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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 preservation2 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
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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 Data3 and Computer-Aided Materials Selection During Structural Design4 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,
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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.5 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.6 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.
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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. 2 In the recently published National Research Council report Preserving Scientific Data on Our Physical Universe (National Academy Press, Washington, D.C., p. 34), the uniqueness of a data set and the cost of replacing it were both cited as primary criteria for deciding whether to archive data. 3 National Research Council, National Materials Advisory Board. 1983. Networking of Materials Property Data. National Academy Press, Washington, D.C. 4 National Research Council, National Materials Advisory Board. 1995. Computer-Aided Materials Selection During Structural Design. National Academy Press, Washington, D.C. 5 See footnote 4. 6 See footnote 3.