[amsat-bb] Re: ARISSat-1 (37772) decay

John Heath g7hia at btinternet.com
Mon Nov 28 14:11:06 PST 2011

Hi Nico,
Good to see postings on this topic.
I plotted daily change in Mean Motion, and then plotted Solar Flux for the same period. (15days).
It'snot obvious from the shapes of the two graphs that SF is producing the daily variation.
I tried the correlation function in Excel which returned a figure of -0.54 for the two data sets. ( 1= perfect correlation)
Fairly new to "orbital decay predictions" so would be interested in any comments you may have, or anyone else on the list who is knowledeable on this subject.
73 John G7HIA

From: Nico Janssen <hamsat at xs4all.nl>
To: amsat-bb at amsat.org 
Sent: Monday, 28 November 2011, 20:36
Subject: [amsat-bb] Re: ARISSat-1 (37772) decay


With its relatively high area to mass ratio, ARISSat 1 is
quite sensitive to space weather changes. In the past two
weeks solar flux values have been relatively low, around
140, while they were around 180 in the weeks before. Also
there have not been any magnetic storms.

As a result of this low solar activity, the expected decay
date of ARISSat 1 has now slipped to the end of December.
My current prediction is 27 December. But if solar activity
stays at these low levels, the decay date will even shift
into early January. So it is still too early to make any
sensible predictions.


On 2011-11-18 15:05, Nico Janssen wrote:
> Hi,
> So far all my analyses of the evolution of the orbit of ARISSat 1
> have resulted in a predicted decay date sometime in December 2011.
> Actually my current predicted decay date for this satellite is
> December 17. Obviously it depends very much on how solar activity
> develops in the coming weeks.
> So now we have seen decay predictions ranging from December 2011
> to April 2012. Let's see how we converge to the actual decay date.
> 73,
> Nico PA0DLO
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