https://cdn.earthdata.nasa.gov/conduit/upload/5182/KeywordsCommunityGuide_Baseline_v1_SIGNED_FINAL.pdf 23.6 2026-03-19T10:41:57.720Z https://gcmd.earthdata.nasa.gov/KeywordViewer/scheme/instruments/f01cb5c4-0ed4-4a83-8c0c-9b954fdb697e POSEIDON-2 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 FactsHeritage: Poseidon-1 radar altimeter (TOPEX/Poseidon)Instrument Type: Dual-frequency radar Altimeter (Ku-band and C-band)Scan Type: Fixed nadir-pointing beamTransmitted Pulse Width: 105 sPulse Repetition Frequency: 2100 Hz (1800 Hz for Ku-band and 300 Hz for C-band)Maximum Radio-Frequency OutputPower 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 cmMass: 52 kg (dual-frequency, dualconfiguration with one antenna)Power: 66 WDC Supply Bus: Unregulated 21\u201332 VDuty Cycle: 100%Thermal Operating Range: -5ý to 35ý CPointing Requirements (platform + instrument, 3Ã): Control (Satellite): 0.33ý; Knowledge: < 0.1ýGroup: 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_GroupEnd_Group