Zachary Robinson
Fifth Gait Technologies, Inc.
Zachary Robinson received his masters degree from the University of Alabama in Huntsville (UAH) in 2015. He wrote his thesis on probabilistic modeling of solar proton episodes under the guidance of Dr. Jim Adams. In August 2015, he was hired at Fifth Gait Technologies and has worked closely with Dr. Jonathan Fisher and Dr. Jim Adams. Since being hired at Fifth Gait, Zachary has been attending UAH part time to finish his PhD.
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
Approved for Public Release LATH
17-MDA-9032 (16 February 17)
Solar energetic particles can produce a dramatic intensification of the space radiation environment compared to the ever-present galactic cosmic ray background. As a result, space systems must use, as a reference for their design, a large solar energetic particle event. The size of this design reference event chosen drives the cost and complexity of the mission. It is therefore important to choose a reference event which will result in a design that achieves the desired level of confidence in the operability and reliability of the missions systems while preventing an unnecessary and expensive over design.
The best approach to choosing an appropriate design reference environment is the probabilistic modeling approach. This approach utilizes the historic data base of solar energetic particle measurements to find the upper bound flux as a function of energy for a user-specified confidence level and specific mission (specified by start date and mission duration). The analysis of the data base produces cumulative distributions of particle flux in a series of energy intervals spanning the particle energies that must be considered in the mission design. This approach is applied to elemental spectra from protons to the heaviest elements that have the potential to drive the mission design.
The methods used to construct a probabilistic model depend on whether the model is to produce an upper bound flux or fluence spectrum and the length of the mission compared to the typical lengths of episodes of solar activity. When missions are long compared to the length of episodes, the model can be formulated using the method developed by Xapsos et al., Solar Physics 183: 157–164, 1998. When the mission is short compared to these episodes, a different method (described in the talk) is needed. This method is based on random sampling of the relevant parts of the data base. In addition to overcoming episode lengths, it avoids inappropriate use of time-independent Poisson statistics. The new probabilistic model is being developed for integration into the Space Ionizing Radiation Environments and Effects (SIRE2) toolkit. SIRE2 is under development via Phase III Small Business Innovate Research Funding.
This talk will review the work on probabilistic modeling and present new results on extending the data base in time and atomic number. New results will also be presented on how to find solutions for short missions. Finally the calculations of design reference environments providing both flux and fluence spectra will be demonstrated for both short and long missions.
