**Previous message:**Phelps Williams: "Re: Standard Magnitude Calculation"**In reply to:**Phelps Williams: "Re: Standard Magnitude Calculation"**Next in thread:**Ralph McConahy: "Re: Standard Magnitude Calculation"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

I made a quick check for a "random" object #32378, now at std mag +2.0, at a position where I searched, gave +9.2 at phase 115 degrees. Changing it to RCS=1.0 gave +15.2, so in SkyMap 1.0 m2 is std.mag=+8.0 ? Changing #01804 Alouette 2 from std=+8.2 to rcs=1 doesn't change +8.4 at phase 150, so Skymap (Rob Matson) uses about +8.1 for 1 m2 RCS at 1000 km With +8.2 at 90 degrees and range 3734 km it gives +10.6, which would be +7.7 at 1000 km, so this confuses me (neither 90 nor 180 phase !?) For #6993 with std=+5.5 it gave +7.2 at 90 d and 2181 km, 90 d phase, which indeed would be +5.5 at 1000 km, so it confirms what I believed - SkyMap uses 90 d for STD MAG definiton ----- Original Message ----- From: "Phelps Williams" <phelpsw@gmail.com> To: "B Gimle @ComHem" <bg_26934@glocalnet.net> Cc: "seesat-l" <seesat-l@satobs.org> Sent: Tuesday, October 14, 2008 7:54 PM Subject: Re: Standard Magnitude Calculation It is this radar cross section to standard magnitude conversion that I am interested in. I will look into SkyMap later this evening. On Tue, Oct 14, 2008 at 1:30 AM, B Gimle @ComHem <b.gimle@comhem.se> wrote: > Most standard magnitudes are derived from actual observations, after > (approximate) conversion to 90 or 180 degrees phase, probably using > ln(1-cos(phase) and 5*log10(range) as correction terms. > Also there are different preferences re using max or average magnitude. > See http://www.io.com/~mmccants/tles/intrmagdef.html > Rob Matson's SkyMap can use the standard magnitude on elset Line0 or in > its > SKYMAP.DAT file. > The SKYMAP.DAT can also contain Radar Cross Sections, which are converted > to > standard magnitudes internally. > > From dimensions, surface form and properties "conversion" is very > difficult, > but I believe that a white sphere of 1 m2 cross-section is +6.4 > > /Björn > > ----- Original Message ----- >> >> I am interested in how standard magnitude is calculated. I have been >> unable to find information on this exact calculation beyond the fact >> that it is based on the surface area of the spacecraft and some >> assumptions about the surface properties. >> >> I cannot find further definition beyond what is mentioned here: >> http://www.io.com/~mmccants/tles/mccdesc.html > > > ------------------------------------------------------------------------- > Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: > http://www.satobs.org/seesat/seesatindex.html > > ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html

**Next message:**Ralph McConahy: "Re: Standard Magnitude Calculation"**Previous message:**Phelps Williams: "Re: Standard Magnitude Calculation"**In reply to:**Phelps Williams: "Re: Standard Magnitude Calculation"**Next in thread:**Ralph McConahy: "Re: Standard Magnitude Calculation"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

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