A very recent article is Scientific American provides more information about Planet Labs' plans for "continuous whole Earth imagery". The constellation of 28 Earth-imaging satellites called “Flock 1” which just rode into space Jan 9 is comprised of 28 “Doves” each weighing about five kilograms. As part of the payload on an Antares rocket the satellites are on their way to the International Space Station from which they will be individually launched into Earth orbits.
By the end of the month “Flock 1” will be in position to photograph the complete surface of the planet at a resolution of 3-5 meters per pixel. This will require storing the equivalent of a 10-terapixel image. Planet Labs plans for the satellites to provide near-continuous pictures of Earth’s surface. This will make Planet Labs the first to capture high-resolution whole-Earth images nearly continuously. Existing Earth observation satellites can provide higher resolution and more spectral range but they only photograph specific targets which are selected by customers and their revisit times are on the order of a day. In effect customers rent the use of a satellite to capture detailed images of very specific small areas of the Earth at particular times. Planet Labs' constellation will photograph the entire Earth's surface very frequently. According to Planet Labs continuous whole-Earth images have the potential to serve many purposes simultaneously, from a single set of data.