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NASA Extreme Environment Mission Operations (NEEMO) is an underwater spaceflight analog that allows a true mission-like operational environment and uses buoyancy effects and added weight to simulate different gravity levels. Three missions were undertaken from 2014–2015, NEEMO 18–20. All missions were performed at the Florida International University's Aquarius Reef Base, an undersea research habitat. During each mission, the effects of communication latencies on operations concepts, timelines, and tasks were studied METHODS: Twelve subjects (4 per mission) were weighed out to simulate near-zero or partial gravity extravehicular activity (EVA) and evaluated different operations concepts for intergration and management of a simulated Earth-based science team (ST) to provide input and direction during exploration activities. Exploration traverses were preplanned based on precursor data. Subjects completed science-related tasks including presampling surveys, geologic-based sampling, and marine-based sampling as a portion of their tasks on saturation dives up to 4 hours in duration that were designed to simulate EVA on Mars or the moons of Mars. One-way communication latencies, 5 and 10 minutes between space and mission control, were simulated throughout the missions. Objective data included task completion times, total EVA times, crew idle time, translation time, ST assimilation time (defined as time available for ST to discuss data/imagery after data acquisition). Subjective data included acceptability, simulation quality, capability assessment ratings, and comments. RESULTS: Precursor data can be used effectively to plan and execute exploration traverse EVAs (plans included detailed location of science sites, high-fidelity imagery of the sites, and directions to landmarks of interest within a site). Operations concepts that allow for presampling surveys enable efficient traverse execution and meaningful Mission Control Center (MCC) interaction across communication latencies and can be done with minimal crew idle time. Imagery and contextual information from the EVA crew that is transmitted real-time to the intravehicular activity (IVA) crewmember(s) can be used to verify that exploration traverse plans are being executed correctly. That same data can be effectively used by MCC (across comm latency) to provide meaningful feedback and instruction to the crew regarding sampling priorities, additional tasks, and changes to the EVA timeline. Text / data capabilities are preferred over voice capabilities between MCC and IVA when executing exploration traverse plans over communication latency.

Phobos is a scientifically interesting destination which offers engineering, operational and public outreach activities that could enhance subsequent Mars surface missions. A Phobos mission would serve to facilitate the development of the human-based Mars transportation infrastructure, unmanned cargo delivery systems, as well as habitation and exploration assets that would be directly relevant to subsequent Mars surface missions. It would also potentially provide for low latency teleoperations (LLT) of Mars surface robots performing a range of tasks from landing site validation to infrastructure development to support future crewed Mars surface Missions. A human mission to Phobos would be preceded by a cargo predeploy of a Phobos surface habitat and a pressurized excursion vehicle (PEV) to Mars orbit. Once in Mars orbit, the habitat and PEV would spiral to Phobos using solar electric propulsion (SEP)-based systems. When a crewed mission is launched to Phobos, it would include the remaining systems to support the crew during the Earth-to-Mars orbit transit and to reach Phobos after insertion into a high Mars orbit (HMO). The crew would taxi from HMO to Phobos in a spacecraft that is based on a MAV to rendezvous with the predeployed systems. A predominantly static Phobos surface habitat was chosen as a baseline architecture. The habitat would have limited capability to relocate on the surface to shorten excursion distances required by the PEV during exploration and to provide rescue capability should the PEV become disabled. PEVs would contain closed-loop guidance and provide life support and consumables for two crewmembers for two weeks plus reserves. The PEV has a cabin that uses the exploration atmosphere of 8.2psi with 34% oxygen. This atmosphere enables EVA to occur with minimal oxygen prebreathe before crewmembers enter their EVA suits through suit ports, and provides dust control to occur by keeping the suits outside the pressurized volume. When equipped with outriggers, the PEV enables EVA tasks without the need to anchor. Tasks with higher force requirements can be performed with PEV propulsion providing the necessary thrust to counteract forces. This paper overviews the mission operational concepts, and timelines, along with analysis of the power, lighting, habitat stability, and EVA forces. Exploration of Phobos builds heavily on the development of the cis-lunar proving ground and significantly reduces Mars surface risk by facilitating the design, development and testing of habitats, MAVs, and pressurized rover cabins that are all investments in Mars surface assets.

This study developed, analyzed, and compared mission architectures for human exploration of Mars' moons within the context of an Evolvable Mars Campaign. METHODS: All trades assumed conjunction class missions to Phobos (approximately 500 days in Mars system) as it was considered the driving case for the transportation architecture. All architectures assumed that the Mars transit habitat would remain in a high-Mars orbit (HMO) with crewmembers transferring between HMO and Phobos in a small crew taxi vehicle. A reference science/exploration program was developed including performance of a standard set of tasks at 55 locations on the Phobos surface. Detailed EVA timelines were developed using realistic flight rules to accomplish the reference science tasks using exploration systems ranging from jetpacks to multi-person pressurized excursion vehicles combined with Phobos surface and orbital (L1, L4/L5, 20 km distant-retrograde-orbit [DRO]) habitat options. Detailed models of propellant mass, crew time, science productivity, radiation exposure, systems and consumables masses, and other figures of merit were integrated to enable quantitative comparison of different architectural options. Options for prestaging assets using solar electric propulsion versus delivering all systems with the crew were also evaluated. Seven discrete mission architectures were evaluated. RESULTS: The driving consideration for habitat location (Phobos surface versus orbital) was radiation exposure, with an estimated reduction in cumulative mission radiation exposure of up to 34% (versus a Mars orbital mission) when the habitat is located on the Phobos surface, compared with only 3% to 6% reduction for a habitat in a 20-km DRO. The exploration utility of lightweight unpressurized excursion vehicles was limited by the need to remain within 20 minutes of solar particle event radiation protection combined with complex guidance, navigation, and control systems required by the nonintuitive and highly-variable gravitational environment. Two-person pressurized excursion vehicles as well as mobile surface habitats offer significant exploration capability and operational benefits compared with unpressurized extravehicular activity (EVA) mobility systems at the cost of increased system and propellant mass. Mechanical surface translation modes (ie, hopping) were modeled and offered potentially significant propellant savings and the possibility of extended exploration operations between crewed missions. Options for extending the use of the crew taxi vehicle were examined, including use as an exploration asset for Phobos surface exploration (when combined with an alternate mobility system) and as an EVA platform, both on Phobos and for contingency EVA on the Mars transit habitat. CONCLUSIONS: Human exploration of Phobos offers a scientifically meaningful first step towards human Mars surface missions that develops and validates transportation, habitation, and exploration systems and operations in advance of the Mars landing systems.