Happy Fourth of July from Project HALO (or at least from its slightly-overworked graduate student supervisor)! The team's payload design has been progressing swimmingly, and soon it should be time to start building. Here are a few highlights from the past week of work:

• Initial setup of the flight computer (a Raspberry Pi 3B+) - this will be the brains at the core of everything our payload does, from taking pictures to transmitting position reports to recording data from the instrument suite. Song, our programming lead, has been hard at work configuring the Pi and writing the main routines for the payload.
• CAD of the payload structure using SolidWorks - thanks to the hard work of the structures team, an initial design for the structural shell of the payload has been conjured into existence in the computer lab. The payload will consist of thick, extruded polystyrene (XPS) walls, with a thin plywood structure inside to add additional support for the internal components, the external antenna, and the parachute attachment points.
• Heat transfer calculations to characterize the thermal environment within the payload throughout the flight - since ensuring that the payload electronics don't freeze, estimating the temperature within the payload enclosure is of paramount importance. Predicting the thermal output of the Raspberry Pi is a challenge, but based on some conservative assumptions, it appears as though the payload will be able to maintain adequate temperature for the Raspberry Pi.
• Trajectory analysis to determine our best launch window - using a variety of online tools (thanks, balloon community!), the Integration team has been running a bevy of simulations to help us develop an understanding of where the payload might land. This will vary with time of day and from day to day, but thus far we have seen a relatively stable touchdown zone stretching from approximately Kokomo to Lebanon(ish) - or to use non-Hoosier terms, about 60 miles east or southeast.
• Design of a quarter-wave ground plane antenna for Automated Packet Reporting System (APRS) - maintaining a link with our payload so that we can track its location will aid immensely in recovering the payload; the Tracking team is hard at work finalizing their software and hardware design for just this purpose. They have designed a ground-plane antenna which will allow the payload to transmit its location on the 2m amateur radio band, where it will be picked up by the ground station network.

So, what's next? After everyone enjoys some grilling and fireworks tonight, we'll be back at work this weekend to finish up our design. We'll aim to start cutting materials and turning our meticulously-laid plans into something tangible and, more importantly, launchable!