Re: Information re elements (ndot)
Bjoern Gimle@tt-tech.se (Gimle@tt-tech.se")
Thu, 29 Aug 1996 17:29:56 +0200
New N0 = 15.89333279 ( actually 35% more increase )
Effect of drag = 0.121765 orbits ( error = 0.025 orbits = 9 deg.?)
Orbits = 111.9677699, or 11.6 degrees less than 112 orbits.
Since inclination is close to 63.4, the perigee has moved very
little (1.16 deg. forward) and MA decreased by almost the same
amount (1.34) since the orbit has low eccentricity, and Epoch
time (usually) is at a time of Ascending Node crossing.
So, the actual prediction error is about 11.6+1.34 = 12.94 degrees.
The SGP4 model uses BStar (the value after "N2" = +48074-3 in the
second elset) instead of N1,N2. This is closely related to the
area/mass ratio of the object, and if large (exponent >= -1 ?)
other factors such as solar radiation pressure and attitude
changes have a larger impact on the orbit.
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