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Hi everyone , I have a question for the math minded members of the group. Studying recent images of the Eutelsat Hotbird satellites at 13 east I have been trying to work out how far one of these birds moves over the period of an hour. The target satellite is listed as having an inclination of 0.9 degrees.(Hotbird 3 : cat number 24931) Comparing the position of the sat in two images taken over 30 minutes apart , and doing a few rough calculations , I have come to the conclusion that the bird drifts at a rate of about 28 km per hour in the inclined plane. Does this sound about right? If it does , it suggests a geostationary spacecraft in a near 1 degree inclined orbit will drift about 170km off the theoretical arc in( 6 times 28 ) a 24 hour cycle.....and "Travel" nearly 700 km every day (4 six hour legs of 170 km). However....and this is where I seem to have messed up......if we assume a radius to the Clarke belt of 38,000 km.... using 2 pi "r" we get 238,761km. Divide this by 360 to find one degree of arc gives a result of 663km ...... four times my original figure of 170km....So either my calculations are wrong , or my target satellite isnt HB3 , but one of the others , with an inclination of about 0.25 degrees. A small animation of the movement is available here : http://www.satcom.freeserve.co.uk/ in the geostationary satellites section. As you can see , I'm not exactly bright in the mathematic department , and would apprecaite any help ironing out the figures. Many thanks, John [ confused ;O) ] ----------------------------------------------------------------- To unsubscribe from SeeSat-L, send a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@satobs.org List archived at http://www.satobs.org/seesat/seesatindex.html

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