Aquarius Mission

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Aquarius Mission Surface Salinity from Space
Gary Lagerloef, Principal Investigator Yi Chao,
Project Scientist Eric Lindstrom, NASA Program
Scientist Eric Ianson, NASA Program Executive
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What this Briefing Covers

• What ocean salinity is
• Why it is important to measure it from satellite
• How we will measure it with the Aquarius mission
• Who is participating in the mission
• More information about the mission

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Project Overview

• Features
• Principal Measurement Sea Surface Salinity
• Coverage Ice-free ocean every 150 km (93 mi)
  monthly
• Science Ocean Circulation, Water Cycle, Climate
• Launch Date June 9, 2011, VAFB, California
  (Delta-II)
• Minimum Operational Life 3 years
• NASA Earth System Science Pathfinder (ESSP)
  Mission
• United States Argentina Partnership

• Science
• Observe seasonal and year-to-year sea surface
  salinity variations
• Investigate links between the water cycle, ocean
  circulation and climate
• Improve ocean models and climate prediction models

Aquarius/SAC-D is presently at the Laboratory for
Integration and Test (LIT) in Brazil
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On Orbit Animation
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What will Aquarius measure?
Sea Surface Salinity
Salt Concentration grams of dissolved salt per
kilogram of sea water Average surface salinity
is 35, range is 32 to 37 Salinity is now
measured by electrical conductivity using a
practical salinity scale Often we refer to
practical salinity units (psu), equivalent to
grams per kilogram
Salinity map from historical ship and buoy data
Mean 35 psu Aquarius Accuracy 0.2 psu
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The Earths Water Cycle
Ocean Salinity and the Global Water Cycle
Global salinity patterns are linked to rainfall
and evaporation Salinity variations are driven by
precipitation, evaporation, runoff and ice
freezing and melting The Atlantic is the saltiest
ocean due to excess evaporation
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Aquarius Mission Science
Salinity Links to Ocean Circulation and Climate
Salinity (along with temperature and therefore
density) drives the ocean circulation, known as
the great conveyor belt.
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Aquarius Accuracy

• Aquarius will detect small salinity changes
• of just 0.2 psu (2 parts in 10,000)
• over a months time
• over a 150 km (93 mile) square patch of ocean

0.2 psu change is the same as adding 1/8 tsp of
salt to a gallon of seawater.
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Salinity, the Missing Piece
Satellites already measure surface temperature,
solar energy, rainfall, evaporation, sea level,
surface wind, to infer ocean circulation, and
ocean color
Aquarius provides the key variable that links
ocean currents and temperature to the fresh water
cycle.
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How Aquarius Measures Salinity
Salinity is determined from microwave brightness
temperature and sea surface temperature
measurements
Brightness temperature variations are very small
Sea Surface Temperature (Celsius)

• The Aquarius instrument design required
  innovative new technologies
• Ultra stable calibration (0.1 Kelvin)
• Integrated microwave radiometer and radar to
  correct for sea surface roughness

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Mission Design and Sampling Strategy
Sun-synchronous exact repeat orbit 6pm ascending
node Altitude 657 km

• Global Coverage in 7 Days
• 4 Repeat Cycles per Month

Beams point toward the night side to avoid sun
glint
In Orbit Checkout
Aquarius will collect as much data during the
first few months of the mission as all previous
conventional ship and buoy measurements.
Launch
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Aquarius 150 km Resolution
Courtesy Y. Chao, JPL
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International Partnership
Satellite Observatory
United States Argentina and other agencies

• Service Platform and SAC-D (Satélite de
  Aplicaciones Cientificas) Science Instruments
• Mission Operations Ground System

• Aquarius Salinity Microwave Instrument
  (Instrument Ops Science Data Processing)
• Launch Vehicle

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Aquarius will address the links between ocean
circulation, the global water cycle and climate
Aquarius sea surface salinity will provide a key
missing link in satellite Earth observations
Aquarius applies innovative new instrument
technologies to obtain unprecedented measurement
accuracy
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Aquarius.nasa.gov
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Backup Material
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Water Cycle, Ocean and Climate
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Aquarius Mission Science
Salinity Links to Ocean Circulation and Climate.
Salinity (along with temperature and therefore
density) drives the ocean circulation, known as
the great conveyor belt.
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Ocean Salinity Trends Links to Water Cycle
Gordon and Giulivi, Oceanography, 21 (1), 2008
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Steps in Science Retrieval
In addition to the surface flat sea emission,
we must account for corrections due to the sky,
atmosphere, ionosphere, land and ice, and
especially surface roughness.
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Salinity Remote Sensing The Basics
Salinity is Derived by Measuring Brightness
Temperature at L-Band (1.413 GHz)
Microwave radiometers measure the emitted power
of a surface in terms of a parameter called the
radiometric brightness temperature (TB), which is
proportional to the ideal black body
radiation. TB is the product of emissivity (e)
and absolute surface temperature (T) in Kelvins
TBeT, where e0.3 for seawater e is a
function of, incidence angle ?, polarization H or
V, sea state and the dielectric coefficient e. e
depends on S, T, and radio frequency (f)
Klein Swift (1977) dielectric model at
microwave frequencies
Sensitivity increases with SST
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Resources for More Information
Oceanography Special Issue March 2008
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Relevance to National Research Programs
Aquarius is a satellite mission to measure
global sea surface salinity. over the global
oceans to a precision of 2 parts in 10,000.
Aquarius will answer long-standing questions
about how our oceans respond to climate change
and the water cycle, including changes in
freshwater input and output to the ocean
associated with precipitation, evaporation, ice
melting, and river runoff. These activities will
address Goals 12.1 and 12.5 of the CCSP Strategic
Plan. U.S. Climate Change Science Program for
FY-2007
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Observatory Configuration
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Specific measurements

• Global sea surface salinity measurements
  (Aquarius).
• Soil moisture (Aquarius).
• Measurements of precipitable water, sea ice
  concentration and sea surface wind speed (which
  will enhance the results of Aquarius
  measurements) (Microwave Radiometer-MWR).
• Measurements of water vapor, cloud liquid water.
  (Microwave Radiometer-MWR).
• Monitoring of hot spots caused by biomass fires
  and volcanic eruptions, estimation of fire
  radiative power (NIRST).
• Measurements of sea surface temperature (which
  also will enhance the results of Aquarius
  measurements in pilot areas) (NIRST).

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Specific measurements

• Measurements of light intensity (urban areas,
  detection of electric storms, snow coverage, sea
  surveillance and aurora studies) (HSC).
• Measurements of atmospheric temperature, pressure
  profiles, and water vapor content (ROSA).
• Measure the high energy radiation environment
  (ICARE).
• Measure the size distribution of micro- particles
  and space debris (SODAD).
• Collect environmental measured parameters (e.g.
  meteorological) (DCS)