This video documents the process of attempting to receive and decode signals from the US military's Defense Meteorological Satellite Program (DMSP) using various surplus and homemade satellite receiving equipment. The DMSP satellites, although somewhat obsolete for military intelligence (originally used to scout weather for film spy satellites), still transmit meteorological data and are notably encrypted for most of the world, only becoming unencrypted over North America/the US. The project involves using different satellite dishes (including an RV dish and camping dishes), an MMDS converter modified for the S-band frequency (around 2.2 GHz), and Software Defined Radios (SDRs) like the HackRF One and RTL-SDR. Challenges included finding suitable S-band equipment, modifying components, accurately tracking the polar-orbiting satellites, and dealing with signal issues and interference. After numerous failed attempts with different antenna setups and tracking methods, the user eventually succeeded in receiving and decoding visible, infrared, and thermal imagery from DMSP satellites (specifically F17), confirming the satellites' encrypted behavior and the limited geographic zone where signals are transmitted unencrypted (primarily the northern US and Canada, seemingly only on northbound passes over the user's location). While the resulting weather images were not particularly exciting or higher quality than publicly available data, the experiment was a successful demonstration of receiving and decoding signals from these restricted military satellites using readily available hobbyist gear.
Snooping on Military Satellites with Junk Gear: A DMSP Reception Experiment
0:00 The video's goal is to receive and decode signals from US military Defense Meteorological Satellite Program (DMSP) satellites using various surplus and homemade satellite dish hardware.
0:34 DMSP satellites have provided critical meteorological information to the US military for over 50 years, primarily for weather forecasting over remote/hostile areas for deployed troops.
1:06 Only two DMSP satellites (F17 and F18) remain operational from an original constellation, some of which exploded due to battery issues.
1:36 A key feature of DMSP satellites is that their signals are encrypted for most of their orbit, only becoming unencrypted over North America/the US, allowing free access to imagery in this region.
1:50 The primary weather sensor on DMSP is the Operational Line Scan System, providing visible and infrared imagery over a 600 nautical mile wide area by sweeping back and forth.
2:45 Unlike public weather satellites (like NOAA) funded by public agencies, DMSP satellites are defense department satellites whose signals are not intended to be publicly available worldwide.
3:00 DMSP originated as a "spy satellite for spy satellites," used to check weather conditions before deploying film-based reconnaissance satellites (like Corona) to avoid wasting film on cloudy areas.
4:46 DMSP satellites transmit in the S-band range, around 2.2 GHz, which is a bit trickier to find commercial equipment for compared to the L-band (around 1.7 GHz) used by some other weather satellites.
5:09 The user tries using an MMDS (Multipoint Multichannel Distribution Service) microwave antenna, typically used in Asia, which operates near the S-band frequency and can down-convert the signal.
6:18 The MMDS unit is modified by replacing its linear feed with a homemade helical feed, which is better suited for the helical polarization used by the DMSP satellites.
7:17 An old RV satellite dish is used as the reflector, with the modified MMDS unit placed at its focal point.
8:25 A bias-T power injector is needed to supply the required 12 volts DC to the MMDS unit via the antenna line, as standard SDRs usually only provide 5 volts.
10:01 Satellite passes are tracked using ino.com and the Stellarium app (though found to be unreliable) or Gpredict software for aiming.
11:31 The first attempt using the HackRF One and large dish failed completely.
11:40 Polar orbiting satellites like DMSP move quickly relative to the ground, requiring active tracking with the dish during their 10-15 minute passes.
13:26 The user switches to the RTL-SDR, relying on the MMDS to down-convert the S-band signal to a frequency the RTL-SDR can receive.
14:11 A promising pass on DMSP 18 shows a signal, and the user observes the signal changing dramatically, appearing to switch from encrypted to unencrypted over the US.
14:31 The first successful decoding attempt yields some data from DMSP 18, though the resulting image is not clear ("not fantastic").
15:06 Wind significantly affected the large dish during morning attempts.
15:38 Additional S-band antenna feeds are explored and tested, including a loop feed and a feed made from a pie pan, but initial results remain poor.
17:06 A later attempt using the pie pan feed yields a slightly more recognizable signal, showing parts of the Great Lakes area.
17:30 The user notes that DMSP F18 seems to decrypt around 40Β° North latitude, remaining encrypted over the southern US.
18:43 To overcome tree line issues and improve tracking, the dish is placed on the roof of the user's car for a pass.
18:53 The signal on the car roof is great, and the user successfully decodes several channels (visible, infrared, thermal, and a combined image) from the OS system on DMSP F17.
19:10 Both DMSP F17 and F18 seem to behave similarly: not transmitting on southbound passes over the user, and only transmitting unencrypted on northbound passes over the northern US and Canada.
20:04 A motorized tracking mount using Gpredict and a security camera pan/tilt unit is tested but the initial results were not as good as manual tracking with the larger dish.
23:59 Returning to the car roof mount proves effective again for a challenging pass, leading to a decent image acquisition.
24:41 A "decent" picture is obtained from DMSP 17, mostly showing clouds, confirming the ability to receive military satellite imagery despite the satellites being somewhat obsolete and the signals having limited availability.
25:17 The project involved many "wild goose chases" and trying frequencies/satellites that didn't behave as expected online, highlighting the iterative nature and learning process of the hobby.
26:06 The video was significantly edited down from about 4 hours of raw footage to focus on the key steps and results, cutting out many failed attempts and dead ends.