Summaries of Major Reports
3.1 Archiving Microgravity Flight Data and Samples
A Report of the Committee on Microgravity Research1
The Need for Archiving
Experiments are conducted in microgravity primarily to add to our store of scientific knowledge and understanding. Their purpose is to acquire critical data and samples needed to test hypotheses and check specific theoretical predictions, and sometimes, to determine how certain phenomena are altered under a specified set of experimental conditions. As in every field of science, the primary method of archiving experimental data and results from microgravity experiments is through publication of the research in peer-reviewed journals. Experiments performed in a low-gravity environment should not be an exception to this practice, and NASA should continue to encourage its investigators to publish their results. However, it is also the case that today’s journals are limited with respect to the amount of data they can publish from any one experiment. This limitation may pose a problem for other scientists interested in the results of experiments performed aboard orbiting spacecraft, because such experiments cannot be easily reproduced, owing in part to the high cost of conducting microgravity experiments, particularly those carried out in the long-duration microgravity environment of a spacecraft. The data and samples arising from such experiments are also costly, especially when compared with their terrestrial counterparts, which can usually be generated at a small fraction of the cost incurred for those returned from space. In addition, access to microgravity is limited through the stringent scheduling restrictions of space launches, making it either difficult or impossible for other scientists to plan repeat experiments and execute them in a timely manner.
A recent, informal survey distributed by MSAD to a limited sample of the microgravity user community suggested little demand for a formal process of data and sample archiving. Some of those scientists surveyed felt that traditional journal articles and other bibliographic sources sufficed for their personal archiving needs. However, it was also clear from their replies that some of the respondents were unaware of the opportunities for searching for and accessing data from an active microgravity archive.
The dual factors of high cost and limited access to space underscore the need for preserving at least some of the data produced in the course of conducting microgravity experiments. Indeed, an effective strategy for archiving data sets from flight experiments represents a prudent protection of NASA’s and the nation’s research investment. The justification for archiving data and preserving samples must consider their value, judged by both the cost of reproducing them and their future utility. Such judgments are, of course, subjective and difficult to quantify.
Purpose and Scope of This Study
To obtain help in evaluating its current strategy for archiving data and samples obtained in microgravity research, NASA’s Microgravity Science and Applications Division (MSAD) asked the Space Studies Board’s Committee on Microgravity Research for guidance on the following questions:
What data should be archived and where should it be kept?
In what form should the data be maintained (electronic files, photographs, hard copy, samples)?
What should the general format of the database be?
To what extent should it be universally accessible and through what mechanisms?
Should there be a period of time for which principal investigators have proprietary access? If so, how long should proprietary data be stored?
What provisions should be made for data obtained from ground-based experiments?
What should the deadline be for investigators placing their data in the archive?
How long should data be saved? How long should data be easily accessible?
As a prelude to making recommendations for optimum selection and storage of microgravity data and samples, the committee in this report briefly describes NASA’s past archiving practices and outlines MSAD’s current archiving strategy. Although the committee found that only a limited number of experiments have thus far been archived, it concluded that the general archiving strategy, characterized by MSAD as minimalist, appears viable. A central focus of attention is the Experiment Data Management Plan (EDMP), MSAD’s recently instituted data management and archiving framework for flight experiments. Many of the report’s recommendations are aimed at enhancing the effectiveness of the EDMP approach, which the committee regards as an appropriate data management method for MSAD. Other recommendations provide guidance on broader issues related to the questions listed above. This report does not address statutory or regulatory records retention requirements.
PAST ARCHIVING PRACTICES AND CHANGING NEEDS
Microgravity research has been identified as a distinct spaceflight activity within NASA’s space science and applications programs since the mid-1970s. Some of the first microgravity experiments and low-gravity demonstrations were conducted by astronauts aboard the Skylab and the Apollo-Soyuz spacecraft. Early materials-processing spaceflight activities carried out under the auspices of the Marshall Space Flight Center (MSFC) led to the first recovery of microgravity spaceflight data and samples. These early experiments and demonstrations produced processed materials and biological samples as well as a wide range of data, including temperatures, pressures, and other physical measurements. The data were recorded in a variety of formats such as photographs, video tape, and cinefilm. Electronic data were sent to MSFC by telemetry or delivered there post-flight, often in the form of magnetic tape.
Principal investigators (PIs) who participated in early microgravity spaceflight activities submitted experiment implementation plans to NASA, the purposes of which were to describe their proposed flight experiments and their anticipated post-flight analyses. After being given a specified period—usually 1 year—for post-flight data analysis, PIs prepared their final report, including a description of the disposition of the data and the microgravity samples. Unused portions of flight samples were to be returned to MSFC, cataloged by the archivist, and treated as “space artifacts.” Scientific results from individual spaceflight experiments usually were published in the form of NASA technical memoranda and as peer-reviewed journal articles. Such publications were tracked through a bibliographic archive also assembled and maintained at the Space Science Laboratory at MSFC. Summaries of experiments performed on the early microgravity missions were published by NASA as a series of Microgravity Materials
Processing technical memoranda. Publication as a NASA technical memorandum of the combined scientific results of multi-investigator spaceflight missions continues to the present day.2
Descriptive information on microgravity experiments and missions, accumulated by NASA and its investigators through 1990, began to be archived several years ago at MSFC. This set of experiment descriptions, originally a PC-based flat file with bibliographic references, was created by a NASA staff member at MSFC and then brought to its current status with the assistance of a contractor. This database has now been ported to the World Wide Web and renamed MICREX. The MICREX database is a useful source of historical microgravity information. Were the MICREX database updated to include descriptions and bibliographic information for all the microgravity experiments conducted after 1990, its value as a historical record would be greatly enhanced.
As NASA’s microgravity research program expanded and matured beyond the early years, entirely new scientific components were added to microgravity research beyond the original emphasis on materials processing. For example, the growth of macromolecular crystals, low-temperature physics, fluid dynamics, combustion science, and the integration of international pay loads were all gradually added. These new science activities have vastly complicated the requirements for archiving samples and data. For example, protein crystals cannot be archived because they degrade rapidly, and so a principal component of the archived data would be the x-ray diffraction data collected from such crystals. These data, when compared with similar data collected from laboratory-grown crystals, provide the primary means of analyzing the results of the protein crystal growth experiments conducted in microgravity. By contrast, mid-deck or glovebox microgravity experiments often yield photographic film and video tape data. These data are usually retained by the responsible NASA center, and the PI is provided the first copy.
International experiments, which are becoming more frequent, further complicate the archiving of data and samples because of the need for data sharing and negotiated sharing of resources and responsibilities among the participating national organizations. Experience has also shown that the methods employed in using, tracking, and returning space-processed materials are not uniform among the world’s space agencies and PIs collaborating on international microgravity research. Contributing to the complications in the archiving of microgravity spaceflight results from international experiments is the fact that the lines of authority and the rules and responsibilities governing non-U.S. PIs, their national funding sources, and the space agencies that develop and support their space facilities are usually different from those for U.S. microgravity investigators.
CURRENT MSAD ARCHIVING STRATEGY AND METHODS
Recently, MSAD has begun implementing a data management and archiving plan whose key feature is the requirement to file a formal Experiment Data Management Plan (EDMP) for each microgravity flight experiment currently funded and manifested for orbital flight by MSAD. MSAD expects each PI to file an EDMP prior to approval of an experiment for flight. An example of the input form now used by MSAD for the EDMP is shown in the appendix. The essential elements of this new procedure are the following:
The PI and NASA sign an agreement—the EDMP—detailing the responsibilities of each with respect to management of data and samples after the mission.
The PI delivers the agreed-upon data to NASA after the mission.
The data are stored at the Johnson Space Center (JSC), the Marshall Space Flight Center (MSFC), the Lewis Research Center (LeRC), or the Jet Propulsion Laboratory (JPL), depending on the type of flight experiment.
The data are stored at the NASA center in a variety of formats, with little subsequent processing of received data.
No on-line access to the stored data is developed.
The data stored at the four centers are actively managed by the MSFC (which also manages the JSC data) and LeRC (which manages the JPL data), and investigators interested in acquiring available data can contact the data manager at either center.
At present NASA has several main data archives covering different aspects of the MSAD research program. The MICREX is discussed above, and two of the archives located at LeRC are described here. The data produced by the two primary microgravity accelerometer systems developed by NASA are stored in archival form at LeRC. The first of these, the Space Acceleration Measurements System (SAMS), is capable of measuring the spectral power density of the acceleration environment along three axes aboard the space shuttle. The SAMS system permits on-board recording and near-real-time telemetry of the microgravity spectrum, including g-jitter over a spectral range from several hundred hertz down to relatively low frequencies of 1 Hz. The second accelerometer system, the Orbital Acceleration Research Experiment (OARE), is designed to measure the steady levels of the microgravity acceleration. Both SAMS and OARE data for the individual microgravity missions that carry these systems are currently available on CD-ROM with on-line access.
Observational data from fluids and combustion experiments are also stored, in the form of film and video, at LeRC. First-generation copies of these data are produced in CD-ROM format and are cataloged on the World Wide Web. Copies are available for distribution upon request.
To allow for analysis of the results of their microgravity experiments, PIs have traditionally been given exclusive access to the post-flight data and samples for 1 year following their delivery to the PI. Often it takes up to several months for the removal of microgravity experiment data from the spacecraft, intermediate processing, and final delivery to the PI. There are no uniform policies for distribution and retention of unaltered space-processed samples, nor are there uniform requirements to preserve key microgravity facility components, such as sample cartridges and flight furnaces—even though some of these might be needed for replication of experiments in terrestrial runs performed after the mission.
RECOMMENDATIONS AND GUIDANCE FOR MSAD’S MICROGRAVITY DATA AND SAMPLE ARCHIVING STRATEGY
Every microgravity experiment conducted under the auspices of MSAD requires review to determine whether or not some of the data and samples warrant archiving and preservation. In this review, consideration should be given to the cost of archiving, the potential future utility of the data, and their intrinsic scientific value. The high costs and limited opportunities for reproducing microgravity data dictate the need for archival preservation3 based on a careful selection process and an ongoing evaluation of archiving costs in relation to the scientific community’s valuation and use of the microgravity data and samples.
Data to Be Archived
Flight experiments performed in the microgravity sciences vary enormously in size, scope, subject discipline, and data output. It is obvious that each experiment will have differing requirements for the archiving of its useful data and, therefore, decisions about what should be archived by NASA will have to be made on a case-by-case basis. The individual investigator, with the assistance of the NASA project scientist, is in the best position to recommend which data can be most usefully archived. Both the form and content of the archived data (such as video, numeric, photographic) will need to be considered prior to and after the flight. Although digital data should be encouraged because of ease of storage, copying, and access, in some cases much of the value of the original data may be lost if only the extracted numeric values are stored.
With proper implementation, NASA’s EDMP process can serve as an appropriate tool for establishing the form and content of data to be delivered for archiving. The committee believes that the categories of information required by the EDMP for each experiment are appropriate and necessary to properly document the data and samples obtained from flight experiments. The committee recommends that the process for establishing a mutually agreeable EDMP take place early in the mission planning process and that the list of data proposed for archiving by the PI be peer reviewed. Several pre-mission science reviews are already in place, such as the Science Readiness Review and the Requirements Definition Review, during which decisions regarding the EDMP
could be peer reviewed. If flight investigators were required to include at least a preliminary list of archival data and samples in the Science Requirements Document required by NASA for their experiment, the list could be peer reviewed and refined at one or both of these pre-mission science reviews.
Samples to Be Archived
In the past, samples returned from some spaceflight experiments have been retained by the flight PIs, and some of these samples have been completely consumed during post-mission analysis. NASA does have a policy that calls for the archiving of unused portions of flight samples, and the committee encourages NASA to give greater consideration to how this policy should be carried out with respect to future microgravity missions. The same arguments justifying the need for archiving data from flight experiments also hold for samples. In addition, continuing advances in analytical instrumentation make it conceivable, if not almost certain, that new information could be obtained from a flight sample in the years following flight.
The great variation in experiments and sample types makes it impractical to develop a single set of decision rules regarding the disposition and archiving of flight samples. Nonetheless, decisions to preserve samples, and archive data, should ultimately rest on a cost-benefit estimate, wherein the potential costs for reproducing the results, their intrinsic scientific value to the user community, and the prospects for future utility are weighed against incurring present costs for storing the data. Some samples, such as protein crystals, degrade so quickly, or require such stringent storage conditions, that long-term archiving becomes impossible. Decisions about the archiving of samples should, therefore, also be made on a case-by-case basis. The committee recommends that the EDMP process also be used to frame, answer, and then review the question of what portion of flight-generated samples will be retained by the investigator, and what portion, if any, should be transferred to NASA for archiving.
Samples should be retained and made available according to accepted archiving practices. This means that samples of sufficient value to warrant archiving also warrant the expense and effort required to store them under conditions that preclude significant contamination or degradation of the material. Archiving of samples entails proper cataloging of samples so that sufficient information, including the necessary sample history, is available to interested scientists, allowing them to make intelligent queries for use of the sample.
NASA should also develop streamlined procedures by which decisions on applications for use of flight samples can be made expeditiously. Unless a situation arises in which there are a large number of conflicting demands for the use of flight-generated materials, loans of the samples to bona fide investigators can be left to the discretion of the responsible discipline scientist or project scientist. If a conflict arises, it might become necessary for the project scientist to consult with the appropriate MSAD discipline working groups (DWGs) to arrive at a decision.
Location of Archives
In general, samples will be more accessible to other interested scientists if they are stored at a limited number of locations, such as NASA centers. The most reliable method of ensuring future access to flight data and samples is for NASA to establish and maintain central archives. NASA centers are the obvious locations for maintaining these archives, and the committee sees no obvious problem with NASA’s current plan to apportion management of its archives between MSFC and LeRC, as long as there are sufficient pointers guiding inquiries between the two. Each of these archives is now managed independently, and NASA may wish to consider, after gaining further experience with the current system, whether greater coordination between the archives is needed.
In some instances, however, it may be decided that archived samples should reside at the laboratory of the flight investigator. In any case, the location of archived samples should be clearly indicated in the EDMP and in published references to the flight experiment. NASA should also consider other means of alerting the science community to the existence of repositories of samples, such as regular notices in science journals, in NASA newsletters and bulletins, and on Internet World Wide Web home pages.
Format and Accessibility of Archived Material
Archived data and samples serve no purpose if they cannot be subsequently retrieved and used. Access issues have been studied previously by a number of groups, and the committee agrees with the conclusions in Networking
of Materials Property Data4 and Computer-Aided Materials Selection During Structural Design5 that menu-driven and intuitively understood search and retrieval interfaces are essential if the archived data are actually to be used in the future. The use of cryptic command-driven interfaces virtually assures that end-user scientists with limited time will rarely spend the time and effort to relearn those commands each time they want to search for information. In addition, data that are stored in inaccessible or unidentified physical formats will also go unused. Examples include digital data archived without the executable program required to read and organize the data, or a video tape that can be played back only on specialized equipment built by the original investigator. Access remains an issue of special concern for any database that is likely to contain many different types of data.
The committee assumes here that interest in the use of these data will be limited primarily to specialists in the same or related field of science in which the experiment was performed. Scientific users can be expected to be aware of the published literature, where the results of the flight experiment will in most cases be recorded. Such users will have an understanding and appreciation of the general types of data used in that scientific field, and even perhaps some familiarity with the specific data types collected on the archived flight experiment. Therefore, an archive can be designed with the specialized user in mind, as is common practice for many scientific and engineering databases. This approach, stressing specificity, serves both to lower the cost of maintaining the archive and to reduce the amount of ancillary interpretive information that must be created and stored with the experiment data.
The information that is required to interpret experimental results is generally referred to as metadata, and its importance is discussed in some detail in Computer-Aided Materials Selection During Structural Design.6 In designing an archiving capability, it is vital to provide for inclusion of information such as the experimental error and the various parameters that make specific data meaningful.7 It is important to know, for example, a particular material’s composition and probably also the methods by which it was produced. Parameters such as temperature, pressure, humidity, environment, and the like are key to understanding the limitations of the application of the data and how they may be compared with other data from older or future experiments. Metadata supporting the experiment data under evaluation are essential, and decisions concerning the metadata to be archived should be included in the EDMP.
It would not be practical to attempt to list all of the different types of data that might be collected from a microgravity flight experiment, or to try to indicate the information and physical devices that should be stored with primary data. The committee recommends, however, that NASA and its PIs consider the following general guidelines when making decisions on which data to archive and how to ensure their accessibility.
All data selected for archiving should be accompanied by sufficient explanatory metadata to allow a knowledgeable scientist, with access to the published literature, to interpret the contents of the archive independently and with ease and accuracy.
Digitally stored data must be accompanied by a copy of one or more computer programs that are capable of accessing, organizing, and properly displaying these data. Such programs should of course be chosen with ease of use and common platform compatibility in mind. Clear directions for the use of the program and data should also be included in the archive.
Attempts should be made to convert data in rare formats (e.g., holographic film) to more accessible formats. In cases where conversion is not practical or the transfer would result in an unacceptable loss of information, NASA should decide, on the basis of cost, whether to maintain the equipment capable of accessing the data in its archived format.
The committee further recommends that NASA maintain running records of when and how often data and samples from a particular microgravity experiment are requested, in order to judge more accurately the awareness of, and demand for, these data and samples by the scientific community.
As with its archives of samples, NASA should make reasonable attempts to ensure that the scientific community is aware of archived microgravity data and has a means of gaining access to it. The committee recommends that NASA take advantage of the growth in the Internet-based World Wide Web to post EDMPs on-line for all of its microgravity flight experiments. On-line EDMPs ought to list and describe in sufficient detail (1) all of the data and samples that are or will be archived from a flight experiment, (2) the exact location and current status of the samples, and (3) the procedures required to gain access to both data and samples. Sufficient links from various NASA Web home pages should be set in place to allow individuals searching the Internet to locate the EDMPs readily. NASA should also consider using other effective means of alerting the scientific community to the availability of microgravity data and sample archives, such as placing timely notices in newsletters, bulletins, and journals. The committee concluded that so long as adequate mechanisms are in place to alert interested scientists and point them to the appropriate NASA contact from whom data can be requested, it is unnecessary to attempt to place all actual flight experiment data on-line. As a practical matter, many of these flight data sets are too large for on-line storage or access, and, in some cases, data are not in digital form, making on-line access to them difficult, if not impossible.
In addition to the EDMPs, MSAD should also maintain an easily accessible, on-line, central catalog of all of the flight experiments for which data and/or samples are archived. In the case of more recent experiments the catalog might merely contain a pointer to the EDMP locations. For older experiments for which no EDMP was created, the catalog should list the various archived samples and data sets, their locations, and the procedures for gaining access to them.
Proprietary Access and Submission to Archives
It has commonly been NASA’s practice to allow flight investigators exclusive access to their own flight data for 1 year following their receipt of these data. In general, a 1-year period of exclusive use should provide reasonable and sufficient time to allow a PI to analyze these data and initiate steps toward publication of the flight results without the concern of being preempted. The committee recognized that instances may arise in which a PI legitimately requires an extension of the period of exclusive use, and NASA should develop a petition process that allows such requests to be considered. At the end of the period of exclusive use, however, the PI should turn over the agreed-upon data to the NASA archives. NASA, in turn, should monitor PI compliance with this policy rather vigorously, because after the passage of 1 year investigators frequently shift their attention to other projects.
Retention of Data and Samples in Archives
In general, advances occurring in most laboratory sciences limit the utility of a data set to fewer than 10 years beyond the time it was collected. The committee recommends that NASA maintain archived data and samples for 10 years, at the end of which period NASA should seek a recommendation from its internal scientific advisory groups as to whether further archiving is merited. Such reviews could best be performed by the appropriate DWGs, and NASA should make available to them its records on the frequency of requests for the archived material over the preceding decade. Should the DWG determine that further retention of the archive is not needed, then it should recommend whether or not the material be turned over to some national archiving group for purely historical purposes. If neither archiving option is recommended by the review group, then the material should be offered by NASA first to the original flight PI, and then to collaborators. As a final option, NASA should consider utilizing these materials for their educational and outreach value. Space-flown samples, for instance, could be a valuable resource for schools and museums attempting to stimulate young people’s interest in science.
It should be pointed out that in situations such as the on-line storage of digital data sets, the costs of retaining the data indefinitely may be trivial. In such cases NASA may wish to consider waiving the review and retaining the data set in perpetuity.
Data and Samples from Ground-based Experiments
The high cost of performing flight experiments and the limited opportunity to reproduce them have both been cited as reasons for archiving data. This argument does not generally apply to ground-based experiments performed by NASA. In most cases, the ease of reproducing ground-based microgravity experiments (such as those done in
drop-towers) and the additional cost incurred in archiving data from such experiments are likely to outweigh the benefits. However, the need for archiving does apply to baseline data collected on Earth that are a critical component of the flight experiment. Similarly, the EDMP should also contain references to publications derived from ground-based experiments that led to microgravity experiments conducted in flight.
The EDMP approach is, in the committee’s opinion, precisely the kind of data archiving and management policy needed by MSAD. It organizes and imposes discipline and uniformity on the highly diverse, sometimes conflicting, archiving requirements of the user community. Implementing a uniform and effective EDMP policy not only will impose order on the process of data archiving but also will help to ensure that NASA meets its responsibility to the public.
To enhance the effectiveness and utility of EDMPs, the committee offers several additional recommendations:
The committee found that not all microgravity flight experiments have EDMPs, owing in large part to the relatively recent implementation of this policy. EDMPs should be required from all flight PIs early in the flight approval process and should become a part of the Science Requirements Document.
The requirement for the submission of EDMPs ought to be described explicitly in each NASA Research Announcement calling for proposals to perform microgravity research. If the EDMP is specified as a requirement at the initiation of research proposals to perform microgravity flight experimentation, PIs will be encouraged to think about the need for archiving their results from the outset.
EDMPs should be an item for discussion at each of the NASA science reviews at which peer review occurs. A tentative EDMP, developed jointly by the PI and the project scientist, should be presented as early as the Science Requirements Review stage, and then subsequently amended at each of the follow-on reviews. These reviews not only should consider the goals of the experiment in determining what should be archived but also should take a broad view of the potential value of the data to science.
The EDMP should contain a current bibliography of all relevant reports in the public domain and of journal articles on related ground-based research authored by the PI prior to flight, and it eventually should be amended to include those published subsequent to flight.
Completed EDMPs vary somewhat in form and content depending on the NASA center overseeing the preparation of the EDMP. For example, some finished EDMPs have cover pages signed by the PI and the project scientist, each agreeing to the content of the EDMP, whereas others do not. EDMPs should be uniform across all of the microgravity flight experiments sponsored by NASA.
The PI and the project scientist should be given joint responsibility for ensuring on-line availability of their EDMP prior to flight. An Internet Web home page is currently recommended as a common access point for all active EDMPs. Subsequent amendment of on-line EDMPs, both prior to and after a flight, should remain the joint responsibility of the PI and the NASA project scientist.
The committee recognizes that EDMPs do not constitute a data archive per se. EDMPs can facilitate effective and convenient access to the actual archive and should be constructed so as to help serve that purpose.
A number of important questions regarding the archiving of microgravity data and samples will remain unanswered until MSAD has built up sufficient experience in this activity. These questions include such issues as the likely demand for the archived materials and MSAD’s level of success in developing appropriate archives. MSAD will need to monitor closely the implementation and performance of the archiving program in its early operational period in order to ascertain actual user needs and make any necessary adjustments. After a suitable period, perhaps 5 years, MSAD should formally reassess its microgravity archiving activities to evaluate their appropriateness and success.
3.2 Review of NASA’s Planned Mars Program
A Report of the Committee on Planetary and Lunar Exploration1
Although Mars has been a primary target for space science missions over the past three decades, the record of success in the last few years has been poor. Indeed there has not been a completely successful Mars mission since the Viking project in the late-1970s. The failure of the Mars Observer mission in 1993 was a particularly hard blow for the planetary science community, because this spacecraft was scheduled to address many of the highest-priority investigations of the Red Planet. To recover from the loss of Mars Observer, NASA initiated Mars Surveyor, an extended program aimed at sending two small spacecraft to Mars during every launch opportunity between now and 2005. Mars Surveyor is cost-capped at $156 million (including operations and launch vehicles) per year, and its announced goals are the study of martian climate, life, and “resources.” The first mission, the 1050-kg Mars Global Surveyor, will be launched in November 1996 and will carry duplicates for much of Mars Observer’s pay load. A Discovery mission, Mars Pathfinder, consisting of a 325-kg lander and a 10-kg roving vehicle, will also be sent to Mars during this launch window. Subsequent missions in the Mars Surveyor program are expected to carry the remaining two instruments from Mars Observer and to conduct more complex observations, both on the surface and from orbit, perhaps in cooperation with international partners.
Given that Mars is one of the highest-priority objects for study identified in COMPLEX’s 1994 report, An Integrated Strategy for the Planetary Sciences: 1995–2010,2 the Space Studies Board asked COMPLEX to review whether the Mars Surveyor and Mars Pathfinder programs, as presently conceived, satisfy the highest priorities for understanding Mars as provided in [this] report. Given that Mars Surveyor’s “smaller-faster-cheaper” philosophy is very different from that of past NASA planetary missions, the current report’s emphases concern not just the planned scientific objectives but also the effectiveness of using numerous, small missions with focused goals to explore Mars; COMPLEX does not assess the specific details of the program, which, especially in the out-years, is more conceptual than specific.
A complete exploration of Mars would require measurements of the planet’s atmosphere, soil, rocks, and interior, as well as the surrounding near-Mars space environment. The missions in the Mars Surveyor program should be able to conduct fruitful experiments on the characteristics of the soil and atmosphere, since these are everywhere available. If a network of miniature meteorology stations were emplaced, then a major objective of atmospheric science could be accomplished. While studies of Mars’s upper atmosphere are currently absent from the Mars Surveyor program, many of this field’s objectives might be achieved through NASA’s planned participation in Japan’s Planet B mission.
Cost and pay load limitations imposed on Mars Surveyor’s small landers might prevent the flight of advanced rovers capable of adequate sampling of the rock record. Because evidence for past climate changes and ancient life, if any, is most likely embedded in the rocks, this is a major shortcoming. Sounding of the interior requires simultaneous operation of at least three widely spaced seismology stations. This may be accomplished in the Mars Surveyor program as currently defined only if sophisticated landers, having less mass than Mars Pathfinder, can be developed; if not, it may become feasible in cooperation with the European Space Agency. A coordinated program with the Russians, in which they land an advanced rover, may alleviate the problem of access to solid rocks; alternatively NASA might develop advanced rovers on its own.
The missions currently planned do, within the Mars Surveyor program, have the potential of adding significantly to our understanding of Mars. Not only does Surveyor recover essentially all of Mars Observer’s objectives, which are essential first steps according to the Integrated Strategy, but it also initiates a challenging program of surface exploration by small landers with highly focused science goals. In addition, some aspects of COMPLEX’s strategy not addressed by Mars Surveyor are being or can be addressed by judicious cooperation with international partners.
Spacecraft instrumentation is of great concern to COMPLEX. Because the Mars Surveyor program is on a fast track, there is inadequate time to allow some instruments to be developed to a sufficient level so that risk is small. Furthermore, although plans are being formulated outside the Surveyor program to reduce significantly the size of spacecraft, schemes to produce complementary and innovative miniaturized instruments are absent. Yet the success of the Mars Surveyor program will depend to a considerable extent on how sophisticated a payload can be flown within the program’s stringent constraints on cost, schedule, and mass. Because funding within the Surveyor program is too limited to foster significant development of so-called microinstruments, the scientific objectives of the program could be seriously undermined unless instrument development is externally supported. Thus, to ensure important scientific advancement either microinstrument development should become an essential component of NASA’s New Millennium spacecraft technology program, or some activity comparable to the existing Planetary Instrumentation Definition and Development Program (PIDDP) should be initiated for microinstruments.
A longer-term concern is that as the program progresses it may become increasingly difficult to make major discoveries with the small landers currently envisaged. In any transition to more ambitious missions, including sample return, long-range rovers equipped with significant instrumentation may be necessary for the definitive resolution of questions concerning past climates and history.
Despite these potential problems, the Mars Surveyor program (as long as NASA continues to interpret “resources” to include martian geology, geophysics, and geochemistry) provides a major opportunity to broaden and deepen our understanding of Mars—its atmosphere and climate, its geochemistry and geophysics, and, to a somewhat lesser extent, its present and past potential for harboring life. Because the program includes many launches over many years, it—like the Discovery program—can, in principle, afford to be bolder and take greater scientific and technological risks than the more restrictive programs of the past. This opportunity for innovation should not be missed. However, substantial technological innovation will occur only if NASA adopts a new attitude toward risk management. As COMPLEX has emphasized previously, the ability to accept the occasional but inevitable disappointments that come when trying innovative solutions must be an integral feature of NASA’s emphasis on small missions.3 While long-established, hard-earned attitudes cannot be expected to change overnight, the smaller-faster-cheaper approach will demand that some additional risk be accepted.
In summary, although NASA’s Mars exploration program does not meet all scientific requirements (e.g., in aeronomy, internal structure, and seismic activity, or with respect to a sophisticated exploration for extant or extinct life), it will be broadly consistent with a significant subset of the scientific priorities outlined in the Integrated Strategy provided that:
The program of global mapping planned to start with Mars Global Surveyor in 1996 is completed by flying the Pressure Modulator Infrared Radiometer in 1998 and the Gamma-Ray Spectrometer in 2001;
The mobility of landers and other vehicles is enhanced beyond that exemplified by Mars Pathfinder’s rover so as to allow measurements to be made on a wide variety of rocks and terrains;
The Mars Surveyor program is kept flexible so that it can respond to scientific and technological opportunities and can encompass a broad range of mission modes;
International partners continue to be involved in order to supplement U.S. capabilities and leverage U.S. resources committed to the program;
An aggressive program for development of miniaturized instruments is initiated; and
The goal of returning samples of martian soil, atmosphere, and, most importantly, rocks remains a central element of NASA’s planning.
3.3 Radiation Hazards to Crews of Interplanetary Missions: Biological Issues and Research Strategies
A Report of the Task Group on Biological Effects of Space Radiation1
NASA’s long-range plans include possible human exploratory missions to the moon and Mars within the next quarter century. Such missions beyond low Earth orbit will expose crews to transient radiation from solar particle events as well as continuous high-energy galactic cosmic rays ranging from energetic protons with low mean linear energy transfer (LET) to nuclei with high atomic numbers, high energies, and high LET. Because the radiation levels in space are high and the missions long, adequate shielding is needed to minimize the deleterious health effects of exposure to radiation.
The knowledge base needed to design shielding involves two sets of factors, each with quantitative uncertainty—the radiation spectra and doses present behind different types of shielding, and the effects of the doses on relevant biological systems. It is only prudent to design shielding that will protect the crew of spacecraft exposed to predicted high, but uncertain, levels of radiation and biological effects. Because of the uncertainties regarding the degree and type of radiation protection needed, a requirement for shielding to protect against large deleterious, but uncertain, biological effects may be imposed, which in turn could result in an unacceptable cost to a mission. It therefore is of interest to reduce these uncertainties in biological effects and shielding requirements for reasons of mission feasibility, safety, and cost.
This report of the Task Group on the Biological Effects of Space Radiation summarizes current knowledge of the types and levels of radiation to which crews will be exposed in space and discusses the range of possible human health effects that need to be protected against (Chapters 1 and 2). It points out that recent reductions in facilities for radiation research raise concerns about how best to acquire needed new knowledge. The report goes on to suggest other steps to be taken and the types of experiments needed to reduce significantly the level of uncertainty regarding health risks to human crews in space (Chapter 3). In Chapter 4 the task group recommends priorities for research from which NASA can obtain the information needed to evaluate the biological risks faced by humans exposed to radiation in space and to mitigate such risks. It outlines, in general terms, the commitment of resources that NASA should make to carrying out these experiments in order to design effective shielding in time for a possible mission launch to Mars by 2018, which would allow for energetically favorable flight trajectories. Chapter 5 addresses additional issues pertinent to carrying out studies on the effects of radiation, and the appendixes provide additional details and clarification as appropriate.
Summarized below are the task group’s conclusions, its recommendations for future experiments, and its estimates of the time needed to carry out these experiments. The data from these experiments should permit NASA to design cost-effective shielding to protect astronauts from the deleterious effects of radiation in space.
The principal risks of suffering early effects as a result of exposure to radiation in space arise from solar particle events (SPEs). It is not too difficult a task to provide appropriate shielding or storm shelters to protect against exposure during SPEs, but surveillance methods to predict and detect solar particle events from both sides of the sun relative to a spacecraft must be improved.
The kinds of biological effects resulting from exposure to the ionizing radiation encountered in deep space do not differ from those resulting from exposure to x rays. However, the quantitative difference between the risks posed by x rays (low-LET radiation) and by heavy high-energy nuclei (high-LET radiation) may be large, and the magnitude of the human biological effects is largely unknown. An understanding of these effects—including cancer induction, central nervous system changes, cataract formation, heritable effects, and early effects on body organs and function—as well as of the shielding necessary to mitigate these effects for crew members, is essential for the rational design of space vehicles built for interplanetary missions.
The task group members generally agreed that the potential late effects of radiation are the major concern in estimating risks to crew members. Of the known late effects, cancer is currently considered to be the most important. However, experimental data suggest that exposure to high-atomic-number and high-energy (HZE)
particles may also pose a risk of damage to the central nervous system (CNS). Since it is estimated that during a 1-year interplanetary flight each 100-µm2 cell nucleus will be traversed by a primary energetic particle of atomic number greater than 4,2 further experimentation is essential to determine if CNS damage is a significant risk.
To estimate the cancer risk posed by exposure of humans to radiation such as HZE particles, for which no human data are available, it is necessary to use data on the Japanese atomic bomb survivors exposed to acute low-LET radiation and then extrapolate, based on experimental data, to estimate the risks posed by high-LET radiation. At present, the only comparative data for cancer are for studies on the induction of Harderian gland tumors in mice. Additional research is required to reduce the uncertainties of the assumptions inherent in this approach. To calculate risks associated with exposure to low-fluence-rate HZE particles, it is assumed, based on cell and animal studies, that there is not a large dose-rate effect.
Biophysical models and data for cell killing and mutagenesis indicate that as the LET increases, the biological effect of the radiation increases to a maximum near a LET of 100 keV/mm and then decreases at higher LET. (See, for example, NCRP Report No. 98.3) However, no such decrease was observed in the one animal tumor for which data were obtained using a number of heavy ions with increasing LET.4 This discrepancy creates uncertainties in estimates of risks associated with exposure to particles at these higher LETs. To resolve these uncertainties, additional systematic studies are needed on the induction in animals of other radiobiologically well characterized cancers, such as leukemia and breast cancer. From a practical point of view, sufficiently accurate data can only be obtained from ground-based experiments using acute doses.
The background frequencies of the heritable changes in humans, which might be increased by exposure to radiation, range from ~10−5 to 3×10−3 per genetic locus.5 The minimum chronic dose that would double these values is ~4 Sv,6 a value greater than that given in NASA’s current lifetime exposure guidelines. Hence, the genetic risk—the absolute increase in the frequencies of heritable changes—to an astronaut will be low. The risk to the gene pool of the overall human population will of course be far lower due to the relatively small number of space-faring humans.
The doses of radiation to which crews are exposed in space are not expected to induce early deterministic effects, with the possible exception of skin damage and a temporary reduction in fertility. Skin damage is likely only following exposure at high doses outside the spacecraft. Experimental studies in dogs indicate that any reduction in fertility per unit dose of radiation may be greater for low-dose-rate, protracted exposure than for acute exposure.7
The space vehicles used for missions of short duration in low Earth orbit have required minimal optimization of radiation shielding for crew protection purposes. In contrast, optimization of shielding for prolonged interplanetary trips will be a major factor in the design and cost of space vehicles. It will be necessary to know, for protons and HZE particles, the basic nuclear cross sections for interactions and fragmentation in shielding. Such data will be used to calculate the particle distributions and energies present behind different types of shielding as a result of the incident radiation passing through the shield material. Such transport calculations must be verified by ground-based experiments.
A knowledge of the particle types and energies present behind types of shielding should be used, with appropriate risk models, to calculate biological effects—cell killing, mutations, chromosomal changes, and tumor induction—in animals exposed to radiation. NASA investigators should also obtain parallel experimental data for the same radiation types and energies and compare these to the results calculated with models. This research is best accomplished at ground-based facilities.
Microgravity has little effect on the responses of simple cellular systems to radiation,8 and uncertainties about the effects of microgravity seem negligible compared with the other uncertainties regarding risk (see 11 below). Doing cell biology and cancer induction experiments in space is costly and difficult and would require that a source of radiation be carried in the spacecraft. Because only a limited number of animals could be investigated, the results would not be statistically significant. Hence, for the study of living systems, radiation experiments in space should have a very low priority compared with ground-based research.
The estimated overall uncertainty in the risks of radiation-induced biological effects ranges from a factor of 4- to 15-fold greater to a factor of 4- to 15-fold smaller than our present estimates because of uncertainties both in the way HZE particles and their spallation products penetrate shielding (particle transport) and in the quantitative way in which these types of radiation affect biological functions.9 In the absence of precise data and calculations, the shielding would have to protect crew members against the higher, but uncertain, estimated risk. The cost of this possibly unnecessary shielding has been estimated by NASA researchers to be in the range of $10 billion to $30 billion.10 In comparison, the cost of a ground-based, dedicated HZE particle research accelerator is estimated (in 1996) to be $18.7 million, with an annual operating cost of about $4 million for 2000 operating hours per year.11,12 The disparity between the excess cost of additional shielding and the annual NASA budget for biology and space radiation physics indicates the need for a significant increase in the research budget for these areas.
Major radiation facilities—including both specialized radiation sources and animal colonies—have been shut down in recent years. At present, there are severe limits on the availability of radiation particle types and particle energies for HZE particle research. NASA can no longer rely on the Department of Energy and the Department of Defense for expertise, research, and facilities. If the necessary facilities, expertise, and funding were available now, it would take approximately 10 years to provide data that NASA needs to assess the best way to provide appropriate safeguards for its spaceflight crews.
Unless NASA obtains access to a reliable source of HZE particles with an appropriate support staff for a significant fraction of each year, it will take well over 10 years, perhaps over 20 years, depending on the level of effort, to reduce the present large uncertainties in particle transport behavior and in the biological response functions for cancer induction. Such a delay will postpone the design of necessary shielding or may result in the use of excess shielding (at a higher cost) and possibly delay any planned Mars mission beyond the next quarter century.
In Chapter 4, the task group outlines its recommendations for research priorities that NASA should follow to obtain the information needed to evaluate the biological risks faced by humans exposed to radiation in space and to mitigate such risks. The research priorities recommended by the task group include extensive physical and biological experiments, including animal studies using light and heavy nuclei up to 1 GeV/nucleon. Such experiments could take more than 20 years at NASA’s present utilization rate of approximately 100 hr/yr of accelerator time at Brookhaven Laboratory’s Alternating Gradient Synchrotron (AGS), the only source for HZE particles supported by NASA.
To carry out needed research expeditiously, NASA should explore a number of possibilities, including international collaborations, so as to increase the research time available for experiments with HZE particles and protons at energies over 250 MeV. Such possibilities include a combination of more running time at the AGS and at lower-energy accelerators, expansion of existing facilities (see Appendix C), the commissioning of new beam lines at existing facilities, and the construction of a new facility. A 1992 National Research Council letter report (Appendix D) emphasized the need for a dedicated HZE particle facility.
The fact that the present report reaches conclusions similar to those in the 1989 report of the National Council of Radiation Protection13 underscores the need for additional resources and facilities in order to understand quantitatively the radiation biology associated with interplanetary flights.
3.4 Assessment of Recent Changes in the Explorer Program
A Report of the Panel to Review the Explorer Program1
Since the 1960s, the Explorer program at the Goddard Space Flight Center (GSFC) has been of crucial importance for the disciplines of space physics and space astronomy. Level-of-effort funding for the Explorer program enabled these disciplines to develop many relatively small, Earth- and moon-orbiting missions that allowed these disciplines to progress, to develop new technologies and instruments, and to foster a substantial body of talented investigators. In the 1980s, Explorer began to depart from its small-and-frequent character and to put its resources into a few larger missions; for example, the X-ray Timing Explorer (XTE) and the Far-Ultraviolet Spectroscopic Explorer (FUSE) each cost in the $200 million range. As the 1990s progressed, however, budget and scientific community pressure mounted for smaller and more frequent missions, forcing a reappraisal of NASA’s general approach to space science missions.
In 1994, the downscoping and restructuring of the FUSE mission signaled the end of the Delta-class Explorers. The new Explorer program consisted of a Mid-class Explorer (MIDEX; capped at $70 million per mission), the existing Small Explorer (SMEX; capped at $35 million per mission), and the University Explorer (UNEX; capped at $5 million). The cap refers to the charge to the Explorer budget line. In March 1995, NASA conducted the first competition for the MIDEX program, with selections made the following spring.
Following this first round of MIDEX selections, NASA’s Office of Space Science requested that the Space Studies Board assess the solicitation and selection process recently concluded in terms of the program’s objectives to optimize science value through a competitive, community-based program of frequent flight opportunities in astronomy and space physics. The Discovery program for solar system exploration was identified as a model for future evolution of the Explorer program. In order to carry out the assessment, which was to consider involvement of the science community, NASA centers, and industry as well as overall scientific effectiveness, the Board established the Panel to Review the Explorer Program. The panel met on September 12–14 to be briefed on the program to date and to evaluate its progress in the terms requested. Following are the findings of the panel and a number of recommendations based on these findings and information provided.
General Finding. The panel believes that most of the perceived problems brought to light after the first MIDEX AO were due to the “dual mode option”2 and the lack of full cost accounting for government contributions. In addition, debriefing of unsuccessful proposal teams was not adequate. While the AO and the selection process both need improvement, and while interaction with the science community also needs to be strengthened, the panel believes that the program is now on the right path and that the new Explorer program should be excellent if properly administered. The perception will probably continue that GSFC and its scientists have an advantage, but the panel is satisfied that the Explorer program management is addressing this issue and that elimination of the recognized flaws will bring about a level playing field for both scientists and industry. Given time and continuing effort, it is the belief of the panel that the astronomy and space physics communities will strongly support the program.
Finding 1. The panel supports use of the “PI mode” by NASA. It brings new vigor to the program at a time when diminishing opportunities could lead to disillusionment amongst the science community. It is an open process that appears to be intrinsically fair. It has exposed a reservoir of ideas for focused science under a cost cap.
Finding 2. The panel believes that the new Explorer program cannot succeed without a high level of support by the science community. In the first (1995) MIDEX solicitation the most readily avoidable errors were failure to consult
adequately with the community in the development of the AO and failure to undertake face-to-face debriefings with investigators after the process. These management errors have led to problems with the science community, but they can be resolved through a thoughtful effort in developing future AOs, and again after selection has taken place.
Finding 3. The panel understands from presentations made to it that the “dual mode option” will be eliminated from future Explorer AOs and that the “PI mode” will be the only management approach allowed. The panel endorses this decision.
Finding 4. The panel concludes that the new Explorer program at GSFC is well managed and is aggressively moving to fully support the “PI mode” management approach. This includes a move to full cost accounting for government contributions.
Finding 5. The panel believes that the restructured Explorer program can be of outstanding value not only for the science performed, but also for its role in maintaining U.S. scientific capabilities in an important area of space science. This double role for the Explorer program has repercussions with respect to mission sizes, foreign participation, and flight rate.
Finding 6. The panel believes that supporting a mix of Explorer mission sizes (MIDEX, SMEX, and UNEX) is an important and valuable feature of the program because it satisfies the needs of multiple constituencies. But this division should not be treated as immutable. Circumstances may change in the future and different cost caps may become preferable.
Finding 7. Based on the response to the 1995 MIDEX AO, the panel believes that the flight rate of Explorer missions could probably be substantially increased without any decrease in mission quality, if resources should become available.
Based on information contained in Explorer and Discovery solicitation documentation, the June 1996 MIDEX lessons-learned workshop report,3 presentations by NASA and industry representatives, and its own findings, the panel offers the following recommendations:
Recommendation 1. The panel recommends that the two-step proposal process and other aspects of the next Explorer AO be discussed at a workshop before the AO is issued. In addition, debriefings for unsuccessful proposers should be expanded to include face-to-face discussions; the successful practice in the Discovery program might be used as a model.
Recommendation 2. The panel recommends that the Explorer and Discovery programs should continue with separate Headquarters management structures for the next few AOs.
Recommendation 3. To reduce excess industry investment in detailed costing exercises for large numbers of missions during Step One, these proposals should be submitted on a “cost-not-to-exceed” basis within broad, AO-defined cost ranges. The responsibility for the cost-not-to-exceed estimate rests with the PI, advised by industrial and NASA center partners. The estimate should be accepted in Step One. A selected Step One effort that later failed to meet promised scientific objectives within the accepted cost limitation would be subject to termination and would be replaced.
Recommendation 4. NASA should clarify its approach to assessing new technology elements in future AOs. The panel notes that PIs and their partners can gain credit by combining new technology and an imaginative approach to managing the risk incurred.
Recommendation 5. The panel recommends that, at least for the next AO, foreign contributions be included in the Explorer cost cap as was done for the 1995 MIDEX AO. After more experience has been gained with foreign contributors and contributions, NASA and the science community should reassess this issue in workshops to be convened for the consideration of future AOs.
Recommendation 6. The panel recommends, in the same spirit as Recommendation 5, that NASA not add to the scope of the Explorer program until more experience has been gained with the next few AOs.