Digital Mobile Radio Support of High Altitude Balloons for a 2017 Total Solar Eclipse Cloud Formation Experiment

Edge of Space Sciences (EOSS, eoss.org) is a Denver, Colorado based non-profit organization that promotes science and education by exploring frontiers in amateur radio and high altitude balloons. Two years prior to the total eclipse of the sun (21AUG17) we were approached by Colorado University Boulder Space Grant Consortium & NASA about flying a pair of balloons with high resolution cameras for the eclipse. They wanted a specific altitude (85,000 foot) at the total eclipse for their cameras which was going to occur in Southeastern Wyoming. They were looking for cloud formation during the eclipse and this was coordinated with three mobile Doppler radar trucks. We did a survey of the predicted landing zone (Southeastern Wyoming/Western Nebraska) and found that there was little to no cellular service and zero amateur repeater coverage. Terrain considerations negated the use of 2M or UHF simplex and HF didn’t have the right propagation. We designed a 4 site Motorola Digital Mobile Radio (DMR) system using IPSite connect with a combination of microwave and VSAT backhaul. We coordinated 4 sets of Emergency Special Event UHF DMR repeater frequencies from the Wyoming Frequency coordinator (W7QQA, Leonard Pearce). We located 4 sites and negotiated with the owners (including the use of the City of Torrington, Wyoming water tower) and ran Longley Rice coverage studies from each location. We rented and programmed 10 Motorola 4550 mobiles and installed them in the tracking and recovery crew vehicles and trained then on how to use them. We programmed up the mobiles with roaming lists and the system “pinged” every 15 seconds (1/4 mile at 60 MPH). All the tracking and recovery teams had to do was push the PTT and wait for the “go tone”. We used the second time slot to communicate with the Goshen County Sheriff Department who’s main 911 dispatcher during the eclipse was a Ham for use in the event there was a public safety issue in a location without cell coverage. We built and tested all of the repeaters and duplexers and double conversion UPS and kitted them up together with the feed lines and antennas. One site used Telewave ANT450D6 antenna set to cardioid pattern to put the RF energy where we needed it. Our Comms team of 6 installed the system over one weekend a week before the event. We did a “drive test” and determined that our Longley-Rice pattern studies were very conservative and the system coverage significantly exceeded the predicted coverage. The system covered more than 7,600 square miles of Southeastern Wyoming.