Terrestrial RaYs Analysis and Detection (TRYAD) Flight Instrumentation and Testing

The Terrestrial RaYs Analysis and Detection (TRYAD) project is a collaboration among the University of Alabama Huntsville, Auburn University, and the Goddard Space Flight Center, whose goal is to develop two CubeSats to detect Terrestrial Gamma Ray Flashes (TGFs), bursts of gamma rays in the upper atmosphere associated with lightning. While TGFs are believed to be produced by bremsstrahlung from accelerating electrons produced in the Runaway Relativistic Electron Avalanche (RREA), the source mechanism of this acceleration is unknown. There are two leading theories that TRYAD will investigate: the Lightning Leader model and the Relativistic Feedback Discharge (RFD) model. The former states that the lightning step leader creates an electric field to accelerate electrons, while the latter predicts that the electrons accelerate within the thunderstorm electric field. The two CubeSats will measure the TGF from different locations simultaneously in order to test these models, which differ in predicting the beam profiles; a wide beam profile implies the Lightning Leader theory, while a narrow profile implies the RFD theory. UAH is responsible for developing the Science Instrument Package (SIP), which includes plastic scintillators and Silicon Photomultipliers (SiPMs) to detect incident gamma rays, and the Data Acquisition board (DAQ), which provides power to the SiPMs and controls signal processing of their output. This summer, there have been updates made to the SIP middle board assembly in order to ease the manufacturing process, as well as to the DAQ design to ensure that output cables from the SIP would have room to connect to the DAQ in the full assembly. In addition, preliminary testing on a SIP prototype, using Am-241 and Cs-137 as gamma ray sources, has produced energy spectra inconsistent with expected results. This is due to increased attenuation and reduced scintillation within the lead-doped plastic scintillators, and further testing with un-doped plastic scintillators will be conducted. Assembly and testing of the full SIP will begin soon, and there is an estimated launch date of 2021.