<div dir="auto">This is not my area of expertise at all. But I have heard people that do know what they're talking about say its very hard to analytically predict re-entry at low altitudes with real satellite geometries.<div dir="auto"><br></div><div dir="auto">With a spherical satellite everything is well behaved but with different drag coefficients at different angles<span style="font-family:sans-serif"> from square-ish satellites</span> the behaviour becomes chaotic and the window of possible solutions widens dramatically. </div><div dir="auto"><br></div><div dir="auto">Not really a useful answer but maybe a interesting thing to think about. </div><div dir="auto"><br></div><div dir="auto">Cheers, </div><div dir="auto">Thomas </div><br><br><div class="gmail_quote" dir="auto"><div dir="ltr" class="gmail_attr">On Sat, 30 Jan 2021, 22:03 , <ground-station-request@lists.openresearch.institute> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Send Ground-Station mailing list submissions to<br>
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Today's Topics:<br>
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1. GMAT vs. STK/HPOP - call for help (Michelle Thompson)<br>
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Message: 1<br>
Date: Fri, 29 Jan 2021 17:28:20 -0800<br>
From: Michelle Thompson <<a href="mailto:mountain.michelle@gmail.com" target="_blank" rel="noreferrer">mountain.michelle@gmail.com</a>><br>
To: Michelle Thompson via Ground-Station<br>
<ground-station@lists.openresearch.institute><br>
Subject: [Ground-station] GMAT vs. STK/HPOP - call for help<br>
Message-ID:<br>
<CACvjz2UOeHpUmGgtvqTS=Y4WQ4_XDLyQRu_7=<a href="mailto:qw13bY_hzevFg@mail.gmail.com" target="_blank" rel="noreferrer">qw13bY_hzevFg@mail.gmail.com</a>><br>
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<br>
For the Debris Mitigation presentation to the FCC, we want to give answers<br>
(and show our work) about how much delta-v we need for some of the proposed<br>
orbits for minimum viable amateur spacecraft in the Amateur Radio Satellite<br>
Service.<br>
<br>
There's a question that Jan King and I have about a critical altitude and<br>
low surface_area:mass ratio spacecraft. It occurred to us that we really<br>
might want to compare results across two or more software packages to build<br>
some confidence.<br>
<br>
Jan has a set of results from a spreadsheet from SMAD.<br>
<br>
<a href="https://smad.com/" rel="noreferrer noreferrer" target="_blank">https://smad.com/</a><br>
<br>
The calculation under review is around 165km with a relatively lightweight<br>
6U spacecraft. It's acting like it wants to do some strange things. Is this<br>
physics, or at a limit of the model?<br>
<br>
We have a couple of people who are good or are getting good at GMAT.<br>
<br>
<a href="https://software.nasa.gov/software/GSC-17177-1" rel="noreferrer noreferrer" target="_blank">https://software.nasa.gov/software/GSC-17177-1</a><br>
<br>
Question: Are the atmospheric models in GMAT good enough for this<br>
calculation?<br>
<br>
Does anyone have access to STK/HPOP to run this calculation, for<br>
comparison?<br>
<br>
<a href="https://www.agi.com/products/stk" rel="noreferrer noreferrer" target="_blank">https://www.agi.com/products/stk</a><br>
<br>
<a href="https://help.agi.com/stk/11.0.1/Content/hpop/hpop.htm" rel="noreferrer noreferrer" target="_blank">https://help.agi.com/stk/11.0.1/Content/hpop/hpop.htm</a><br>
<br>
Thank you,<br>
-Michelle W5NYV<br>
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