Spacecraft Probe to Listen for ARRL Field Day Signals

The Enhanced Polar Outflow Probe (e-POP) onboard the Canadian CAScade Smallsat and Ionospheric Polar Explorer (CASSIOPE) satellite will again support Amateur Radio citizen science by listening for signals during ARRL Field Day, June 24-25. The HamSCI citizen science initiative says that, from a radio science perspective, Field Day is an ideal time for e-POP to study the structure of Earth’s ionosphere using participants’ transmissions. HamSCI was started by ham-scientists who study upper atmospheric and space physics.

One of e-POP’s instruments is the Radio Receiver Instrument (RRI), a digital receiver with four 3-meter monopole antennas. Its scientific objective is to study natural and artificial radio emissions from 10 Hz to 18 MHz. The RRI’s monopoles can be electronically configured into a crossed-dipole setup, and it has two data channels — one for each dipole. Each channel is sampled at 62.5 kHz and passed through a 30-kHz bandpass.

During Field Day 2015, the receiver was activated for 2 minutes while e-POP was just north of Milwaukee, on a southeasterly heading. RRI was in a crossed-dipole configuration, with its two channels tuned to 3.525 and 7.525 MHz, respectively. A spectrogram that summarizes the results shows that not only were CW transmissions visible on the 40-meter channel (B), but they were only observed for about the first 30 seconds, even though the Reverse Beacon Network (RBN) showed that these stations transmitted throughout the experiment period. No signals were received on the 80-meter channel (A), and, at least theoretically, those signals should not have been able to penetrate the ionosphere and propagate to the receiver during the experiment.

The signals heard can be used to study HF propagation, and the advantage of using Amateur Radio transmissions is that call signs readily identify a signal’s source, which can be fed into a HF ray trace model, and then used to elucidate the properties of the ionosphere during the experiment. During Field Day 2015, 23 call signs were identified.

One hypothesis under investigation is that is that the ham signals disappeared as the spacecraft headed south into latitudes where the ionosphere was denser and blocked the transmissions.

For Field Day 2017, e-POP will dedicate all of its resources to studying HF radio wave propagation using ham radio transmissions. The Radio Receiver Instrument will be tuned to the 40 and 80-meter CW bands, although precise frequencies have not yet been determined. It is scheduled to be activated 6 times, in 10-minute increments, over Field Day weekend.

All 2017 Field Day participants are encouraged to transmit on the 40 and 80 meters during the times indicated in this chart.

Pass Date Time (UTC) Alt (km) Direction Region
1 June 24 2232-2242 800 NS East Coast
2 June 25 0013-0023 800 NS Central
3 June 25 0154-0204 800 NS West Coast
4 June 25 1135-1145 1350 SN East Coast
5 June 25 1317-1327 1350 SN Central
6 June 25 1458-1508 1350 SN West Coast

The spacecraft’s mission and science operations are headquartered at the University of Calgary, and its operations are funded by the European Space Agency (ESA).