Two ultrastable oscillators, a TUSO for the transmitter on the Huygens Probe and a RUSO for the receiver on the Cassini Orbiter, are being constructed as identical units within one and the same USO program in order to minimize costs. The contractor for this work is Daimler-Benz Aerospace (DASA), Satellite Systems Division, in Ottobrunn (near Munich), Germany. The DASA design concept is based on a space-qualified rubidium oscillator "physics package" supplied by Ball Efratom Elektronik GmbH. The TUSO/RUSO combination represents the first use of rubidium oscillators on a deep space planetary mission.
A total of six USO models are being built.
The single Structural, Thermal and Pyrotechnic Model (STPM) was
delivered for system testing on schedule in April 1994.
The two Electrical Models (EM), one TUSO and one RUSO,
were delivered in November 1994 to the System AIV (Assembly,
Integration and Verification) Program at DASA.
Three interchangable units of flight standard (FM) are presently
under fabrication: one TUSO FM, one RUSO FM, and one Qualification
Flight Spare (QFS) - a refurbished unit used for qualification testing
at unit level.