On 8/24/96 Jim Varney wrote: <... The only drawback would be the need to store two sets of elements, HANDE and TLE, in order to run both HANDE- and SGPx-based programs. Storage is hardly an issue in this era of gigabyte hard drives. Out of curiosity, how do the HANDE and TLE elsets compare? What are the elements that appear in HANDE that do not appear in TLE's, and are any elements in TLE's dropped and do not show up in HANDE? Is solar flux one of the HANDE elements? > Response: since Space Command never made the switch-over to producing HANDE 3-line element sets, you're stuck with the 2-line elements currently released. There is a subroutine within HANDE to convert 2-line elements to pseudo-3-line elements for use by the HANDE algorithm. Obviously this doesn't buy you much over, say, SGP4, with the exception of the different (and presumably better) atmospheric model. If they ever DO switch over to producing 3-line element sets, the first 2-lines are identical to the current 2-line element sets, except BSTAR is replaced by B. The 3rd line contains all the new extra parameters. In order, they are: n-zero triple dot/24: the third time rate of change of "mean" mean motion at epoch n-zero quad dot/120: the 4th time rate of change of "mean" mean motion at epoch e-zero dot: the time rate of change of "mean" eccentricity at epoch e-zero double dot/2: the 2nd time rate of change of "mean" eccentricity at epoch e-zero triple dot/6: the 3rd time rate of change of "mean" eccentricity at epoch i-zero dot: the time rate of change of "mean" inclination at epoch capital omega-zero dot: the time rate of change of "mean" right ascension of ascending node at epoch lower-case omega-zero dot: the time rate of change of "mean" argument of perigee at epoch M-zero dot: the time rate of change of "mean" mean anomaly at epoch I am curious why Space Command never made the switchover. Was it a lack of funding? Or was SGP4 considered to be "good enough" that they didn't bother? --Rob