P. Encrenaz

PRONAOS: a balloon-borne experiment for submillimeter radioastronomy with a 380-GHz heterodyne spectrometer

A balloon-borne observatory (PRONAOS) including a two meter telescope associated with a submillimeter heterodyne spectrometer for radioastronomy is supported by the French space agency (CNES) to prepare the future space programs in astrophysics. This instrument will be used to simultaneously detect the 368 GHz O2 and the 380 GHz H2O lines in the interstellar medium. Observations in this part of the spectrum require low atmospheric water vapor and oxygen molecule emission, so that the telescope will fly under a 1,000,000 m3 balloon at an altitude of approximately equals 37 km. The receiver, under development at Meudon Observatory, includes a SIS mixer using Nb/AlOx/Nb tunnel junctions operating at 4 K, a 6 GHz IF low-noise cooled preamplifier, a LO quasi-optically injected with a phase locked Gunn oscillator and two cascaded frequency multipliers. Noise temperature as low as 300 K has been obtained; less than 200 K is expected. An 800 MHz Acousto-Optical Spectrometer (AOS) is used for the high resolution (800 kHz) spectral analysis. The optimization of the frequency resolution of the spectrometer was obtained in the design and building of a new kind of Bragg cell in LiNbO3 centered at 2 GHz.

The search for the 7Be line at 478 keV and its implications

The search for the 7Be line at 478 keV with the OSSE telescope on board the COMPTON Gamma Ray Observatory (GRO) is described as well as i/ the search for the redshifted LiH line at 1.3 mm, ii/ their implications in cosmology, in chemical history of the Galaxy, in explosive nucleosynthesis models.