International workshop on new standard radiation belt and plasma models

Space systems are designed to function in and withstand harsh radiation belt and plasma environments that are defined primarily with the use of the decades-old AP-8 and AE-8 models. These models are esteemed for their extensive spatial coverage and user friendliness, but contain inaccuracies due in part to the limitations of the data-collecting instruments available at the time, as well as to extrapolations in time, space, and energy spectra that were required to cover measurement gaps when they were initially developed. As a result of these inaccuracies, mission designers tend to overestimate the expected operational radiation environment, leading to costly overdesign of space systems. To begin rebuilding the infrastructure required to develop new space radiation belt and plasma models, the Working Group Meeting on New Standard Radiation Belt and Space Plasma Models for Spacecraft Engineering, sponsored by NASA's Living With a Star (LWS) program, met on 5–8 October, 2004 in Adelphi, Maryland. Such new models will facilitate smarter space system design and assure the safety of astronauts. The workshop was chaired by Janet Barth at NASA and was planned by a steering committee composed of Barth, Bern Blake from the Aerospace Corporation, Don Brautigam of the Air Force Research Laboratory, and Eamonn Daly from the European Space Agency. Over the course of the workshop, the international community of space environment modelers worked together with industry and agencies to identify the current status of modeling efforts and data availability and the needs of the end users. More than 50 people participated in the workshop, which led to drafting preliminary road maps for creating a new standard radiation environment model. There is a significant amount of post-AP-8/AE-8 data and subsequent modeling that has not been fully utilized due in part to a lack of a formal process to peer review data set calibration and new models. Data quality and calibration are key to model formation. Reiner Friedel, a workshop member from the Los Alamos National Laboratory, described the calibration process as “having to build the road before we can build a car.” Given that the development of a new standard model is an international effort, the consensus of the workshop was that the Committee on Space Research/Panel on Standard Radiation Belts should play a central role in managing the standardization of data sets and models. The workshop members then started a dialogue on future models that would include the differing motivations of the engineering and scientific communities. Those who would use the models stressed a need for fine temporal resolution of average and worst-case energy fluxes, and greater precision of model estimates for the 1000 km to geosynchronous altitude environment as being among the most critical requirements for cost reduction and improved performance of space system designs. To begin to address these needs, the attendees devised plans for interim models based on orbit regions and considered the necessary steps to achieve the goal of one unified model. Two such interim models were deemed ready for standardization: POLE, a model of geostationary orbit electrons produced jointly by the French National Aerospace Research Establishment and Los Alamos National Laboratory, and an inner-belt proton model produced by SAIC and the Belgian Institute for Space Aeronomy. These interim models provide improved temporal resolution and accuracy over AP-8/AE-8 for their respective regions as well as some statistical information. Planned future missions that will begin to address the shortcoming of data in the regions of space between low-Earth and geostationary orbits were also presented at the workshop. These missions include NASA's LWS Geospace Missions and the proposed Canadian Space Agency's Outer Radiation Belt Injection, Transport Acceleration and Loss Satellite (ORBITALS). ORBITALS will provide much-needed data in the slot region between the inner and outer radiation belts, while both missions will expand the equatorial coverage of data sets. The workshop thus pulled together the current space environment prediction capabilities and data sets, identifying the improvements since the development of the industry-standard AP-8 and AE-8 models, and presented future data sources. The attendees used this information to draft road maps and committed themselves to working together to obtain the resources and broader community support to reach their goal of developing replacement models. Jean-Marie Lauenstein is an electrical engineer with Muñiz Engineering, Inc., at NASA Goddard Space Flight Center in Greenbelt, Maryland.

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