[amsat-bb] Orbit visualization & antenna performance

[Leffke, Zachary]

Not a direct answer to your question...but for 'orbit visualization'....

System's Tool Kit (STK) from AGI:  https://www.agi.com/products/stk
There is a free license for non commercial use (e.g. Ham Radio.....).  With this you can quickly pull in TLEs for the spacecraft of interest and get very nice 3D and 2D displays to visualize orbits.  You can also do things like run pass predictions ('accesses' in STK speak), get high time resolution az, el, range, and range rate (for Doppler and link analysis math) reports (in CSV format), and they have lots of tutorials for getting up and running.  What you *can't* do with the free version is incorporate things like the Comm toolbox for direct antenna pattern visualization and link analysis within STK.  From experience during my Master's work, the combination of 'free STK', 4NEC2 (and outputting theta/phi/Gain matrix), and Python can be a pretty powerful combo.....but lacks the 'visualize' part unless you want to code that up too....

The General Mission Analysis Tool (GMAT) is the free an open source competitor to STK from NASA:  https://software.nasa.gov/software/GSC-17177-1.  I have less experience (...i mean no experience...) with this package, so not sure how easy it is to use and whether or not is has antenna modelling features, but I know a lot of folks use it (including folks on this list) for orbit modelling.

Finally, speaking of Python, the skyfield package (https://rhodesmill.org/skyfield/) is a great way to 'get rid of STK' for your own projects.  Skyfield provides a baked in SGP4 propagator to handle TLEs.  That, plus modules such as pandas, matplotlib, openGL modules (for good graphics / 3D visualization), could make for a pretty nice package that gives you full control (and is free).....but this is a double edged sword as it would all need to be coded up, which can eat precious 'project time.' (I mention it because its somewhere way down on my project list...and there might already be something out there on this).

Hope this helps!

-Other Zach, KJ4QLP (the Zach with the Hat).

-- 
Research Associate
Aerospace & Ocean Systems Lab
Ted & Karyn Hume Center for National Security & Technology
Virginia Polytechnic Institute & State University
Work Phone: 540-231-4174
Cell Phone: 540-808-6305


-----Original Message-----
From: AMSAT-BB <amsat-bb-bounces at amsat.org> On Behalf Of Zach Metzinger via AMSAT-BB
Sent: Thursday, July 23, 2020 12:16 PM
To: AMSAT BB <amsat-bb at amsat.org>
Subject: [amsat-bb] Orbit visualization & antenna performance

Hello all,

In order to evaluate antenna effectiveness in the 70cm downlink band, 
I'm trying to visualize the orbits of the following satellites:

AO-27
SO-50
RS-44

I can find the perigee/apogee and output power on these, and, so far, I 
have:

AO-27	788x801 km	1W/0.5W/0.1W
SO-50	603x713 km	0.25W
RS-44	1175x1511 km	5W

On the FM birds: My observed data shows that SO-50 is difficult to hear 
while AO-27 is booming, so I hypothesize that AO-27 is transmitting with 
0.5W or 1W.

RS-44's beacon seems to be fairly weak, while CW/SSB signals on the 
transponder are quite strong.

Does anyone know where I might find more details on RS-44's construction 
such as antennas and power output for the beacon?

Thanks,

--- Zach
N0ZGO
EM12jw




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