|Instrument: USO : Ultra-Stable Oscillator|
Earth Remote Sensing Instruments
Instrument Class: Passive Remote Sensing
Instrument Type: Positioning/Navigation
Instrument Subtype: Radio
Wavelength Keyword: Radio
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The Ultra-Stable Oscillator (USO) employs a temperature-stabilized "oven" to keep its output frequency as stable as possible. During Cassini's flight, telecommunications engineers calibrate the USO by observing it for a number of hours every few months. By maintaining records and formulating a model of how the USO's output frequency changes over time, the USO can provide for moderately accurate Doppler data for navigation and Radio Science.
[Summary provided by NASA.]
The GRACE Instrument Processing Unit (IPU) is part of the GRACE Instrument System (IS) consisting of an Ultrastable Oscillator (USO), a K-band Ranging Assembly (KBR), a Star Camera Assembly (SCA) and an Accelerometer (ACC). Most of these systems are fully redundant.
The function of the USO is to provide a stable reference clock for the K-band Ranging Assembly.
[Summary from GRACE IPU Specification Document (GFZ)]
Instrument Owner: USA/NASA