Fwd: Jason-1 Ocean Satellite Takes Final Bow

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Date: July 4, 2013 10:34:21 AM GMT-06:00
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Long-Running Jason-1 Ocean Satellite Takes Final Bow

 

 

Artist's concept of the joint NASA/CNES Jason-1 ocean altimetry satellite. During its 11-1/2-year life, Jason-1 helped create a 20-plus-year climate record of global ocean surface topography, providing new insights into ocean circulation, tracking our rising seas and enabling more accurate weather, ocean and climate forecasts. Image credit: NASA/JPL-Caltech
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July 03, 2013

PASADENA, Calif. - The curtain has come down on a superstar of the satellite oceanography world that played the "Great Blue Way" of the world's ocean for 11-1/2 years. The successful joint NASA and Centre National d'Etudes Spatiales (CNES) Jason-1 ocean altimetry satellite was decommissioned this week following the loss of its last remaining transmitter.

Launched Dec. 7, 2001, and designed to last three to five years, Jason-1 helped create a revolutionary 20-plus-year climate data record of global ocean surface topography that began in 1992 with the launch of the NASA/CNES Topex/Poseidon satellite. For more than 53,500 orbits of our planet, Jason-1 precisely mapped sea level, wind speed and wave height for more than 95 percent of Earth's ice-free ocean every 10 days. The mission provided new insights into ocean circulation, tracked our rising seas and enabled more accurate weather, ocean and climate forecasts.

"Jason-1 has been a resounding scientific, technical and international success," said John Grunsfeld, associate administrator of NASA's Science Mission Directorate in Washington. "The mission met all of its requirements, performed an extended mission and demonstrated how a long-term climate data record should be established from successively launched satellites. Since launch, it has charted nearly 1.6 inches (4 centimeters) of rise in global sea levels, a critical measure of climate change and a direct result of global warming. The Jason satellite series provides the most accurate measure of this impact, which is felt all over the globe."

During parts of its mission, Jason-1 flew in carefully coordinated orbits with both its predecessor Topex/Poseidon and its successor, the Ocean Surface Topography Mission/Jason-2, launched in 2008. These coordinated orbit periods, which lasted about three years each, cross-calibrated the satellites, making possible a 20-plus-year unbroken climate record of sea level change. These coordination periods also doubled data coverage.

Combined with data from the European Space Agency's Envisat mission, which also measured sea level from space, these data allow scientists to study smaller-scale ocean circulation phenomena, such as coastal tides, ocean eddies, currents and fronts. These small-scale features are thought to be responsible for transporting and mixing heat and other properties, such as nutrients and dissolved carbon dioxide, within the ocean.

"Jason-1 was an exemplary and multi-faceted altimeter mission and contributed so much to so many scientific disciplines," said Jean-Yves Le Gall, CNES president in Paris. "Not only did Jason-1 extend the precise climate record established by Topex/Poseidon, it made invaluable observations for mesoscale ocean studies on its second, interleaved orbit. Even from its 'graveyard' orbit, Jason-1 continued to make unprecedented new observations of the Earth's gravity field, with precise measurements right till the end."

The in-orbit Jason-2 mission, operated by the meteorological agencies of the United States and Europe (the National Oceanic and Atmospheric Administration and EUMETSAT, respectively) in collaboration with NASA and CNES, is in good health and continues to collect science and operational data. This same U.S./European team is preparing to launch the next satellite in the series, Jason-3, in March 2015.

Contact was lost with the Jason-1 satellite on June 21 when it was out of visibility of ground stations. At the time of the last contact, Jason-1 and its instruments were healthy, with no indications of any alarms or anomalies. Subsequent attempts to re-establish spacecraft communications from U.S. and French ground stations were unsuccessful. Extensive engineering operations undertaken to recover downlink communications also were unsuccessful.

After consultation with the spacecraft and transmitter manufacturers, it was determined a non-recoverable failure with the last remaining transmitter on Jason-1 was the cause of the loss of contact. The spacecraft's other transmitter experienced a permanent failure in September 2005. There now is no remaining capability to retrieve data from the Jason-1 spacecraft.

On July 1, mission controllers commanded Jason-1 into a safe hold state that reinitialized the satellite. After making several more unsuccessful attempts to locate a signal, mission managers at CNES and NASA decided to proceed with decommissioning Jason-1. The satellite was then commanded to turn off its magnetometer and reaction wheels. Without these attitude control systems, Jason-1 and its solar panels will slowly drift away from pointing at the sun and its batteries will discharge, leaving it totally inert within the next 90 days. The spacecraft will not reenter Earth's atmosphere for at least 1,000 years.

"Like its predecessor Topex/Poseidon, Jason-1 provided one of the most comprehensive pictures of changes in the tropical Pacific Ocean, including the comings and goings of El Nino and La Nina events," said Lee-Lueng Fu, Jason-1 project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "These Pacific Ocean climate cycles are responsible for major shifts in sea level, ocean temperatures and rainfall every two to five years and can sometimes be so large that worldwide weather patterns are affected. Jason-1 data have been instrumental in monitoring and predicting these ever-changing cycles."

In the spring of 2012, based on concern over the limited redundancy of Jason-1's aging control systems, NASA and CNES moved the satellite into its planned final "graveyard" orbit, depleted its extra fuel and reconfigured the mission to make observations that will improve our knowledge of Earth's gravity field over the ocean, in addition to delivering its oceanographic data products.

The first full 406-day marine gravity mission was completed on June 17. The resulting data have already led to the discovery of numerous small seamounts, which are underwater mountains that rise above the deep-sea floor. The data also have significantly increased the resolution of Earth's gravity field over the ocean, while increasing our knowledge of ocean bathymetry, which is the underwater depth of the ocean floor.

JPL manages the U.S. portion of the Jason-1 mission for NASA's Science Mission Directorate. CNES manages the French portion of the mission.

For more information on Jason-1, visit: http://sealevel.jpl.nasa.gov and http://www.aviso.oceanobs.com .

The California Institute of Technology in Pasadena manages JPL for NASA.

Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov

Steve Cole 202-358-0918
NASA Headquarters, Washington
Stephen.e.cole@nasa.gov

Julien Watelet 011-33-6-88-06-11-48
Centre National d'Etudes Spatiales, Paris, France
Julien.watelet@cnes.fr

2013-213

Images

Jason-1 contributed to this 20-year data record of the global mean sea level change, providing the first direct measurement of this important indicator of global climate change. Jason-1 data (shown in green) were cross-calibrated with its predecessor, the NASA/CNES Topex/Poseidon satellite, and its successor, the NASA/CNES/NOAA/EUMETSAT Ocean Surface Topography Mission (OSTM)/Jason-2 satellite. This first ever cross-calibration of altimeter missions allows scientists to maintain a consistent climate data record built by successive missions using mixed technologies. Image credit: University of Colorado
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Regional changes in sea level based on the 19-year trend from 1993 through 2012, as measured using radar altimeter data from several satellites, including the NASA/CNES Jason-1 mission. Reds and purples represent the largest increases in sea level, with blues representing the largest decreases. These changes reflect the impact of decadal-scale climate variability on the regional distribution of sea level rise. Image credit: University of Colorado
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Ocean satellite dies after 11½-year mission

Associated Press

 

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Associated Press - FILE -This undated artist's rendering shows the Jason-1 satellite. The U.S.-French science satellite that tracked rising sea levels for more than a decade and helped forecasters make better …more 

PASADENA, Calif. (AP) — Jason-1, a satellite that for more than a decade precisely tracked rising sea levels across a vast sweep of ocean and helped forecasters make better weather and climate predictions, has ended its useful life after circling the globe more than 53,500 times, NASA announced Wednesday.

The joint U.S. and French satellite was decommissioned this week after its last remaining transmitter failed, according to a NASA statement.

Launched on Dec. 7, 2001, Jason-1 was designed to have a lifespan of three to five years but it lasted for 11 ½ years.

Every 10 days, its instruments scanned the ocean surface, mapping sea level, wind speed and wave height for more than 95 percent of the planet's ice-free ocean area. It was one of three oceanographic satellites that contributed to a 20-year record of sea-level changes, NASA said.

"Jason-1 has been a resounding scientific, technical and international success," said John Grunsfeld, associate administrator of NASA's Science Mission Directorate in Washington.

Since its launch, Jason-1 recorded a rise of nearly 1.6 inches in global sea levels that are "a critical measure of climate change and a direct result of global warming," Grunsfeld said in a statement. "The Jason satellite series provides the most accurate measure of this impact, which is felt all over the globe."

Last year, the 1,100-pound satellite was moved into a final "graveyard" orbit where, its extra fuel depleted, it was assigned to observe Earth's gravity field over the ocean, NASA said.

A 406-day scan completed on June 17 led to the discovery of many underwater seamounts and increased knowledge of the depth of the ocean floor, researchers said.

"Even from its 'graveyard' orbit, Jason-1 continued to make unprecedented new observations of the Earth's gravity field, with precise measurements right till the end," said Jean-Yves Le Gall, president of France's Centre National d'Etudes Spatiales in Paris.

Contact with the satellite was lost on June 21 and efforts to re-establish it failed. On Monday, the satellite was ordered to turn off its attitude control systems. Jason-1 will slowly turn away from the sun and its solar-powered batteries will drain within the next 90 days, NASA said.

Jason-1 will remain in orbit for at least 1,000 years before it falls back into Earth's atmosphere, NASA said.

Jason-1 was one of three oceanographic satellites that carried a radar altimeter and bounced radio pulses off the Earth, enabling sea surface height to be determined to within a few centimeters.

Sea surface height changes with temperature so altimeter measurements are means to determine how much heat is stored in any given area of the ocean and how that changes.

From the data, scientists have improved their models of ocean circulation and monitored events such as El Nino, where large masses of warm water pool in the eastern Pacific Ocean.

"These Pacific Ocean climate cycles are responsible for major shifts in sea level, ocean temperatures and rainfall every two to five years, and can sometimes be so large that worldwide weather patterns are affected. Jason-1 data has been instrumental in monitoring and predicting these ever-changing cycles," said Lee-Lueng Fu, Jason-1 project scientist at NASA's Jet Propulsion Laboratory in Pasadena.

Jason-1 worked in tandem with and then replaced Topex-Poseidon, which was launched in 1992 and was decommissioned in 2006.

Jason-2 was launched in 2008 and is still operating. Another satellite, Jason-3, is scheduled for launch in March 2015.

The satellite data was combined with information from the European Space Agency's Envisat mission, which also measured sea level from space.

 

Copyright © 2013 The Associated Press. All rights reserved. 

 

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