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Overview: Mission Basics

An example of 8 days of Aquarius Sea Surface Salinity (SSS) data.
An example of 100 days of Aquarius Sea Surface Salinity (SSS) data.
Aquarius is a mission of original exploration:
  • Sea Surface Salinity (SSS) has never been observed from space
  • Salinity has been sparsely detected at sea, limited mostly to summertime observations in shipping lanes: if you look at a map of Earth overlaid by 1° latitude by 1° longitude squares, about 25% of the grid over ice-free oceans have never been sampled
  • Aquarius will more data collect more data in two months than had been amassed by ships and in-water sensors during the 100 years before launch
  • Aquarius will be able to resolve global SSS changes from month-to-month, season-to-season, and year-to-year
The data-related goals of Aquarius are:
  • Provide the first global observations of SSS, covering Earth's surface once every 7 days
  • Deliver monthly 150-kilometer resolution SSS maps over a 3-year mission lifetime
  • Achieve SSS accuracy of 0.2 psu: this is about a "pinch" (i.e., 1/6 of a teaspoon) of salt in 1 gallon of water
The research-related goals of Aquarius include a better understanding of:
  • The water cycle - 86% of global evaporation and 78% of global precipitation occur over the ocean; thus SSS is the key variable for understanding how fresh water input and output affects ocean dynamics
  • Ocean circulation - With temperature, salinity determines seawater density and buoyancy, driving the extent of ocean stratification, mixing, and water mass formation
  • Climate - As computer models evolve, Aquarius will provide the essential SSS data needed to link the two major components of the climate system: the water cycle and ocean circulation
Download the mission overview foldout from NASA's priorities through the scientific return [2.1 MB PDF]
Download a two-page overview of Aquarius Mission objectives, instruments, timeline, and partners [1 MB PDF]

ocean scene

Glossary Words
buoyancy: The tendency or capacity to remain afloat in a liquid; the upward force that a fluid exerts on an object less dense than itself.

climate: The prevailing or normal pattern of weather at a place, or in a region, averaged over a long period of time; in contrast to weather, which is the state of the atmosphere at a particular time.

conductivity: A measure of the ability of a material to conduct or transmit an electric charge.

density: Mass per unit volume of a substance. Usually expressed as grams per cubic centimeter. For ocean water with a salinity of 35 at 0oC, the density is 1.028 grams per cubic centimeter.

dynamics: The physical forces that produce motion and change; the study of the relationship between motion and forces affecting motion.

evaporation: The physical process of converting a liquid to a gas. Commonly considered to occur at a temperature below the boiling point of the liquid.

fresh water: Non-saline water.

mixing: Combining or blending into one mass or mixture rendering the constituent parts indistinguishable.

model: System of data, inferences, and relationships, presented as a description of a process or entity.

practical salinity unit (psu): Used to describe the concentration of dissolved salts in water, the UNESCO Practical Salinity Scale of 1978 (PSS78) defines salinity in terms of a conductivity ratio, so it is dimensionless. Salinity was formerly expressed in terms of parts per thousand (ppt) or by weight (parts per thousand or 0/00). That is, a salinity of 35 ppt meant 35 pounds of salt per 1,000 pounds of seawater. Open ocean salinity is generally in the range from 32 to 37.

precipitation: Water released from the atmosphere in the form of rain, snow, hail, or sleet from the atmosphere onto Earth's surface.

resolution: The fineness of detail that can be distinguished in image, as on a computer screen or map.

salinity: A measure of the quantity of dissolved solids in ocean water. In general, salinity reflects the total amount of dissolved solids in ocean water in parts per thousand by weight after all carbonate has been converted to oxide, the bromide and iodide to chloride, and all the organic matter oxidized. Salinity is now measured as practical salinity units (psu).

stratification: Development of different layers; for example, the layering of seawater based on density.

system: 1) A regularly interacting or interdependent group of items forming a unified whole. 2) A manner of classifying. 3) A group of interacting bodies under the influence of related forces.

water mass: A body of water identifiable by its temperature, salinity, or chemical content.

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