Return of the Explorers.
Faced with growing concern about terrestrial problems ranging from the ozone hole to deforestation, the National Research Council's Committee on Earth Sciences (CES) as recommended that NASA revive a satellite-planning approach that began in the space agency's formative years. NASA already plans a series of sophisticated, unstrument-laden "platforms" whose orbits will carry them over Earth's poles to look down on the entire planet. But the CES urges NASA to develop a program of smaller, less costly Earth Explorer satellites to fill gaps in the primary program and to respond on shorter notice to newly perceived research needs.
NASA usually emphasizes big, individually managed projects, such as interplanetary probes, whose completion depends on annual appropriations from Congress for each satellite. However, a series of satellites called Explorers long has followed a different budgetary path. NASA seeks money each year to finance the Explorer effort as a whole, rather than seeking funds for each specific satellite in the series, whose missions have ranged from earth science and astronomy to space physics. The CES urges a separate, Explorer-type program to focus on the earth sciences.
CES also recommends the Earth Explorer satellites use standardized satellite designs, rather than creating a new design for each new mission. Having several craft built with the same basic design and buying more than one at a time would allow "important economies of scale." The same approach was advocated earlier by NASA's Solar System Exploration Committee for planetary flights, but missions using the first such standardized design have yet to win dudget approval from the White House and Congress.
One crucial element, according to the report, is "flexibility." For example, rather than producing a whole Earth Explorer satellite for each new sensor, the committee suggests looking for alternative routes to orbit, such as putting earth sciences sensors on satellites from other U.S. agencies or even from other countries.
A Total Ozone Mapping Spectrometer (TOMS), for instance, has been at work on the Nimbus 7 weather satellite since 1978, but the report notes that "global ozone measurements are too important" to allow a long "date gap" in case Nimbus 7 fails before the proposed polar platforms are ready. U.S. and Soviet officials have thus been discussing the possibility of installing the next TOMS on a Soviet satellite. The United States and Japan are considering a joint Tropical Rainfal Measuring Mission, whose measurements would require an orbital inclination and altitude too low for the polar platforms.
NASA launched 41 Explorer satellites in its first decade (1958-'67), 27 of which related to what the CES lumps together as the earth sciences. The next 10 years saw only 21 Explorers, eight of them in earth sciences. In NASA's third decade, the numbers dropped to 9 and 4.
Why did the Explorer program slow so dramatically, given its relatively modest effects on NASA's tight money supply? In part, notes CES Executive Secretary Paul F. Uhlir, the individual Explorer satellites became more elaborate and costly. The CES report envisions a long-term congressional commitment to provide the program about $75 million a year, effectively removing Explorer craft from the annual budget battle.
With NASA's eye on its pocketbook, does the Earth Explorer program stand a chance? Perhaps not in bureaucratic Washington. "A program like this is seen by the budgeting authorities as representing a loss of control," says a National Research Council official. One program might arise, he says, when the Office of Management and Budget must decide whether to support what is called a "level-of-effort program" rather than "micro-managing the individual projects."
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|Title Annotation:||Earth Explorer satellites|
|Date:||Dec 17, 1988|
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