Glossary – O

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Oort Cloud

A spherical shell of cometary bodies believed to surround the sun far beyond the orbit of Pluto and from which some are dislodged when perturbed (as by a passing star) to fall toward the sun.

OPAG

Outer Planets Analysis Group

OPR

OSTP

Office of Science and Technology Policy

overarching

Dominating or embracing all else.