As defined by the President's Panel on Ocean Exploration (NOAA, 2000), exploration is discovery through disciplined, diverse observations and the recording of findings. Exploration is an early component of the research process; it focuses on new areas of inquiry and develops descriptions of phenomena that inform the direction of further study.
NASA is the exploration agency of the Federal Government. NASA Earth observing satellites often open up new vistas for earth science research. All are meant to explore the envelope of what is known and understood about the physical, chemical and biological processes of the planet.
No suite of NASA Earth Science missions more exemplify the spirit of exploration than the Earth System Science Pathfinder (ESSP) missions. These missions generally try to measure a geophysical parameter that has been poorly sampled or unattainable from in situ platforms and bring to bear new cutting-edge technology to address the problem.
Two NASA ESSP missions address ocean exploration right now. First, the Gravity Recovery and Climate Experiment (GRACE) currently on orbit is exploring hitherto undetectable variations in the mass field of the ocean - important for climate and ocean circulation studies. Second, the Aquarius mission to be launched in 2008 will explore the salinity of the ocean from space. Historically, salinity measurements have been difficult to make in situ and so our knowledge of the spatial and temporal variability of ocean salinity is quite poor. Using microwave remote-sensing technology Aquarius will "reveal" for the first time the detailed patterns of salinity at the surface of the ocean. Ocean surface salinity is known to be an important, but poorly understood factor within
the climate system.
NASA supports the research and preparation of explorers for all its missions. For the ocean, the basic research programs in physical and biological oceanography support the background developments needed to launch new explorations of the ocean (from space).
Previous NASA explorations of the ocean have lead to knowledge and technology that is now used widely in research and application (ocean surface togography topography as measured by precision altimeters, ocean vector winds as measured by scatterometers, and ocean color as measured by radiometers are three excellent examples where NASA initiated the field through is exploration initiative).