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An Analysis of the Precursor Measurements of Mars Needed to Reduce the Risk of the First Human Mission to Mars

David W. Beaty (Mars Program Office-JPL/Caltech), Kelly Snook (JSC/NASA HQ), Carlton Allen (JSC), Dean Eppler (SAIC), Bill Farrell (GSFC), Jennifer Heldmann (ARC), Phil Metzger (KSC), Lewis Peach (USRA), Sandy Wagner (JSC), and Cary Zeitlin (Lawrence Berkeley), on behalf of the Mars Human Precursor Science Steering Group (MHP SSG)


June 2, 2005

Contributors

Dust/Soil Focus Team

Sandy Wagner, Dust/Soil Focus Team Leader

Luther Beegle

Luigi Colangeli

Julianna Fishman

Jim Gaier

Mike Hecht

Jim Ippolito

John James

Jeffrey Jones

Kriss Kennedy

Joseph Kosmo

Mark Lemmon

John Marshall

Terry Martin

M.K. Mazumder

Atmosphere Focus Team

Bill Farrell, Atmosphere

Focus Team Leader

Donald Banfield

Steven Cummer

Greg Delory

Stephen Fuerstenau

Mike Hecht

Joel Levine

John Marshall

James Murphy

Scot Rafkin

Nilton Renno

Paul Withers

Biohazard Focus Team

Carlton Allen, Biohazard

Focus Team Leader

Joe Bielitzki

Penny Boston

Ben Clark

Bob Gershman

Daniel Glavin

Richard Henkel

Gerda Horneck

Greg Kovacs

Daniel Kraft

Jennifer Law

Margaret Race

Perry Stabekis

Hunter Waite

Radiation Focus Team

Cary Zeitlin, Radiation

Focus Team Leader

James H. Adams

Francis Cucinotta

Lawrence Heilbronn

Richard Mewalt

Larry Townsend

Ron Turner

Jeff Jones

Greg Delory

Daniel Winterhalter

ISRU Focus Team

Ben Clark

Jeff Taylor

Mike Hecht

Dave Vaniman

Don Rapp

Jerry Sanders

Steve Clifford

Geotechnical Focus Team

Phil Metzger, Geotechnical Focus Team Leader

Susan Batiste

Robert Behringer

David M. Cole

Jim Jenkins

Michel Louge

Masami Nakagawa

Otis Walton

Allen Wilkinson

Terrain Focus Team

Dean Eppler, Terrain

Focus Team Leader

Melissa Lane

Steve Hoffman

Jeff Moersch

Matt Golombek



Other

Lewis Peach

Joe Fragola

Becca Marler

Jennifer Trosper

John Connolly

Frank Jordan

Bob Easter

Charley Kohlhasse

Janice Bishop

Jennifer Heldmann

Marguerite Syvertson

T/I Team

Noel Hinners, leader

Bobby Braun, leader



This report has been approved for public release by JPL Document Review Services (CL#05-0381), and may be freely circulated.




Recommended bibliographic citation:


Beaty, D.W., Snook, K., Allen, C.C., Eppler, D., Farrell, W.M., Heldmann, J., Metzger, P., Peach, L., Wagner, S.A., and Zeitlin, C., (2005). An Analysis of the Precursor Measurements of Mars Needed to Reduce the Risk of the First Human Missions to Mars. Unpublished white paper, 77 p, posted June, 2005 by the Mars Exploration Program Analysis Group (MEPAG) at http://mepag.jpl.nasa.gov/reports/index.html.

Executive Summary

The Mars Human Precursor Science Steering Group was chartered by MEPAG in June 2004 to analyze the priorities for precursor investigations, measurements, and technology/infrastructure demonstrations that would have a significant effect on the cost and risk of the first human mission to Mars. Based on this analysis, the MHP SSG proposes the following revised phrasing for MEPAG’s Goal IV, Objective A, and within it the investigations that follow (in priority order). The measurements needed to carry out these investigations are described in the subsequent sections of this white paper.


All of the measurements listed below, which are listed in priority order by the degree of impact on risk reduction, would have value to planning the human exploration of Mars (and most particularly the first human mission to the martian surface, for which our lack of knowledge will be greatest). However, the authors of this report are not in a position to determine how much risk needs to be removed in order for the first human mission to be judged acceptably safe. Thus, we cannot a priori determine how many of these measurements need to be successfully completed (i.e. required) before the first human mission can fly. Obviously, a larger precursor program will reduce the risk more than a smaller precursor program. However, the decision on safety thresholds must be deferred to others.
Recommended revision to MEPAG Objective IVA.

Objective A. Obtain knowledge of Mars sufficient to design and implement a human mission with acceptable cost, risk and performance.
The following four investigations are of indistinguishable high priority.

1A. Characterize the particulates that could be transported to mission surfaces through the air (including both natural aeolian dust and particulates that could be raised from the martian regolith by ground operations), and that could affect hardware’s engineering properties. Analytic fidelity sufficient to establish credible engineering simulation labs and/or performance prediction/design codes on Earth is required.

1B. Determine the variations of atmospheric dynamical parameters from ground to >90 km that affect EDL and TAO including both ambient conditions and dust storms.




1C. Determine if each martian site to be visited by humans is free, to within acceptable risk standards, of replicating biohazards which may have adverse effects on humans and other terrestrial species. Sampling into the subsurface for this investigation must extend to the maximum depth to which the human mission may come into contact with uncontained martian material.

1D. Characterize potential sources of water to support ISRU for eventual human missions. At this time it is not known where human exploration of Mars may occur. However, if ISRU is determined to be required for reasons of mission affordability and/or safety, then, therefore the following measurements for water with respect to ISRU usage on a future human mission may become necessary (these options cannot be prioritized without applying constraints from mission system engineering, ISRU process engineering, and geological potential):



The following investigations are listed in descending priority order.

2.  Determine the possible toxic effects of martian dust on humans. 

3. Derive the basic measurements of atmospheric electricity that affects TAO and human occupation.




4. Determine the processes by which terrestrial microbial life, or its remains, is dispersed and/or destroyed on Mars (including within ISRU-related water deposits), the rates and scale of these processes, and the potential impact on future scientific investigations.

5. Characterize in detail the ionizing radiation environment at the martian surface, distinguishing contributions from the energetic charged particles that penetrate the atmosphere, secondary neutrons produced in the atmosphere, and secondary charged particles and neutrons produced in the regolith.

6. Determine traction/cohesion in martian soil/regolith (with emphasis on trafficability hazards, such as dust pockets and dunes) throughout planned landing sites; where possible, feed findings into surface asset design requirements.

7. Determine the meteorological properties of dust storms at ground level that affect human occupation and EVA.




  1. Introduction and Background

    1. General

Over the past five years or so, there have been two major studies of the robotic program needed to serve as a precursor to the first human mission to the martian surface: MEPAG [2001; revised 2004] and the NRC’s Safe on Mars report [NRC, 2002]. Although these studies are both important, for several reasons it was necessary to reconsider them. NASA’s new Vision for Space Exploration (announced January 2004) includes a number of important planning details that previously had been missing (e.g. general objective, timing and budget), and requires reconsideration of precursor priorities. In addition, the recent discoveries of the unprecedented orbital campaign at Mars, with the Mars Global Surveyor, Odyssey and ESA Mars Express missions, as well as the extraordinary, and surprising findings of the Mars Exploration Rovers on the surface of Mars, have provided a rich set of data that has dramatically altered our understanding of Mars, in a way that both enhances the feasibility of conducting human missions to Mars (i.e., the apparent abundance of near-global, subsurface water, at some depth), while also presenting new potential hazards that must be mitigated (i.e., particularly the increased possibility of biohazards if liquid water is found to be present, and accessible, below the martian surface). Finally, the NRC study was limited to hazards related to the martian environment, and mission planning also needs to include risks of other kinds, as well as precursor technology demonstrations and infrastructure emplacement.
The MHP SSG prioritizations also differ from previous roadmapping activities (e.g. the Bioastronautics roadmap, where risk priorities were solely based on potential impacts to crew health, possibly long term) for two reasons. First, the MEPAG analysis addressed overall mission risks, including system and hardware risks, not just risks to humans. Second, the MHP SSG ranked risk priority based on evaluation of how Mars flight measurements could buy-down that risk. Even if risk was high, if measurements could not buy it down, then priority ranking decreased.


HOW DOES THIS REPORT EXTEND NRC’S (2002) SAFE ON MARS REPORT?

  • The NRC focused on environmental hazards to humans; this report also considers Mars-related risks to the flight or surface systems that could affect the probability of achieving full mission success.

  • This report determines the relative priority to the identified investigations and measurements, as input to future risk-cost-schedule-engineering trade-off analysis.

  • This report considers the precursor program needed to support a single landed human mission in 2030; NRC had an open-ended analysis with no constraint on the number of human missions and the possibility of a nearer-term first human mission.

  • This report distinguishes between Long and Short mission surface stay times, with separate priorities and risk assessments.

  • This report is focused on the specific measurements needed, including the required precision and accuracy.




For all of these reasons, in 2004, MEPAG chartered the Mars Human Precursor Science Steering Group (MHP SSG) to reconsider the description of its Goal IV (Preparation for Human Exploration). The charter for the MHP SSG is attached to this report as Appendix 1. In summary, the purpose is to determine, in priority order, the ways in which the risk of a human mission to the martian surface can be reduced by means of flight missions to Mars. In carrying out its charter, the MHP SSG was organized into two major teams: The Measurements subteam, and the Technology/Infrastructure subteam. This white paper represents the report of the Measurements subteam.


Because human missions to Mars will face a large number of risks, it is easy to think of LOTS of precursor investigations and demonstrations that will have some effect on risk reduction. However, the size of the impact of different precursor efforts on risk reduction is far from equal. In a cost-constrained program, it is important to understand these relative priorities. MEPAG measurement prioritizations presented here can be integrated into broader planning activities for human missions by outlining high priority measurements to be made on upcoming missions (both lunar precursor testbed missions and robotic missions to Mars).


    1. Assumptions

    • Assume that there will be a series of robotic missions to Mars, of as yet unknown character and timing, that will be capable of carrying out investigations and measurements, and doing technology/infrastructure demonstrations.

    • Assume the first dedicated robotic precursor mission is scheduled for flight in the 2011 launch opportunity, and that the first human mission is scheduled in approximately 2030.

    • Assume that a separate sequence of Mars missions, with a primary objective of robotic scientific exploration, will be carried out in addition to the human precursor sequence.

    • Assume that the infrastructure associated with the science missions (e.g. the telecommunications infrastructure) is available for use by the human precursor missions.

    • Assume for the purpose of this analysis that the 2030 mission and all of the precursor missions are funded by NASA without financial support from international partners.

    • Assume the first human mission includes a landed human element.

    • Assume that both the “short-stay” (~30 sols) and “long-stay” (~300 sols) missions are still under consideration; separate analyses of the precursor program are needed for each.

    • For the purpose of this study, an analysis of the precursor program needed to support only the first human mission to Mars has been developed. The timing and character of human missions beyond the first one are too uncertain at this time. Obviously, additional precursor investigations may be needed to support recurring human missions.




    • The human site will have been certified for landing safety with data from robotic missions before the humans land. 



    1. Scope

The scope of this analysis is the investigations of Mars by precursor robotic missions for the purpose of reducing mission risk/cost and increasing performance of a human mission to Mars. The authors note that in order for the program to be complete, the following kinds of precursor investigations also need to be considered, but they are considered within this analysis only to the extent required to directly support robotic flight missions.

    • Investigations that can be carried out at the Moon.

    • Investigations that can be carried out in Earth-based laboratories or in Mars-analog field environments on Earth (other than on returned martian samples).

    • Investigations of the space environment of relevance to a human mission other than those specifically at Mars.




    1. Definitions

    • Soil. The unconsolidated material at the surface of Mars, without implication as to whether it contains an organic component. As used in this report, this term encompasses the following three components: dust which is widely circulated, presumably homogeneous, and fine grained; dune material which presumably is coarser grained and may not be globally mixed and may not account for a large fraction of material; and the regolith which includes material derived from bedrock with an unknown size frequency distribution and origin (presumably a combination of physical and chemical weathering).

    • Acronymns: All acronyms are listed in Appendix 2.

NOTE:  This document is intended to support future planning, and as such it mentions possible future flight projects that have not been approved. NASA’s flight missions can be implemented only after they have achieved compliance with National Environmental Policy Act and Council on Environmental Quality (CEQ) laws.  Additionally, some proposed missions would also require launch approval by the Office of the President.




  1. Risk/Cost Analysis

    1. Introduction

The MHP SSG was asked to analyze the precursor missions that would reduce the cost, reduce the risk, and increase the performance of the first human mission to Mars (Appendix 1).

  • Cost. After extensive discussion, we concluded that a reasonably complete analysis of cost-reduction approaches would need to begin with a baseline cost model, which in turn would need to start with baseline mission engineering. Since we do not have either of these at this time, with one exception we deferred all discussion of cost reduction precursors to a future analysis team. That one exception is ISRU, which has a very obvious potential impact on mission cost (see section 3.5).

  • Performance. The specific objectives and basic functionality of the first human mission have not yet been established. Without this starting point, it is not possible to do a meaningful analysis of the precursor program that would increase the performance. We considered starting from the de minimus mission, and evaluating performance increases relative to that, but we could not realistically define even this starting point. Again, the MHP SSG chose to defer this analysis to a successor team, when the baseline mission is better understood.

  • Risk. The MHP SSG therefore spent most of its efforts on risk analysis, and on the precursor investigations and measurements that could reduce those risks.




    1. Assumptions, Methodology

Terminology.

  • Hazard - A state or condition that could potentially lead to undesirable consequences, depending on how a mission interacts with it.

  • Risk - The combination of 1) the probability (qualitative or quantitative) and associated uncertainty that a program or project would experience an undesired event; and 2) the consequences, impact, severity and/or associated uncertainty of the undesired event were it to occur.

  • Opportunity - A state or condition that could potentially lead to desirable consequences.



Design Risk. There are many different types of risk, including cost risk, schedule risk, astronaut safety risk, risk to mission objectives, and many others. For a human mission, all of these types of risk would eventually be analyzed using systematic, quantitative, risk analysis methods. However, quantitative risk analysis requires a specific engineering implementation, which we do not currently have. The MHP SSG study therefore focused on what could be called design risk--the risk that the mission would use a faulty design because of incomplete information. It is clear that many other risks, such as the safety risk, would depend on the architectural approach, or mission scenario, and a primary purpose of the precursor program is to reduce uncertainty about the martian environment so that correct engineering design decisions can be made.

Risk Threshold. All risks for the first human mission will need to be dealt with in one of two ways: accept the risk, or mitigate against the risk through engineering. The latter, of course, requires information about the hazard to be mitigated in order to arrive at an improved design that has lower risk. Although the MHP SSG found that it could assess risk magnitudes in a qualitative way and could place risks in relative priority order, it is not in a position to determine the maximum overall acceptable risk to the mission, and therefore which risks MUST be mitigated in order to achieve that threshold.

Expected value of perfect information. An important concept in risk mitigation is the expected value of perfect information. In considering investing in precursor information (either by flight missions, or by research), one needs to ask, ‘if we knew this information perfectly, what value would be added as compared to where we are today with our imperfect data set?’ Note that in the real world, this will represent an upper limit on potential risk reduction, since actual research and flight experiments may not generate perfect information for a variety of reasons. A key point is that if perfect information from a given investigation does not have the desired effect on risk reduction, the investigation may not be worth doing. Since the purpose of a precursor measurement program is to buy down the risk by investing in advance knowledge, the value of the information must exceed its cost in order to be justified. Risk levels with precursor missions (Table 1) were determined assuming data is successfully collected on the precursor mission in accordance with the measurement criteria outlined in this document.


    1. Risk Categories

The first human mission to Mars would be exposed to a very large number of risks. A preliminary version of an overall risk taxonomy was developed as a part of the MHP discussions, but it needs further refinement before it can be usable in planning. The MHP SSG found that when considered from the perspective of design risk that can be reduced by precursor measurement, this set of risks could be grouped into 6 major categories. Each was assigned a team of experts to analyze the issues and trades in detail, and their analyses are reported in Section 3 of this report.

  • Risks related to biohazards

  • Risks related to martian particulates originating both from airborne dust and soil

  • Risks related to radiation hazards

  • Risks related to the atmospheric hazards

  • Risks related to terrain and trafficability hazards

  • Risks related to ISRU (assuming it is part of the human mission)

  • Risks related to regolith geotechnical properties




    1. Integrated Risk Priorities

      1. Prioritization Criterion

Each of the expert teams listed in Section 2.3 prepared an analysis of the risks in their subject area, along with an analysis of the possible precursor investigations that could reduce those risks. An important point is that each of these expert teams was asked to identify only precursor investigations for which there is no potential to obtain minimum necessary information in a less expensive way than by flying a mission to Mars (e.g. in an Earth-based laboratory, by computer simulation, in the Space Station, or on the Moon). These risks and investigations were merged in a major integration meeting in September 2004. Priorities for measurements were based on how robotic measurements can reduce all mission element risks, including crew health and safety as well as hardware and system functions. The prioritization criterion was straightforward: The magnitude of the expected effect of a precursor flight measurement on risk reduction.
In applying this criterion, the integration team encountered several examples of each of the following conditions, both of which result in the assignment of low priority to a proposed precursor investigation. This has caused some differences with prior studies.

  • Large risks for which precursor measurements have a small effect.

  • Small risks for which precursor measurements have a large effect.

Finally, for the purpose of this study we analyzed only the precursor investigations needed to reduce the risk of the first human mission, rather than a sustained campaign. This also has resulted in overall investigation priorities somewhat different from previous studies. We recommend subsequent studies to address additional risk factors that might result from other mission scenarios, such as sustained long-term human presence on Mars, which would require investigations that are beyond the scope of this study.


2.4.2 Process

The MHP SSG took a rigorous and structured approach to prioritizing the risk categories for a human Mars mission and determining the relative value of a robotic precursor investigation for each identified risk. This process is described below.


1. The discussions of the MHP SSG took place at two scales. One was in focus teams organized along technical lines (Biohazard, Dust/Soil, Radiation, Atmosphere, Terrain & Trafficability, ISRU), and the other was in broader integration exchanges that included representatives of each of the focus teams.
2. A long list of potential risks to the human mission was identified by the MHP SSG (the highest-priority portion of which is shown in Table 1). These risks are listed as “Risk Categories” in Table 1.
3. The relative magnitude of these risks was assessed for both the long- and short-stay human mission scenarios assuming the absence of a robotic precursor mission. The MHP SSG discussed risk to mission safety, risk to mission performance, and cost, but ultimately all of these can be integrated into design risk. Assumptions for risk in the absence of a precursor program assume basic engineering and for many of these risks there are engineering-based partial preventive solutions. Each “Risk Category” was rated 1 (low risk) to 5 (high risk). The assignment of risk level is subjective and risk levels cannot be directly compared to each other. These rankings are shown in Table 1 under “risk/cost, no precursor”.
4. “Risk Categories” were then assessed for both the long- and short-stay human mission scenario assuming a robotic precursor mission is conducted prior to sending humans. This analysis again considered the impact on risk to mission safety, mission performance, and cost. This analysis assumed “perfect information”: The necessary information to mitigate the corresponding risk would be collected from the appropriate location at the appropriate time by the precursor mission and would yield the maximum benefit in terms of increasing our knowledge to mitigate the risk. This analysis thus assumed the maximum potential benefit from the precursor mission in terms of risk reduction. Each “Risk Category” was rated 1 (low risk) to 5 (high risk). These rankings are shown in Table 1 under “Risk W. Mars precursor”.

5. The relative reduction in risk to the human mission given a successful robotic precursor mission was then determined. This was accomplished by comparing the risk without a precursor mission with the risk assuming a successful precursor mission. The difference in the risk with and without the precursor mission is the delta () value shown in Table 1. Risk categories with the highest  values thus represent risks that can be mitigated to the highest degree with a successful precursor mission.


2.4.3 Findings

The “Risk Categories” in Table 1 are listed in descending order of their  value for the long stay mission; hence risks closer to the top of the table could be reduced the most with a precursor program. Items in yellow have either a risk of 3 or higher or the value of the precursor measurement is at least 1.  Thus, these are the most valuable applications of a precursor program.


There are key differences in the risk profiles for the short and long stay mission scenarios. For the long-stay mission, the number of risks with high priority is much longer than for a short stay mission. Risk category 1 in Table 1 (which relates to ISRU) was not assessed for the short stay mission. The MHP SSG recognizes the possibility that ISRU may not be a required component of a short stay mission and for this reason, we could not include it within a comparative prioritization process—it will likely turn out to be either very important or irrelevant. The MHP SSG recommends further study of the relationship between ISRU, the duration of the first surface stay, and possible multi-mission human scenarios.
Several key findings related to risk buy-down and prioritization of precursor measurements are as follows:

  • There is a high emphasis on understanding the distribution, accessibility, quality, and quantity of water as well as technology validation for ISRU for a long stay mission scenario. Recent robotic missions including Mars Global Surveyor, Mars Odyssey, and Mars Express have increased our knowledge about the abundance of water resources on Mars and ISRU is considered essential for a long stay human mission. ISRU-related risks can be significantly mitigated with a precursor missions ( value = 3.0). Additional details can be found in Section 3.6.

  • Characterization of atmospheric wind shear and turbulence is a high priority investigation. Successful EDL and TAO activities rely on accurate knowledge of the martian atmosphere to predict and compensate for spacecraft trajectory anomalies. Risks associated with EDL and TAO can be significantly mitigated with precursor measurements ( value = 3.0). Additional details can be found in Section 3.2.

  • Characterization of the radiation environment both on the surface of Mars and in orbit are needed in order to validate the radiation transport models. The models are expected to be accurate but have known weaknesses that can best be probed by comparing their predictions to data obtained in situ, both above and below the atmosphere. Radiation-related risks are listed under Risk Categories 12 and 13 in Table 1. Additional details can be found in Section 3.4.

  • Characterization of the martian dust (including particulates raised from the regolith during surface operations) is a relatively high priority item. Such investigations are important for mission hardware design to mitigate the effects of abrasion, adhesion, corrosion, and damage from potential electrical discharge, or arcing, as well as to mitigate potential adverse effects on human health from dust inhalation, and exposure ( values range from 2.0-3.0). Additional details can be found in Section 3.3.

  • The greatest biohazard risk is back contamination and the associated potential hazards to terrestrial biota if martian life is transported back to Earth. Forward contamination of Mars and the potential false positive indication for life on Mars and/or hybridization with martian life is the next h ighest biohazard risk. Both risks can be significantly mitigated with a precursor mission ( values range from 1.5-3.0). Additional details can be found in Section 3.1.
Table 1. Relative Priority of Risks to the Short- and Long Stay Missions, and the Effect of Precursor Measurements on changing those Risks.










Short Stay Mission

Long Stay Mission

Ref.

Risk Category

risk/cost, no precursor

Risk w. Mars precursor



risk/cost, no precursor

Risk w. Mars precursor



1

Water accessibility/usability at the landing site not as assumed.

N/A

N/A

####

5

2

3.0

2

Wind shear and turbulence affects EDL and TAO.

5

2

3.0

5

2

3.0

3

Back PP--Martian life affects Earth's biosphere.

5

2

3.0

5

2

3.0

4

DUST: Adverse effects of dust on mission surfaces.

5

2

3.0

5

2.5

2.5

5

Direct dust hazards to crew (toxicity).

4

2

2.0

5

3

2.0

6

Dust storm electrification, affecting TAO.

4

2

2.0

4

2

2.0

7

Geotechnical risks associated with near-surface materials (regolith).

4

2

2.0

4

2

2.0

8

Forward PP--Terrestrial contamination affects science.

4

2.5

1.5

5

2.5

2.5

9

Deleterious dust storm effects on surface operations.

2

1

1.0

3

2

1.0

10

Proliferation (and mutation?) of terrestrial life in s/c, hab.

2

1

1.0

2

1

1.0

11

Terrain impedes rover trafficability.

2.5

2

0.5

3

2

1.0

12

Chronic radiation exposure exceeds career safety limits.  

1

1

0.0

3

2.5

0.5

13

Acute radiation exposure (e.g. in a severe solar event).  

1.5

1

0.5

2

1.5

0.5

14

Photochemical reactions in the atmosphere--adverse effects.

1.5

1

0.5

2

1.5

0.5

15

Landing site hazards (e.g. cliffs, large rocks).

1.5

1

0.5

1.5

1

0.5

16

Comm. losses & nav alterations caused by atm. and topographic conditions.

1.5

1

0.5

1.5

1

0.5

17

Lander attitude is inadequate for egress or TAO.

1

0.5

0.5

1

0.5

0.5

18

Slope hazards--affects both EDL and rover mobility.

1.5

1.5

0.0

1.5

1.5

0.0

19

Risk from previously-ignored radiation sources.

1

1

0.0

1

1

0.0

20

Seasonal condensation causes electrical failures.

1

1

0.0

1

1

0.0




  1. The Effect of Precursor Investigations and Measurements on the Reduction of the Risk of Human Missions to Mars




    1. Measurements related to biohazard risks


3.1.1 Introduction

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