Robin sphere

From Glossary of Meteorology

robin sphere

An inflatable sphere released at apogee from a sounding rocket.

The sphere is inflated by evaporation of a contained liquid on release. A corner reflector is ejected as the sphere inflates, permitting track during descent by a precision radar. Winds and density data are derived from the position and fall velocity of the sphere. ("Robin" is an acronym for "rocket-balloon-instrument.")