Mission Phases

DEVELOPMENT

The development phase began with the start of mission funding in January, 2003. During this phase, the science and technology requirements were tested and analyzed, and the spacecraft and mission were designed. The instruments and spacecraft were developed and tested at Lockheed Martin in Denver, CO before delivery to Cape Canaveral. The design of the spacecraft trajectory and mission operations were also determined during this period.

LAUNCH

The launch phase for each vehicle began at the final countdown through spacecraft separation from the upper stage. Phoenix was launched August 4, 2007, at 926 UTC (526 EDT) from launch complex 17A at Cape Canaveral Air Force Station, Florida. The launch azimuth was 93 degrees. The boost portion of the launch vehicle trajectory took approximately 10 minutes, and was followed by a short coast phase in a parking orbit for approximately 15 minutes. After third stage burnout, the upper stage despun the stack using a yo-yo despin system. Separation of the third stage occurred approximately 36 minutes after launch.

CRUISE

The cruise phase for each spacecraft began soon after separation from the third stage and ended 60 days before entry into the Mars atmosphere. The duration of cruise phase will be about 236 days for Phoenix. The major activities during this phase include: checkout and maintenance of the spacecraft in its flight configuration, monitoring, characterization and calibration of the spacecraft and payload systems, software parameter updates, attitude correction turns, navigation activities for determining and correcting the vehicle's flight path, and preparation for EDL and surface operations, including EDL X-band communication tests. No science investigations will be conducted during cruise, except for instrument health checkouts.

APPROACH

The approach phase was dedicated to the activities necessary to ensure a successful Entry, Descent, and Landing for the spacecraft, beginning 60 days before entry into the Martian atmosphere and ending at the atmospheric entry interface point 125km from the surface of Mars. The main activities during this phase were: acquisition and processing of navigation data to support development of the final trajectory correction maneuvers and activities leading up to the final turn to the entry attitude and separation from the cruise stage 7 minutes before entry.

ENTRY, DESCENT, AND LANDING

The EDL phase lasts approximately seven minutes from entry through touchdown, and is broken into hypersonic, parachute, and terminal descent subphases, all of which require the spacecraft to be in a different configuration. Phoenix can land safely if the conditions allow the spacecraft to stay within its defined entry corridor. However, if it drifts away from the nominal parameters, there is a steep rise in the chance of failure. Graceful degradation is the desired situation and it is difficult to achieve for Phoenix. Therefore, the working group has spent several years finding the best set of parameters such as the entry angle, the atmospheric properties on the day of landing (Michaels and Rafkin, 2008), the speed at which the parachute is released, and the transition to powered descent (see EDL timeline in Fig. 5). In addition, the rock distribution and ground slopes determine the final touchdown success rate. Thousands of Monte Carlo calculations, each with a randomly selected set of incoming trajectory, atmospheric, and landing site parameters, are used to predict the percentage of successful landings.

Landing day, May 25, 2008, at about 4:30 pm PDT, will be controlled from JPL and is devoted to deploying the solar arrays, extending the SSI mast, releasing the MET mast, and opening the bio-barrier. A small number of SSI images will be taken both of the spacecraft to verify deployments as well as the surface. All available downlinks will be used to gather data needed to assess the health of the spacecraft so that the science activities can begin. Once the spacecraft is power positive, has two-way communications, and is thermally stable then the control is transferred to the UA Science Operations Center in Tucson. [GUINNETAL2008]

CHARACTERIZATION PHASE

The characterization phase of the mission will begin after the Sol 0 activities have been completed. This phase will last 8 Martian sols (each sol being 24.66 hours) after landing for Phoenix, while the performance of the lander's power, thermal, and UHF subsystems as well as the MECA, TEGA, and MET instruments will be characterized and prepared for operation. Data collected on Sol 0 will be relayed to the ground, and the SSI will image the lander and surrounding environment. The DSN is scheduled for 10 sols. The Robotic Arm will be unstowed and complete several practice sample transfers to prepare the lander equipment for the primary mission. [GUINNETAL2008]

PRIMARY MISSION (DIGGING PHASE)

Phoenix's primary missions will last for 90 Martian sols from time of landing. During this phase, a wealth of science and engineering information will be collected from the lander and instrument payload. Activities during this digging phase will include the digging of a trench in front of the lander with the RA and analyzing soil samples from various depths with the lander instruments. The instruments will also photograph and take measurements related to the martian atmosphere.

Source: Phoenix Mission Catalog File