RASPBERRY PI BASED WEATHER SATELLITE RECEIVER
August 2020
In August 2020 I built a weather satellite receiver using a QFH antenna, an LNA, and a Raspberry Pi. The image above was received on my station from the METEOR M-2 satellite in September 2020, and shows cloud cover over the northeast. The QFH circular polarized antenna I built for this project is shown in the next image.
QFH Antenna
The next images below were received from the polar orbiting NOAA19 satellite, and they indicate smoke (yellow clouds) from the devastating California wildfires in September making its way to the east coast.
QFH ANTENNA
The dimensions of the QFH antenna were provided using the J. Coppens calculator at jcoppens.com, for a center frequency of 137.5 MHz. The wiring, winding and dimensions of the antenna are what establish circular polarization. At the top of the antenna, the wiring needs to be connected such that the center conductor of the coaxial cable is connected to an adjacent wire, as shown in the left diagram below. The other two wires are soldered to the outer conductor of the coaxial cable.
In order to establish right-hand circular polarization (RHCP), the antenna needs to be wound counterclockwise from bottom to top. At the the bottom side of the antenna, all three non-coaxial wires, indicated by the colored wires in this diagram are soldered to the outer conductor of the coax.
Receiver Software
The weather satellite receiver schedules the RTL-SDR to record at set times each day when NOAA and METEOR satellites pass overhead at a maximum elevation above 45 degrees. GPredict is used to schedule each pass.
The functions to schedule, record, and process satellite passes were written in bash scripts. When a satellite pass is scheduled this job is entered into the crontab of the Raspberry Pi, which calls the recording and processing functions at the times corresponding to each satellite pass.
The image on the right below shows the METEOR demodulator QPSK constellation received from LRPT data transmitted from the satellite. The open source used for demodulation is meteor_demod. The demodulated data is then decoded using open source from the medet_arm repo.
Pass Example with METEOR M-2
The screenshot below of the CubicSDR program shows what the waterfall plot looks like for a METEOR pass, which is shown at the location relative to Somerville in the adjacent image.
RASPBERRY PI BASED GOES GEOSTATIONARY WEATHER SATELLITE RECEIVER
January 2021
RECEIVING GEOSTATIONARY WEATHER IMAGES
In January & February 2021 I built a receiver for the GOES-16 and GOES-17 weather satellites. The images below were received using the goestools open source SDR software on a Raspberry Pi using an RTL-SDR and a GOES sawbird LNA by Nooelec. Since the communications are coming from a GEO satellite, the antenna had to be pointed very accurately for an extended period of time.
