New Generation Ground-Based Optical/Infrared Telescopes 733
FIGURE 16 Cumulative
discoveries of near-Earth asteroids.
The total number of large
near-Earth asteroids (larger than
1 km) is increasing at a slower rate
since most of the easy-to-detect
NEOs have already been
discovered. The remaining
unknown NEOs are on orbits that
are intrinsically more difficult to
detect and therefore require a
longer time to discover. (From
NEO.)(Courtesy of Alan
Chamberlin.)There are three major ground-based sky surveys cur-
rently under development or study (see Table 2). The Dis-
covery Channel Telescope is a 4.2-m telescope that is un-
der construction near Flagstaff in Northern Arizona and
should be operational by 2009. Another survey telescope
that is under development is Pan-STARRS, which consists
of four 1.8-m telescopes (with a combined aperture approx-
imately equivalent to a 3.6-m telescope) to perform rapid
wide-field surveying of the entire sky on a weekly basis. It
is hoped that the full system will be operational by 2010,
but a prototype single telescope unit will be operational on
Haleakala on Maui by the end of 2007. The proposed Large
Synoptic Survey Telescope is currently under engineering
and design study and is envisioned to be a monolithic 8.4-m
wide-field telescope (with a collecting area equal to a 6.7-m
telescope). With its large diameter and fast focal ratio it
should be capable of reaching 24thmagnitude in single 10-s
exposures. Due to their extreme depth and wide-field cov-
erage each of these surveys should reach 99% completion
for NEOs larger than 1 km diameter within two years of
beginning operation.
6. Concluding Remarks
Space does not allow coverage of all of the relevant subjects
related to the vibrant topics of novel telescope construction,
optical fabrication techniques, advances in mirror figure
control, adaptive optics, and detector improvements at vis-
ible and infrared wavelengths. The topics covered in this
chapter can only hint at the tremendous advances that have
taken place in recent years and that carry on unabated. Since
the invention of the refractive and reflective telescopes by
Galileo and Newton, the construction of ground-based tele-
scopes continues to challenge the very best minds in physics
and engineering. At the present time there are strong scien-
tific drivers to build larger telescopes in the 20–50 m range.
It seems only a matter of time before such extremely large
telescopes are built.
Solar system astronomy is driven by the need to have
large telescopes in order to study very faint objects in the
Kuiper Belt and very faint NEOs that may present a haz-
ard to Earth. It is also necessary to have the highest spa-
tial resolution possible by working at the diffraction limit
of large telescopes. This will enable researchers to study
the surface and atmospheric features of the outer planets,
dwarf planets, and their satellites. Large telescopes also al-
low the study of exo-planets, and thus bring about a merg-
ing of studies of our solar system with those around distant
stars.
Another driver of solar system astronomy is to detect and
characterize NEOs that may present an impact hazard to
the Earth. Numerous sky survey programs are underway to
detect at least 90% of all NEOs larger than 1 km, and there is
a push at the present time to expand this program to detect
at least 90% of all NEOs larger than 140 m. These survey
programs will play a significant role in greatly expanding
our knowledge of the building blocks of our solar system—
the asteroidal and cometary bodies from the inner to the
outer reaches of the solar system. These studies are likely
to profoundly affect understanding of the formation of our
solar system and life itself.