have developed a program of complementary balloon-borne
experiments to measure the Cosmic Microwave Background
Radiation (CMBR) anisotropy on angular scales from 0.33
to 180 degrees between 2.3 and 23 icm (70 and 660 GHz
or 0.4 and 4.4 mm).
measurements have become increasingly important for
providing information on the initial conditions from
which the large-scale structure of the Universe has
evolved. The recent detections on large angular scales
by COBE and our FIRS experiment have completed the discovery
phase for CMBR anisotropy studies.
now enter a detailed measurement phase which promises
quantitative answers to some of the fundamental questions
of structure evolution in our Universe: How did matter
first distribute itself to eventually form the bubbles,
voids and galaxy clusters that we observe? What is the
amplitude of the quantum fluctuations which existed
before the Universe entered the `inflationary' epoch,
approximately 10-35 seconds after the Big
Bang? Is the bulk of the matter in the Universe composed
of a new kind of non-baryonic, nonluminous matter, as
proposed by Cold Dark Matter theories? These questions
have guided us to formulate the following program of
current and planned experiments.