Radio
USO
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