Surface operations are planned in relation to martian days, which are known as sols. Because Mars rotates slightly slower than Earth, sol is 40 minutes longer than our planet's 24-hour day. A strategic plan is created that outlines operations two weeks into the future. This strategic plan is used to create a more detailed tactical plan which decides surface activities that will take place for the next two sols. Daily science and engineering data is used to assess the status of the strategic and tactical plans, and the plans are updated as necessary.
The sophisticated landing system on Phoenix allows the spacecraft to touch down within 10 km (6.2 miles) of the targeted landing area. Thrusters are started when the lander is 570 m (1900 feet) above the surface. The navigation system is capable of detecting and avoiding hazards on the surface of Mars. (Artist Rendition: Corby Waste of the Jet Propulsion Laboratory)
Immediately after Phoenix touches down on the surface of Mars (sol 0), critical instruments such as the solar arrays and SSI mast are deployed. Later in the afternoon of sol 0, EDL data and MARDI images are sent to Earth. On sol 1, TEGA, MECA and RAC are turned on and checked out, and the RA is deployed. SSI begins taking images of the landing site and the area where the robotic arm will be digging, and MET begins to sample the weather at the landing site.
On sols 2 through 9, the instruments aboard Phoenix continue to take initial measurements. TEGA takes measurements of the martian atmosphere using its mass spectrometer. The RA acquires a sample of martian soil and delivers it to TEGA on sol 4. This sample is analyzed by the differential scanning calorimeter in TEGA on the following sol. Another sample is delivered on sol 7 for analysis using MECA.
The Phoenix Lander begins to shut down operations as winter sets in. The far northern latitudes on Mars experience no sunlight during winter. This marks the end of the mission because the solar panels can no longer charge the batteries on the lander and the frost covering the region as the atmosphere cools will bury the lander in ice. (Artist Rendition: Corby Waste of the Jet Propulsion Laboratory)
The digging operations phase is planned to take place on sols 10-90. SSI and RAC images will be analyzed to determine where the RA should dig. Phoenix will dig for up to 2.5 hours per sol during this period. As the RA digs into the martian surface, SSI and RAC images will help determine when new samples should be delivered to the scientific instruments on Phoenix. Samples will be delivered to TEGA about every 15 cm (5.9 in) or when layering is obvious. The four MECA cells will be reserved for samples from different layers that are expected to be encountered while digging. One cell will analyze a sample from the surface, another will analyze the dry regolith overburden, and one will be kept in reserve for the icy layer. One MECA cell will be kept for a repeat measurement or to examine another layer.