A coordinated effort should include the following:
- An increase in the level of effort, presently that of about 1 person per
year to that of 5-10 persons per year. All available time on Schmidt telescopes
with apertures 60 cm and larger would be used. Smaller telescopes would not
detect enough asteroids to make efficient use of the observers' search time.
- Construction of a 60-cm Schmidt telescope dedicated to the search for near-Earth
asteroids. This facility could be built in 1 year, would cost from $200 000
to $300 000, and should allow investigators to discover 5 to 10 near-Earth
asteroids per year. At this rate of discovery, the number of candidate asteroids
for near- Earth rendezvous missions would be adequate within just a few years.
- Construction of a 120-cm Schmidt telescope dedicated to the search for
near-Earth asteroids. Such an instrument could photograph approximately 700
fields each year. The development of automatic scanning systems has eliminated
the immense task of visually scanning these plates for trailed images. This
next-generation search instrument is needed to achieve the goal of discovering
400 to 500 near-Earth asteroids in the next 20 years. The survey would allow
the choice of an asteroid for detailed investigation possibly leading to mining
operations. This telescope wou1d take about 3 years to complete and cost from $3 million
to $4 million. The search program would require the work of about 6 persons per year.
Discovery rates with this facility should be from 2,0 to 30 near-Earth asteroids per year.
- Assembly and monthly update of a central index of wide-field plates. This
cooperative effort would allow rapid access to all images containing the asteroid,
including those recorded before the asteroid was recognized, and would thus contribute
to the precise determination of its orbit. This effort would require the equivalent of
about 1 person's work per year.
- Application of radar to the study of near-Earth asteroids. Radar has only recently
been successfully applied to asteroid studies, primarily from the Arecibo facility (see fig. 7).
Because signal strength is related to the inverse fourth power of the distance to the target and
because the target asteroids are relatively near, radar promises to be a very powerful technique
for studying them. Radar can provide information on size, shape, and rotation rate. And radar
wavelengths will be responsive to composition (e.g., metal content) and surface structure.
Without an accelerated discovery program, we will probably continue to discover
only a few near-Earth asteroids each year. Only a small number of these are easily
accessible to spacecraft. Therefore, in order to utilize asteroidal resources
within the next 20 to 30 years, we need an expanded search program to find near-Earth
asteroids and we need measurements of their physical properties to evaluate their
usefulness.
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