Introduction to special section on the Phoenix Mission: Landing site characterization experiments, mission overviews, and expected science

Phoenix, the first Mars Scout mission, capitalizes on the large NASA investments in the Mars Polar Lander and the Mars Surveyor 2001 missions. On 4 August 2007, Phoenix was launched to Mars from Cape Canaveral, Florida, on a Delta 2 launch vehicle. The heritage derived from the canceled 2001 lander with a science payload inherited from MPL and 2001 instruments gives significant advantages. To manage, build, and test the spacecraft and its instruments, a partnership has been forged between the Jet Propulsion Laboratory, the University of Arizona (home institution of principal investigator P. H. Smith), and Lockheed Martin in Denver; instrument and scientific contributions from Canada and Europe have augmented the mission. The science mission focuses on providing the ground truth for the 2002 Odyssey discovery of massive ice deposits hidden under surface soils in the circumpolar regions. The science objectives, the instrument suite, and the measurements needed to meet the objectives are briefly described here with reference made to more complete instrument papers included in this special section. The choice of a landing site in the vicinity of 68°N and 233°E balances scientific value and landing safety. Phoenix will land on 25 May 2008 during a complex entry, descent, and landing sequence using pulsed thrusters as the final braking strategy. After a safe landing, twin fan-like solar panels are unfurled and provide the energy needed for the mission. Throughout the 90-sol primary mission, activities are planned on a tactical basis.