@conference {581,
	title = {Construction and Operation of a HamSCI Grape Version 1 Personal Space Weather Station: A Citizen Scientist{\textquoteright}s Perspective},
	booktitle = {American Geophysical Union Fall Meeting},
	year = {2021},
	month = {12},
	publisher = {American Geophysical Union},
	organization = {American Geophysical Union},
	address = {New Orleans, LA},
	abstract = {<p>Measurement of Doppler shifts of high frequency (HF) radio signals emitted by precision frequency transmitters is a well-established technique for the detection of traveling ionospheric disturbances and other perturbations in the bottomside ionosphere. Because Doppler measurements require minimal instrumentation, this technique naturally lends itself to crowdsourced data collection, and purpose-built instrumentation platforms are desirable in order to maximize consistency and repeatability. However, even the best system only has value if it is used, and a robust and engaged community of citizen scientists is vital to sustaining instrumentation platforms. The Ham Radio Science Citizen Investigation (HamSCI) has developed a prototype, low-cost system for making HF Doppler shift measurements of signals from standards stations such as WWV (Fort Collins, Colorado, USA) and CHU (Ottawa, Ontario, Canada). This system, known as the Personal Space Weather Station Grape Version 1, consists of a low intermediate frequency (IF) mixer board, GPS disciplined oscillator, and Raspberry Pi. In collaboration with funded project scientists and engineers, volunteer HamSCI community members developed instructions for building and operating a Grape Version 1 on the HamSCI website. In this presentation, we explain the process for constructing a Grape Version 1 and discuss the experiences of volunteers who have built and are now operating this system. We also discuss preliminary data from these stations, which show dramatic Doppler shifts during sunrise and sunset and during solar events. Concurrent data from multiple proximal stations show shared features and can be used for validation. These stations constitute the first iteration of the Personal Space Weather Station network.</p>
},
	url = {https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/845691},
	author = {Hobart, Joseph R. and Farmer, James O. and Mikitin, Gary and Waugh, David and Benedict, Robert and Cerwin, Stephen A. and Collins, Kristina V, and Kazdan, David and Gibbons, John and Romanek, Veronica I. and Frissell, Nathaniel A.}
}
@proceedings {572,
	title = {Experimental and Computational Methods to Analyze Complex Doppler Behavior of Ionospherically Induced Doppler Shifts on HF Signals (Proceedings)},
	year = {2021},
	month = {09/2021},
	publisher = {ARRL-TAPR},
	address = {Virtual},
	url = {https://youtu.be/MHkz7jNynOg?t=18161},
	author = {Cerwin, Stephen A. and Collins, Kristina V. and Joshi, Dev Raj and Frissell, Nathaniel A.}
}
@conference {583,
	title = {Experimental and Computational Methods to Analyze Complex Doppler Behavior of Ionospherically Induced Doppler Shifts on HF Signals},
	booktitle = {American Geophysical Union Fall Meeting},
	year = {2021},
	month = {12},
	publisher = {American Geophysical Union},
	organization = {American Geophysical Union},
	address = {New Orleans, LA},
	abstract = {<p>The HamSCI community has been studying apparent frequency shifts in the reception of HF skywave signals from radio station WWV in Ft. Collins, CO. Causes for frequency shifts in the received signal are recognized as complex and varied. Leading candidates are Doppler shifts resulting from dynamic changes in refraction layer height and the behavior of modes at incidence angles at the cusp between escape into space and refraction back to earth. Observations have shown the most radical frequency disturbances occur during the diurnal transitions between night and day, with the morning transitions exhibiting more radical behavior than evening. Other changes in solar radiation such as passage of an eclipse shadow or solar flares produce similar results. In all cases the frequency swings were found to follow the rate of change of propagation path length. Specific behaviors studied include mode splitting, where the Doppler shift diverges into multiple overtone-related tracks, modes that abruptly manifest and disappear during the transition, and asymptotic behavior where Doppler tracks exhibit a rapid frequency change followed by extinction. A morning transition spectrogram showing some of these characteristics is shown in the accompanying figure. This paper describes experiments and analytical procedures devised to better understand these phenomena. They include Time-of-Flight measurements reconciled with a geometric model of the ionosphere to infer propagation modes, use of the geometric model to calculate layer height changes from measured Doppler shifts, and comparison of specific features between spectrogram and ionosonde data sets. Data from two morning transitions and the 2017 total eclipse are given. Plausible explanations for several aspects of observed frequency swings are postulated.</p>
},
	url = {https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/849071},
	author = {Cerwin, Stephen A. and Collins, Kristina V. and Joshi, Dev Raj and Frissell, Nathaniel A.}
}
@proceedings {561,
	title = {HamSCI Personal Space Weather Station (PSWS): Fall 2021 Update},
	year = {2021},
	month = {09/2021},
	publisher = {ARRL-TAPR},
	address = {Virtual},
	url = {https://youtu.be/MHkz7jNynOg?t=1990},
	author = {Frissell, Nathaniel A. and Joshi, Dev Raj and Collins, Kristina and Montare Aidan and Kazdan, David and Engelke, William D. and Atkison, Travis and Kim, Hyomin and Cowling, Scott H. and McDermott, Thomas C. and Ackermann, John and Witten, David and Madey, Jules and Silver, H. Ward and Liles, W. and Cerwin, Stephen A. and Erickson, Phillip J. and Miller, Ethan S, and Vierinen, Juha}
}
