Downloading Images From US Military Satellites

This is my first try at receiving data from the Defense Meteorological Satellite Program (DMSP). Designed in the 1960s & 70s, these supported spy planes and spy satellites by monitoring weather and cloud patterns around the world. Since early reconnaissance satellites used film, the government didn't want to waste any on overcast areas. The DMSP satellites were declassified in the 1970s, but the radio signals are still encrypted for most of their orbital path. They only switch to clear transmissions when over the poles and over the Northern part of North America.

I had mixed luck decoding some of these. In particular, I couldn't reliably receive DMSP when the satellites were passing Southbound over the US. I'm not sure if this is a quirk of my antenna hardware or just how the system operates. I had the best luck on Northbound passes, but the encryption only switched off above about 40 degrees North Latitude, so I could see the Great Lakes and points North.

I'm using a modified C-band TV dish, a fold-up model generously provided by a fellow ham radio operator. My feed is a loop of copper wire inside an old aluminum dish, tuned for 2.2GHz. (I've since learned that this might not be ideal for circular signals, as the loop actually has linear polarization)

I also tried a helical feed designed by ‪@dereksgc‬, I had mixed luck with it but didn't realize until later that I was only receiving Northbound passes. You can find info on building helical feeds here:

Some archival footage is from "The DMSP History", published by the US Government, used as public domain:    • The DMSP History  

A lot of technical documents on the DMSP system can be found here: https://eogdata.mines.edu/products/dm...

Orbit animations are from the ‪@usradioguy‬ Vlog (used with permission):    • The two types of orbits that have the...  

You can find lots of useful satellite info at https://usradioguy.com/

I used a couple devices in this video, including the HackRF One (https://amzn.to/3yNXWWe) and RTL-SDR v4 (https://amzn.to/3SWO7fC). The RTL-SDR is cheaper but has fewer features than the HackRF.

For S-Band signals I used an MMDS device to amplify and down-convert 2.2GHz. I used one like this (make sure to get the "1998" version which uses a 1998MHz Local Oscillator): https://www.aliexpress.us/item/325680...

I also used a Bias-Tee like this one to power my MMDS: https://amzn.to/4dwbFQy (There are other options like this which don't require soldering: https://amzn.to/4fPZksb)

For recording radio signals I use SDR++ (https://www.sdrpp.org/) and for decoding I use SatDump (https://www.satdump.org/)

If you're interested in trying easier satellite reception, I have a video about NOAA weather satellites here:    • How To Get Live Satellite Images Dire...  

And I have an intro to L-band satellites here:    • How To Receive And Decode L-Band Weat...  


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