Introduction
Recently I started to experiment receiving satellite weather from NOAA15/18/19 (Ref.1/2). I decided to see if I could do the same thing with the Raspberry Pi4, since this would add yet another functionality to a compact and efficient platform (Ref.3).
Tracking Software
For tracking, we can use Predict developed by John Magliacane KD2BD (Developer of Splat!) or GPredict by Alexandru Csete (Developer of Gqrx). Predict can be downloaded and installed with instructions on the GitHub site (Ref.4). Gpredict can simply be installed from the RPi repository by Adding/Removing software (Ref.5). Predict & Gpredict require you enter your QTH location Lat/Long/Elev and also update the Satellite .tle Kepler orbit files (Ref.6). The RPi4 clock has to be updated for this step (Internet or entered manually).
As I did previously, I downloaded a 10day prediction of the NOAA satellites, Figure 1, from N2YO (Ref.7). Then I decided which was the optimum orbit as in Figure 2. Running both Predict, Figure 3, and Gpredict, Figure 4, you can cross check the satellite orbits and AOS times.
Decoding Software
In order to decode the images, I used noaa-apt developed by Martin Bernardi. This program can be downloaded from the author’s website (mini course in NOAA reception!) or Github site (Ref.8). Unzip the file, and cd to the directory it is located in. Double click the shell script “run-noaa-apt.sh”, this will launch the program. If there is no shell script, then cd to the directory with terminal and run “./noaa-apt”. Load the Gqrx WAV file received, decode & process. An example is shown in Figure 5.
Equipment Configuration
Figure 6 shows the equipment block diagram. I used the OpenPlotter Headless setup for RaspberryPi4 as described in a previous blog post (Ref.9). The RPi4 clock needs to be updated first, then update the Kelers for Gpredict. NOAA satellite signals are received on a Vee dipole and enter a SAW bandpass filter/amplifier. They are then received by an RTL-SDR version 2. The RTL-SDR and BPF/LNA are powered from the RPi4 which in turn is powered by a portable Lithium battery. The RPi4 connects to a remote laptop screen/keyboard by VNC server.
Figure 7 shows Gqrx receiving NOAA18 on 137.9125MHz. The decoded audio is saved as a WAV file. This file is then opened and decoded in noaa-apt as shown in Figure 8.
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References
#1. – “APT Automatic Picture Transmission for NOAA Satellites – Scicos/Gnurc Simulation”
https://jeremyclark.ca/wp/telecom/apt-automatic-picture-transmission-for-noaa-satellites-scicos-gnurc-simulation/
#2. – “RTL-SDR for NOAA15/18/19 Satellite Weather on SDRangel”
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-noaa15-18-19-satellite-weather-on-sdrangel/
#3. – “RTL-SDR on Raspberry Pi4”
https://jeremyclark.ca/wp/telecom/rtl-sdr-on-raspberry-pi4/
#4. – “Predict Satellite Tracking” John Magliacane KD2BD
https://github.com/kd2bd/predict/
#5. – “Gpredict Satellite Tracking” by Alexandru Csete
https://github.com/csete/gpredict
#6. – “CelesTrack Orbital Data – TLE File”
https://celestrak.com/NORAD/elements/
#7. – “N2YO.com Satellite Tracking”
https://www.n2yo.com/satellite/?s=28654
#8. – “nooa-apt image decoder”
https://noaa-apt.mbernardi.com.ar/
https://github.com/martinber/noaa-apt/releases/download/v1.3.1/noaa-apt-1.3.1-armv7-linux-gnueabihf.zip
#9. – “OpenPlotter – RPi4_a Headless”
https://jeremyclark.ca/wp/telecom/openplotter-rpi4-headless_a/
