NOAA ITOS High Resolution Picture Transmission (HRPT)
 | |
|---|---|
| Frequencies | 1697.5 MHz |
| Frequency Range | 1697.5 MHz - 1697.5 MHz |
| Mode | WFM |
| Modulation | FM |
| ACF | — |
| Emission Designator | — |
| Bandwidth | 1000 kHz |
| Location | Worldwide |
| Short Description | An analog signal broadcast from NOAA ITOS polar satellites that transmitted images from the VHRR radiometer. |
| I/Q Raw Recording | — |
| Audio Sample | |
The NOAA ITOS (Improved TIROS Observation Satellite) series of satellites transmitted high-resolution pictures from the VHRR (main radiometer) and calibration/telemetry data over an analog HRPT link. The same signal transmitted stored data.
The signal was an analog video signal, FMFrequency Modulation-modulated, encoded over an FMFrequency Modulation link. The main payload of HRPT was VHRR data composed of two channels in the visible and infrared spectrum; additionally, telemetry similar to APT is included in the image, and the data are transmitted at 360 lines per minute (LPM).
This signal is not to be confused with the more modern, digital HRPT signal used by the ATN (POES) series of satellites, or with the variant used by Russian METEOR-M satellites.
Data transmitted[edit]
- 2 channels from VHRR radiometer: an infrared and a visible one.
- Calibration data for VHRR channels
- Spacecraft telemetry and monitoring (TLM)
Signal characteristics[edit]
- Right-hand circular polarization
- FMFrequency Modulation modulation encoding an FMFrequency Modulation analog video signal
- 1 MHzMegaHertz (MHz) 10^6 Hz bandwidth
- 5-watt transmitted power
Satellites transmitting HRPT[edit]
All ITOS satellites are officially decommissioned. However, NOAA-2 (ITOS-D), launched over 50 years ago, started transmitting a signal that matches the original specifications again. No imagery is transmitted, but the telemetry lines are visible.
The signal was on for a minute and off for about two minutes while the satellite was passing; no signal is transmitted at night. Furthermore, from Scott Tilley's observations in 2021 on the initial discovery of this satellite being active, it would appear its rotation or tumble is slowing over time.
"The NOAA 2 spacecraft is tumbling with a period of about 88.6s. The on/off duty cycle is asymmetrical with it on for about ~28s and off for ~61s." Scott Tilley on X detailing signal characteristics in 2021
Last known working reception and decode was on September 17th, 2025, in Northeast Ohio, USA.
| Satellite | Frequency | Notes |
|---|---|---|
| NOAA 2 (ITOS-D) | 1697.5 MHzMegaHertz (MHz) 10^6 Hz | Only while not eclipsed; no imagery transmitted, only telemetry. |
Baseband recording[edit]
Decoding tutorial[edit]
A note: Xerbo's NOAA-2 GNUradio flowchart seems to be more sensitive and able to pick up the signal than the one by RAD750 on GitHub. If you can find an official link, please add it here.
For better decoding performance, when recording the baseband you should set your SDR to have a noise floor from -80 to -60 dBM and adjust gain to best suit your LNA. The GNUradio decoders very easily lose sync with excessive background noise.
Additional Links[edit]
- File:Noaa 31338.pdf
- Article by Derek OK9SGC about the satellite
- GNU Radio decoder file (see the tutorial above)
Additional Images[edit]
|
|
