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Spacecraft-Based Earth Science in the 21st Century: Opportunities and Challenges for Student/Teacher/Scientist Partnerships

David R. Brooks
Research Associate Professor, Department of Mathematics and Computer Science
Principal Investigator, GLOBE Haze/Aerosols Project
Drexel University, Philadelphia, Pennsylvania, USA

Based upon a presentation at:
Workshop on Environmental Education at the School Level in the Field of Air Quality
Santorini, Greece
8-9 September, 2000


It has long been recognized within the education community that traditional models for teaching and learning science need to be revised, and to focus more on hands-on learning involving "authentic" science. However, such models have proven difficult to implement. The reasons for this difficulty include the culture of teacher education and the structure of science curricula. Even the best science teachers tend to think of themselves as teachers rather than scientists, a perception that persists even when teachers-in-training are required to demonstrate proficiency in the science areas they expect to teach. The science curriculum (in the U.S., at least) must respond to the demands of state and national guidelines and standards. As a result, science teaching tends to be very "unit-driven," with a limited amount of time devoted to each topic in an attempt to address all the topics considered vital to a well-rounded science education.

Even though national and U.S. state science standards invariably promote new teaching/learning models, including hands-on investigation-based learning, the fact remains that whenever scientists review science textbooks, the result is predictable: the textbooks are too broad, too shallow, and do not promote in-depth knowledge or the actual doing of "real" science. A recently reported study by the American Association for the Advancement of Science (National Science Teachers Association, 2000) concluded that "ten of the most widely used high school biology textbooks and several of the most widely used algebra textbooks have major shortcomings that can prevent students from mastering the two subjects." The AAAS review concluded that biology texts focus on "trivial details... and ignore or obscure important... concepts." There is no reason to believe that reviews of texts in other fields would yield significantly better results.

How can the science community address these problems? In the U.S., The National Aeronautics and Space Administration (NASA) has a long history of providing education and public outreach (E&PO) programs. Indeed every major NASA project includes a specifically funded E&PO component. However, such programs have tended to be "one-way" efforts in which NASA provides educational materials, public access to data, and opportunities for teachers and students to learn about NASA programs. More recently, NASA has offered chances for more active participation through its Student Involvement Program, in which student teams can design experiments that can be launched on a Sub-Orbital Student Experiment Module (SubSEM) rocket or carried aboard the Space Shuttle (NASA, 2000a).

The Reform of Science Education and the "Big Leagues" of Earth Science

An important next step in science education is to involve teachers and students as full and active partners in doing real science. Although not all areas of science may be well suited for student participation, this is an entirely feasible step in the area of earth science. The major undertakings in earth science for the 21st century -- the "big leagues" of earth science -- are space-based. Fortunately, the specific demands of monitoring the earth and its atmosphere from space lend themselves quite easily to student participation. NASA's Earth Science Enterprise (ESE) consists of several space-based programs. The ESE programs and their partner programs from around the globe constitute one of the major science initiatives in any field for the 21st century. The largest element of ESE is the Earth Observing System (EOS), "a program of multiple spacecraft designed to provide measurements of the key, multi-disciplinary parameters needed to understand global climate change." [Asrar, 1999]. The first EOS spacecraft, EOS-Terra, was launched in December 1999. The others, EOS-Aqua and EOS-Aura, will follow in the next few years. Each of these spacecraft includes international partners, for example, Finland and Netherlands for EOS-Aura's Ozone Monitoring Instrument (OMI). The instruments aboard Terra and the spacecraft that follow will initiate the most comprehensive studies of the earth ever undertaken. These spacecraft will examine the physical and radiative properties of clouds, air-land and air-sea exchanges of energy, carbon and water; measurements of trace atmospheric gases, and volcanology. Figure 1, an artist's rendering showing the location of EOS-Aura's major instruments, shows a typical solar-powered spacecraft for these projects.

Figure 1. Artist's rendering of the EOS-Aura spacecraft, showing the location of its major instruments.

The three EOS spacecraft will join other missions from around the world, including several small spacecraft such as Jason-1 (jointly with France), and a series of Earth Probe missions including a Total Ozone Mapping Spectrometer (TOMS) flying on a Russian Meteor spacecraft. The ESE Pathfinder missions include the US/French Pathfinder Instruments For Cloud And Aerosol Spaceborne Observations-Climatologie Etendue des Nuages et des Aerosols (PICASSO-CENA). In some cases, spacecraft orbits will be coordinated to provide overlapping coverage of the earth's surface and atmosphere.

Figure 2 (from Hansen et al., 1998) provides an introduction to some of the questions EOS and other programs are designed to address. It shows sources of "climate forcings" -- contributors to changes in the atmosphere that can modify the earth's climate. As is well known, the primary climate forcing since the dawn of the Industrial Age in the second half of the 19th century is due to increased levels of CO2 (from biomass and fossil fuel burning) and other so-called greenhouse gases. However, there are other significant contributions that must be taken into account in order to model accurately the current state and future course of the earth's climate. Among these are clouds, stratospheric ozone, and aerosols. Aerosols are small solid and liquid particles, suspended in the atmosphere and having diameters of roughly 1 mm or less. They affect the earth directly by scattering, reflecting, and absorbing solar radiation and thermal radiation from the earth. In Hansen et al.'s study, the climate forcing effect of tropospheric aerosols (for example, those that result from industrial pollution, biomass burning, and automobiles) is negative. These kinds of aerosols scatter and reflect sunlight, thereby cooling the earth's atmosphere, on average. However, the uncertainty in the magnitude of this effect is large. Other aerosols, such as the "sooty" aerosols produced by large volcanic eruptions, can also absorb sunlight, thereby warming the agmosphere. Figure 2 indicates that even the sign of the net effect from volcanic aerosols is uncertain.

Figure 2. Natural and anthropogenic sources of climate forcing (used by permission from Hansen et al., 1998).

Note also, in Figure 2, the negative contribution (a cooling effect) and large uncertainty due to "forced" cloud changes. These are human-induced changes in the nature and amount of clouds (including, for example, airplane contrails). Such changes are caused indirectly by aerosols, which serve as the primary source of condensation nucleii around which cloud droplets form. Thus, it is clear from Figure 2 that a thorough understanding of the global distribution and temporal variability of aerosols is critical for understanding and modeling the earth's climate.

It is tempting to think that spacecraft, with their global coverage and sophisticated instrumentation, should be able, on their own, to answer the important questions about the temporal and spatial distribution of aerosols and other quantities. However, for all their sophistication, spacecraft instruments cannot directly measure these quantities or their effects on the earth's climate. Despite the proliferation of images from space, including what can fairly be called digital photographs of the earth, it is not possible simply to take a "photograph" of aerosol concentrations from space.

The limitations of spacecraft-based instruments create some important opportunities for student participation. Consider Figure 3, a TOMS image of the “aerosol index” for August 31, 2000 (NASA, 2000b). (The aerosol index is a quantity related to, but not the same as, aerosol optical depth.) Consider Figure 3, a TOMS image of the "aerosol index" for August 31, 2000 (NASA, 2000b). Clearly, this is not a "picture" in the usual sense. It is, instead, a digital representation -- a visual interpretation -- of the results of applying a series of algorithms to TOMS instrument responses to produce a value that is related to aerosol concentrations in the atmosphere. This image shows dust blowing up from Northern Africa out over the Mediterranean Sea; note in particular the large "blob" of dust concentrated just west of Greece.

The presence of African dust over the Mediterranean is a common occurrence, and it is not difficult to make the connection between the conditions pictured in Figure 3 and the more human-friendly reality of an actual (although still digital) photograph. Santorini is famous for its colorful sunsets. Marine aerosols, which give the nearby islands a persistent whitish hazy appearance during the day, and conditions such as shown in Figure 3, are the reasons. Figure 4 shows a sunset viewed from Santorini. The date of this photograph (Santorini website, 2000), is unknown, although it predates the TOMS image in Figure 3. Nonetheless, the extensive reddish-orange sky glow and the obscured sea-sky boundary shown in Figure 4 is almost certainly due to dust drifting over the Mediterranean in a pattern similar to that shown in Figure 3.

Figure 3. Total Ozone Mapping Spectrometer aerosol index, August 31, 2000.

Beyond the visual interest of Figure 3 and its qualitative link to Figure 4, the value of the kind of data used to produce an aerosol index image (for climate modeling, for example) depends critically upon quantitative accuracy. In order to maximize the quantitative value of data collected from space, it is necessary to conduct an ongoing program of measurements made on the ground. "Ground truth" validation is required to develop, test, and monitor the performance of algorithms used to convert instrument responses to physical quantities. All space-based measurements of the earth and its atmosphere require ground-based validation, for which there is no substitute.

Figure 4. Sunset viewed from Santorini, used by permission of the webmaster,

Can Schools Provide Ground-Truth Validation for Space-Based Earth Science?

The basic answer to this question is: "Yes, in some cases." Using the example of aerosols, it is clear that, ideally, ground measurements should come continuously from around the globe, from a wide variety of climates. However, there are very few aerosol monitoring sites around the globe. Professional sun photometers to measure aerosol concentrations (expressed as a quantity called aerosol optical thickness) cost thousands of dollars apiece -- the CIMEL sun photometers used in NASA's AERONET network (Holben, et al., 1998) cost at least $25,000 each. These instruments rely on optical interference filters to restrict their response to a narrow range of wavelengths, but such filters are fragile and subject to unpredictable optical degradation. As a result, filter-based sun photometers are difficult to maintain and calibrate, especially in remote locations. Filter-based sun photometers are essential for research applications and they can be used in small networks, but they are impractical for use in a global monitoring network that is dense enough to meet the needs of spacecraft-based earth science.

In 1998, the GLOBE Program initiated the Haze/Aerosols Project to develop an inexpensive sun photometer based on the work of Forrest Mims (1992). This instrument uses light emitting diodes (LEDs) as spectrally selective detectors of light. LED-based sun photometers are inexpensive (less than US$25 in parts), optically stable, and virtually indestructible, thus making them ideal for use by students. Although there are obviously tradeoffs involved in the design of a $25 instrument -- it must be used by a real person, rather than operating remotely, for example -- the credibility of LED-based sun photometers has now been examined and accepted by the atmospheric science community (Brooks and Mims, 2000).

A global student network of inexpensive sun photometers can be used to help meet the ground validation needs of any space-based instrument that produces aerosol data. The GLOBE Haze/Aerosols Project is already providing sites for ground validation of EOS-Terra aerosol products. In the week prior to this conference, the first Terra aerosol results were distributed to these GLOBE sites. During the next several months, GLOBE project scientists (Brooks and Mims) will work with Terra project personnel to package these data in a way that makes them accessible to participating GLOBE students and teachers and, most importantly, to examine the relationships among aerosol data from Terra, GLOBE, and other ground sites such as those in the AERONET network. As a result of this undertaking, GLOBE's vision of students, teachers, and scientists working side-by-side in a true partnership will become a reality.

The joint US/French PICASSO-CENA project can also use student aerosol data because it, too, needs global ground validation data to support the development of its data analysis algorithms. One of its primary objectives is to measure aerosol optical thickness -- a quantity that can be compared directly with appropriate ground-based measurements. Plans are now underway to establish a partnership between PICASSO-CENA and GLOBE's aerosol project scientists so that PICASSO-CENA's own E&PO program can make use of GLOBE sun photometers, data collection protocols, teacher training, and online infrastructure.

EOS-Aura, third in the series of three EOS spacecraft, offers a less obvious but equally important application of GLOBE sun photometer technology. In this case, the Ozone Monitoring Instrument (OMI, developed jointly by the Netherlands' Agency for Aerospace Programs and the Finnish Meteorological Institute) will be used to produce estimates of ground-level UV-B radiation. This is far from a direct measurement, and involves extensive modeling of the atmosphere in addition to space-based measurements. Among the uncertainties are local cloud conditions (another GLOBE protocol) and ground-level UV-A radiation. Using an LED that detects ultraviolet light at about 380 nm, GLOBE students can measure both the optical thickness at that wavelength and the full-sky UV-A radiation. NASA's Goddard Space Flight Center is currently funding a project to develop these instruments, again with E&PO funding.

It is not surprising to find that some scientists involved in space-based earth science may view E&PO funds with some jealousy and resentment: "Why should we 'waste' money on education and public outreach when we could be using this money ourselves to do the science we need to do?" Fortunately for science education, there are compelling reasons for maintaining even the more traditional kinds of E&PO activities -- one obvious reason is to increase students' interest in pursuing science careers in order to insure an adequate supply of qualified scientists in the future. However, the kinds of partnerships that are now possible through GLOBE and other programs make a different and more compelling argument: Teachers and students supported through E&PO programs can provide real data that scientists need and, as a practical matter, cannot obtain in any other way.

What Do Schools Need to Know and Do to Play in the "Big Leagues" of Earth Science?

The partnership opportunities described above should play an important role in science education because they present such clear examples of authentic science in areas that will profoundly impact our understanding of the earth and its system. However, because of the level of commitment required, not every school, teacher, and student will wish to participate in these kinds of endeavors. For those that wish to do so, there are some serious issues to consider.

1. Science curricula are fragmented and jump from subject to subject.
         This is a major obstacle to establishing long-term working partnerships within the "big leagues" of earth science (and, in general, to changing the way science is taught and learned). In order for ground-based measurements to be useful to scientists, they must be made regularly over periods of time that are long relative to the timeframes of traditional science education.

Although the most obvious reason for this requirement is that space-based missions themselves last (hopefully) for years, that is not the only reason. Scientists need to establish confidence in working relationships with teachers and students that are different from relationships with their peers. The justification for making specific measurements in a very specific way must be clearly given. Protocols need to be established and tested. Lines of personal and data communication must be established. Project goals must be presented in an appropriate way, and scientists and teachers must work together to integrate these goals into the overall process of science education. Scientists must be willing to deal with the fact that even the best teachers, with a good grasp of science content, will almost certainly be less well informed in a specific field than other professional colleagues. All these steps require time, and schools that are seriously interested in real science partnerships need to make multi-year commitments that parallel the commitments scientists themselves have made.

2. School schedules do not match science schedules.
         In the U.S. and elsewhere, school vacations have always been the weak link for data collection within the GLOBE program. Even active GLOBE schools often do not collect data on weekends or during extended holidays. This is a serious problem for earth science, whether earth- or space-based. Aerosols, for example, tend to peak during the summer months when photochemical activity peaks, which is why the GLOBE aerosol protocols ask that measurements be made every day, weather permitting. Thus, the first scheduling issue that must be addressed for serious partnerships is how to manage long-term data collection that meets the needs of a particular project.

Scheduling problems also exist on shorter time scales. When measurements must be made to coincide with satellite overflights of a site, this imposes a restriction that otherwise may not exist. Most GLOBE atmospheric measurements are supposed to be made within an hour or so of local solar noon. This is a wide time window that is easy to accommodate. Sun photometer measurements can, in general, be made any time during the day when observing conditions are otherwise appropriate. However, if measurements are to be used for ground-truth validation, then the measurement opportunity will be restricted to within the few minutes surrounding the overflight. Thus, the second scheduling issue that must be addressed is how to provide for measurements coincident with satellite overflights.

3. Teachers tend to be careless with intellectual property.
         This issue is perhaps more a matter of perspective than of ethics. After all, E&PO programs typically produce information specifically for unrestricted use by teachers and their students. In addition, doctrines covering "fair use" of intellectual property within an educational setting give teachers a great deal of leeway in how they use information.

However, it is important for teachers to understand that scientists and others involved in major science projects may devote literally years of their professional careers to a single project. They feel a strong sense of proprietorship over data, which they may obtain often only at the end of a very long and often frustrating process.

Certainly, this is true for EOS-Terra scientists who have waited for years to see aerosol retrievals based on data collected by Terra's Moderate-Resolution Imaging Spectroradiometer (MODIS) instrument. The satellite launch in December 1999 was followed by weeks of testing satellite systems and instruments. The first data and images were not publicly released until April, and it was well into the summer before preliminary ("beta") versions of some data products were distributed outside the Terra project. GLOBE is fortunate to have been given access to beta-version aerosol data. However, this access comes with responsibilities, chiefly to publish or otherwise disseminate data only in collaboration with the Terra project.

At some point, of course, scientific data from publicly funded projects must become truly public. However, when schools, teachers, and students work directly with scientists, they must be willing to participate in a science culture that understands and respects the prerogatives and legitimate self-interests of individuals whose professional careers and reputations are heavily invested in a single project.

Note that one issue not appearing in this list is concern about the ability of students to collect data in a professional way. General experience with programs such as GLOBE and specific experience with students making sun photometer measurements have demonstrated that concerns still raised by some members of the scientific community are unjustified. We are confident that properly trained teachers and students, working with appropriate equipment and carefully designed protocols, can be reliable sources of high-quality data once other issues have been resolved.

What Do Scientists Need to Know and Do To Work Successfully With Teachers and Students?

Finally, here are a few issues that scientists must address in order to work successfully with teachers and students.

1. Scientists (a term which also includes engineers and other professionals) must be honest in assessing their own aptitude for working with teachers and students.
         Not all professionals are particularly adept even at traditional teaching and mentoring roles. Real partnerships with teachers and students require a great deal of patience, very careful and detailed descriptions of objectives and methods, and a large commitment of personal time. Whereas professionals can usually assume that their colleagues share their enthusiasm for a project to which they have a joint commitment, this is not necessarily a good assumption when working with students and teachers. There are many competing demands, including (fortunately or unfortunately, depending on one's point of view) the need to direct a considerable amount of time and energy just toward scoring well on standardized tests. Thus, there are many opportunities both for rewards and frustration and disappointment in doing this kind of work.

2. Scientists must work with educators to define realistic science objectives, develop detailed age-appropriate written protocols, select or develop appropriate equipment, provide thorough teacher training, and maintain motivation over the long haul.
         This task must be a true partnership between scientists and educators. There are still too many examples of student/teacher/scientist "partnerships" (which often have a global online presence) in which teachers and students are misled with respect to the actual scientific value of activities. Collecting, reporting, sharing, and analyzing meteorological and environmental data is interesting and pedagogically useful, but it requires a great deal of collaborative work to raise the level of such activities to the point where they produce scientifically useful data. In order to bridge this gap, scientists and educators must work together to provide pedagogically sound programs that honestly represent their scientific potential.

GLOBE has pioneered this kind of program and is spreading it successfully around the world. (There are now more than 90 countries participating in GLOBE.) There is a growing consensus that the weakest link in this process is insuring the quality and continuity of ongoing measurements once the initial enthusiasm of a new and challenging undertaking wanes. The best way to strengthen this link is for scientists to remain more involved in the process. GLOBE itself is much too small to undertake this task on its own. So, it is enthusiastically embracing partnerships with scientists both inside and outside its own programs.

3. Scientists must provide appropriate acknowledgement of the contributions of teachers and students.
         An obvious form of recognition is to include teachers and students as co-authors in publications. However, although publication is the essential currency for rewarding achievement within the scientific community, this does not necessarily work as a motivation for teachers and students. Other forms of recognition, such as media coverage, help in applying for and implementing grants, teaching awards, and trips to earth science laboratories may be more successful.


The path is now clear for students and teachers to participate as full partners in the major earth science initiatives of the 21st century. There are several opportunities for providing ground validation data for space-based projects that, as a practical matter, cannot be obtained in any other way. Using sun photometers to measure aerosol optical thickness is one example that is already sufficiently well developed to serve as a working model. The remaining issues are organizational and pedagogical, rather than technical. These issues must be addressed by scientists, teachers, and school administrators as they consider the role they wish to play in these new partnerships.

There still remains within some parts of the science community a residual belief that students and teachers cannot contribute significantly to advancing science. Student contributions to space-based earth science during the next few years, through GLOBE and similar programs, will demonstrate that this attitude can no longer be justified.


Asrar, Ghassem R., testimony before the Subcommittee on Space and Aeronautics, Committee on Science, House of Representatives, February 11, 1999. (

Brooks, D. R., and F. M. Mims III, Development of an Inexpensive Handheld LED-Based Sun Photometer for the GLOBE Program, J. Geophys. Res.: Climate and Physics of the Atmosphere, accepted 2000.

Hansen, J., M. Sato, A. Lacis, R. Ruedy, I. Tegen, and E. Matthews, Climate forcings in the industrial era. Proc. Natl. Acad. Sci., 95, 12753-12758, 1998.

Holben, B. N., T. F. Eck, I. Slutsker, D. Tanré, J. P. Buis, A. Setzer, E. Vernote, J. A. Reagan, Y. J. Kaufman, V. Nakajima, F. Lavenu, I. Jankowiak, A. Smirnov: AERONET - a Federated Instrument Network and Data Archive for Aerosol Characterization, Remote Sens. Environ. 66, 1-16, 1998. (Online at

Mims. F. M. III: Sun photometer with light-emitting diodes as spectrally selective detectors, Appl. Opt. 31:33, 6965-67, 1992.

National Aeronautics and Space Administration, 2000a. (

National Aeronautics and Space Administration, 2000b. (

National Science Teachers Association, NSTA Reports!, 12, 1, September 2000. (

Santorini website, 2000. This photograph has kindly been provided by the webmaster of for use in this presentation.