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(no) Sun Outage for Geostationary Satellite

Submitter: Koos Kegel
Description: Editor's note: The high-tech nature of ASTRON sometimes offers special opportunities for children of employees. This is of course a particularly effective form of outreach.

The curriculum for Dutch pre-university schools includes a thesis related to the student's future study. The subject my son selected was to check if the power of the 12 GHz signal from a geostationary ASTRA broadcast satellite is strong enough to overcome "outage" (=blocking) of the TV signal due to the Solar radiation coming from the same direction. This was tested when ASTRA was briefly in conjunction with the Sun, i.e. the satellite crossed the line-of-sight between Hoogeveen and the Sun. Information about this "eclipse" was found at http://www.satellitecalculations.com/Satellite/sunoutagestatus.php.

From the ASTRA satellite-link budget-calculations, and the emission from the Sun at 12GHz as a "black body" radiator, it may be shown that some interference is unavoidable. The question remained whether or not it affects the quality of the television signal.

The setup consisted of a 60cm satellite dish antenna and a satellite settopbox (thanks Albert!) tuned to the BVN channel at 12.515GHz, some RF components and a spectrum analyser borrowed from Anritsu (thanks to Patrick van der Burg!).

When the eclipse was at its maximum on October 12th, the measurements showed indeed a rise in the noise floor, albeit not enough to block the satellite signal. The first picture shows the sunlight focused onto the front-end of the dish antenna that was pointing towards the satellite (and thus the Sun). The two spectral plots show the received signal power around 1000MHz, and the noise power around 500MHz. The top one without interference, and the bottom one with interference during the eclipse.

The conclusion of this test is that, with a well aligned dish antenna, the power from the Sun is not strong enough to block broadcast satellite reception.
Copyright: Kegel
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