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Koller, Josef

Publications and source records attributed to Koller, Josef.

10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

IMPACT Project: Integrated Modeling of Perturbations in Atmospheres for Conjunction Tracking - A New Orbital Prediction Model to Avoid Collisions in Space

We are developing a new physics-based satellite drag model to accurately predict satellite paths and to prevent collisions in space. Institutional Computing resources have been used to develop a data assimilative thermospheric density model and employ Direct Simulation Monte Carlo calculations of the satellite drag coefficient.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2013

Modeling of the radiation belt megnetosphere in decisional timeframes

Systems and methods for calculating L* in the magnetosphere with essentially the same accuracy as with a physics based model at many times the speed by developing a surrogate trained to be a surrogate for the physics-based model. The trained model can then beneficially process input data falling within the training range of the surrogate model. The surrogate model can be a feedforward neural network and the physics-based model can be the TSK03 model. Operatively, the surrogate model can use parameters on which the physics-based model was based, and/or spatial data for the location where L* is to be calculated. Surrogate models should be provided for each of a plurality of pitch angles. Accordingly, a surrogate model having a closed drift shell can be used from the plurality of models. The feedforward neural network can have a plurality of input-layer units, there being at least one input-layer unit for each physics-based model parameter, a plurality of hidden layer units and at least one output unit for the value of L*.

79 ASTRONOMY AND ASTROPHYSICS↗