April 14, 2011

Satellites You Need to Know: Jason-1, Jason-2 and the Ocean

The Jason-1 and Jason-2 satellites were built and run by
France and the United States and launched on December 7, 2001 and June 20, 2008
respectively. As the successor
satellites to the TOPEX/POSEIDON
mission that began in 1992, the Jason satellites
were designed to study the ocean. To this end, the satellites capture images of approximately 90
percent of the
non-ice ocean surface every 10 days.  

This is an important mission for understanding climate
change, as the oceans are an essential component of the Earth’s climate
equation. As a
NASA publication on Jason-2 notes
, “The ocean acts as Earth’s thermostat,
storing energy from the sun and keeping Earth from heating up quickly.” This
makes the ocean, “the
single most important influence on Earth’s weather and climate.

The Jason satellites monitor different aspects of the ocean.
The central task of the Jason satellites is to map ocean surface topography. Ocean
surface topography is defined as, “the height of the
earth surface relative to Earth’s geoid
(a hypothetical Earth surface that
represents the mean sea level if there were no winds, currents and most tides).”
To simplify, the satellites capture the height of the mountains in the ocean,
as well as the depths of ocean valleys.

But beyond this central task, the Jason mission provides
data that can be utilized for a number of other functions. For example, the Jason
satellites monitor wave height and speed which
allows meteorologists to more accurately predict the weather
. More
pertinent to our natural security audience, the Jason satellites also track the
average sea level of the ocean to the nearest millimeter. Along with the data
collected by the TOPEX/Poseidon mission, this has given scientists data on sea
level rise for nearly two decades, allowing them to better understanding how
climate change is affecting Earth.

This last mission, calculating average sea level, highlights
the importance of having time series data that requires uninterrupted monitoring
over a number of years. To have a constant flow of data, it is essential that
the mission receives continuous funding to build a new satellite and launch
into orbit before the previous one has run its course. Fortunately, in this
regard, the Jason mission seems set to continue in the coming years. In February
2010, France and the United States signed a contract that
agreed to have a Jason-3 satellite
replace Jason-1 in 2013.

Jason-2 launches at Vandenberg Air Force Base in California on June 20, 2008. Courtesy of Carleton Bailie and the United Launch Alliance.