National Academy of Sciences

National Academy of Engineering

Institute of Medicine

National Research Council

Space Studies Board

Commission on Physical Sciences, Mathematics and Applications

March 3 2000

Dr. Ghassem R. Asrar

Associate Administrator for Earth Science

Code Y

NASA Headquarters

Washington, D.C. 20546

Dear Dr. Asrar:

At your request the National Research Council established a task group to evaluate the scientific aspects of the Triana mission. The charge to the Task Group on the Review of Scientific Aspects of the NASA Triana Mission was to review (1) the extent to which the mission’s goals and objectives are consonant with published science strategies and priorities, (2) the likelihood that the planned measurements can contribute to achieving the stated goals and objectives, and (3) the extent to which the mission can enhance or complement other missions now in operation or in development.

Triana is a mission designed to be deployed into a stable orbit, at roughly a million miles from Earth in the direction of the Sun. An orbit at this location, known as Lagrangian point 1 (L1), is stable in the sense that the satellite remains on the Sun-Earth line and views the full sunlit disk of Earth continuously. From L1 Triana will observe Earth with two instruments, and a third will monitor the space environment in the direction of the Sun. Observed data are expected to be delivered in near real time to ground stations.

As proposed, Triana is an exploratory mission to investigate the scientific and technical advantages of L1 for Earth observations. The continuous view of the full sunlit disk of Earth will complement and extend observations from low Earth orbit (LEO) or geostationary Earth orbit (GEO) satellites. Triana will provide a global synoptic view (a continuous, from sunrise to sunset, simultaneous view of the sunlit side) of Earth in a range of wavelengths including ultraviolet, visible, and infrared to observe variations in ozone, aerosols, clouds, and surface ultraviolet radiation and vegetation. Triana is a flight opportunity to extend and improve observation of the solar wind and space weather at a most meaningful site, supplementing the data from the Advanced Composition Explorer satellite.

A detailed analysis of instrumentation, data collection and reduction, systems operation, and management was beyond the scope of the task group’s effort and was precluded by the time and budgetary constraints placed on the preparation of this report. Nevertheless, the task group agreed on a number of general issues related to the likely scientific success of the mission based on its review of relevant documents and reports and briefings by NASA’s Triana science team. In its evaluation, the task group relied heavily on presentations from NASA and members of the Triana science team, and on detailed questioning of the presenters.

In the attached more detailed technical assessment, the task group relates Triana’s scientific objectives and deliverable data products to the research strategies and priorities proposed in earlier National Research Council and government reports. The task group found that the scientific goals and objectives of the Triana mission are consonant with published science strategies and priorities for collection of climate data sets and the need for development of new technologies. However, as an exploratory mission, Triana’s focus is the development of new observing techniques, rather than a specific scientific investigation. The apparent spaceflight heritage of some of the Triana technology and the applicable legacy of the data reduction algorithms should contribute to the achievement of the mission’s objectives. The task group concluded that the planned measurements, if successfully implemented, will likely contribute to Triana’s stated goals and objectives. It did not attempt to evaluate the applicability of this heritage for a mission at L1.

The task group also found that the Triana mission will complement and enhance data from other missions because of the unique character of the measurements obtainable at the L1 point in space, which allows continuous imaging of the full sunlit disk of Earth and monitoring of the space environment upstream from Earth. Furthermore, the full-disk Earth observations provide a unique perspective from which to develop new databases and validate and augment existing and planned global databases. As an exploratory mission, Triana may well open up the use of deepspace observation points such as L1 for Earth science. The task group believes that the potential impact is sufficiently valuable to Earth science that such a mission might have been viewed as an earlier NASA priority had adequate technology been available at reasonable cost. The task group is concerned, however, that because of the compressed schedule there may not be adequate time for instrument testing and calibration prior to launch.

The task group is also concerned that significant development, testing, and validation of the operational algorithms are needed, and it recommends that this work start immediately. The scientific success of the Triana. mission will be judged, in large part, on the quality of the initial data delivered to the scientific community. The task group therefore recommends that NASA seriously consider increasing the level of effort invested in development and testing of data reduction algorithms for the core Earth data products as soon as possible. In addition, it is concerned that there may be insufficient funding for scientific analysis of the data. If Triana lasts longer than its nominal 2 years, it will be important for NASA to support the data processing activities for the mission’s useful duration.

The task group lacked the proper expertise, resources, and time to conduct a credible cost or cost-benefit analysis (such an effort might take many months and much detailed analysis) or an analysis of the mission goals and objectives within the context of a limited NASA budget or relative to other Earth Science Enterprise missions. However, based on the available information, the task group found that (1) the cost of Triana is not out of line for a relatively small mission that explores a new Earth observing perspective and provides unique data; (2) since a significant fraction of the Triana funds (according to NASA and the Triana principal investigator, 50 percent of total funding and 90 percent of instrument development money) have already been expended, weighing cost issues would lead to only limited opportunities to save or transfer funds to other projects. In addition, the task group endorses the statement by Congress that the delay in the mission mandated to produce this report may mean additional costs.

The task group emphasizes that the attached discussion of the ability of Triana to achieve the mission’s stated goals and objectives is predicated on the assumption that the instruments and satellite have been, and will continue to be, subject to all necessary and appropriate exploratory-mission technical and quality control reviews. Under no circumstances should this report or the statements contained in it be used as a replacement for these technical evaluations.


James J. Duderstadt

Chair, Task Group on the Review of Scientific Aspects of the NASA Triana Mission

Eric J. Barron Chair, Board on Atmospheric Sciences and Climate

Mark Abbott

Acting Chair, Space Studies Board

Raymond Jeanloz

Chair, Board on Earth

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