alti_sur_chassisThe Poseidon-3 altimeter is the main instrument on the Jason-2 mission. Derived from the Poseidon-1 altimeter on Topex/Poseidon and Poseidon-2 on Jason-1, it measures sea level, wave heights and wind speed. It operates at two frequencies and is also able to estimate atmospheric electron content.

Poseidon-2 being integrated on Jason-1. Poseidon-3 on Jason-2 is similar
(Credits CNES/Alcatel)


Poseidon-3 measures range (the distance from the satellite to the Earth’s surface), wave height and wind speed.



The altimeter emits a radar beam that is reflected back to the antenna from the Earth’s surface (see how altimetry works for details). Poseidon-3 operates at two frequencies (13.6 GHz in the Ku band and 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.

Technical data

Poseidon-3, or SSALT (for Solid State ALTimeter), uses solid-state amplification techniques.

Emitted Frequency (GHz) Dual-frequency (Ku, C) – 13.575 and 5.3
Pulse Repetition Frequency (Hz) 2060 interlaced {3Ku-1C-3Ku}
Pulse duration (microseconds) 105
Bandwidth (MHz) 320 (Ku and C)
Antenna diameter (m) 1.2
Antenna beamwidth (degrees) 1.28 (Ku), 3.4 (C)
Power (W) 7
Redundancy Yes
Specific features Solid-State Power Amplifier.
Dual-frequency for ionospheric correction,
High resolution in C band (320 MHz)

Further information on Jason-2 (Aviso website)