Exploring the Unknown - NASA's History Office

182
OBSERVING THE EARTH FROM SPACE
storms, size and intensity would vary geographically. A meteorologist given a clear picture
of the cloud distribution, as here portrayed, could without difficulty sketch in a very useful
weather chart showing location of the various stormy and fair weather areas; in fact, he
would have a much better idea of the large-scale weather distribution than his Earthbound
colleague, who is forced to rely on scattered observations taken at or near the
Earth’s surface.
As for obtaining two or more “fixes” on storms within 12 hours, this would be possible
as the vehicle makes successive passages toward the Poles—and the closer to the Pole
the storm is located the more such fixes could be made. For example, the large fully developed
storm depicted over Hudson Bay would be visible first on one leg of the path, again
4 hours later on the next leg, and again 4 hours later on a third leg. This would, by reference
to known surface features, enable tracking of the storm in the 12-hour interval. A
word of caution is necessary since the clouds which on one hand make possible the visual
identifications of the storm will hinder its location with respect to known surface features.
Nor would trying to track the storm by observing the edge of its cloud shield
necessarily give an accurate track, since the changing cloud pattern associated with such
large, usually dissipating storms may give spurious motions, as they form on one side and
dissipate on the other. Thus, there will not be too good an accuracy for tracking these
large storms, but this is not too important since their speed of motion is usually slow anyway.
On the other hand, the incipient or developing storm, so important for future weather
developments, is faster moving and has a less extensive cloud system associated with it
so that more accurate fixes should be possible. The hurricane, with its cloud bands, similar
to the arms of a spiral nebula, and its open “eye” at the centre, will be a much easier
storm to detect and follow accurately. Cloud systems associated with cold fronts and squalllines
will also lend themselves to accurate tracking.
As the days pass, however, and the Earth moves in its orbital motion about the Sun,
the vehicle will cross each latitude about 4 minutes earlier than the preceding day. Thus,
if motion northward is started at noon on March 21, this will change on June 21 to 6 a.m.
moving north, and 6 p.m. moving south; in this case, the field of view in daylight will be
mostly to the east (going north) and to the west (going south) and the efficiency of the
vehicle as a cloud patrol will have diminished considerably. On September 21 its efficiency
will increase again as it moves south at noon and north at midnight. However, on
December 21 its efficiency will drop again—and to its lowest point as far as the Northern
Hemisphere is concerned. It will move north at 6 p.m. and south at 6 a.m.—but because
of the low solar declination at this time and consequent lack of daylight hours, its usefulness
as a cloud and storm detector will be greatly impaired. This is a serious defect because
the winter season is the busiest period for storms in the Northern Hemisphere. This suggests
as a better [276] solution that the preceding plan, the initial movement northward
or southward at noon on December 21. This will then give optimum conditions for winter
weather patrol—excluding the Arctic and some distance south where little or no daylight
will prevail.
This visual cloud reconnaissance might be taken automatically by a television camera
in an unmanned vehicle and relayed to Earth to various collection centres for study, analysis
and exchange with other forecast offices to obtain a truly global weather picture. If the
vehicle could be properly manned and equipped, then other valuable geophysical and
solar data could be obtained as follows:—
(a) Temperature of the Earth’s surface and a rough average temperature of the intervening
atmosphere by observing the infrared spectrum.
(b) Precipitation Areas (rain, snow, etc.) could be detected by radar as well as the
heights of their formation above the surface; also the height of the freezing level
which shows as a bright band in the radar scope.