Phoenix Mission

The Mars Scout mission consisted of one spacecraft and Scout hardware, which included Phoenix lander [SMITH2008 and GUINNETAL2008]. Phoenix was launched August 4, 2007, on a Delta II 7925 launch vehicle. The spacecraft design was based on the Mars Surveyor Program 2001 (MSP'01) configuration for cruise and entry, descent, and landing. The spacecraft will follow a long coast trajectory from Earth to Mars, with Phoenix landing in the Northern Plains on May 25, 2008 UTC. The Earth-Mars range will be 1.84AU at the time of Phoenix's landing.

The day after a successful launch, the spacecraft was commanded out of Safe Mode and setup for transition to nominal cruise phase operations. During the nearly 10-month cruise to Mars, both the spacecraft and the science instruments will be checked out via a number of planned activities. Also during cruise, the teams that will be operating the spacecraft during the critical 'end game', Entry, Descent, and Landing (EDL), and early surface timeframes will be practicing their roles via a series of Operational Readiness Tests (ORTs). As with all NASA planetary missions, telecommunications with the spacecraft are enabled by the Deep Space Network (DSN). A downlink (D/L) bit rate of 40 bps from Phoenix is required to be supportable at all days past launch.

From Entry minus 60 days onward, the mission is in a subphase of cruise known as approach, within which the activity level dramatically increases. During this phase there will be continuous DSN coverage (21 passes/week is equivalent to 24/7 coverage) and four TCMs as the spacecrafts flight path is fine tuned for delivery into the martian atmosphere. Seven minutes prior to atmospheric entry the spacecraft separates from the cruise stage and reorients itself to the entry attitude. The EDL (Entry, Descent, and Landing) 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.

Following its soft touchdown between 65 degrees N to 72 degrees N latitude, the Lander will, after waiting 20 minutes for the dust to settle, perform a number of critical activities. These 'Sol 0' (a sol is a mars day) activities include deployments of the landed solar arrays, the bio-barrier covering the Robotic Arm (RA), and the Surface Stereoscopic Imager (SSI) and Meteorological (MET) masts, after which the Lander will go to sleep to conserve energy. The Lander will wake up for 10 minutes for the first post-landed UHF communication pass one ODY or MRO orbit period (approximately 2 hours) after landing. After relaying eagerly anticipated data to the orbiter(s) during that first pass, the Lander will go to sleep again. Sol 1 activity is expected to begin at roughly 9 a.m. Local Mean Solar Time (LMST) the following sol.

The first seven sols after Landing are known as the characterization phase, with pre-planned activities running from a minimum of 3 hours on Sol 1 to a maximum of 6.5 hours on Sol 6 (the Lander is active for up to 7 hours during the nominal surface or digging phase). The performance of the spacecraft's power, thermal, and UHF subsystems will be thoroughly characterized during this phase, and the Thermal and Evolved Gas Analyzer (TEGA), Microscopy, Electrochemistry, and Conductivity Analyzer (MECA), and MET instruments will go through their initial checkouts and prepare for nominal operations. Concurrent with these activities, the EDL and Sol 0 data that were stored in the non-volatile (flash memory) will be relayed to the ground. The SSI will image as much of the Lander as it can see and characterize the workspace and surrounding environment. Most important for mission success will be the 'unstow' of the RA and the subsequent practice sample transfers that it will perform on Sol 5. The Robotic Arm Camera (RAC) located on the 'wrist' of the RA will be used to image the footpads and the TEGA cover, as it is the only imager that can be maneuvered into the proper viewpoint for these pictures. The seventh sol does not currently contain any planned activities because it will be used for margin against activities that fail or otherwise require additional time to complete during characterization.

After the Robotic Arm is checked out, the digging phase commences. The digging phase activities include digging a trench in front of the Lander, and the analysis of soil samples at various trench-depths by the Lander instruments. This phase continues until the End-of-Mission on Sol 90. Operations during this phase will be conducted at the University of Arizona and the mission operators will be working on Mars time (one martian sol is equivalent to 1.02749125 Earth days, or 24 hours, 39 minutes, 35.244 seconds).

Mission Objectives

The mission has a set of science and technology objectives. The science is closely aligned with the Mars Exploration Program objective of determining the degree to which Mars provided conditions necessary for formation and preservation of prebiotic compounds and whether life started and evolved. This objective can be broadly stated as defining habitability of Mars and providing an understanding of roles of tectonic and climatic processes in possibly providing the conditions that led to life. The presence of water and its interaction with crustal materials is of fundamental importance. Thus, the primary objectives are focused on investigating the history of water in all forms on Mars and assessing the biological potential of the soil-ice boundary. The four primary science goals are: (1) to study the history Of the ground-ice and its emplacement mechanisms, (2) to address the affect that subsurface ice has on the local surface geomorphology, (3) to characterize the climate and local weather of the landing site, and (4) to address the habitability of the icy soil. these Science objectives are subdivided into four primary categories in order to align with the management structure of the four Science Theme Groups.

The science objectives in relation to characterizing the present climate include: (1) to determine the daily and seasonal variations in temperature, dust opacity, pressure, and humidity at the landing site, (2) to determine the exchange of water vapor with the subsurface, including D/H ratios of the atmosphere and surface samples, near-surface air temperature and surface temperature, and atmospheric water-vapor abundance throughout the mission, (3) to determine the bulk atmospheric composition, including isotopic ratios of 3 major elemental components C,O, and Ar, and (4) to measure the acceleration during EDL to constrain models of the atmospheric density profile.

The next several goals are those of the geomorphology and physical properties theme group and will be related to the RA instrument goals of digging a trench to an impenetrable layer or 50cm below the surface and gathering samples from the surface to the trench bottom and delivering them to the instruments on deck. These objectives include: (5) image regional and local landforms and surface deposits and place observations in the context of orbital data, (6) identify any subsurface layering and distribution of subsurface water ice, (7) determine subsurface mechanical properties as a function of depth and correlate with visual, textural, chemical, and mineralogical data, (8) use image data to determine the morphology, topography, reflectance, and photometric behavior of excavated minerals, and (9) characterize surface and subsurface physical properties.

Additional objectives for the lander will be investigated in the chemistry and mineralogy themed group and include: (10) measure the concentration and gradient of elements and minerals in the surface and subsurface, particularly organics, salts, hydrated minerals, sulfates, carbonates, oxidants, and other volatile-rich substances, and correlate these with ice, and (11) Verify the presence and identify the form of H2O on the surface and within the subsurface and provide this data for validation of models.

The final theme group is the biological potential theme group, dedicated to incorporating the data from the other science teams to (12) measure the biological potential of the surface and subsurface environments by determining if liquid water has been present, measuring compounds formed from the biogenic elements C, H, N, O, P, S, by measuring the concentrations of biologically relevant ions including K, Ca, Mg, Na, and by assessing the redox potential. These objectives will provide the basis for addressing the first four goals of the Phoenix mission, based on the objectives determined by the Mars Exploration Program.

Source: Phoenix Mission Catalog File