Hi Jonathan and list, Jonathan was inquiring about how to approximate a satellite's visual magnitude when only its RCS is given. As others have eluded, you can't really. RCS is very sensitive to the geometry of the object in question. For example, if a tiny portion of the satellite has three mutually perpendicular surfaces forming a concave cavity (i.e. a corner reflector), you will have a deceptively huge RCS. Fortunately, most orbiting objects behave better than this, such that increasing RCS tracks fairly well with increasing satellite projected area. Around a decade ago, I wrote a program to compare the correlation between RCS and standard magnitude for several thousand objects for which both values were known. I basically made a scatter plot of RCS vs. standard magnitude in order to find the slope of the best fit line. (I think I also eliminated the largest RCS and brightest satellites from the analysis, reasoning that my goal was to estimate visual magnitudes for the thousands of objects that have reported RCS values, but unknown standard magnitude.) Turned out an object with an RCS of 1 m^2 had an average standard magnitude of about +8. I've long since lost track of the data, so don't know what the 1-sigma error bars were on that value. In any case, I modeled SkyMap on this 1 m^2 = +8 mag assumption. So the conversion would be: Std. mag = 8 - 2.5*LOG(RCS) where RCS is in square meters. I've just downloaded Mike McCants' latest RCS.ZIP file, so at some point I'll try the analysis again to see what answer I get. Cheers, Rob ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
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