, but the possibility of requesting special permits for some of the beach sites has been proposed, although never investigated.  The line of sight criterion can be predicted using a Geocontext Profiler tool [http://www.geocontext.org/publ/2010/04/profiler/en/], which generates an elevation map between two points. Creating an offline software tool for generating terrain profiles would be an excellent project.
Cloud formation may pose problems for optical communication satellites, due to the requirement of a clear path to the receiver from a point in spaceThe extent of this problem has not yet been determined.


In the next year, the group hopes to test at 100km and 300km, which will require substantial research into good long-range test sites.  The cost of testing increases with distance to and between locations, so it will be important to identify and evaluate promising sites carefully.  The [[current amateur record]] holders completed their successful test across the Great Salt Lake Desert [http://www.modulatedlight.org/optical_comms/optical_qso_173mile.html].
[[Category:Optical Communications]]

Latest revision as of 06:12, 11 August 2015

SSI's Optical Communications team has had many encounters with fog. Rain makes optical communication links difficult, due to the scattering properties of drops of water in the optical path. Fog tends to cause even more problems than rain, due to the large number of very fine water droplets.

On a typical night, fog forms where the coast meets the Pacific Ocean and is blown inland and over the top of the Santa Cruz mountains. The Skyline Boulevard test site is in the Santa Cruz mountains, and is quite often host to very dense fog as the temperature drops below the dew point with nightfall. To date, this phenomenon has severely interfered with three 10 km OpComms tests.

The OpComms team has gained some very basic weather prediction knowledge from studying this area. Real-time weather information can be viewed at an Amateur Radio operator’s home weather station [1], as well as many other locations in the area. Typical fog forming conditions involve a temperature and dew point within 4-5 degrees Fahrenheit. It is also important to look for unfavorable wind conditions (those that blow wet air from the ocean into the mountains) and dropping barometric pressure, which tends to herald cloudy weather.

For the most recent test, this problem was addressed by moving the time window earlier in the day, setting up in daylight, and completing the test before the fog rolled in. This time frame seems to be a successful compromise between fog formation and the optical need for darkness, but is still not immune to inclement weather.

Cloud formation may pose problems for optical communication satellites, due to the requirement of a clear path to the receiver from a point in space. The extent of this problem has not yet been determined.