Communications for the TechEdSat5/PhoneSat5 Mission
Session
Session 2: Communications
Abstract
The TechEdSat5/PhoneSat5 (T5/P5) Mission continues the series of orbital CubeSats from NASA Ames Research Center that incorporates advanced avionics and communications to support the testing of an exo-atmospheric parachute. This “exo-brake” slows down a spacecraft allowing controlled deorbit and recovery of payloads from International Space Station (ISS) by modulating the drag coefficient. The T5/P5 spacecraft consists of baseline avionics from the TechEdSat line together with new avionics based on the Intel Edison that forms the PhoneSat core. The T5 avionics controls solar power generation and power management, and provides spacecraft telemetry and is the primary control unit. The P5 avionics supports additional sensors and cameras, using separate communication systems for low-rate uplink and downlink and a high-speed downlink based on WiFi technology operating in the 2.4 GHz ISM frequency band. Orbit determination is performed using an on-board GPS unit, which is powered up every day to gather precise orbital location information. The T5/P5 CubeSat supports a compact wireless sensor module that uses radio signals to communicate temperature, barometric, translational and rotational acceleration and a magnetometer to the avionics. Two cameras take pictures of the exo-brake after deployment, confirming the shape and modulation of the effective area. The telemetry, sensor data and image data are downlinked via the Iridium communication link or through the high-speed ISM-band downlink to our Wallops Flight Facility ground station. Commands are received through two Iridium modems, one for T5 and the other for P5 avionics. The paper will describe the spacecraft, the communication links, mission operations and the results from the deorbit experiment. The power management of the various T5/P5 subsystems is described in the context of available power generation from the new solar panels. Of particular interest is the number of telemetry packets sent and commands received during the low-earth orbital mission using the Iridium satellite constellation. Communication is only possible when proper alignment between the CubeSat antenna and an Iridium satellite occurs, so the probability of message transfer is a key operational issue. The use of image compression for sending pictures down this low-rate link is demonstrated as well. In comparison, the number of successful passes and the data volume received using the WiFi ISM-band downlink to the dedicated ground station is analyzed, comparing actual link margin to that predicted. This analysis provides insight into potential improvements in uplink and downlink capability for subsequent CubeSat missions.
Presentation
Communications for the TechEdSat5/PhoneSat5 Mission
The TechEdSat5/PhoneSat5 (T5/P5) Mission continues the series of orbital CubeSats from NASA Ames Research Center that incorporates advanced avionics and communications to support the testing of an exo-atmospheric parachute. This “exo-brake” slows down a spacecraft allowing controlled deorbit and recovery of payloads from International Space Station (ISS) by modulating the drag coefficient. The T5/P5 spacecraft consists of baseline avionics from the TechEdSat line together with new avionics based on the Intel Edison that forms the PhoneSat core. The T5 avionics controls solar power generation and power management, and provides spacecraft telemetry and is the primary control unit. The P5 avionics supports additional sensors and cameras, using separate communication systems for low-rate uplink and downlink and a high-speed downlink based on WiFi technology operating in the 2.4 GHz ISM frequency band. Orbit determination is performed using an on-board GPS unit, which is powered up every day to gather precise orbital location information. The T5/P5 CubeSat supports a compact wireless sensor module that uses radio signals to communicate temperature, barometric, translational and rotational acceleration and a magnetometer to the avionics. Two cameras take pictures of the exo-brake after deployment, confirming the shape and modulation of the effective area. The telemetry, sensor data and image data are downlinked via the Iridium communication link or through the high-speed ISM-band downlink to our Wallops Flight Facility ground station. Commands are received through two Iridium modems, one for T5 and the other for P5 avionics. The paper will describe the spacecraft, the communication links, mission operations and the results from the deorbit experiment. The power management of the various T5/P5 subsystems is described in the context of available power generation from the new solar panels. Of particular interest is the number of telemetry packets sent and commands received during the low-earth orbital mission using the Iridium satellite constellation. Communication is only possible when proper alignment between the CubeSat antenna and an Iridium satellite occurs, so the probability of message transfer is a key operational issue. The use of image compression for sending pictures down this low-rate link is demonstrated as well. In comparison, the number of successful passes and the data volume received using the WiFi ISM-band downlink to the dedicated ground station is analyzed, comparing actual link margin to that predicted. This analysis provides insight into potential improvements in uplink and downlink capability for subsequent CubeSat missions.
