Figure 8 (Was: Variations in the Eumetcast signal)
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Ernst Lobsiger
John,
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I had a closer look at the diurnal changes of signal quality with respect to the figure 8 movement of Eutelsat 10A. As a first approximation we can expect variations in elevation of +/- i (inclination) which is +/- 0.062 ° in my latest keps. I installed good old command line tool predict on one ob my GNU/Linux boxes and found a figure 8 of +/- 0.07° in azimuth and +/- 0.08° in elevation as seen from here in Switzerland. Our dishes used have half power beamwidths of 1.0 to 1.5°. So it's very unlikely that diurnal variations can be caused by the figure 8 movement. And as usual I forgot that this discussion is not new. Alan Sewards pointed that out in message 20659 with more discussions following on that list. Cheers, Ernst ---In MSG-1@yahoogroups.com, <geojohnt@...> wrote :
In a message dated 16/07/2017 19:35:25 GMT Summer Time,
MSG-1@yahoogroups.com mailto:MSG-1@yahoogroups.com writes: If the orbital plane of a geostationary sat is not 100% identical with the equator plane of the earth we see the sat moving in a small figure 8 once per day. You should point your antenna to the center intersection of this 8. If your elevation is too high or too low (and you have a big dish) you will see diurnal variations of signal strength and SNR. Hello Ernst, Genau - aber ....... I have tried two official agencies to obtain the inclination data for EUTELSAT-10A to find out the equator crossing point, but failed. I have checked, with updated keps on WXtrack EUTELSAT-10A's movements. The satellite is over the equator between 04:29 to 04:57 UTC. And between 16:30 to 16:58. Now, I cannot guarantee those times are correct, they are purely from 'watching the inclination on WXtrack. Regards, John.
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