Mission 04: Weather Satellite Imagery

2026-05-07

Receive and process analog meteorological data directly from orbiting NOAA satellites.

receivecapturerecon

Complexity Rating

Receive3/5

Decode2/5

Analysis2/5

System Studied

NOAA APT (Automatic Picture Transmission)

Hardware Requirement

rtlsdr

Software Suite

SDR++noaa-aptWXtoImg

1. Field Methodology: Capture

Wide-band AM reception on 137 MHz during a high-elevation satellite pass using a circularly polarized antenna.

Gear Selection NoteA V-Dipole or Turnstile antenna is essential to handle the signal's polarization as the satellite passes overhead.

2. Analysis Workflow: Decode

Decoding the rhythmic audio subcarrier into a line-by-line grayscale image using specialized APT software.

Atmospheric Intercept: Doppler Shift

At orbital velocities (~17,000 mph), the signal frequency shifts significantly during a pass. This simulation demonstrates how to track the center frequency to maintain a phase lock.

NOAA 19

AOS (Acquisition)

+3.5 kHz Shift

137.1035 MHz

TCA (Closest Approach)

0 kHz Shift

137.1000 MHz

LOS (Loss of Signal)

-3.5 kHz Shift

137.0965 MHz

Simulated Telemetry Lock: ACTIVE

Signal Reconstruction: APT Decoding

The Automatic Picture Transmission (APT) protocol uses an AM-modulated subcarrier. Below is a recreation of the rhythmic "tick-tock" audio and its conversion into scan-line data.

NOAA_19_PASS.wav

Click to route audio

WXtoImg Engine v2.1

0% DECODED

3. Findings & Limitations

Analog weather data is a reliable, open-source resource for global situational awareness, broadcast in the clear for over 40 years.

Legal & Ethical Briefing

Receiving satellite broadcasts is legal and a standard part of amateur and professional meteorology.

What to study next

Move up to GOES (Geostationary) satellites for high-resolution digital HRIT imagery.

Continue Mission