Re: Lewis elements (real) and Question

Bjoern Gimle (b_gimle@algonet.se)
Sun, 24 Aug 1997 14:17:14 +0200

>97044A                                           306 x 289 km
>1 24909U 97044A   97235.32519495 -.00000752  23767-5  00000-0 0    11
>2 24909  97.5672 129.1917 0012406 241.7350 118.2672 15.91645130    09
>
>Inclination is also 0.17 degrees higher too.  The RAAN is within 0.06 degree.
>
Congratulations on the excellent RAAN. You could expect a larger error
without knowing the ascent profile or orbital insertion parameters.

>My prelim elset is below:
>
>Lewis, Launch 23 Aug 97, 0651 UT
>1 99999U 970xxA   97235.28541667  .00000027  00000-0  00000+0 0    18
>2 99999  97.4020 129.3000 0001011 253.5528 242.3000 15.16900000    00
>
>Other than the difference in mean motion,  there are differences in MA,
>arg of perigee and epoch.   If someone with better understanding of the
>interrelationships can look at the two elsets and determine if I made
>any bad assumptions..please advise.  IT may be that the differences in
>these three values are trivial since they are interrelated...and a delta
>in one is essentially corrected by a change inthe others.
>
Yes, they are corrected. MA is the time since perigee, measured in 
1/360 of an orbit. NASA elsets usually have their epoch within a few
seconds of Ascending Node time. So, for a near circular orbit,
AOP + MA usually is close to 360. Your elset is 253.6 + 242.3 = 495.9
or 135.9 degrees. With a nodal period of about 1/15.16 or 0.06596,
previous AN crossing would be 135.9/360*0.06596 days = 0.0249 days before, 
and the next one 0.0410 after ( 97235.2605 and 97235.3264 )

Lewis, Launch 23 Aug 97, 0651 UT
1 99999U 970xxA   97235.28541667  .00000027  00000-0  00000+0 0    18
2 99999  97.4020 129.3000 0001011 253.5528 242.3000 15.16900000    00

Actual elset:
97044A                                           306 x 289 km
1 24909U 97044A   97235.32519495 -.00000752  23767-5  00000-0 0    11
2 24909  97.5672 129.1917 0012406 241.7350 118.2672 15.91645130    09

You can get more accurate results with Vec2TLE - either execute
Compute TLE.../ Re-epoch TLE at Asc.Node... to get 
Lewis, Launc
1 99999U 970xxA   97235.26054373  .00000027  00000-0  00000-0 0    10
2 99999  97.4020 129.2757 0001011 253.6393 106.4729 15.16900000    07

or select Settings.../ Epoch Control.../ Ascending Node and
execute Compute TLE.../ Impulsive delta-V.../ Ignition Time
YYYYDDD.ddd=1997235.33 and Burn Duration = 0 to get
Lewis, Launc
1 99999U 970xxA   97235.32650970  .00000027  00000-0  00000-0 0    23
2 99999  97.4020 129.3401 0001011 253.4099 106.7024 15.16900000    17

The remaining differences are mainly due to your lower MM.
Will Lewis start climbing like OrbView-2/SeaStar ?

 

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