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 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-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) |
