Jason-3 Design

On the Proteus platform, Jason-3 will be carrying a payload of several instruments : the Poseidon-3B altimeter, the AMR radiometer, three location systems and two experimental instruments.

Jason-3 showing instruments

The primary instrument on Jason-3 is a radar altimeter. The altimeter will measure sea-level variations over the global ocean with very high accuracy (1.3 inches or 3.3 centimeters, with a goal of achieving 1 inch or 2.5 centimeters).

Continual, long-term, reliable data of changes in ocean surface topography will be generated and will be used by scientists and operational agencies for scientific research and operational oceanography for the benefit of society.

Payload instruments

Poseidon-3 Altimeter

The Poseidon-3B (supplied by Europe), is the mission's main instrument, derived from the altimeters on Jason-1 and Jason-2. It allows measurement of the range (the distance from the satellite to the Earth's surface), wave height and wind speed. This new altimeter implements a mixed mode allowing on-board automatic transitions between the Diode/DEM mode and the acquisition/tracking mode with respect to the satellite position. Jason-3 will autonomously switch between the two altimeter modes, to improve measurements over coastal areas, inland waters and ice.

Advanced Microwave Radiometer (AMR)

The AMR (supplied by the US) measures radiation from the Earth's surface. Each frequency is combined to determine atmospheric water vapour and liquid water content. Once the water content is known, the correction to be applied for radar signal path delays is determined. Following lessons learned from Jason-2, some minor designs changes have been made and improvements made to the instrument thermal control and stability.

Location systems

Doppler Orbitography and Radio-positioning Integrated by Satellite (DORIS)

DORIS (supplied by Europe) uses a ground network of 60 orbitography beacons around the globe, which send signals, in two frequencies, to a receiver on the satellite.

The relative motion of the satellite generates a shift in the signal's frequency (called the Doppler shift) that is measured to derive the satellite's velocity.

These data are then assimilated into an orbit determination models to keep permanent track of the satellite's precise position (to within three centimetres) in its orbit.

Following lessons learned from Jason-2 improvements in modelling solar panels position have be made. Current model improvements will be integrated — albedo and infrared pressure, ITRF 2008, pole prediction, Hill along-track empirical acceleration and on-board USO frequency prediction — allowing for a more accurate Diode navigation tool.

Global Positioning System Payload (GPSP)]

The GPSP (Global Positioning System Payload) (supplied by the US) uses the Global Positioning System (GPS) to determine the satellite's position by triangulation.

At least three GPS satellites are needed to establish the satellite's exact position at a given instant.

Positional data are then integrated into an orbit determination model to continuously track the satellite's trajectory.

On Jason-3 it will be a different receiver but with the same basic (blackjack) design as on Jason-1 and 2. There won't be any changes to data processing or products. Performance is expected to be the same as, or better than, Jason-2.

Laser Retroreflector Array (LRA)]

The LRA (supplied by the US) is an array of mirrors that provide a target for laser tracking measurements from the ground. By analysing the round-trip time of the laser beam, we can locate where the satellite is in its orbit and calibrate altimetric measurements.

Passenger instruments

The Environment Characterization and Modelisation-3 or Carmen-3 (supplied by CNES) is a dosimeter used to improve knowledge of particularly aggressive radiation in Jason's orbit (Doris, electronic risk assessment).

The Light Particle Telescope (LPT) is an another dosimeter, provided by JAXA and CNES.

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