Charlotte Harbor

Since the International Space Station became operational in November 2000, astronauts on board have taken more than 600,000 images of the Earth’s land surface, oceans, atmospheric phenomena, and even images of the Moon from orbit using handheld film and digital cameras as part of the Crew Earth Observations experiment.

Despite this large volume of imagery and clear capability for Earth remote sensing, the space station historically has not been perceived as an Earth observation platform by many remote sensing scientists. With the installation of new facilities and sophisticated sensor systems on the International Space Station over the past two years—and more to come—this perception is changing.

So what can the station offer in terms of Earth remote sensing that free-flying, robotic satellite systems cannot?

Images With a Variety of Lighting Conditions

Unlike many of the traditional Earth observation platforms, the station orbits the Earth in an inclined equatorial orbit that is not sun-synchronous. This means that the station passes over locations on the Earth between 52 degrees north and 52 degrees south latitude at different times of day and under varying illumination conditions. Remote satellite-based Earth observing sensors are typically placed on polar-orbiting, sun-synchronous platforms like Landsat7 or Terra in orbits designed to pass over the same spot on the Earth’s surface at approximately the same time of day. These satellite platforms will revisit a location about every two weeks. While collecting imagery in similar lighting conditions is good for producing uniform data for a specific place, it restricts the time that data is collected (near local solar noon in most cases). If a scientist is interested in a surface process that typically happens in the early morning or late in the afternoon (for example, patterns in coastal fog banks), the data will be difficult to collect from the polar-orbiting, sun-synchronous satellites.