[Ground-station] Ground-Station Digest, Vol 34, Issue 21

[Thomas Parry]

I'm not sure if you're still wondering about the original question, but I
passed it on to my friend who's day job is modelling re-entry simulations.
This was his response:


"The 2020 release of GMAT (
https://sourceforge.net/projects/gmat/files/GMAT/GMAT-R2020a/) seems to
have the MSISE90 atmospheric model.  This is one of the best ones at
present to use for re-entry simulations since it can model the whole
atmosphere up to 1000 km.  It also has extensive options for things like
solar flux, and can even return different values based upon longitude,
latitude, and the time of year.



The only one that’s better for this application is the NRLMSISE00 model,
which as far as I know is calculated using the same methods (spherical
harmonics) but with additional measurements.  The other packages that are
mentioned (STK/HPOP) appear to have options for multiple models, including
both MSISE90 and NRLMSISE00."


I hope that helps.

If there are any more questions I can you put you contact with him to tap
his expertise.


Cheers,

Thomas

On Sat, 30 Jan 2021 at 22:51, Thomas Parry <yrrapt at gmail.com> wrote:

> 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.
>
> With a spherical satellite everything is well behaved but with different
> drag coefficients at different angles from square-ish satellites the
> behaviour becomes chaotic and the window of possible solutions widens
> dramatically.
>
> Not really a useful answer but maybe a interesting thing to think about.
>
> Cheers,
> Thomas
>
>
> On Sat, 30 Jan 2021, 22:03 ,
> <ground-station-request at lists.openresearch.institute> wrote:
>
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>> Today's Topics:
>>
>>    1. GMAT vs. STK/HPOP - call for help (Michelle Thompson)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Fri, 29 Jan 2021 17:28:20 -0800
>> From: Michelle Thompson <mountain.michelle at gmail.com>
>> To: Michelle Thompson via Ground-Station
>>         <ground-station at lists.openresearch.institute>
>> Subject: [Ground-station] GMAT vs. STK/HPOP - call for help
>> Message-ID:
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>> qw13bY_hzevFg at mail.gmail.com>
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>>
>> For the Debris Mitigation presentation to the FCC, we want to give answers
>> (and show our work) about how much delta-v we need for some of the
>> proposed
>> orbits for minimum viable amateur spacecraft in the Amateur Radio
>> Satellite
>> Service.
>>
>> There's a question that Jan King and I have about a critical altitude and
>> low surface_area:mass ratio spacecraft. It occurred to us that we really
>> might want to compare results across two or more software packages to
>> build
>> some confidence.
>>
>> Jan has a set of results from a spreadsheet from SMAD.
>>
>> https://smad.com/
>>
>> The calculation under review is around 165km with a relatively lightweight
>> 6U spacecraft. It's acting like it wants to do some strange things. Is
>> this
>> physics, or at a limit of the model?
>>
>> We have a couple of people who are good or are getting good at GMAT.
>>
>> https://software.nasa.gov/software/GSC-17177-1
>>
>> Question: Are the atmospheric models in GMAT good enough for this
>> calculation?
>>
>> Does anyone have access to STK/HPOP to run this calculation, for
>> comparison?
>>
>> https://www.agi.com/products/stk
>>
>> https://help.agi.com/stk/11.0.1/Content/hpop/hpop.htm
>>
>> Thank you,
>> -Michelle W5NYV
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