Jason-2 is Five Years Old
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June 21, 2013
Thursday, June 20, 2013, marked the fifth anniversary of the launch of the Ocean Surface Topography Mission on the Jason-2 satellite (Jason-2) from Vandenberg Air Force Base in California. In just a few hours after its early morning launch, the spacecraft had made its first full revolution around Earth. The satellite has now made more than 25,550 orbits around our planet, keeping its highly accurate radar altimeter tuned to measure changes in the dynamic topography of our ocean. Day-by-day, month-by-month, and year-after-year, Jason-2 has continued to seamlessly add to the more than 20-year record of global sea surface height measurements begun by TOPEX/Poseidon in 1992. TOPEX/Poseidon and follow-on missions proved the usefulness of spaceborne radar altimeters for measuring sea surface height. These measurements have made a vast improvement in our understanding of ocean circulation and events such as El Niño and La Niña, which have global effects on weather and climate. With dedicated teams from research and operational agencies in the United States and Europe - NASA and NOAA in the U.S.; CNES and Eumetsat in Europe - Jason-2 is the first truly operational ocean radar altimetry mission. Data from the spacecraft are supporting the normal operation of oceanographic, weather and climate, fisheries, and recreational organizations. Organizations such as these, along with the Ocean Surface Topography Science Team are looking toward the launch of the Jason-3 satellite in 2013 to continue to provide and further extend this important dataset. It's hard to believe it has already been five years since the launch of Jason-2, but as the mission managers say, "Time flies when you are having fun!" / "Le temps passe vite lorsqu'on s'amuse !" Congratulations to the OSTM/Jason-2 mission teams and to the Ocean Surface Topography Science Team on this important milestone. Return to News Archive |
WASHINGTON
-- 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
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) 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 (JPL) 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:
and
NASA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
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