[amsat-bb] Re: Telemetry system on ISS, MM

Nate Duehr nate at natetech.com
Tue Mar 17 21:14:57 PDT 2009

On Mar 17, 2009, at 6:09 AM, MM wrote:
> Link to audio:
> http://www.savefile.com/files/1655618
> One aircraft in recording:
> http://registry.faa.gov/aircraftinquiry/NNumSQL.asp?NNumbertxt=38U&cmndfind.x=0&cmndfind.y=0
> Jody
> North Georgia

Hi Jody,

Interesting recording.

The female voice clearly says, "Calling today, this is Memphis  
Center?"... a Center controller picking up an aircraft in-flight,  
probably for VFR "flight following" services, or she just missed a  
call-up.  Standard phraseology.  Seems to match the "flight following"  
thing since then...

The analysis of the tail number is incorrect.  Later she talks a  
couple of times to "Cessna 38U".

Tail numbers on-air are shortened to the last three characters of the  
tail number, if no conflicting callsigns are on the frequency -- to  
save airtime.  Therefore that's not "N38U" as the full callsign (a  
glider based out of Boulder, CO as you noted with the FAA registry),  
but is a Cessna with a tail number ending in 38U, flying somewhere in  
Memphis Center's controlled airspace.

At one point the flow of the conversation through standard phraseology  
would indicate that the Cessna or another aircraft she's talking to is  
at 5500' MSL.  Making her a "low-altitude" sector at Memphis, or dual- 
controlling (transmitting on more than one frequency) multiple  
sectors, depending on time of day and traffic load.

There's also communications with a King Air, but I need to go get the  
headphones out to pick that callsign out.


Right at the very end you also hear an aircraft call up "right  
downwind", likely ISS has moved far enough East that Memphis Center  
can no longer be heard, and the frequency is re-used by the FAA at a  
towered airport somewhere further East.

At the very beginning of the recording, it sounds like the receiver is  
wide enough that it's hearing some other stuff that's not on its  
center frequency on the West Coast... or wherever the ground track  
took ISS this particular day and time of this recording.

Thanks for sharing, neat to listen to...

Nate Duehr, WY0X
nate at natetech.com

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