THE DIMMING OF STARLIGHT
THE STANDARD CASE FOR EXPLORATION
The supporters of space exploration do not feel overwhelmed by the challenge. They believe their case is straightforward: space exploration can contribute greatly to the reduction of human misery, the improvement of human life, and the preservation of the environment. In fact, it already has. To appreciate the actual and potential contributions of space, we need only pay attention to the function of satellites, the indirect consequences of space technology (spinoffs), and the opportunities that future exploration may create for humankind. And once we gain an appreciation of these contributions, we will have an answer to the social and ideological critics.
Weather satellites have extended the range and accuracy of weather forecasts appreciably. The reason is simple: from space we see weather patterns that otherwise could be discerned only with great difficulty and never very accurately. Now we see them and track them. Weather satellites warn us about freezes, hurricanes and tornados, thereby saving crops, buildings, and human lives. And when disaster nonetheless strikes, communication satellites enable us to come to the assistance of those in peril or in need of relief.
Apart from this reduction in human misery, the drastic improvement in weather forecasting techniques is of great help to farmers in planting and harvesting, with obvious beneficial consequences for agriculture and the food supply of a hungry world.
Land satellites (LANDSATs and their descendants) are a useful complement to weather satellites. LANDSATs survey the Earth's resources from space, identifying minerals or types of vegetation by their responses to infrared, visible, or ultraviolet radiation. Often, a computer assigns contrasting colors (e.g., gold and purple) to slightly different frequencies (e.g., the frequencies of two closely related browns) that reflect from different materials (e.g., a mineral ore and dry vegetation). This use of “false color” and other computer tricks of remote sensing permit practically instant visualizations of the distribution of natural resources.
We can observe these patterns even on cloudy days, for we can take pictures at wavelengths of the electromagnetic spectrum not absorbed by water droplets. So we can reliably use LANDSATS to look for oil and other mineral deposits; make crop inventories; and carry out surveys of ice in lakes and of snow accumulation on mountains, thus helping to determine the likelihood of flooding. We can also measure the availability of water where it depends on snow melt; estimate forest land; and determine the degree to which urban sprawl affects the surrounding environment. And finally, although the list could go on, we can often monitor the spread of pollution.
Since we can make estimates of the distribution of many resources, and of the productivity of many enterprises, we can see how space technology may be of great assistance in the fight against poverty. Remote sensing technology may also enable us to perform the inventories needed for the preservation of agriculture, wild lands, and wildlife. It seems then that land, weather, and communication satellites begin to answer the concerns of the social and ideological critics of space exploration (see Figures 2.1 and 2.2).
We must recall also the revolution in communications made possible by satellites. We now transmit information and contact people in ways that were unattainable prior to the launching of Sputnik I in 1957. Today, in the comfort of our living rooms, we can watch live on television a sporting or cultural event that is taking place on another continent, or have a telephone conversation with a friend at the opposite side of the world. The significance of these changes becomes evident when an emergency prompts our call to the other side of the world, or when the satellites are used, as in India, to bring education to large rural areas for the first time. And do not forget that the global Internet would not be possible without communication satellites. All these changes in people's daily lives are mirrored by improvements in the practice of commerce, the gathering of news, and the relief of disaster.
The Space Shuttle, as well as other piloted vehicles and the various kinds of space stations, complement these functions of satellites. A 1994 Space Shuttle flight yielded preliminary radar measurements of hitherto undiscovered structures around Angkor Wat, a famous archeological site in Cambodia. NASA’s Jet Propulsion Laboratory then developed a sophisticated airborne radar system that allowed archeologist Elizabeth Moore and her team to discover four to six more temples and gain a better picture of the massive waterworks that were an integral part of the complex.
Few of these accomplishments were likely through more conventional methods. Surveys from the ground could not compete with a perspective that permitted us to detect, at a glance, large patterns and to take inventories of minerals and vegetation. It might be imagined that perhaps airplanes could have flown high above the clouds to do a similar job for less money. But whereas satellites give us pictures of exactly the same spot time and again so we can make comparisons, the flight path of airplanes is never that precise. Nor are airplanes as reliable – they are subject to mechanical problems and the vagaries of weather. Moreover, it would have taken a fleet of thousands of airplanes to do what a single satellite does in passing over the Earth at its very high orbital speed. Using airplanes might have well cost us hundreds of times more and the results would have been vastly inferior. Today we are beginning to use new generations of light planes and other flying devices to obtain more specific local information, normally interpreted in the larger context provided by satellite data.
In any event, many crucial jobs can be done only from space. For a variety of reasons, many weather and communication satellites must be placed exactly over the same spot on the Earth. For example, a satellite fixed overhead is extremely convenient, since we can then transmit and receive from it at any time. As the Earth rotates, the satellite must rotate with it so as never to lag or move ahead. Only a special orbit, called a geosynchronous orbit, 36,000 Km. (22,000 miles) over the equator satisfies these requirements.
Of course, this is only the beginning. New generations of satellites will do far more. Future LANDSATs, for instance, may be helpful in estimating agricultural yields (which would be an important refinement over the presently available crop estimates), once we have a better knowledge of the connections between cloudiness, rainfall, and soil moisture. Merely two decades ago, the very idea of cellular telephones, to say nothing of tracking devices for trucks and mountain climbers, had an aura of science fiction. Now we can expect that future SEASATs and navigation satellites will not only survey the oceans, but also contribute to the safety of travelers and cargo.[v] All in all, new kinds of satellites will improve in new ways the lives of billions and billions of human beings.
. Until 1980 weather satellites led to significant improvements in weather predictions mostly in the southern hemisphere and over the oceans, not in the advanced, populated areas of the northern hemisphere. The reason is that temperature and pressure at different altitudes could be better determined by other technological means. And improvement in the computer weather programs in 1980 led to new and more powerful forecasting techniques in which satellites played a crucial role. Future generations of weather satellites will provide more refined measurements.
 The number of hurricane casualties shows a steady decline. In the 1900 Galveston Hurricane, for example, about 8,000 people died. Death tolls around 1,000 resulted from hurricanes in 1919 and 1926. It was not uncommon to see even higher casualties in the first part of the 20th Century. By the 1960s and 70s, the numbers were more typically in the low hundreds. Today they are in the dozens.
The one disastrous exception is hurricane Katrina, which may have caused close to a thousand deaths in Louisiana, Mississippi, and Alabama. Here we have a case, however, in which the warning was delivered but not properly heeded. In many cases, it seems, the reduction of casualties over the last two decades made some people overconfident, and many refused to leave the area. To make matters worse, the evacuation plan for the city of New Orleans was not followed, even though a run-through a year earlier showed that more than 100,000 people were likely to stay in the city unless city and school buses (and probably additional transportation from the state of Louisiana) were pressed into service. For over twenty years it was known that a hurricane that strong would destroy the levees and flood the city. But no one took steps to prevent the calamity. A tragedy of errors turned a serious but still manageable problem into probably the worst natural disaster in the history of the country. One shudders at the thought of what would have happened without the satellite warnings. Incidentally, military and civilian satellites, including Ikonos, a private imaging satellite operated by Space Imaging, are already giving us a reliable assessment of the damage.
. Science News, Vol. 153, February 21, 1998, p. 117.
. For details see The Impact of Space Science on Mankind, op. cit., p. 82. For a summary of the benefits derived from Landsats and environmental satellites, see the same work, pp. 67- 111. In it there are also discussions of communication and weather satellites.