A proposed new policy for planetary protection

In order to control contamination of planets by terrestrial microorganisms and organic constituents, U.S. planetary missions have been governed by a planetary protection (or planetary quarantine) policy which has changed little since 1972. This policy has recently been reviewed in light of new information obtained by planetary exploration during the past decade and because of changes to, or uncertainties in, some parameters used in the existing quantitative approach. On the basis of this analysis, a new planetary protection policy, with the following key features, is proposed: deemphasizing the use of mathematical models and quantitative analyses; establishing requirements for target planet/mission type (i.e., orbiter, lander, etc.) combinations; considering sample return missions a separate category; simplifying documentation; and imposing implementing procedures (i.e., trajectory biasing, cleanroom assembly, spacecraft sterilization, etc.) by exception, i.e., only if the planet/mission combination warrants such controls. Interpretation of the new policy for missions like Galileo, Mars Surface Sample Return, Saturn Orbiter with Twin Probes, and missions to comets are considered. In general, the new policy proposes elimination of all but documentation requirements for most planetary missions and simplification of the remaining compliance procedures.     

Implementing planetary protection requirements for sample return missions.

NASA is committed to exploring space while avoiding the biological contamination of other solar system bodies and protecting the Earth against potential harm from materials returned from space. NASA's planetary protection program evaluates missions (with external advice from the US National Research Council and others) and imposes particular constraints on individual missions to achieve these objectives. In 1997 the National Research Council's Space Studies Board published the report, Mars Sample Return: Issues and Recommendations, which reported advice to NASA on Mars sample return missions, complementing their 1992 report, The Biological Contamination of Mars Issues and Recommendations. Meanwhile, NASA has requested a new Space Studies Board study to address sample returns from bodies other than Mars. This study recognizes the variety of worlds that have been opened up to NASA and its partners by small, relatively inexpensive, missions of the Discovery class, as well as the reshaping of our ideas about life in the solar system that have been occasioned by the Galileo spacecraft's discovery that an ocean under the ice on Jupiter's moon Europa might, indeed, exist. This paper will report on NASA's planned implementation of planetary protection provisions based on these recent National Research Council recommendations, and will suggest measures for incorporation in the planetary protection policy of COSPAR.     

An ethical approach to planetary protection

What hazards might biological contamination pose to planets, comets and other celestial bodies visited by probes launched from Earth? What hazards might returning probes pose to Earth and its inhabitants? What should be considered an acceptable level of risk? What technologies, procedures and constraints should be applied? What sort of attitude has to be chosen concerning human crews, who themselves could become both contaminated victims and contaminating agents? The vast issue of planetary protection must, more than ever, spark ethical debate. Space treaty, COSPAR recommendations offer borders and context for this reflection, which has to be introduced in the actual humanist: never has been anthropocentrism so practical and concerned, in the same time, by the next generations, because of the historical character of life. At least an ethics of risk is necessary (far from the myth of zero-risk) for all the three types of contamination: other celestial bodies (forward contamination), Earth (backward contamination) and astronauts.     

Legal aspects of planetary protection for Mars missions.

The planning and execution of manned and robotic missions to Mars present a wide range of jurisprudential issues. Provisions to prevent the disruption of natural celestial environments, as well as damage to the environment of Earth by the return of extraterrestrial materials, are important components of the law applicable to mankind's activities in outer space, and have been supplemented by scientifically instituted planetary protection policies. However, divergent legal regimes may exist, as the space treaties in force are neither uniform in their provisions, nor identical as to the states which have signed, ratified, or adopted the international agreements. The legal requirements applicable to a specific mission will vary depending on the entities conducting the program and specific mission profile. This article analyzes the divergent international legal regimes together with the factors which will influence the determination of the standards of conduct which will govern manned and robotic missions to Mars.     

Sailing with solar and planetary radiation pressure

Literature on solar sailing has thus far mostly considered solar radiation pressure (SRP) as the only contribution to sail force. However, considering a sail in a planetary mission scenario, a new contribution can be added. Since the planet itself emits radiation, this generates a radial planetary radiation pressure (PRP) that is also exerted on the sail. Hence, this work studies the combined effects of both SRP and PRP on a sail for two case studies, i.e. Earth and Venus. In proximity of the Earth, the effect of PRP can be significant under specific conditions. Around Venus, instead, PRP is by far the dominating contribution. These combined effects have been studied for single- and double-sided reflective coating and including eclipse. Results show potential increase in the net acceleration and a change in the optimal attitude to maximise the acceleration in a given direction. Moreover, an increasing semi-major axis manoeuvre is shown with and without PRP, to quantify the difference on a real-case scenario.     

Wireless sensor networks for planetary exploration: Experimental assessment of communication and deployment

Planetary surface exploration is an appealing application of wireless sensor networks that has been investigated in recent years by the space community, including the European Space Agency. The idea is to deploy a number of self-organizing sensor nodes forming a wireless networked architecture to provide a distributed instrument for the study and exploration of a planetary body. To explore this concept, ESA has funded the research project RF Wireless for Planetary Exploration (RF-WIPE), carried out by GMV, SUPSI and UPM. The purpose of RF-WIPE was to simulate and prototype a wireless sensor network in order to assess the potential and limitations of the technology for the purposes of planetary exploration.     

Designing planetary protection into the Mars Observer mission.

Planetary protection has been an important consideration during the process of designing the Mars Observer mission. It affected trajectory design of both the interplanetary transfer and the orbits at Mars; these in turn affected the observation strategies developed for the mission. The Project relied mainly on the strategy of collision avoidance to prevent contamination of Mars. Conservative estimates of spacecraft reliability and Martian atmosphere density were used to evaluate decisions concerning the interplanetary trajectory, the orbit insertion phase at Mars, and operations in orbit at Mars and afterwards. Changes in the trajectory design, especially in the orbit insertion phase, required a refinement of those estimates.     

U.S. planetary protection program: Implementation highlights

The implementation of planetary protection in the United States space program has reflected the trend in policy from an absolute to a probabilistic prohibition of the contamination of the celestial bodies of the solar system. The early emphasis on spacecraft sterilization (e.g. Ranger) was replaced by the imposition of contamination control procedures on later missions such as Pioneer, Viking, and Voyager. Similarly, analytical and laboratory techniques were developed to demonstrate compliance with probabilistic requirements. Microbial burden reduction methods that are not hazardous for spacecraft reliability supplanted the abstract concept of sterilization. The United States implementation of planetary protection has been completely successful. In an exploration program that has included Mercury, Venus, Mars, the Jovian system, and the Saturnian system, there have been no accidental impacts or detection of false positives (terrestrial microbes). Further, the contamination control and microbial burden procedures have proved beneficial to spacecraft systems and on-board science instruments. We review in this paper the implementation of planetary protection procedures by the Pioneer (10 and 11), Viking and Voyager projects.     

An alternative approach to solar system exploration providing safety of human mission to Mars.

For systematic human Mars exploration, meeting crew safety requirements, it seems perspective to assemble into a spacecraft: an electrical rocket, a well-shielded long-term life support system, and a manipulator-robots operating in combined "presence effect" and "master-slave" mode. The electrical spacecraft would carry humans to the orbit of Mars, providing short distance (and low signal time delay) between operator and robot-manipulators, which are landed on the surface of the planet. Long-term hybrid biological and physical/chemical LSS could provide environment supporting human health and well being. Robot-manipulators operating in "presence effect" and "master-slave" mode exclude necessity of human landing on Martian surface decreasing the level of risk for crew. Since crewmen would not have direct contact with the Martian environment then the problem of mutual biological protection is essentially reduced. Lightweight robot-manipulators, without heavy life support systems and without the necessity of returning to the mother vessel, could be sent as scouts to different places on the planet surface, scanning the most interesting for exobiological research site. Some approximate estimations of electric spacecraft, long-term hybrid LSS, radiation protection and mission parameters are conducted and discussed.     

A consensus approach to planetary protection requirements: recommendations for Mars lander missions.

Over the last several years, the nature of the surface conditions on the planet Mars, our knowledge of the growth capabilities of Earth organisms under extreme conditions, and future opportunities for Mars exploration have been under extensive review in the United States and elsewhere. As part of these examinations, in 1992 the US Space Studies Board made a series of recommendations to NASA on the requirements that should be implemented on future missions that will explore Mars. In particular, significant changes were recommended in the requirements for Mars landers, changes that significantly alleviated the burden of planetary protection implementation for these missions. In this paper we propose a resolution implementing this new set of recommendations, for adoption by COSPAR at its 30th meeting in Hamburg. We also discuss future directions and study areas for planetary protection, in light of changing plans for Mars exploration.     

Societal issues as Mars mission impediments: planetary protection and contamination concerns.

Societal and non-scientific factors represent potentially significant impediments for future Mars missions, especially in areas involving planetary protection. This paper analyzes public concerns about forward contamination to Mars and back contamination to Earth, evaluates major areas where lack of information may lead to uncontrollable impacts on future missions, and concludes that NASA should adopt a strategy that actively plans both the generation and subsequent management of planetary protection information to ensure that key audiences obtain needed information in a timely manner. Delay or avoidance in dealing with societal issues early in mission planning will increase the likelihood of public opposition, cost increases and missed launch windows. While this analysis of social and non-scientific considerations focuses on future Mars missions, the findings are also relevant for RTG launches, nuclear propulsion and other NASA activities perceived to have health, safety or environmental implications.     

Modern aspects of planetary protection and requirements to sterilization of space hardware.

The viewpoint of working group of Russian experts on the problem of planetary protection for future manned and unmanned Mars mission is presented. Recent data of Martian environment and on survival of terrestrial microorganisms in extreme conditions were used for detailed analysis and overview of planetary protection measures in regard to all possible flight situations including accidental landing. The special emphasis on "Mars-94" mission was done. This analysis resulted in revised formulation of spacecraft sterilization requirements and possible measures for their best implementation. New general combined approach to spacecraft sterilization was proposed. It includes penetrating radiation and heat treatment of spacecraft parts and components which is to be carried out before the final assembly of spacecraft and gaseous radiation sterilization of the whole spacecraft during the flight to Mars (or from Mars for return missions).     

Some photometric techniques for atmosphereless solar system bodies.

We discuss various photometric techniques and their absolute scales in relation to the information that can be derived from the relevant data. We also outline a new scattering model for atmosphereless bodies in the solar system and show how it fits Mariner 10 surface photometry of the planet Mercury. It is shown how important the correct scattering law is while deriving the topography by photoclinometry.     

X-ray pulsar-based navigation system with the errors in the planetary ephemerides for Earth-orbiting satellite

The objective of this paper is to investigate and reduce the impact of the errors in the planetary ephemerides on X-ray pulsar-based navigation system for Earth-orbiting satellite. Expressions of the system biases caused by the errors in the planetary ephemerides are derived. The result of investigation has shown that the impact of the error in Earth’s ephemeris is must greater than the errors in the other ephemerides and would greatly degrade the performance of X-ray pulsar-based navigation system. Moreover, the system bias is modeled as a slowly time-varying process, and is handled by including it as a part of navigation state vector. It has been demonstrated that the proposed navigation system is completely observable, and some simulations are performed to verify its feasibility.     

Planetary protection issues in advance of human exploration of Mars.

Current planetary quarantine considerations focus on robotic missions and attempt a policy of no biological contamination. The presence of humans on Mars, however, will inevitably result in biological contamination and physical alteration of the local environment. The focus of planetary quarantine must therefore shift toward defining and minimizing the inevitable contamination associated with humans. This will involve first determining those areas that will be affected by the presence of a human base, then verifying that these environments do not harbor indigenous life nor provide sites for Earth bacteria to grow. Precursor missions can provide salient information that can make more efficient the planning and design of human exploration missions. In particular, a robotic sample return mission can help to eliminate the concern about returning samples with humans or the return of humans themselves from a planetary quarantine perspective. Without a robotic return the cost of quarantine that would have to be added to a human mission may well exceed the cost of a robotic return mission. Even if the preponderance of scientific evidence argues against the presence of indigenous life, it must be considered as part of any serious planetary quarantine analysis for missions to Mars. If there is life on Mars, the question of human exploration assumes an ethical dimension.     

Planetary protection policy overview and application to future missions.

The 1967 treaty on the peaceful uses of outer space reflected both concerns associated with the unknown nature of the space environment and the desire of the world scientific community to preserve the pristine nature of celestial objects until such times as they could be studied in an effective manner. Since 1967, NASA has issued policy directives that have adopted the guidelines of COSPAR for protecting the planets from contamination by Earth organisms and for protecting the Earth from the unknown. This paper presents the current status of planetary protection (quarantine) policy within NASA, and a prospectus on how planetary protection and back contamination issues might be addressed in relation to future missions envisioned for development by NASA either independently, or in cooperation with the space agencies of other nations.     

Chemical evolution of primitive solar system bodies.

In this paper we summarize some of the most salient observations made recently on the organic molecules and other compounds of the biogenic elements present in the interstellar medium and in the primitive bodies of the solar system. They include the discovery of the first phosphorus molecular species in dense interstellar clouds, the presence of complex organic ions in the dust and gas phase of Halley's coma, the finding of unusual, probably presolar, deuterium-hydrogen ratios in the amino acids of carbonaceous chondrites, and new developments on the chemical evolution of Titan, the primitive Earth, and early Mars. Some of the outstanding problems concerning the synthesis of organic molecules on different cosmic bodies are also discussed from an exobiological perspective.     

Dark matter in the outer solar system.

There are now a large number of small bodies in the outer solar system that are known to be covered with dark material. Attempts to identify that material have been thwarted by the absence of discrete absorption features in the reflection spectra of these planetesimals. An absorption at 2.2 micrometers that appeared to be present in several objects has not been confirmed by new observations. Three absorptions in the spectrum of the unusually red planetesimal 5145 Pholus are well-established, but their identity remains a mystery.     

Performance analysis of an attitude control system for solar sails using sliding masses

This paper deals with the attitude control performance analysis of a square solar sail. Two sliding masses are moved inside and along mast lanyards for the control around the pitch and yaw axes. An optimal linear controller with a feedback and a feedforward part is used to control the attitude of the sail. Numerical simulations have been carried out to investigate the system’s ability of performing precise and near-time-optimal reorientation maneuvers as well as the controller’s sensitivity with respect to the sail parameters, as the center of pressure to the center of mass offset or the sail’s size. Our simulation results are finally shown and discussed.     

Selection of sterilization methods for planetary return missions.

Two tasks must be accomplished to provide planetary protection for Mars return missions: (1) sterilization of the scientific module to be landed on Mars and (2) reliable sterilization of all material returned to Earth, while ensuring the scientific integrity of martian samples. This paper examines similarity and differences between these two tasks, and includes a discussion of technological implementation conditions and the nature of terrestrial and hypothesized martian microflora. The feasibility of a number of chemical and physical (ultraviolet and ionizing radiation and heating) methods of sterilization for use on the ground and onboard are discussed and compared. A combination of different methods will probably be selected as the most appropriate for ensuring planetary protection on the return mission.