Viii. Gravitation Research Academic and Research Staff

In this region of the electromagnetic spectrum there is some important astrophysics, such as the spectral peak of the alleged 2.7" K isotropic cosmic black-body radiation, thermal radiation by interstellar and possibly intergalactic dust, as well as intense radiation from galactic centers, and doubtless other information concerning the early history of an evolving universe. An experiment carried out with a balloon-borne far infrared radiometer in the fall of 1969 indicated that the isotropic background radiation may not have a thermal spectrum and may be dominated by a strong line between 10 cm and 12 cm These results are tentative, since we were not able to vary several important parameters in the experiment. An improved radiometer is under construction which is scheduled to fly in the spring of 1971. Future flights will measure the spectrum of the isotropic background with a liquid helium-cooled lamellar grating interferometer that has -l I cm-1 resolution. Measurements of the smalland large-scale spatial isotropy of the background radiation are planned.