Quarterly Bulletin

Volume 10, Issue 4

December 1999

From the Chair

There is a story about how Sam Walton, the late founder of Walmart, was a man of few words. When asked to what he attributed his success, he replied "Good decisions." And how had he learned how to make good decisions? "Bad decisions."

Learning from mistakes is something much on the minds of NASA and the space research community. The back-to-back failures of both Mars missions this fall, followed several other losses earlier in the year (see column by SSB Director Joe Alexander). It is likely, as the media were quick to note, that these problems have something to do with NASA's emphasis on conducting missions "faster, better and cheaper" than in the past. The real question is what in the present approach needs fixing. What is it that went wrong and how much needs to be changed to make it right in the future?

The confusion over metric vs. imperial units that doomed Mars Climate Orbiter might well have been caught in a program with more comfortably funded checks and balances, and the same might be said for the problems with the explorer satellites, TERRIERS and WIRE. We may never be sure what happened to Mars Polar Lander, but this too was a lean program with limited budget and ambitious schedule. A review panel led by Tom Young, a hero of the space community who can be counted on to get to the bottom of the issue, will be reporting within a few months.

It is likely that in all these missions, extreme pressures to deliver a minimally capable payload with tight constraints on both cost and schedule led to increased technical risk. After all, that is part of the "faster, better, cheaper" philosophy, since achieving very high levels of reliability inevitably means incurring very high costs (though high costs do not guarantee high reliability). The challenge is managing risk along with the other variables and keeping it at acceptable levels. Another problem is that what might be acceptable risk in a technical, cost/benefit analysis may be politically unacceptable. As one former NASA official once opined, "faster, better, cheaper will succeed only when the agency starts rewarding managers for cheap failures."

To me, the biggest danger is that the system will over react to these failures and swing the pendulum too far away from the "faster, better, cheaper" philosophy. In the most extreme scenario, high levels of risk aversion could add significant multiples to the cost of every upcoming science mission and reduce the renewed vitality that more frequent missions have brought to space research. We should remember that there have been many more successes than failures this year, and the latter, though costly in lost dollars and missed science returns, represent a small fraction of NASA's research expenditures. More useful would be to take the lessons we learn from these unfortunate occurrences and make marginal improvements in selected areas of technical and risk management. We need to nurture an effective faster-better-cheaper implementation approach in the context of a balanced portfolio of mission sizes. (The Board's upcoming report on the size mix for Earth and space sciences will address these issues.) Or in a few words, "Emulate Sam Walton".

BOARD DIRECTOR'S COLUMN

The deluge of retrospectives and calendar milestone commentaries that flooded our consciousness in the closing weeks of 1999, should give any writer (or reader) pause. So also should the rather extraordinary mix of events that marked high and low points in space research during the year. But fools rush in, as Alexander Pope said, and so this writer will fearlessly try to draw a few lessons from the recent past.

That past saw the often delayed but finally successful launches of Landsat-7, Chandra, Terra, and the HST servicing mission. Other successful flights included the launches of Stardust, QuickScat, FUSE, and the ESA XMM telescope aboard an Ariane 5 rocket. Tempering those and other successes were launch failures of two Titan-4 rockets, an Athena-2, a Delta-3, two Protons, and a Japanese H2 vehicle. Perhaps even more painful for the space research community were the in-flight failures of Mars Climate Orbiter, Mars Polar Lander, two Deep Space-2 Mars penetrators, and the WIRE and TERRIERS missions. In August federal S&T budgets were threatened with fearsome cuts, especially at NASA, but members of Congress who were favorable to those programs were able to work nearly miraculous solutions in the final days of the appropriations process.

One might ask whether there are any common themes or underlying messages in this collection of events. Some are obvious, but they may be worth repeating, and remembering. First, this is rocket science. Space research is complex, it is difficult, and it has inherent risks. Since all of the easy things have been done, or may not be worth doing, new efforts require new tools and innovative approaches.

The challenge, though, is to see where to draw the line in terms of saving older proven methods and where to replace them. For example, the government assessment of the string of U.S. launch vehicle failures concluded that manufacturers were tempted to cut corners on some testing and quality assurance practices and to substitute approaches that were less robust. 1 We may be learning that, regardless of whether the issue is the changing roles of government and industry in launch vehicles or the changing approach to science missions, the conscious act of defining acceptable risks-both in terms of how much and what kind-is critical.

The inherent complexities of space activities probably also figure into the explanation for the past year's nearly disastrous budget story. In spite of the popular fascination with dramatic results from HST, Galileo, or TOMS, neither members of the public nor legislators readily understand the purpose of data-analysis grants, or advanced instrument technology funds, or definition studies of next-generation observing systems. If the funding needs, the societal benefits, and the nature of the inherent risks aren't clear to decision makers, then the rationale for continuing funding becomes ephemeral.

In the environment described above, in which complexity and risk are fundamental, complacency is an enemy. One can never afford to be complacent either about attending to the details of technical challenges or about articulating and communicating about the rationale, risks, and benefits of the programs. The good news appears to be that most observers agree that things aren't fundamentally broken. Corrections may be in order, but major overhauls don't seem to be called for. To be sure, there are a number of troubling questions to be addressed-such as have new approaches to space systems design and management tried to move too far and too fast; are we seeing effects of burn-out or loss of corporate memory in key project positions; and why were congressional budget knives turned so abruptly toward space research in 1999?

The Space Studies Board seeks to contribute constructively in this period of change in a number of ways. For example, two new study reports are slated for release in the first quarter of 2000 that examine, from a scientific perspective, issues regarding trade-offs for different mission sizes for Earth and space science missions. 2 That topic may be addressed further in the Board's upcoming review of the new strategic plan for NASA's Office of Space Science and in the Board's upcoming report on implementing the integration of research and operational Earth observing satellite systems, to cite two other examples.

The SSB has had a long-standing role in developing and articulating the scientific rationale for space research programs; SSB "strategy reports" provide one means to communicate about the complexity and the value of space research. As these pages have noted before, a major current operational goal for the Board is to improve and enhance the dissemination and communication of its work, not only to federal agencies and the scientific community but also to the wider community of stakeholders, including the interested public. We invite readers' ideas and support in pursuing that goal.

1 See Department of Defense Assessment of Space Launch Failures, http://www.af.mil/lib/misc/spacebar99.htm.

2 The Role of Small Satellites in NASA and NOAA Earth Observing Programs and Assessment of Mission Size Trade-offs for Earth and Space.

Board and Committee News

Space Studies Board

The SSB held its 129th meeting on November 8-10 at the Stennis Space Center (SSC) in Mississippi. A main focus of the meeting was on the commercial remote sensing work of the Center. There were presentations by SSC staff and tours of the virtual products and visualization labs and a presentation by the NASA Headquarters director for expendable launch vehicle requirements on a number of current expendable launch vehicle issues. Plans for the Board's review of NASA's Office of Space Science (OSS) Strategic Plan were reviewed, and presentations from the OSS Galveston planning workshop were discussed.

Status reports were presented on behalf of the standing committees: Committees on Earth Studies, Astronomy and Astrophysics, Planetary and Lunar Exploration, and Microgravity Research. A statement of task for a new study by the Committee on Solar and Space Physics was discussed and suggestions for revisions were made. Director Joseph Alexander reported on the Executive Committee's discussion of the internal assessment of the effectiveness and impact of the SSB and focused on findings, implications and actions needed. Alexander reported on the continuing activity of the Task Group on Technology Development in OSS and on new projects about to begin on life-detection techniques (via the Committee on Astrobiology) and on scientific aspects of the Triana mission (via an ad hoc task group). Staff member Pam Whitney reported on NRC activities involving export control issues.

Chair Claude R. Canizares gave a science talk summarizing early results from the Chandra X-ray astrophysics mission. Prof. J. Leonard Culhane, chair of the European Space Science Committee (ESSC), summarized ESSC activities since their last visit one year ago.

Members of the Board discussed four draft reports: Review of the NASA Biomedical Research Program, by the Committee on Space Biology and Medicine; Preventing the Forward Contamination of Europa, by the Task Group on the Forward Contamination of Europa; Institutional Arrangements for Space Station Research, by the Task Group to Review Alternative Institutional Arrangements for Space Station Research; and Assessment of Mission Size Trade-offs for Earth and Space Science Missions, by the Ad Hoc Committee on the Assessment of Mission Size Trade-offs for Earth and Space Science Missions.

Preliminary approvals were given to the Review of the NASA Biomedical Research Program and Institutional Arrangements for Space Station Research. The full Board will review the next drafts of Preventing the Forward Contamination of Europa and Assessment of Mission Size Trade-offs for Earth and Space Science Missions reports.

The Ad Hoc Committee on the Assessment of Mission Size Trade-offs for Earth and Space Science Missions (also known as the Limits Group) met on November 10-11 at SSC to make revisions to its draft report in response to Board review. During the meeting the group had the opportunity to hear the briefing of the Mars Climate Orbiter Failure Review Board, which was broadcast live on the NASA TV channel. The committee's report will be sent to external review in early January and the final report is expected to be available in late February 2000.

The SSB-NASA Planning Support Group, consisting of Board staff members and Drs. Guenter Reigler of OSS, Roger Crouch of OLMSA, and Ms. Dolores Holland, of OSS, met on December 10 at the NRC. Gregory Williams of OES, was unable to attend. Recent events in each of the three science offices were discussed. Board staff presented plans of the committees for their projects and relayed information from the November Board meeting. The next meeting is scheduled for March 17 at NASA Headquarters.

The next meeting of the Space Studies Board will be March 6-8 in Washington, DC. Invitations to participate will be extended to the NASA Administrator, Chief Engineer, Chief Scientist and the science Associate Administrators.

The committee is planning a workshop on climate data in Washington, DC, on February 7-8. The workshop will address needs and opportunities to maximize the utility of data from future operational weather satellites for climate research. A committee meeting will follow on February 9-10 when members will draft a report from the workshop and respond to Board review of the NPOESS-2 report.

The committee will meet on January 24-25 in Washington, DC, to focus on possible future activities on issues related to U.S. export controls and international cooperation and a follow on workshop with Japan's Earth, life and microgravity research institutions.

Although the discussions concerning biomarkers and life detection techniques were conducted in the context of an on-going study, The Certification and Quarantine of Martian Samples, it became apparent that the subject matter raised important questions relating to many different aspects of solar system exploration. As a result, a charge for a potential new study, Organic Synthesis in the Solar System, was drafted and subsequently approved by the Board. Work on the drafting of a charge for a possible study on the future exploration of Venus was begun. The committee's tentative plan is, subject to NRC approval, to initiate the organic synthesis study at the spring 2000 meeting and to initiate the Venus study at a later date.

Work was also begun on the drafting of the committee's input to both the Board's review of NASA's OSS Strategic Plan and the draft of NASA's Solar System Exploration Roadmap. The latter was verbally requested by NASA's Science Program Director for Solar System Exploration. Work on the former was facilitated by the presence of a committee representative, Wendy Calvin, at the Galveston meeting.

The committee's report, A Science Strategy for the Exploration of Europa, was released in printed form in late December.

Future committee meetings are scheduled to be held March 29-31 in Irvine, CA, July 17-21 in Washington, DC, and October 2-4 in Woods Hole, MA.

The possibility of extraterrestrial life holds an endless fascination for most of us. Just think of the countless books and movies involving alien life forms. But the quest for life beyond Earth is not just the stuff of science fiction. Scientists, too, are intrigued by the possibility. For decades researchers have looked to Mars as the solar system's most likely abode of extraterrestrial life. In recent years, however, a new candidate has come to the fore thanks to the growing evidence that Europa, one of Jupiter's large moons, is hiding a global ocean beneath its icy surface. That is why a the Space Studies Board's Committee on Planetary and Lunar Exploration (COMPLEX) is urging NASA to accord the exploration of Europa a scientific priority equal to that given to the exploration of Mars.

The presence of water is key to the origin of life. Indeed, many researchers believe that life is virtually inevitable in any environment containing liquid water and a source of energy from, for example, sunlight or volcanic activity. Although the Red Planet is cold and arid today, it must once have been warmer and wetter because the planet's landscape was clearly shaped by flowing water. Indeed, a prime reason NASA dispatched its ill-fated Mars Polar Lander to Mars' southern polar cap was to discover the fate of all the water that once must have flown across the martian surface.

For Mars, the era of abundant liquid water is a distant memory. Not so for Europa. We know that its surface is made of water ice. But this is not too surprising since most of the satellites in the outer solar system are icy. However, close-up images of Europa from NASA's Galileo spacecraft show few if any impact craters. The absence of craters is a tell-tale sign that Europa is a geologically active world, erasing evidence of impacts almost as quickly as they occur. Other images show that large areas of Europa's surface appear to have broken up, drifted to new positions, and then frozen in place like icebergs trapped in pack ice.

Moreover, theoretical studies suggest that the heating resulting from Europa's tidal interactions with Jupiter and its neighboring satellites may be sufficient to melt some or all of Europa's interior ice. This and other circumstantial evidence points to the existence of a subsurface ocean beneath Europa's icy crust. But definitive evidence for water is tantalizingly just beyond our grasp.

If the water is there, what are the chances for life? Just as our knowledge of planetary environments had greatly increased in recent years, so has our understanding of terrestrial life. It is now known that hot springs and deep-sea volcanic vents-environments we might expect to find on Europa-can support life. Indeed the organisms thriving in such seemingly inhospitable niches appear to be among the most primitive know. Europan life, therefore, may be analogous to that found in extreme terrestrial environments. If so, the discovery of europan life may help us test theories for the origin of life on Earth.

Congress has already approved NASA's plan to launch a Europa orbiter mission in 2003. We should know whether water is present relatively soon after the spacecraft's arrival in 2008. If water does exists, NASA should resist the inevitable and understandable calls for an expedited program to search this oceanic world for signs of life. Rather, the agency should adopt an incremental approach to exploring Europa. The exploration of Mars and, in particular, the Viking missions of the 1970s revealed that the search for life is best performed in the context of a thorough understanding of the environment in which the living organisms evolved. This will require a series of missions over a period of 10 to 20 years.

The possibility of life existing within Europa is too great a research opportunity to pass up. But NASA's plans for the exploration of Europa, Mars, and other bodies in the solar system and beyond must be coordinated with efforts to study life in unique terrestrial environments to maximize the potential scientific return. Such efforts will serve to engage scientists and non-scientists alike in one of humanity's greatest endeavors.

Bruce Jakosky, a professor of geology at the University of Colorado, was the lead author of COMPLEX's report A Science Strategy for the Exploration of Europa. David H. Smith of the Space Studies Board's staff directs COMPLEX's activities.

The lecture series continued this quarter with the presentation by Maria Zuber, Massachusetts Institute of Technology, "Rediscovering the Red Planet: Latest Results from the Exploration of Mars." Dr. Zuber's upbeat presentation of the stunning results from MOLA and other instruments on the highly successful Mars Global Surveyor did much to dispel the somber mood resulting from the loss of the Mars Polar Lander and Deep Space 2 missions less than a week before her December 10 presentation.

As with past lectures in this series, Dr. Zuber's presentation was videotaped for later distribution on public access television channels in the Washington, DC area. Plans for more extensive broadcast dissemination of the lectures are currently under discussion.

The remaining space science lectures for the 1999-2000 session, scheduled at 5:00 pm in the NAS Auditorium, are:

SSB Readership Survey Update

We would like to thank the readers who completed the survey enclosed with the September Newsletter. We realize that many of you may not have had the opportunity to complete and return the survey; however, we want to let you know that we would appreciate hearing from you at your earliest convenience. As we said previously, the information you supply will be used for in-house purposes only, and will help us to better assess the needs of the space science community as they relate to the particular products of the Board, and how we can deliver a more informative and timely Newsletter. Thank you for your continued support of the Space Studies Board and its activities.

New Report(s) from the SSB

Copies of reports are available from the SSB office at 202/334-3477.

A SCIENCE STRATEGY FOR THE EXPLORATION OF EUROPA

INSTITUTIONAL ARRANGEMENTS FOR SPACE STATION RESEARCH

U.S.-EUROPEAN-JAPANESE WORKSHOP ON SPACE COOPERATION

This report, by the Space Research Committee, Science Council of Japan, European Space Science Committee, European Science Foundation and Committee on International Space Programs, NRC, will be available on the Board's web site shortly. The study was staffed by Pamela Whitney, Study Director, and Carmela Chamberlain, Senior Program Assistant.

A trilateral workshop on space cooperation hosted by the Space Research Committee (SRC) of the Science Council of Japan-and including representatives of the Committee on International Space Programs (CISP) of the Space Studies Board (SSB), National Research Council (NRC), and the European Space Science Committee (ESSC) of the European Science Foundation (ESF)-was held in Tokyo at the Science Council of Japan on May 19-21, 1999. The purpose of the workshop was to:

1. Assist independent space science advisory bodies in Europe and the United States to establish a relationship with like bodies in Japan;

2. Begin this relationship by examining the nature of trilateral, cooperative space missions conducted during the last decade;

3. Understand better the primary factors that led to successful collaboration, explore the benefits and costs of cooperation, and identify major problems; and

4. Review the status of several embryonic projects and consider broader issues such as the possibility of coordinated, international strategic planning for space science and other policy issues likely to be significant in the future.

INTRODUCTION

The trilateral workshop originated, in part, from a joint SSB/CISP-ESSC study, U.S.-European Collaboration in Space Science, which recognized the need to consider interactions with other spacefaring partners such as Russia and Japan. Following publication of the joint study in 1998, both the ESSC and the SSB/CISP began to pursue relations with space science entities in Japan and agreed to initiate communications together. The SSB and ESSC identified the SRC under the Science Council of Japan as a similar entity with which to establish relations. Initial discussions among representatives of the SRC, SSB, and ESSC were held at the 32nd Scientific Assembly of the Committee on Space Research (COSPAR) on July 16, 1998, in Nagoya, Japan, and led to an agreement to hold a tripartite workshop on space cooperation. The general scope of the workshop, which was to include surveys of three cooperative missions, analysis of the lessons learned from such missions, and discussion on how to improve future cooperative missions, was agreed upon in Nagoya. Specifically, the workshop would include U.S., European, and Japanese perspectives on each of the missions to be surveyed. In addition, the workshop would focus on space science (astronomy and astrophysics, planetary sciences, and space and solar physics), recognizing that other disciplines and areas of cooperation might be studied later. The workshop agenda and a list of participants are included in Appendix B.

Professor A. Nishida, chair of the SRC and director general of the Institute of Space and Astronautical Science (ISAS), selected Geotail, Yohkoh (previously Solar-A), and the Advanced Satellite for Cosmology and Astrophysics (ASCA; previously Astro-D) as the three cooperative missions to be examined. Planning for the workshop entailed identifying individuals from the United States, Europe, and Japan who had worked on these missions and would share their insights on the cooperative experience. Speakers were asked to focus on the lessons learned from the missions and on aspects of mission success and to elaborate on any problems within the collaboration, as well as on other concerns and issues that might affect future cooperative activities. Speakers were provided with a template of questions to guide them in preparing their remarks. The speakers at the workshop rated collaborations on all three missions as successes, although there were also lessons learned.

LESSONS LEARNED

Framework

Lessons extracted from the mission surveys were sorted into five general categories:

RADIATION AND THE INTERNATIONAL SPACE STATION: RECOMMENDATIONS TO REDUCE RISK

This report, by the Committee on Solar and Space Physics (CSSP), and the Committee on Solar-Terrestrial Research (CSTR), will be available on the Board's web site shortly. The study was staffed by Art Charo, Study Director, Elbert (Joe) Friday, Jr., Director, BASC, Ronald Turner, Consultant, Tenecia A. Brown, Senior Project Assistant, Carmela Chamberlain, Senior Program Assistant, and Theresa Fisher, Senior Program Assistant.

Executive Summary

INTRODUCTION

This report originated with a request from the National Aeronautics and Space Administration (NASA). To construct the International Space Station (ISS) and maintain it during construction, astronauts and cosmonauts will work in space suits outside their spacecraft in shifts, each of which is projected to last for 6 hours, for a total amount of time estimated to exceed 1,500 hours. According to the present construction schedule, these extravehicular activities (EVAs) will occur over a 4-year period that straddles the peak in activity of the current solar cycle. After the 4-year period, one or two EVAs per month will probably continue for the life of ISS. The peak in the solar cycle combines with the station's high-inclination orbit to add a new concern for managers of radiation risk.

Unlike the originally planned low-inclination orbit (28 degrees), the finally approved high-inclination orbit (51.6 degrees) cuts through high-latitude radiation environments that are sometimes quite harsh, as was noted when the redesign was contemplated in the early 1990s. These high-latitude radiation environments (energetic particles from solar storms and relativistic electrons in Earth's outer radiation belt) vary greatly over time, from benignly calm to severely stormy. At the height of their storminess, they can be intense enough to pose a radiation hazard to astronauts engaged in EVAs, although doses estimated for even worst-case scenarios fall short of life- threatening. The principal risk to astronauts that increased exposure to radiation in ISS orbit poses is the increased probability of developing cancer later in life. The principal concern for flight directors that increased exposure of astronauts to radiation raises is the potential impact on flight schedules and crew rotation if a radiation event pushes an astronaut over an allowable radiation limit. Astronauts are also concerned that crossing an allowable radiation limit will restrict flight opportunities. Storms bearing intense radiation are relatively rare, but EVAs during ISS construction flights are relatively frequent, which raises a concern that the two might by chance coincide. Information obtained during the course of this study puts at near-certainty the likelihood that on one or more occasions an ISS construction flight will be in progress when a high-latitude radiation event (described below) occurs.

This finding naturally raises the question, What is the status of radiation risk management as it pertains to ISS construction? It would seem to be a simple matter, for example, for the Space Environment Center (SEC) of the National Oceanic and Atmospheric Administration (NOAA) or for NASA's own satellites to identify solar events that could cause radiation problems and to get such information to the flight director in time to take appropriate action. But an overly restrictive flight rule and the lack of operationally calibrated models bar the path between the flight director and such sources of information. The problematic (albeit unofficial) flight rule is the "real-time, on-site data" rule, which says that changes in flight plans in response to a radiation situation must be based on real-time, on-site data only. The first recommendation of CSSP/CSTR addresses this flight rule.

Recommendation 1: Because it denies access to valid information and thus unnecessarily restrains flight-director options, flight directors should not adhere rigidly to the (unofficial) real-time, on-site data rule.

As mentioned, the second obstacle in the path between the flight director and data sources is the lack of operationally calibrated models. In important cases, however, the state of radiation modeling is advanced enough, or with directed effort could quickly become advanced enough, to justify a flight rule that allows use of validated procedures to infer and, in some cases, to predict on-site radiation conditions from off-site data. The report cites such cases.

CSSP/CSTR notes that Russians performing EVAs will be directed out of the Russian mission control center in Moscow. Further, it is likely that U.S. and international crew members on ISS will also participate in EVAs directed out of mission control-Moscow. However, flight rules at mission control-Moscow pertaining to radiation may differ from those at NASA's mission control center. Although this report is directed at NASA, CSSP/CSTR believes that some of its recommendations could also be implemented by mission control-Moscow.

SOLAR PARTICLE EVENTS AND THE INTERNATIONAL SPACE STATION

Based on the assumption-the best now available-that the radiation characteristics of the current solar cycle will resemble those of the last cycle, there is nearly a 100 percent chance that at least 2 out of 43 planned ISS construction flights will overlap a significant solar particle event (SPE) and a 50 percent chance that at least 5 flights will overlap such an event. Moreover, the high-latitude zones to which solar energetic particles have access show a marked tendency to widen over the polar latitudes reached by the ISS orbit when SPEs are in progress, a tendency that becomes more pronounced as SPEs intensify. Two storms during 1989, near the maximum of the last solar cycle, illustrate the point. The areas around the poles accessible to SPE particles enlarged until they engulfed more than a quarter of the ISS orbit, and the flux of particles was high enough to have pushed an astronaut over the short-term limit for irradiation of skin and eyes during a single ill-timed 6-hour EVA. These results would seem to call for an aggressive program aimed at reducing solar radiation risk to astronauts during ISS construction. Recommendation 2 addresses means of implementing the elements of such a program.

Recommendation 2: For real-time SPE risk management, carry out the steps needed to make usable by SEC and the Space Radiation Analysis Group (SRAG) at Johnson Space Center (JSC) models that use real-time data to specify the intensity of SPE particles and the geographical size and shape of the zones accessible to them.

NASA, NOAA, the U.S. Air Force (USAF), and the distributed space physics community have the capability for implementing this recommendation. The project implied in this recommendation is one of the important projects that could be implemented early enough to have an impact on SPE radiation risk management during ISS construction. It should receive high priority for early implementation.

RELATIVISTIC ELECTRONS AND THE INTERNATIONAL SPACE STATION

For a portion of nearly every day, some fraction of the ISS orbit lies within the outer radiation belt, where relativistic electrons reside. At its maximum, this fraction is about 20 percent. During occasions called relativistic electron events, which happen on average about once per month and last several days, the intensity of relativistic electrons in the belt increases by up to four orders of magnitude. When the intensity of relativistic electrons is greatest, a single ill-timed EVA could deliver a radiation dose big enough to push an astronaut over the short-term limit for skin and eyes. To minimize the possibility of scheduling EVAs during such events, procedures can be implemented to specify and forecast at least approximately the intensity of relativistic electrons in the outer belt. NOAA Polar-Orbiting Operational Environmental Satellites (POES) provide measurements of relativistic electron fluxes that can be used to calculate with reasonable accuracy the relativistic electron environment at ISS. These measurements are available only about every hour and a half, however. NOAA Geostationary Operational Environmental Satellites (GOES), on the other hand, provide relativistic electron measurements continuously, but these measurements are not so directly transferable to the ISS orbit. Nonetheless, the intensity of GOES measurements tracks the intensity of POES measurements in the outer belt. Thus, in combination, POES and GOES measurements would allow radiation risk managers to quantitatively follow variations of electron intensity in the outer belt. A crucial piece of hardware that the ISS project should provide is an electron dosimeter attached outside the station. This would allow SRAG to test the quality of the specifications and forecasts that are possible from measurements taken by POES and GOES. These considerations lead to three related recommendations.

Recommendation 3a: NASA should implement a procedure for using POES and GOES measurements of relativistic electrons in the outer radiation belt to specify and forecast the electron radiation environment at ISS. (Such a procedure is outlined in Section 3.3.)

Recommendation 3b: As soon as possible, JSC should install an electron dosimeter and an ion dosimeter outside the ISS that can return data in real time to SRAG at JSC.

Recommendation 3c: A project should be initiated to develop a protocol for identifying the conditions that produce highly relativistic electron events based on the demonstrated good correlation between changes in solar wind conditions and the onset of such events. The recommended project might be a candidate for support by one of the affiliated agencies of the National Space Weather Program (NSWP).

SPACECRAFT SOURCES OF OPERATIONAL RADIATION DATA

Data that could contribute to reducing radiation risk are currently being acquired by a strategically placed multiagency fleet of research and operational spacecraft. This fleet can provide information on the radiation environment of ISS orbit in real time and in advance of real time. Some spacecraft monitor the Sun and its corona in multiple wavelengths and so can diagnose the X-ray potency of solar flares and warn of oncoming material spewed from the Sun by solar storms. They also monitor SPE fluxes to give direct information on the radiation intensity within zones accessible to SPE particles. Other spacecraft monitor solar wind parameters, which can be used to compute the size and shape of SPE-accessible zones. Spacecraft in relatively low-altitude, polar orbits monitor the flux of relativistic electrons in the outer radiation belt, which the ISS orbit transects. Recommendation 4 addresses a need to channel the relevant information to SRAG at JSC.

Recommendation 4: Promptly convene a meeting of pertinent NASA Space Science Enterprise, SRAG, and SEC managers with the principal investigators of satellite instruments. The meeting would (1) consider ways to extend the capabilities of the current spacecraft fleet to provide real-time radiation data for driving models and specifying the ISS radiation environment and (2) formulate an implementation plan for swiftly channeling such data to radiation risk managers at JSC.

INTERAGENCY CONNECTIONS

A major obstacle stands in the way of implementing any of the improved scientific data and modeling resources that are currently available from research programs in NASA and the National Science Foundation (NSF). Both SEC and SRAG are fully tasked in maintaining their daily program of data collection and analysis. Ongoing operations require that these be maintained. Incorporation of improvements thus becomes a secondary activity, and the lack of adequate resources and agency support in both organizations limits the rate at which improvements can be made. The next two recommendations address this condition.

Recommendation 5a: NASA, NOAA, and the USAF should cooperate to support the activities that would lead to an operational space weather forecasting capability.

Recommendation 5b: NOAA should extend the range of its SPE predictions from the present ³10 MeV to biologically effective energy ranges. Forecasts of particle energies at several steps between 10 and 100 MeV would be a significant improvement for space radiation use as well as for other users who operate satellites and systems in space.

INTRA-NASA CONNECTIONS

There are other major programs at NASA besides the manned flight program that require an accurate knowledge of Earth's radiation environment. The kind of knowledge required varies from program to program, but the range of knowledge needed extends from the basic science, physical processes, and generation mechanisms of the radiation belts and particle events, to net integrated radiation doses averaged over a long period of time. The trend in recent years at NASA has been toward smaller and cheaper spacecraft with heavy use of microelectronics, smaller instruments, and more onboard data processing. For this and other reasons, the working knowledge of Earth's radiation environment (models, forecasts of particle events and disturbances, integrated doses, etc.) needs to be improved to address current planning and development requirements in just about every area of NASA activity.

Recommendation 6: To coordinate intra-NASA activities and concerns related to radiation, NASA should establish an agency-level radiation plan and task force. It should also establish a multidisciplinary steering committee to advise the task force.

SPACE WEATHER MODELS APPLIED TO RADIATION RISK REDUCTION

The above recommendations address means to exploit currently available resources to allow a rapid augmentation of the tools available for radiation risk management during ISS construction. Looking beyond these recommendations, there are actions of a tactical nature that can be taken to strengthen radiation risk management in the late phases of ISS construction and during ISS operations. These actions entail the selective implementation of space weather modeling efforts. Space weather modeling is the discipline responsible for developing models that take information from where instruments happen to be and use it to specify and forecast the space environment at places where the information is wanted.

Appendix A identifies research projects that address specific elements of an effort that would provide high-quality information on the parameters most crucial to assessing radiation risk. Two projects deserve particular attention, the first because its potential impact on radiation risk reduction is especially crucial, the second because the maturity of its models promises early, tangible results:

These projects could be undertaken in the near term by one or more of the affiliated agencies of the NSWP.

Last update 12/22/00 at 3:16 pm