Progress 59 decay estimate

From: Ted Molczan via Seesat-l <>
Date: Thu, 7 May 2015 20:37:07 -0400
Using the numerical integrator in GMAT 2014a, I found Cd=2.2 and A/m=0.0029 m^2/kg sufficient to account for the decay
over the span of USSTRATCOM's TLEs of epoch 15127.69108536 and 15127.81228385. 

Allowing the propagation to continue until decay, results in impact (10 km altitude) on 2015 May 08 near 03:42 UTC. The
uncertainty is 1.6 h, based on the rule of thumb of 20 percent of the estimated time remaining to decay, measured from
the epoch of the latter of the two TLEs.

The decay time derived from recent TLEs has been trending later. Using the epoch 15127.50860911 and 15127.63013248 TLEs
as the starting point to calibrate the A/m, resulted in unrealistically low values, that would have put the decay at
least 2 h later. USSTRATCOM issued three TLEs near the epoch of 15127.69. That of epoch 15127.69108536 was issued well
after the other two, and somewhat increased the altitude. Using this as my starting point for calibration, yielded the
above A/m value, which is in line with earlier values for this object, and within the range I consider reasonable, given
its dimensions and approximate mass (my impression has been that it retains most of its fuel, but I am not certain of

I converted the epoch 15127.69108536 for propagation by GMAT using TLE Analyzer 2.12. I configured GMAT to use its
Dormand-Prince 78 numerical integrator, with the EGM-96 gravity model (degree 90, order 90), and the MSISE90 atmosphere

Ted Molczan

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Received on Thu May 07 2015 - 19:37:55 UTC

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