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

<https://gcmd.earthdata.nasa.gov/kms/concept/f01cb5c4-0ed4-4a83-8c0c-9b954fdb697e>
  ns0:resource [ ] ;
  ns0:altLabel [ ] ;
  skos:definition """Poseidon-2 is a nadir-looking radar altimeter that maps the topography of the sea surface. Derived from the Poseidon-1 (ALT) altimeter on Topex/Poseidon, it measures sea level, wave heights and wind speed determined from the shape and strength of the radar-return pulse. The altimeter emits a radar beam that is reflected back to the antenna from the Earth's surface. Poseidon-2 operates at two frequencies (13.6 GHz in the Ku-band, 5.3 GHz in the C-band) to determine atmospheric electron content, which affects the radar signal path delay. These two frequencies also serve to measure the amount of rain in the atmosphere.

Poseidon-2 was designed by Alcatel Space Industries (ASPI) for CNES Toulouse Space Center, and is essentially an improved version of the Poseidon-1 altimeter that flies on TOPEX/Poseidon. Poseidon-2 improves on Poseidon-1 by adding a second frequency at 5.3 GHz, changing to digital technology, and using a new more powerful rad-hard microprocessor. It makes these improvements while keeping the same compact mass and size as its predecessor.

Key Poseidon-2 Facts
Heritage: Poseidon-1 radar altimeter (TOPEX/Poseidon)
Instrument Type: Dual-frequency radar Altimeter (Ku-band and C-band)
Scan Type: Fixed nadir-pointing beam
Transmitted Pulse Width: 105 s
Pulse Repetition Frequency: 2100 Hz (1800 Hz for Ku-band and 300 Hz for C-band)
Maximum Radio-Frequency Output
Power to Antenna: 38.5 dBm (Ku-band); 44 dBm (C-band)
Transmission Frequency: 13.575 GHz (Ku-band), 5.3 GHz (C-band)
Dimensions: Radio Frequency Unit (RFU): 42.2 cm ý 24.6 cm ý 24.5 cm;
Power Control (PC) Unit: 26.8 cm ý 20.5 cm ý 24.9 cm
Mass: 52 kg (dual-frequency, dual
configuration with one antenna)
Power: 66 W
DC Supply Bus: Unregulated 21\\–32 V
Duty Cycle: 100%
Thermal Operating Range: -5ý to 35ý C
Pointing Requirements (platform + instrument, 3Ã): Control (Satellite): 0.33ý; Knowledge: < 0.1ý


Group: Instrument_Details
   Entry_ID: POSEIDON-2
   Group: Instrument_Identification
      Instrument_Category: Earth Remote Sensing Instruments
      Instrument_Class: Active Remote Sensing
      Instrument_Type: Altimeters
      Instrument_Subtype: Radar Altimeters
      Short_Name: POSEIDON-2
      Long_Name: JASON-1 RADAR ALTIMETER
   End_Group
   Group: Associated_Platforms
      Short_Name: JASON-1
   End_Group
   Group: Spectral_Frequency_Information
      Wavelength_Keyword: Microwave
      Spectral_Frequency_Coverage_Range: 38.5 dBm (Ku-band); 44 dBm (C-band)
   End_Group
   Online_Resource: http://sealevel.jpl.nasa.gov/technology/instrument.html
   Online_Resource: http://www.jason.oceanobs.com/html/missions/jason/instruments/poseidon2_uk.html
   Sample_Image: http://topex-www.jpl.nasa.gov/science/images/invest-jason-1-th.gif
   Creation_Date: 2007-04-16
   Group: Instrument_Logistics
      Data_Rate: 22.5 kbps
      Instrument_Start_Date: 2002-01-15
      Instrument_Owner: NASA
      Instrument_Owner: CNES
   End_Group
End_Group"""@en ;
  skos:prefLabel "POSEIDON-2"@en ;
  skos:inScheme <https://gcmd.earthdata.nasa.gov/kms/concepts/concept_scheme/instruments> ;
  skos:broader <https://gcmd.earthdata.nasa.gov/kms/concept/92ddaaca-40b2-4936-bc1a-28cc5743e8b8> ;
  a skos:Concept .

<https://gcmd.earthdata.nasa.gov/kms/concept/92ddaaca-40b2-4936-bc1a-28cc5743e8b8>
  skos:prefLabel "Radar Altimeters"@en ;
  a skos:Concept ;
  skos:narrower <https://gcmd.earthdata.nasa.gov/kms/concept/f01cb5c4-0ed4-4a83-8c0c-9b954fdb697e> .