Cosmic ray experiments outside the Earth's atmosphere are
subject to severe restrictions on the mass of the
instruments. Therefore, it is important that the experimental
information that can be obtained per unit detector mass is
maximized. In this paper, tests are described of a thin (1.4
lambda_int deep) hadron calorimeter that was designed with this goal
in mind. This detector was equipped with two independent active
media, which provided complementary information on the showering
hadrons. It is shown that by combining the information from
these media it was possible to reduce the effects of the
dominant leakage fluctuations on the calorimeter performance.