@prefix skos: <http://www.w3.org/2004/02/skos/core#> .
@prefix ns0: <http://gcmd.gsfc.nasa.gov/kms#> .

<https://gcmd.earthdata.nasa.gov/kms/concept/7561d126-2baf-4583-a6cc-f8159ebf8e94>
  skos:prefLabel "Radio"@en ;
  a skos:Concept ;
  skos:narrower <https://gcmd.earthdata.nasa.gov/kms/concept/06beae62-5db5-4e77-9326-0ee1debf2622> .

<https://gcmd.earthdata.nasa.gov/kms/concept/06beae62-5db5-4e77-9326-0ee1debf2622>
  ns0:altLabel [ ] ;
  skos:definition """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"""@en ;
  skos:prefLabel "USO"@en ;
  skos:inScheme <https://gcmd.earthdata.nasa.gov/kms/concepts/concept_scheme/instruments> ;
  skos:broader <https://gcmd.earthdata.nasa.gov/kms/concept/7561d126-2baf-4583-a6cc-f8159ebf8e94> ;
  a skos:Concept .