Recent Submissions

  • A Software-Defined Radio Transmitter for Variable-Coded Modulation on a CubeSat

    Mullet, John; Thorsen, Denise L.; Raskovic, Dejan; Bossert, Katrina (2020-05)
    The large volume of satellites sharing the same spectrum and the complexities of communications in Low-Earth Orbit (LEO) pose challenges to the downlink of large volumes of data on a platform that is bandwidth, power, and time limited. LEO satellites operate in a highly variable communications environment due to variations in inter-satellite or satellite-to-ground geometries, weather, and interference. Therefore, there is motivation for implementing satellite communication techniques that manage these issues to increase the data throughput. One such technique is variable-coded modulation which shows improvement by taking advantage of the dynamic nature of a satellite link. As part of the Air Force Research Laboratory University Nanosatellite Program, and in collaboration with NASA, this project focuses on the development of an S-band software defined radio for CubeSats that utilizes variable-coded modulation defined by the Digital Video Broadcasting-Satellite-Second Generation standard. This project defense discusses the initial development and testing using GNU Radio, and the challenges for full implementation, as well as the current status of the transmitter, and future work.
  • Conceptual design of a test bed for miner rescue

    Munny, Rowshon Ara Mannan; Hatfield, Michael; Wies, Richard; Bossert, Katrina (2019-08)
    In the mining industry, miners are constantly exposed to various safety and health hazards associated with often unpredictable conditions. When an accident occurs, it is difficult for the rescue team to come up with a proper plan for the rescue mission without having adequate knowledge of the situation. One possible approach to managing these hazards is to provide the rescue team with situational awareness such as real-time data regarding the environment (fire, poisonous or explosive gasses), as well as the location and physical condition of the trapped miners. Before starting the rescue mission, and in order to eliminate or reduce the dangers of exposing more humans to the explosive mining environment for information collection, a combination of unmanned ground vehicles (UGVs) and unmanned aerial vehicles (UAVs) is proposed. In this project, a conceptual test bed is designed to collect one specific set of information about a trapped miner (in this case, heartrate data). This test bed collects the required data from a heart rate sensor on the trapped miner and transmits it wirelessly to a nearby UAV which will receive the data and send it back to the rescue team via a UGV.
  • Infrared video tracking of UAVs: Guided landing in the absence of GPS signals

    Graves, Logan W.; Hatfield, Michael C.; Lawlor, Orion; Raskovic, Dejan (2019-05)
    Unmanned Aerial Vehicles (UAVs) use Global Positioning System (GPS) signals to determine their position for automated flight. The GPS signals require an unobstructed view of the sky in order to obtain position information. When inside without a clear view of the sky, such as in a building or mine, other methods are necessary to obtain the relative position of the UAV. For obstacle avoidance a LIDAR/SONAR system is sufficient to ensure automated flight, but for precision landing the LIDAR/SONAR system is insufficient for effectively identifying the location of the landing platform and providing flight control inputs to guide the UAV to the landing platform. This project was developed in order to solve this problem by creating a guidance system utilizing an infrared (IR) camera to track an IR LED and blue LEDs mounted on the UAV from a RaspberryPI 3 Model B+. The RaspberryPI, using OpenCV libraries, can effectively track the position of the LED lights mounted on the UAV, determine rotational and lateral corrections based on this tracking, and, using Dronekit-Python libraries, command the UAV to position itself and land on the platform of the Husky UGV (Unmanned Ground Vehicle).
  • Improving CubeSat downlink capacity with active phased array antennas

    Klein, Jonathan; Hawkins, Joe; Thorsen, Denise; Raskovic, Dejan (2017-08)
    Power budgets on small satellites are restricted by the limited surface area for solar panels. This limits the power available for radio communications, which constrains the downlink budget. The limited transmit power translates to low downlink data rates on small satellites. Antenna gain from directive antennas may be a power efficient way of improving the downlink budget, thereby increasing the downlink rate of small satellites. This project focuses on the design and development of a prototype low-power, electrically-steered S-band phased array RF front-end suitable for a CubeSat that could efficiently increase the EIRP, permitting higher data rates. A prototype of the array has been constructed and tested in an anechoic chamber. The four element array provides a minimum gain of 2.5 dB and average gain of 5 dB compared to a single patch antenna element with a 5W power envelope across a range of up to 60 degrees from broadside of the array.