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The Whole Heliosphere Interval is an internationally coordinated observing and modeling effort to characterize the 3-dimensional interconnected solar-heliospheric-planetary system - a.k.a. the "heliophysical" system.

WHI observing campaigns begin with the 3-D solar structure from solar Carrington Rotation 2068, which runs from March 20 - April 16, 2008. Observations and models of the outer heliosphere and planetary impacts will extend beyond those dates as necessary; for example, the solar wind transit time to outer planets can take months. Specific dates are determined according to each science topic.

WHI will transpire during the International Heliophysical Year, on the 50th anniversary of the International Geophysical Year (IGY). IGY included the launch of Sputnik (the first spacecraft) and Explorer I, which brought the first scientific observations of space.

Now, 50 years later, we have observations of the outer reaches of the heliosphere, and we are poised to make great advances in our understanding of our extended heliophysical domain and our relationship with interstellar space. WHI will take full advantage of the 50 years of scientific progress of IGY by coordinating state-of-the-art models and observations to address the entire interconnected heliophysical system.

One solar cycle after the first Whole Sun Month campaigns, WHI will benefit from dramatic improvements in observations, including new 3-D measurements, higher temporal/spatial/spectral resolutions, and expanded synoptic observations from deep in the solar interior extending through the heliosphere to the Earth.

Ulysses Mission Orbit from Ulysses' Position Angle during Quadrature (with STEREO locations) by S. Suess and Giannina Poletto

WHI occurs during solar minimum, which optimizes our ability to characterize the 3-D heliosphere and trace the structure to the outer limits of the heliosphere. The Ulysses Mission will be completing its transit over the northern pole of the Sun, and the STEREO Mission will be in a configuration optimal for 3-D studies of the Sun and inner heliosphere. The five THEMIS spacecraft will likewise be in an ideal configuration to perform 3-D studies of the Earth's magnetosphere. Voyager I and II will continue their exploration of the outer heliosphere and termination shock, and in June 2008 Interstellar Boundary Explorer (IBEX) will begin to provide images and measurements of the heliosphere's 3-D structure. Truly this is a significant era in space observations! To add to these new 3-D capabilities, there are over 200 instruments and observatories participating in IHY Coordinated Investigation Programs, and these additional measurements from around the globe will ensure that the WHI integrated observations and models will give us a "new view" of the heliophysical system.

The heart of the WHI campaign is the study of the interconnected 3-D heliophysical domain, from the interior of the Sun, to the Earth, outer planets, and into interstellar space. The WHI Science Team has determined a set of scientific topics to be addressed by the observations and models.

Many participating observatories will be running a continuous "synoptic" set of observations, to provide baseline measurements of the heliophysical system. These synoptic observing programs will be run throughout WHI.

There are also scientific studies of focused topics that are ideally addressed in the context of global structures. targeted observing campaigns have been identified. These campaigns involve day-to-day coordination of observations of heliospheric sub-regions, to address specific scientific questions.

Another key strength of WHI is the involvement of theoretical models and simulations in planning the observations. Models are essential to complete the 3-D picture of the heliosphere, especially in connecting magnetic structures across the heliophysical system. By understanding the needs and limitations of current models, WHI's campaigns can be optimized for interpretation.

There is a comprehensive list of observatories, instruments and missions participating in WHI, and our Science Team welcome new observers and modelers who are interested in participating.