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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)]
Group: Instrument_Details
Entry_ID: USO
Group: Instrument_Identification
Instrument_Category: Earth Remote Sensing Instruments
Instrument_Class: Passive Remote Sensing
Instrument_Type: Positioning/Navigation
Instrument_Subtype: Radio
Short_Name: USO
Long_Name: Ultra-Stable Oscillator
End_Group
Group: Associated_Platforms
Short_Name: GRACE
End_Group
Group: Spectral_Frequency_Information
Wavelength_Keyword: Radio
End_Group
Online_Resource: http://xenon.colorado.edu/grace.html
Creation_Date: 2007-02-06
Group: Instrument_Logistics
Instrument_Owner: USA/NASA
End_Group
End_Group
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