4.2.3.1.1. Poseidon-2

The Poseidon-2 altimeter is the main instrument on the Jason-1 mission. Derived from the Poseidon-1 altimeter on Topex/Poseidon, 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 (Credits CNES/Alcatel)

Function

Poseidon-2 measures range (the distance from the satellite to the Earth's surface), wave height and wind speed.

Principle

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-2 operates at two frequencies (13.6 GHz in the K_u 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-2, 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-1 (Aviso website)