CubeSat CANVAS on GNURadio – Telecommunications, Navigation & Electronics

Introduction

This past year I was able to successfully receive CubeSats ENSO, Veronika and EIRSAT-1 (Ref.1/3). All three CubeSats have since decayed from orbit according to the SatNOGS database. Doing a search, I found a recent CubeSat launch CANVAS (Ref.4). So I thought I would try reception using my 2m/70cm yagi. I previously used an ATSC yagi. CANVAS is a 4U Cubesat, transmit frequency 437.250MHz GMSK 9600bd. It is designed to measure LF activity due to lightening and other sources. It is equipped with a three-axis magnetic search coil and two electric field dipole antennas (Ref.5).

Reception Parameters

Fig.1 Equipment & Software Setup CANVAS CubeSat Reception

Fig.2 GNURadio gr_satellites Schematic Decoding CubeSat 9600GMSK

Figure 1 shows the equipment setup. The 70cm Yagi is pointed due East. The 433MHz BPF/LNA/RTL-SDR is connected to the Yagi and secured to the aluminum tripod with a bungee cord. A long usb cable then feeds a laptop indoors. SDR# is used and the sampling rate is set at 250Ksps to keep file size down. The frequency is set 20KHz above or below the satellite frequency. The reason for this is to allow for Doppler shift. On playback, you can measure the actual packet receive frequency then set this in the GNURadio Frequency Translation Filter. The Baseband IQ recorder is used and I start recording the minute my QTH appears in the satellite footprint. The satellite pass is typically about 5-8 minutes so the files get big. You can trim them later in Audacity. I keep the gain low at 19.7-29.7dB, but this depends on the active QRM, so I adjust this for minimum intermod. Figure 2 shows the GNURadio schematic used with gr_satellites Satellite Decoder set for 9600GMSK.

Signal Capture June 4_2026

Fig.3 CANVAS Path from SatNOGS DB June 4th_2026 0840EDT

Fig.4 CANVAS Doppler shift from -20KHz to -28KHz

Fig.5 CANVAS Decodes for Freq Shift Values 23KHz to 25.5KHz

Figure 3 shows a close pass of CANVAS on June 4th_2026. Previous observations of ENSO/VERONIKA/EIRSAT-1 showed passes coming from the North/South and moving to the West. This is the opposite case, moving towards the EAST with a more horizontal trajectory. Figure 4 shows the Spectrum analyzer looking at the input IQ pulses with maximum hold on. They start around -20KHz below Fc and move to about -28KHz below Fc. Figure 4 shows hex decodes for -23KHz/-25.5KHz.

Signal Capture June 6_2026

Fig.6 CANVAS Path from SatNOGS DB June 6th_2026 0741EDT

Fig.8 CANVAS Decode for Freq Shift Values 24KHz

Figure 6 shows a pass of CANVAS on June 6th. This pass was not as close as June 4th but one strong pulse was received for a decode as shown in Figure 7. This time I was tuned 20KHz below and the frequency shift was +24KHz.