Aquarius Project
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| Aquarius Project | |
|---|---|
| Name | Aquarius Project |
| Mission type | Earth science |
| Operator | NASA / CONAE |
| Launch date | June 2011 |
| Launch vehicle | Delta II |
| Orbit | Low Earth orbit |
| Instrument | radiometer/salinity sensor |
| Manufacturer | NASA Jet Propulsion Laboratory / CONAE |
| Launch site | Vandenberg Air Force Base |
Aquarius Project
The Aquarius Project was a collaborative NASA–Comisión Nacional de Actividades Espaciales (CONAE) satellite mission designed to measure global sea surface salinity from space. It aimed to link oceanographic processes observed by Argo floats, surface fluxes studied by TAO/TRITON, and climate variability monitored by TOPEX/Poseidon and Jason series, providing a synoptic perspective used by NOAA, National Oceanography Centre, and academic institutions worldwide.
Overview
Aquarius combined microwave radiometry and scatterometry heritage from missions such as SMOS and SMAP to quantify surface salinity signals influenced by freshwater input from Amazon River discharge, precipitation associated with El Niño–Southern Oscillation, and evaporation linked to subtropical gyres studied by Sverdrup Commission-era oceanographers. The project was a joint effort between NASA and CONAE, with instrumentation and science leadership from NASA Jet Propulsion Laboratory, participation by Caltech, and data stewardship involving NOAA National Centers for Environmental Information and the European Space Agency community. Aquarius supported applications in research programs carried out by teams at Woods Hole Oceanographic Institution, Scripps Institution of Oceanography, and universities in United States, Argentina, and Spain.
History and Development
The concept originated in proposals to the Earth Science and Applications from Space program and evolved alongside proposals for the Hydrosphere State (HYDROS) mission and follow-ons to Aqua. Early design studies referenced technological advances from the Microwave Imaging Radiometer with Aperture Synthesis project and lessons learned from the SeaWinds scatterometer on QuikSCAT. Formal partnership between NASA and CONAE was established in the 2000s, with hardware responsibilities split among NASA Jet Propulsion Laboratory, CONAE, and industrial partners in United States and Argentina. Launch on a Delta II vehicle placed Aquarius into a sun-synchronous orbit in 2011, following integration and testing at Vandenberg Air Force Base and final calibration campaigns involving shipborne salinometers coordinated with Global Drifter Program assets.
Objectives and Scientific Goals
Primary objectives included producing global maps of sea surface salinity to characterize regional and basin-scale salinity variability, quantify freshwater fluxes from major river plumes such as the Amazon River and Ganges River, and examine salinity-related signals associated with El Niño–Southern Oscillation and the Atlantic Meridional Overturning Circulation. Science goals targeted improved constraints for coupled models used by the Intergovernmental Panel on Climate Change and data assimilation systems at NOAA Climate Prediction Center and European Centre for Medium-Range Weather Forecasts. Aquarius aimed to support process studies at institutions like Lamont–Doherty Earth Observatory and Plymouth Marine Laboratory, and to provide validation datasets for satellite missions such as SMOS and SMAP while informing operational groups including Naval Research Laboratory.
Design and Instrumentation
Aquarius employed a microwave radiometer operating near the L-band frequency used by passive salinity sensors, influenced by heritage from SMOS and engineering developments at Jet Propulsion Laboratory. The instrument suite included a three-beam radiometer combined with a scatterometer-like active component to correct for surface roughness effects, drawing on techniques from SeaWinds and ERS scatterometry. The spacecraft bus incorporated avionics and power systems from contractors previously involved with Landsat and ICESat programs. Calibration relied on on-orbit references and coincident in situ observations from Argo floats, GLOSS tide gauges, and research cruises organized by International Council for the Exploration of the Sea. Ground systems at NASA Goddard Space Flight Center and CONAE processed telemetry and performed instrument health monitoring.
Mission Operations and Data Products
Operations were coordinated through mission control centers at NASA Jet Propulsion Laboratory and CONAE facilities, with routine science planning involving investigators from Caltech, Scripps Institution of Oceanography, and Woods Hole Oceanographic Institution. Aquarius produced geophysical data records including brightness temperature, retrieved sea surface salinity, quality flags, and ancillary geophysical corrections such as sea surface temperature from MODIS and wind speed from ASCAT. Data distribution followed open-access policies familiar from NASA Earth Observing System missions; processed Level 2 and Level 3 gridded salinity products were archived at NASA Distributed Active Archive Center partners and mirrored at CONAE archives, with validation datasets provided by Argo and shipboard CTD casts conducted by the UNESCO Intergovernmental Oceanographic Commission community.
Results and Impact
Aquarius delivered the first consistent global maps of sea surface salinity at L-band continuity between missions, revealing signals from the Amazon River plume, salinity anomalies tied to El Niño–Southern Oscillation, and seasonal variability in subtropical gyres. Results influenced data assimilation schemes at NOAA and ECMWF, and informed studies of hydrological cycle intensification discussed in IPCC Fifth Assessment Report. Publications by teams at Scripps Institution of Oceanography, Woods Hole Oceanographic Institution, Lamont–Doherty Earth Observatory, and Caltech demonstrated improved understanding of surface freshwater fluxes, coastal plume dynamics, and mesoscale salinity fronts. The mission legacy supported follow-on efforts such as SMAP salinity-related analyses and proposals for dedicated salinity missions within NASA and international partnerships, while datasets continued to be used by operational centers including NOAA National Centers for Environmental Information and academic modelers at University of California, San Diego and University of Southampton.