  Robots with increasing autonomy progress our space exploration capabilities,
particularly for in-situ exploration and sampling to stand in for human
explorers. Currently, humans drive robots to meet scientific objectives, but
depending on the robot's location, the exchange of information and driving
commands between the human operator and robot may cause undue delays in mission
fulfillment. An autonomous robot encoded with a scientific objective and an
exploration strategy incurs no communication delays and can fulfill missions
more quickly. Active learning algorithms offer this capability of intelligent
exploration, but the underlying model structure varies the performance of the
active learning algorithm in accurately forming an understanding of the
environment. In this paper, we investigate the performance differences between
active learning algorithms driven by Gaussian processes or Bayesian neural
networks for exploration strategies encoded on agents that are constrained in
their trajectories, like planetary surface rovers. These two active learning
strategies were tested in a simulation environment against science-blind
strategies to predict the spatial distribution of a variable of interest along
multiple datasets. The performance metrics of interest are model accuracy in
root mean squared (RMS) error, training time, model convergence, total distance
traveled until convergence, and total samples until convergence. Active
learning strategies encoded with Gaussian processes require less computation to
train, converge to an accurate model more quickly, and propose trajectories of
shorter distance, except in a few complex environments in which Bayesian neural
networks achieve a more accurate model in the large data regime due to their
more expressive functional bases. The paper concludes with advice on when and
how to implement either exploration strategy for future space missions.

Robotics;Machine Learning