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Home , Ocean surface topography, Sea level, Tide clock

Ocean Surface Mission/Jason 2

While our small cosmic outpost is called , currents carry heat away from Earth’s equatorial it might more aptly be called , since ocean regions toward its icy poles. Just as blow covers more than 70 percent of our planet. Be- around the extensive highs and lows of atmo- sides being the source of our life-sustaining spheric surface , these ocean currents and providing food for Earth’s inhabitants, the circulate in enormous “gyres” around regions of ocean acts as Earth’s thermostat, storing energy raised or lowered level—the hills and valleys from the and keeping Earth from heating up of . The heat carried by quickly. In fact, the ocean stores the same amount these currents is slowly released into the atmo- of heat in its top three meters (10 feet) alone as sphere, regulating our . Earth’s entire atmosphere does. Heat and mois- By bouncing a radar signal off the surface of the ture from this great reservoir are constantly being ocean from a and precisely measuring exchanged with our atmosphere in a process that how long it takes the signal to return, scientists drives our weather and climate. can map the topography of the ocean surface to Looking out at the ocean, it’s hard to imagine it within a few centimeters. Accurate observations of as anything but flat. Yet from space we can see variations in ocean surface topography tell a larger that it has hills and valleys too, as do Earth’s con- story about the ocean’s most basic functions—how tinents. These hills and valleys can vary globally it stores vast amounts of energy from the sun by up to two meters (6.5 feet) in from one and how it moves that energy around the globe region to the next. These small departures of the through ocean currents. Understanding where sea surface from a level surface are called ocean this heat is and how it moves within the ocean as surface topography, which is caused by large- currents and into the atmosphere are critical to scale ocean currents. understanding global climate. Driven by blowing winds that pile up or depress the ocean surface, and directed by the Mission Overview force (an Earth rotational effect that deflects ocean The international OSTM/Jason 2 satellite mis- currents to the right in the Northern Hemisphere sion will extend into the decade of the 2010s the and to the left in the Southern Hemisphere), ocean continuous climate record of precise sea surface height measurements begun in 1992 by the joint NASA/Centre change with time National d’Etudes Spatiales (CNES) Topex/Poseidon mission Measure global change and continued in 2001 by the NASA/CNES Jason 1 mission. Improve ocean models, including coastal Data from this new mission will be used to help scientists better understand the strong relationship between ocean circulation Payload Overview and climate. The mission will also monitor the slow, steady OSTM/Jason 2 will carry five primary science instruments rise in global sea level, one of the most important indicators of that are similar to or upgraded versions of those flown on global . Jason-1: Data from OSTM/Jason 2 will help scientists such as meteo- The Poseidon 3 , provided by CNES, is the rologists, oceanographers and climatologists better understand mission’s main instrument. It measures the distance from the how the ocean interacts with Earth’s atmosphere and conti- satellite to Earth’s surface by sending radar waves to the sea nents to control and change our climate. Information collected surface and measuring how long they take to bounce back. It from OSTM/Jason 2 will help us improve predictive models also calculates the speed of ocean surface currents and pro- of Earth’s ocean and atmosphere and will also help improve vides data on and speed. hurricane forecasts. It will also allow us to identify and track The Advanced Microwave Radiometer, provided by NASA, large ocean/atmosphere phenomena such as El Niño, La Niña, measures the amount of water vapor in the atmosphere, which and climate oscillations that operate on time scales spanning can delay the return of radar pulses to the satellite, interfering multiple decades. with sea level measurement accuracy. OSTM/Jason 2 will serve as a bridge to transfer future col- Three location-finding systems are used to measure the lection of these measurements to the world’s weather and spacecraft’s precise position in orbit: the Doppler Orbitography climate forecasting agencies. These agencies will use the data and Radio-positioning Integrated by Satellite (Doris) provided for short- and seasonal-to-long-range weather and climate by CNES; the Global Positioning System Payload, provided forecasting. by NASA; and the Laser Retroreflector Array, also provided by OSTM/Jason 2 data will be used in a variety of everyday NASA. applications such as routing ships, improving the safety and ef- Advances in OSTM/Jason 2’s instruments will allow scientists ficiency of offshore industry operations, managing fisheries and to monitor the ocean in coastal regions with increased ac- tracking marine mammals. curacy, almost 50 percent closer to coastlines than previously possible. Launch and Orbit Three “passenger,” or experimental, instruments will also OSTM/Jason 2 will be launched on a United Launch Alliance be flown on OSTM/Jason 2. In addition to their own scientific Delta II launch vehicle from California’s Vandenberg Air Force objectives, these instruments are expected to improve the Base. The spacecraft will orbit at an of 1,336 kilome- performance of the Doris location-finding system: ters (830 miles), the same orbit as Jason 1, where it will map The Environmental Characterization and Modelisation-2 95 percent of the world’s ice-free every 10 days. Once (Carmen-2), provided by CNES, will study the effects of radia- OSTM/Jason 2 is in place and its data have been calibrated tion in the satellite’s environment on advanced components. and validated, Jason 1 will be moved into a parallel ground The Time Transfer by Laser Link instrument, provided by track midway between two OSTM/Jason 2 ground tracks and CNES, will use a laser link to compare and synchronize remote the two spacecraft will conduct a tandem mission that will ground clocks with high accuracy. further improve tide models in coastal and shallow and The Light Particle Telescope, provided by Japan, will study improve our understanding of the dynamics of ocean currents radiation in the satellite’s environment. and eddies. Partners Mission Duration OSTM/Jason 2 is a collaboration among NASA; the National OSTM/Jason 2 is designed to operate for at least three Oceanic and Atmospheric Administration (NOAA); CNES; and years. At the end of that time, if useful data are still being the European Organisation for the Exploitation of Meteorologi- collected, the mission may be extended by two years, or any cal (EUMETSAT). CNES is providing the spacecraft, additional period agreed upon by the mission partners. NASA and CNES are jointly providing the payload instruments, and NASA’s Launch Services Program at the Kennedy Space Science Objectives Center is responsible for Delta II launch management and Extend the time series of ocean surface topography mea- related services. After completing on-orbit spacecraft com- surements beyond Topex/Poseidon and Jason 1 to complete missioning, CNES will hand over operation and control of the two decades of high-precision altimetry observations spacecraft to NOAA. NOAA and EUMETSAT will generate the Determine how ocean circulation varies over long time near-real-time products and distribute them to users. NASA’s periods using the combined data record from Topex/Poseidon Jet Propulsion Laboratory, Pasadena, Calif., manages the mis- and Jason 1 sion for NASA’s Science Mission Directorate, Washington. Improve the knowledge of ocean circulation that does not

National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, Calif. 91109

NASA Facts

2008-05-19