1. INTRODUCTION

Manned Mars missions are likely to occur in the next twenty or thirty years and will typically last for two and half to three years, including an interplanetary journey of approximately six months, a surface stay of six months to two years and the return interplanetary leg of six months (Horneck et al., 2006; Hoffman & Kaplan, 1997).

Mars analogs on Earth are used to assess the feasibility of different aspects of the crew's surface activities, to conduct in-situ Mars related science investigations and to field test equipment and instrumentation. Among all of the available Mars analogs on Earth, two are commonly used by crews of The Mars Society to live and conduct scientific exploratory and experimental work in isolation: the Flashline Mars Arctic Research Station (FMARS) in the Canadian Arctic Circle, and the Mars Desert Research Station (MDRS) in the Utah desert.

The MDRS is composed of several elements: the habitat; an experimental greenhouse; a tele-operated observatory; a rudimentary radio-telescope; and a set of ATVs (All Terrain Vehicles, single-passenger four wheel quad-bikes). A more detailed description can be found in (http://desert.marssociety.org/MDRS/; Pletser, 2009). The MDRS facility is supported by an external engineering area, hidden behind a close-by sand dune, which includes diesel power generators, fuel tanks, water tanks, a gas tank, spare parts, etc. Technical parts of the habitat are usually maintained by a Mars Society maintenance crew every year at the beginning of the operating season. Generator fuel, ATV fuel and potable water are replaced on request by a local support provider. The simulations conducted at MDRS emphasize on how different crews organize themselves to conduct their investigation program, which is proposed and agreed by The Mars Society taking into account the existing state of the provided facilities. The facilities at MDRS as summarized above have a low fidelity with respect to future extra-terrestrial planetary bases in terms of external interfaces, as they rely mainly on external engineering (power, communications, etc.) and logistic support (water, food, etc.), and field operations may be conducted in EVA or non-EVA modes depending on specific goals of the field activities. In other words, the simulation is as realistic as the crew wants to make it. If the main goal of the simulation is to conduct field investigations, a mixed approach (some field outings in EVA mode and some in non-EVA mode) is acceptable, whereas if the goal is to study how crews would organize themselves and conduct field investigations like a real Mars crew would, then more stringent operational rules have to be followed. This would include confining the crews in the habitat without any direct contact with the outside world and conducting all field investigations following EVA rules and protocols (wearing unpressurized EVA suits, delay in radio-communications, self-autonomy at all stages, etc).

In order to assess several human and scientific aspects of future manned missions on extra-terrestrial planetary surfaces, the EuroGeoMars project was proposed to The Mars Society in 2009. Upon acceptance, it was agreed that the EuroGeoMars project would last for five weeks as follows: first, a technical preparation week (24-31 January 2009) for instrumentation deployment, followed by a first rotation of a crew of six scientists and engineers (MDRS crew 76, 1-15 February 2009) for further deployment and utilization, and concluded by a second rotation of another crew of six scientists and engineers (MDRS crew 77, 15-28 February 2009) for further utilization and in-depth analysis.

The goals of the EuroGeoMars project were to field test science and technical instrumentation and to conduct extra-terrestrial planetary characterization and exploration. The EuroGeoMars project encompassed two groups of experiments:

1) human crew related investigations: (i) crew time organization in a planetary habitat, (ii) an evaluation of the different functions and interfaces of this habitat, (iii) an evaluation of science and technical equipment human-machine interfaces;

2) a series of field science experiments that can be conducted from an extra-terrestrial planetary surface in geology, biology, astronomy/astrophysics and the necessary technology and networks to support these field investigations.

This paper will summarize the lessons learned from the first group of experiments: human crew related investigations. Recommendations are drawn regarding the overall design of a planetary human habitat with respect to human interfaces and crew time utilization. These are not exhaustive, but are intended to be used for future studies on the next generation of extra-terrestrial planetary habitats. Results of the second group of experiments relating to field science are not addressed in this paper and can be found elsewhere (Foing et al., 2009a; Peters et al., 2009; Borst et al., 2009; Ehrenfreund et al., 2009; Hendrikse et al., 2009; Mahapatra et al., 2009; Petitfils et al., 2009).

2. SOCIAL AND OPERATIONAL ASPECTS DURING SIMULATIONS

Prior to the simulation campaign, several classroom and simulated field training sessions took place at different locations in Europe for the crew members to get acquainted with each other, train on the various instruments and equipment to be used during the simulation campaign, and rehearse investigation procedures and protocols.

The low fidelity of the MDRS with respect to an extra-terrestrial planetary base was found acceptable and the facility was used 'as is' to conduct the EuroGeoMars project investigations. A mixed simulation approach was followed, emphasizing field investigations in non-EVA mode with some more demanding outings in EVA mode.

All field and laboratory scientific equipment (for geophysics and biology investigations) and technical equipment (for other engineering investigations on the use of tele-operated rovers, positioning, and network communications) were shipped to MDRS in advance of the campaign. Unfortunately, some of the equipment arrived late, during the first crew rotation.

As part of the simulation organized by The Mars Society, a certain amount of dehydrated food and pre-defined prescribed food (part of another on-going experiment over the entire simulation season) was present in the habitat. This was complemented by some fresh food bought locally at a nearby village. A vehicle (family van) was made available for the crews when they were not participating in the simulation.

Two international crews of scientists and engineers of mixed gender and seven nationalities (Austria, Belgium, France, Germany, South Africa, The Netherlands, United Kingdom, and USA) participated in the two consecutive rotations. Both crews included a Commander (CMDR), an Executive Officer (EXO), an Engineer (ENG) and three Scientists (SCI).

As the Commander of the first crew 76 had participated in two previous campaigns at FMARS in 2001 and MDRS in 2002, the same organization of chores, maintenance responsibilities, and group social activities was proposed and agreed on by both crews. Crews ate all their meals together, during which they planned, briefed and debriefed outings and crew activities. Other team activities were conducted in the evenings, such as seminars presented by each crew member in turn, watching DVDs and listening to music. All chores were shared equally, for example, each day a different person was responsible for preparing meals and completing kitchen chores. Other specific chores included refilling of the water tank every other day by the whole crew, maintaining the power generator, and small maintenance and cleaning taken in turns by crew members. Water usage was not restricted for food preparation and personal consumption, but was restricted for personal hygiene (showers were allowed every two or three days, the toilet was flushed irregularly, etc.), cleaning, dish washing, and so on.

Both crews organized their respective fieldwork in semi-confinement and semi-isolation modes, i.e. some of the outings and field expeditions were conducted in non-EVA modes and some in EVA mode, using EVA suits and protocols depending upon the specific goals of the field activity (reconnaissance/exploration, field science investigation, repair/maintenance of habitat systems).

Failures occurred regularly and were dealt with by either the rotation engineer and commander or the whole crew as needed, which impacted the science operation schedule on some days. The power generator failed several times and had to be repaired and eventually replaced with external help. On one occasion, power was unavailable for an entire day, completely preventing any activity (no power meant no instrumentation nor computers). EVA suits and backpacks were repaired as much as possible, but eventually some suits became unusable. Internet access was limited in bandwidth (1.5 Mb/s for download and 365 kb/s for upload, with a maximum transfer of 300 MB per day) which severely delayed or even made impossible the communication of scientific data to the remote science team (Pletser, 2009; Pletser et al., 2009 a, b; Foing et al., 2009b).

Communication with the outside world (Mission Support Centre, remote science support teams, family and friends) consisted of e-mails and internet connections. Outside e-mails covered MDRS related work (approx. 45%), other professional related work (approx. 45%), and private communications (approx. 10%). Computing support took time, with most of it on internet issues related to intermittent connections and poor upload bandwidth. Memory sticks were used for the internal exchange of data between personal computers.

Both crews reported excellent morale and team spirit during their respective rotations. However, one incident during the first crew rotation is worth mentioning. Two crew members of opposite gender were engaged in a romantic relationship which was detrimental to the unity of the group and team social activities. Public manifestations of this romantic relation included holding hands, spending exclusive time together in the evenings and while performing chores and various duties. Fortunately, privacy prevailed behind closed doors. Apart from this, the overall spirit was excellent despite wide variations in temperature (relatively warm during the day, and freezing cold at night), numerous habitat system failures (power, heating, EVAs suits and systems, etc.) and constraints (limited internet bandwidth, water restriction, etc.). The time spent in the habitat in semi-confinement and semi-isolation (in excess of two weeks) developed bonds between crew members and one could observe a mutually supportive and cooperative spirit that increased over time.

3. HUMAN CREW RELATED INVESTIGATIONS

3.1 Background Studies on planetary habitat design and crew organization are of paramount importance to prepare for future extra-terrestrial planetary missions. Investigations similar to the EuroGeoMars human crew experiments were conducted in previous MDRS and FMARS simulations: see e.g. (Clancey, 1999; 2000; 2001; 2006) and references therein.

Clancey (2006) conducted a study in 2002, asking the following five questions: (1) What effect do chores have (e.g., life support maintenance) on science productivity? (2) How do plans develop and change during the mission? (3) How do individual and group activities interact during the day? (4) How can Earth-based mission support understand and assist Mars surface exploration?; and (5) How can the habitat's layout be improved? This study was conducted as an exploratory methodology experiment, using the methods of participant observation, i.e. a crew member conducts the study.

His conclusions were mainly that (1) adjusting the group activity schedule creates more useful time for working (before lunch, before and after dinner); (2) interruptions significantly affect productivity: power failures, group activities, assigned chores, requests for assistance, computer network problems, incoming emails, etc. (3) timing and counting activities (systematic recording) is essential for detecting patterns and making work system design recommendations; (4) tasks involving reading and manipulating data are prime candidates for automation. Although the crew reported lack of time as the main frustration, one solution is to redesign the reporting products required and hence the schedule.

Therefore, the work conducted during the EuroGeoMars campaign was to continue in this direction and to obtain additional inputs to be used in design of future habitats.

3.2 Method Used. To implement the EuroGeoMars human crew related experiments, several forms and questionnaires were filled in by all crew members: time and location evaluation sheets (daily) and two questionnaires (crew interfaces and crew impression questionnaires, once per rotation).

The goal of the time and location evaluation sheets was to find out how crew members utilized their time, where they spent most of their time and for which purposes. They allowed the most time-consuming activities to be identified, and helped to answer the question of to what extent productivity and efficiency could be improved with a better organization, time management, or habitat layout (Clancey, 2006).

Crew members were asked to fill in, at their discretion, their location (in or out of the habitat) and the type of activity they were performing during every day, with a minimum unit of five minutes. For example, bedrooms were used mainly to sleep (main function), but some crew members preferred also to work on their computer in their bedroom instead of on the rather crowded computer table.

The crew interface questionnaire focused on several aspects for three types of location: the working area (lab, instrument storage/deployment room, EVA preparation room, etc.), the common living area (living room, kitchen, etc.), and the personal area (bedrooms, bathroom, toilet, etc.). Crew members were asked to comment using four priority levels of safety, operational, productivity, and comfort (see further in section 3.4) on (1) the inside layout, (2) interfaces between different areas, (3) overall comfort conditions for working inside and outside (during EVAs), (4) planning, and (5) communication.

The crew impression questionnaire dealt with several aspects of (1) daily work, (2) sleeping and relaxing, (3) overall habitat, (4) overall EVA impressions, (5) overall simulation impressions, and (6) reporting and communication impressions.

In summary, the time and location evaluation sheet gave information about who was where and when, helping to understand the reasons behind problems of space or layout (for example, too many people in a room or room to small for its purpose). It also helped to understand which areas were the busiest, in order to improve the layout. The crew interface questionnaire shed light on how the habitat layout, interfaces between different areas and instrument protocols effected crew productivity, while the crew impression questionnaire allowed more room for subjective remarks and descriptions of experiences.

3.3 Time and location evaluation The first crew filled the time and location evaluation sheets regularly, with a filling ratio of 82% (i.e. 82% of the crew time for all crew members could be reconstructed). Some crew members forgot to fill it in on one or two days, especially at the end of the rotation, and the information became less precise toward the end of the rotation as the amount of other scientific tasks and reports was increasing.

Fig. 1 shows how and where the commander of the first crew typically spent his time for the first ten days. The smallest time unit is 5 minutes and 13 typical activities are shown: sleep, use of the bathroom/toilet, common meals, common activities (briefing/debriefing/talks/evening activities), work in bedroom, work inside the habitat, work outside the habitat, EVA preparation and outing, chores inside, maintenance inside, maintenance outside, other motorized outdoor activities, and non-EVA outings.

Regarding common activities, Fig. 2 shows the time evolution of the four main common activities, i.e. breakfast (always coupled with the day's morning briefing), noon lunch, evening dinner and evening common activities (debriefing, discussion, seminars or watching a DVD all together). All common activities were performed in the habitat living room.

Total durations and averages ± standard errors (i.e. St. Dev./√n) values are given in Table 1 for a two week period.

Breakfast starting times and durations were approximately constant, except for Sundays, at approx. 9 hours and lasted approx. 45 minutes. Morning briefings were held during breakfasts and rarely lasted longer. Depending on operations and habitat failures, lunch started between 1300 and 1400 and lasted between 45 minutes and 1 hour. Dinner started also between 1930 and approximately 2030 and lasted for about 1 hour. Delays in lunch and dinner toward the end of the simulation were due to a long outing in the morning. Evening group activities started usually straight after dinner and ended between 2200 and midnight. The total time of daily common briefing/debriefing/discussion, including daily briefings during breakfasts, amounted to 17 hours and 55 minutes for the entire two week rotation.

Other time parameters of significance are the duration of sleep and the time spent doing chores and maintenance. Figs. 3 and 4 show the time evolution of sleep and maintenance durations for the first crew and Table 2 gives averages ± standard errors of sleep and maintenance time. The last value corresponds to a hypothetical crew member whose sleep and maintenance times are the averages of the six crew members, i.e. approximately 8 hours 30 minutes and 1 hour 23±10 minutes, respectively. Although maintenance is essential to the safe running of a habitat, this last value of time spent on maintenance by a hypothetical average crew member can be considered as a lot of unproductive time which could have been used for field science and technical investigations, considering that most of the maintenance time was spent on repairs and fixing habitat subsystems that failed due to either inappropriate design or aging. This hampered the crew when attempting to conduct their nominally planned technical or scientific tasks.

Figure 5 shows the time evolution of the time spent doing chores for the first crew.

Each crew member performed their chores in turn, either alone or helped by another crew member. The time spent doing chores was calculated for each crew member for every day; if another crew member helped, both had that time counted as doing chores. The average time spent per day on chores was 3 hours, 8±18 minutes without help and 3 hours, 18±15 minutes with help. Averages differ for the first and second weeks: 3 hours, 41±21 minutes and 2 hours, 30±13 minutes without help, respectively; and 3 hours, 42±53 minutes and 2 hours, 50±44 minutes with help, respectively.

A certain periodicity is seen during the first week depending on which crew member was on duty, the Executive Officer (EXO) and the Engineer ENG (both male) taking a more efficient approach in reducing the time spent on chores to 2 to 3 hours, with respect to the average time of the first week. The time spent on chores tended to decrease over the second week for all crew members, possibly showing again a more efficient approach to the chores, mainly in the kitchen.

The time spent on chores can also be considered to be a lot of unproductive time, i.e. non-productive with respect to conducting scientific and technical investigations. However, not all of this time was unproductive, as from a group psychological point of view, spending time preparing meals for special occasions (birthday, celebrations, etc.) - although not contributing directly to productive scientific work - does promote social bonds among crew members, which can be seen as having a positive psychological effect that influences work quality.

Summarizing the average unproductive time, one could say that a hypothetical average crew member would sleep an average of 8 hours, 26±07 minutes, eat breakfast during an average of 44±02 minutes, lunch for 48±02 minutes and dinner for 57±01 minutes, spend an average of 3 hours, 08±18 minutes doing chores and 1 hour, 23±10 minutes doing maintenance, and spend an average of 1 hour, 35±13 minutes on evening common activities, which sums up to 17 hours, 01±53 minutes, leaving only approximately 7 hours for scientific work. Even if this average estimation is very crude, it shows that the remaining average time for scientific work is significantly low and that a lot of time is spent on unproductive tasks, chores and maintenance.

These data are consistent with previous findings for crew 5 in 2002 (Clancey, 2006) in terms of activity duration: the approximate average durations for morning briefing, noon lunch, dinner and evening activities were 1 hour, 05 minutes; 36 minutes, 55 minutes; and 2 hours, 40 minutes, respectively. The duration of breakfast (coupled with the morning briefing) was kept shorter for crew 76 compared to crew 5 (the first morning briefing of crew 5 lasted approximately 2 hours). Sleep durations were similar (between 8 hours, 09 minutes and 6 hours, 21 minutes for crew 5), and the time spent on chores varied between approximately 3 hours, 20 minutes and 6 hours, 50 minutes per day (average of 4 hours, 23 minutes) for kitchen and habitat cleaning chores, to which should be added twice 45 minutes per day for refuelling the generator (two crew members conducted this operation), amounting to a daily average of 5 hours, 53 minutes for all chores performed by crew 5, which is much more than the average over the two weeks for crew 76 of about 3 hours. Maintenance times were not recorded separately in this previous study.

3.4 Crew Interface Evaluation. Both crews filled the questionnaires by themselves, mostly at the same time after the evening dinner, with a touch of humor to alleviate the monotony of the task. This was counted as a crew common activity.

The questionnaire allowed an assessment of the advantages and the drawbacks of the habitat design and investigated how it could be improved in the future. The different aspects considered were: layout (size and shape of bedrooms, location of different rooms, traffic areas), interfaces between different areas (were all the needs covered?), organization (could the team organization improve the productivity or the comfort in the current layout and composition?). Crew members were also invited to add new improvements, suggestions or requests. For each aspect, the questions were repeated and adapted to the places, and crew members were asked to keep in mind the order of priorities: Is it safe? Is it operational? Is it productive? Is it comfortable?

The main remarks and suggestions from the crew interface questionnaire are given in (Pletser, 2009; Boche-Sauvan, 2009; Boche-Sauvan et al., 2009 a, b). Note that the comments made in the questionnaires were made anonymously. A summary follows.

Although some of these remarks may sound like simple requests for more comfort, they summarize the general feeling that the habitat as it exists is not a comfortable place to work and live, and more importantly, they suggest that some issues affect the overall safety of everyday life.

In order to understand the scale of the problem, Figs. 6 and 7 show the working and living areas of the habitat upper and lower decks, which are shared by six people with different needs and different goals carrying out different scientific and technical tasks simultaneously.

3.5 Habitat Layout and Traffic Analysis

The above remarks yield the following analysis regarding areas and traffic. For the lower deck, the lack of space felt by the scientists in the laboratory is mainly due to the multiple uses of this room. It is a biology laboratory, a geology laboratory, and also the central room in the lower deck, leading to large traffic between experiment and sample analysis areas (see Fig. 8).

Traffic (double curved blue arrow in Fig. 8) moves between the stairs and the bathroom, between the toilet and the lab sink, and for the engineer, from the stairs to the engineering air lock (for daily checks) and from anywhere to the workshop (for repair activities, e.g. from the EVA preparation room to the workshop to fix EVA equipment). This lack of space led to an uncomfortable working environment, which required items to be moved or stored under the tables. This in turn did not allow the crew to sit properly and decreased the available space in the area through which traffic was moving.

This lack of space hampered productivity, and worse, presented a safety issue. For example, temporary stowage on the floor (light green ellipse in Fig. 8) was potentially dangerous for scientists who could stumble on to sharp instruments or tools.

Moreover, organization was important for the scientists, as they did not have the same needs: geologists needed to crush samples and relative darkness for analysis, while biologists needed a minimum of dust and good light for biosample analysis. In order to share the use of the single laboratory room, both groups of scientists had to work alternately during nights (Fig. 9).

Having a lack of space in a planetary base is usual, as its overall design, mass and dimensions are limited by the size and capability of the launcher. However, improving the layout would allow a better use of its internal space.

In order to optimize the laboratory space and provide dedicated places for each activity, temporary partitions could suffice to separate the geology and biology areas (see Fig. 10).

However, this may not be sufficient as some instruments and equipment used for biological experiments are very susceptible to large amounts of dust and malfunctions or defects could result. Instead of temporary partitions, either permanent spatial separation with separated dedicated laboratory rooms or temporary spatial separation using gloveboxes and inflatable clean rooms would be more desirable. In order to improve internal traffic on the lower deck, a dedicated traffic area could be created in the middle to lessen the distance between the workshop area and anywhere else. The different laboratory areas, EVA room, workshop and other utility areas could be distributed more radially from a central corridor (see Fig. 10).

Another aspect that was commented on was the lack of stowage areas. During simulations, the lack of permanent and temporary stowage room was evident. Containers, books, papers, procedures, workshop tools, science instrumentation, collected samples, personal items, consumables (food, water, etc.) were placed where room was available in dedicated (cupboards, shelves) and undedicated areas (under tables, in laboratories, under stairs, on top of bedrooms, etc.) This situation led to overcrowded areas in the habitat, hampering both productivity and sometimes safety. Generally speaking, before being stowed, items should be divided into two categories: what should be kept and what could be discarded. The items to be kept should then be prioritized according to their importance. Other means of stowage taking less volume should be investigated, e.g. papers, books, and written procedures should be digitized and properly referenced. This would keep written procedures to a minimum. Those procedures to be used by the crew in cases of emergency or of loss of power that would render computers inoperative would be kept on paper as a backup. Tools and sciences instrumentation should be kept to a strict minimum, considering also some redundancy for those on which repair, maintenance and science operation depend critically. Collected samples (see e.g. Fig. 9, right) should be discarded after characterization and analysis in the lab, except for those that are of interest and which deserve further studies and an eventual return to an Earth laboratory.

4. RECOMMENDATIONS

In order to maximize the productive time of a crew in an extra-terrestrial planetary habitat, the following ten general recommendations are given including two for crew time optimization, seven for habitat design and one for communication optimization. These are by far not exhaustive but should be considered as a minimum in the design of future extra-terrestrial planetary human habitats or Earth-based Mars Analog facilities.

4. 1 Crew Time Utilization: Minimal use of crew time for maintenance. As crew time is the most unique and important mission resource, especially for qualified researchers conducting field science, crew members should not be requested to perform daily certain chores and maintenance due to failure of habitat subsystems.

Generally speaking, an extra-terrestrial planetary habitat must be designed such as to be as reliable as possible and to minimize the use of crew time to perform habitat maintenance. However, crew members should be called to perform maintenance or repair only in exceptional circumstances and not as part of a baseline daily routine.

4.2 Crew Time Utilization: Optimization of reporting. During simulations at MDRS, several reports are normally prepared either daily or every other day. The mandatory daily reports include the Commander's check-in report (on crew overall health and performance, and main habitat system status), the Commander's report (detailing various activities that took place during the day), the Engineer's check-in report (detailing technical statuses of habitat systems). Other reports, although optional, are strongly suggested and have to be sent in regularly every other day: science reports (experiments and preliminary results obtained), EVA reports (after each EVA, on duration, range, activity, results, interpretations, etc.), journalist reports (on more anecdotic aspects of habitat life or expeditions), and a selection of up to six photos of the day's activities. The daily preparation of these various reports was extremely time consuming (about 1 to 2 hours per day for every crew member). Beside the obvious communication aspect, from an operational point of view, the only report that is needed daily is the Engineer's check-in report on all detailed habitat system statuses. All other reports are 'nice to have' but are not necessary and should be left at the discretion of crew members. In particular, scientists, despite usually maintaining daily logs on their on-going experiments, cannot be pushed to write something everyday to report to the general public about their research work and preliminary results.

Furthermore, the writing of reports on computers and their uploading are time consuming, considering also the limited bandwidth and the intermittent unavailability of the satellite connection.

In order to save crew time, reporting from a planetary habitat or an Earth-based Mars analog facility should be reduced and be kept to a minimum: a single engineer check-in daily report should be sufficient. Furthermore, it is worth investigating the possibility of self-reporting by machine or automated systems in the future and whether or not habitat subsystems could report on their own statuses. Finally, audio file reports, and to a certain extent video file reports on an 'as needed' basis, should be preferred to typed reports, for further typing and editing by Mission Support.

This is in line with previous findings of 2002, as it was reported that "The crew created far more public documents than anyone had time to read" (Clancey, 2006).

4.3 Habitat design: Continuous habitat power. A planetary habitat or a research laboratory cannot function without continuous power. For extra-terrestrial planetary habitats, a reliable power source, either from a generator or a power plant is essential. In case of an Earth-based analog facility, connection to the main electrical power network would be an acceptable alternative for a habitat that would be designed to support only certain kinds of analog investigations and not full simulations.

4.4 Habitat design: Continuous water supply. In order to avoid wasting crew time on water refill chores, a planetary habitat or an Earth-based analog facility needs a continuous supply of hot and cold water and should be designed such as to provide, within specified daily limits, running hot and cold water.

4.5 Habitat design: Habitat structural integrity. During previous simulations at MDRS, it was noticed that sand and dust entered the habitat during continuous sandstorms. In addition, the roof hatch was blown away several times by strong winds, necessitating temporary fixes using ropes and straps.

In order to improve crew safety and comfort and to avoid potentially dangerous situations, the design of a planetary habitat or an Earth-based analog facility should be structurally fail-safe against environmental conditions (quakes, rain, strong winds, etc.) at the habitat location, whether on Earth or on an extra-terrestrial planetary surface.

4.6 Habitat design: Heating, ventilation and noise comfort. In order to provide the necessary minimum crew comfort with respect to noise and ambient temperature (i.e. providing the bare minimum for the crew to rest adequately at night and a normal temperature inside the habitat), the design of a planetary habitat or an Earth-based Mars analog facility needs to include silent and efficient heating systems for all habitat decks and areas.

4.7 Habitat Design: Modularity. Some of the habitat's subsystems and its internal layout need to be regularly maintained or replaced. The lack of modularity in certain subsystems was usually apparent in the overlaying of several temporary fixes on top of one another throughout the years. This accumulation of layers of temporary fixes means that the functioning of the overall habitat and crew comfort (and sometimes safety) was compromised and could certainly be improved and optimized. Some of these subsystems were either not functioning or failed regularly, requiring quite a large amount of crew time to investigate the problem, repair it or install workaround solutions.

Considering that an extra-terrestrial planetary habitat or an Earth-based Analog facility shall be used over several years or several tens of years, and in order again to save crew time and to improve crew safety and comfort, the design of an extra-terrestrial planetary habitat or an Earth-based analog facility needs to incorporate sufficient modularity to allow for upgrades over time of main subsystems like structural parts, pressurized vessels, internet connections, computer and electronic equipment working stations, robotic and automatic subsystems, communication systems and other habitat subsystems that may show signs of 'wear and tear' or which simply fail over the years. Regular servicing and general overhauls should be foreseen after a certain number of years (to be decided upon during the design and validation phases). Furthermore, modularity in the design may also be important in the incorporation of new technologies to replace existing ones in the habitat or to increase habitat functions with new capabilities.

4.8 Habitat Design: Stowage room. Lack of permanent and temporary stowage room was a problem during simulations. In order to optimize the available space, the design of a planetary habitat or an Earth-based analog facility needs to incorporate sufficient stowage room, allowing also dynamic stowage, i.e. applying a 'temporary stow and discard' policy that allows an approach of 'keep a minimum', coupled with an efficient system of referencing and retrieving of data on a digital support (central computer, intranet, etc).

4.9 Habitat Design : Areas and partitioning Scientists from both crews had to share the single laboratory area for different scientific usage with opposite requirements (low illumination and generating dust for geologists versus good light and dust-free environment for biologists). The compromise found was a time-sharing alternate use of the laboratory facilities during the nights. If this solution is acceptable for a simulation of a few weeks, it is certainly not for missions lasting several years. In order to optimize the available space, the design of a planetary habitat or an Earth-based analog facility needs to include either separate laboratories or in case of lack of available volume (constrained by the overall habitat design), temporary partitions of the single laboratory area or spatial separation of different laboratory areas.

4.10 Communication: Continuity and bandwidth for digital communication. During simulations, both crews had to face two problems regarding communication means. The first was the limited available bandwidth precluding transmission of large files, limiting drastically the exchange of scientific files and information between the field crew and the remote science support teams and limiting the science operations. The second was the regular failure of the transmitting antenna or the unavailability of signal, which caused all communications to stop.

Obviously, this is not acceptable in an environment where cutting-edge field science is conducted.

A habitat needs a reliable communication system including internet, with a sufficiently large bandwidth to support mission and science operations and data exchange with remote ground support teams. It can be imagined that communications and the necessary bandwidth will evolve over time and will depend on the resources available to the crew (antenna size, power and technology available) and on mission goals, possibly mainly exploration and reconnaissance at the beginning and more complex field science investigations later on, which would necessitate larger bandwidth capabilities.

5. CONCLUSIONS

Although the low fidelity of the MDRS with respect to an extra-terrestrial planetary base was found acceptable to conduct the investigations of the EuroGeoMars project, it was found that the numerous failures (power generator, heating system, etc.) and constraints (limited communication bandwidth, failing communication system, etc.) encountered in the basic functioning of the different MDRS facilities hampered the attainment of simulation goals, which were to conduct field science and engineering investigations. Although the results reported in this paper are mainly idiosyncratic to the MDRS, some of the lessons learned could be translated to general recommendations for future planetary habitat design.

It was further shown from an analysis of crew time and location evaluation sheets that the main unproductive activities were, in descending order of duration: sleep, daily chores, collective evening activities, maintenance, and meals. 'Unproductive activities' should be understood as activities which did not contribute directly to the achievement of the goals set for this simulation. As sleep, collective evening activities and meal times can not be compressed in order to provide enough rest and relaxing periods to the crew, meal times were optimized by holding, informally, the general morning briefings during breakfasts and the general evening debriefings during dinners. More specific briefings and debriefings were held during the day as called for by operational constraints.

Daily chores and maintenance were left as the most time-consuming activities, to which should be added off-nominal maintenance due to habitat system failures. In average these consumed about 3 hours per day for chores and about 1 hour, 30 minutes per day for maintenance. These could be drastically reduced by improving the internal layout and the design of the habitat and its subsystems. Nominal maintenance can also be reduced by adapting the internal layout and design to specific working needs of crew members. Off-nominal maintenance could also be reduced to a minimum by implementing some of the recommendations above. Again, this is along the lines of previous findings (see the second conclusion of Clancey, 2006, in section 3.1).

Regarding the time sharing of single facilities, scientists usually adapt their methodology as results are obtained: their schedules are therefore not always predictable. In future missions, this dynamic adaptation of laboratory schedules will be a challenge.

Crew comfort is an issue that cannot be ignored. A Mars mission will last for typically three years. So comfort must be provided to the crew to work and live in the habitat for this period of time. The habitat does not need to be the equivalent of five-star hotel, but should provide the bare minimum to allow expedition crews to rest and relax properly in between working periods. Hence, basic recommendations were given on crew time optimization, habitat design and methods of communication. Future work will focus on translating these recommendations into design requirements for future generations of extra-terrestrial planetary habitats and Earth-based analog habitats.

ACKNOWLEDGEMENTS: This work was performed under the good auspice of ESA's Directorate of Human Space Flight. The Mars Society is acknowledged for allowing the EuroGeoMars team to use the MDRS station. The help of the Mission Support team and of the remote Science support teams was invaluable in conducting all the science and engineering experiments. The crew 76 and 77 members are thanked for their participation in these crew human aspect investigations. The work of L. Boche-Sauvan is acknowledged in the analysis of the crew questionnaires and of the habitat interfaces and internal traffic. S. Espinasse, J. McClean, A. Jaime and two anonymous referees provided useful comments during the manuscript preparation.