> There may not be a accepted international definition inscribed in a treaty > somewhere, but there is precise mathematical definition and that's good > enough for me: Oh Brian, I couldn't disagree more! I'm familiar with that paper and similar calculations, of course, but that's a definition of the sun-synchronous property. There are NO satellites which PERFECTLY have this property. For a practical definition of an orbital regime you MUST define a range. (It's not physics if it doesn't have error bars :-)) At http://planet4589.org/space/log/stats/sso.html I have plotted currently orbiting debris objects and active payloads versus their departure from perfect sun-synchronicity, using the most recent TLE data available to me. I think the data clearly show that a sensible pragmatic definition of SSO, in agreement with the wild guess I made before doing these plots, is about plus or minus one hour per year in drift rate. I propose that this range, corresponding to a first order precession rate of 0.9446 to 1.027 deg/day, be adopted as a working definition. (This would exclude the postulated 88 deg orbit of the NK satellite). > Sure, being off by a few fractions of a degree in inclination is not a huge > deal, but in the case of North Korea (which is what started this > discussion) the inclination based on their announced azimuth isn't even > retrograde. And so what? As Bob Christy pointed out this corresponds to a few minutes plane drift over the probable life of the mission, so as a *practical* implementation of sun-sync ("are we monitoring the weather at the same local time each day?") they may consider it fair enough even if it's not what the rest of the world would call sun-sync. I agree it's a stretch, if that's their intention, but I don't think it rises to the level of a falsehood. - Jonathan _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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