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Jan 25 2022. 


article from prior work: ADS-B.pdf

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Try this: https://www.rtl-sdr.com/rtl-sdr-quick-start-guide/

Nope. 

Try this: sudo port install gqrx

had to 'accept' Xcode license- sudo xcodebuild -license

then 

sudo port install gqrx

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So the time difference is 3 hours, eight predictions per 24 hour cycle. Predictions go out 10 days. Wow. 
We can validate this using all-sky camera data in daytime

Let's take 40 m/s as typical wind speed at 30,000 feet ~ 10 km. Angular rate is 40/1e4 = 0.2 degrees per second. 
Imagine width is ~100m so that's 0.6 degrees. So if wind is cross-contrail it moves its width in a few seconds. That seems about right. 
If wind is cross-contrail then in about 10 seconds is traverses LSST FOV. That's consistent with what is posted above. 
But if wind is parallel to contrail it can persist in the sky at fixed alt-az. If we're tracking on the horizon the telescope moves 15 arcsec/sec * 15 sec = 0.06 degrees so 1/10th the width of the contrail. 
Tracking is totally subdominant

SO here is a possible approach: 

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