CASSINI
The remarkable accomplishments yet to be uncovered by the Cassini mission to the Saturn system will be as significant as any deep space mission sponsored by JPL. APL built and delivered the USO on the main satellite for the purpose of radio science and study of propagation effects. This USO is stable to the 8 x 10^-14 level over a 10 second integration period. The reliability of precision quartz resonators and the inherent ruggedness of the USO design supports great assurance in these type of missions.

COBE
The suite of experiments on the COsmic Background Explorer were designed to examine the microwave signature of the Big Bang remnant to look for fluctuations from an ideal black body radiator. The results of COBE’s measurements of this radiation have substantially narrowed the model of the universe’s expansion and established significant foundations to 21st Century cosmology. APL built USOs for COBE’s radio receiver and data converters.

GRACE
APL designed and built a quartet of ultra-stable quartz oscillators for NASA/JPL for their Gravity Recovery and Climate Experiment (GRACE) mission launched March 17, 2002 . The science objective of the GRACE mission is to improve the global model for geopotential by measuring the relative velocity between two satellites in the same orbit. This difference in velocity can be interpreted as the difference in gravitational potential between the satellites. NASA expects to achieve millimeter-ranging accuracy using APL's oscillators.

Mars Global Surveyor
Launched in 1996, Mars Global Surveyor (MGS) is currently orbiting Mars and continues to collect science data. The radio science capability is enabled by the JHU-APL built USO.

TOPEX
Launched in 1992 into Earth orbit, TOPEX continues to monitor our oceans giving insight into El Ninos and other weather patterns. The JHU-APL Frequency Reference Unit (FRU) provides frequency references for the altimeter and timekeeping functions on the spacecraft.