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OCR for page 98
Ultraviolet, Optical, and
Infrared Astronomy
I. SUMMARY AND RECOMMENDATIONS
The program of ultraviolet, optical, and infrared (W OIR)
astronomy for the 1980's involves a great diversity of
astronomical objectives and means for attaining them.
Some facilities are already well established, others are
just coming into operation, some are now planned for
construction, and still others are new initiatives for
the coming decade. In this section, we present the major
recommendations of highest priority, call attention to
those ongoing and planned programs that are fundamental
to the W OIR science program for the 1980's, and summa-
rize the scientific achievements and opportunities that
have led us to these recommendations.
A. Recommendations for Major Initiatives
We recommend:
1. A program to increase dramatically the angular
resolution and light-gathering capability of ground-based
astronomy through the construction in this decade of a
national New Technology Telescope (NTT) of the 15-m class
for optical and infrared observations at an excellent
site. We also recommend the construction at good sites
98
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of several smaller national telescopes with apertures
between 2.5 and 5 m that exploit new cost-saving tech-
niques and the allocation of matching federal funds to
encourage the construction of state and private tele-
scopes. The astronomy of the 1980's will urgently
require us to extend and augment our capabilities for
spectroscopy, photometry, and imaging in the wavelength
region between 0.3 and 30 Em.
2. A program leading to the construction of a Large
Deployable Reflector (LDR) of the 10-m class for observa-
tions in the far-infrared and submillimeter spectral
regions from space, with construction starting in the
late 1980's. m is facility will provide diffraction-
limited spatial resolution and high spectral resolution
in the 30-1000-pm range, where the Earth's atmosphere
is opaque. These capabilities are crucial for detailed
investigation of star-forming regions and energetic
extragalactic sources.
3. The deployment of a far-ultraviolet spectrograph
in space. This facility, incorporating a telescope in
the 1-m class, will provide high spectral resolution in
the wavelength region 900-1200 A, with possible exten-
sion down to a few hundred angstroms. For technical
reasons these wavelength regions are inaccessible to
Space Telescope (ST) and the International Ultraviolet
Explorer (IUE) satellite but are important for probing
high-temperature regions of the interstellar medium,
galactic halos, and the outer atmospheres of stars.
4. A free-flying Advanced Solar Observatory (ASO) in
space. This facility, launched in time to study the 1991
solar maximum, would provide the necessary time baseline
for detailed observations with very high spatial resolu-
tion of the evolution of active regions on the Sun, in-
cluding the development of flares, over spectral regions
ranging from the optical and ultraviolet to x-ray and
gamma-ray wavelengths.
5. m e development and utilization of advanced
detector systems and instruments throughout the W OIR
region. Efficient instrumentation and detectors are
essential to the realization of the full potential of all
existing and future W OIR facilities. In particular, the
technology is ripe for the introduction of area detectors
that will achieve very high two-dimensional spatial
resolution in the infrared region when used with a very
large telescope. Funding for two-dimensional photon-
counting devices and charge-coupled devices (CCD's)
should also be made available.
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100
The above recommendations are for major new elements
in a large set of programs--some ongoing, some soon to be
implemented, and others still in the conceptual stage--all
of which will be fundamental elements of WOIR astronomy
for the 1980's. The broad W OIR science program requires
the full and effective use of existing ground-based, air-
borne, balloon, and space facilities. Effective use of
the major planned and recommended facilities will also
require the successful completion of sensitive all-sky
surveys in several infrared wavelength bands, in the space
ultraviolet, and in the optical region (through extension
of previous ground-based optical surveys).
It is also critical to the health of the science that
the following National Aeronautics and Space Administra-
tion (NASA) programs, which are already planned, be
implemented:
.
Space Telescope (ST), which will provide unrivaled
spatial resolution and sensitivity over an extensive wave-
length range. The development and support of a healthy,
vigorous, and independent Space Telescope Science Insti-
tute (STScI) to operate ST is critical to ensuring maxi-
mum scientific return from this facility. The periodic
refurbishment and reinstrumentation of ST are also
vitally important.
· Shuttle Infrared Telescope Facility (SIRTF), a
cryogenically cooled infrared telescope that will be an
extremely powerful photometric and moderate-resolution
spectroscopic tool for use in the 3-1000-pm region.
The development of advanced instrumentation, together
with adequate flight frequency and duration are essential
in order to realize the full scientific potential of
SIRTF.
.
Solar Optical Telescope (SOT), a Shuttleborne
telescope that will provide the capability to study solar
structures and their evolution, the dynamics of active
regions, and solar magnetic fields with significantly
higher spatial resolution than previously possible.
The Panel furthermore wishes to underscore its belief
that various sources of new federal funds are critically
needed for operation of ground-based optical observa-
tories. Fully effective use of many major facilities,
which represent major capital investments, is now pre-
cluded by inadequate support. In several cases, private
and state support alone is no longer sufficient for
optimum operation.
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101
In addition, we recognize the great value of the
Explorer series of NASA satellites for all facets of the
W OIR effort and urge the significant augmentation of
this successful program to offset the corrosive effects
of inflation. In particular, we support the Infrared
Astronomy Satellite (IRAS) Explorer, the Cosmic Back-
ground Explorer (COBE), and the Extreme W Explorer (E WE)
missions; we endorse the Solar Coronal Explorer to study
acceleration processes in the solar wind; and we endorse
the Solar Dynamics Explorer, which will provide an oppor-
tunity to measure solar internal structure and dynamics.
The Kuiper Airborne Observatory is, and the Spacelab
payload program promises to become, extremely successful
scientifically. Both programs should be augmented sig-
nificantly. There is, in addition, a clear need for a
variety of specialized telescopes and facilities. For
example, the Panel notes the great scientific potential
of optical/infrared interferometry. There is also an
urgent need for dedicated astrometric and infrared tele-
scopes in the southern hemisphere; furthermore the astro-
metric community urgently requires additional computer-
controlled measuring machines to make optimum use of
existing and new-plate material. Finally, many of the
exciting discoveries made by the deep-space planetary
probes of the 1970's could be extended and better under-
stood if a 1-m-class imaging and spectroscopic telescope
were placed in near-Earth orbit and dedicated to planetary
observations.
B. Scientific Achievements and Opportunities
The past decade has witnessed a series of discoveries
that have fundamentally altered our understanding of the
Universe. The x-ray satellites launched during the
1970's discovered a number of binary-star systems that
contain neutron stars or perhaps even black holes. The
strange Galactic source SS 433 appears to be ejecting
matter at velocities equal to nearly 30 percent of the
velocity of light. X-ray and radio observations have
revealed evidence of gas between the galaxies in clusters
of galaxies. Radio observations, and deep optical
photographs using modern emulsions, have detected faint
luminous material lying far outside the normal optical
images of a number of galaxies. Studies of the Sun have
revealed unexpected periodic oscillations and have begun
to uncover the roles played by magnetic fields in con-
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102
trolling astrophysical plasmas. We are also beginning to
suspect that the Sun may undergo quasi-periodic changes
with a time scale of centuries. Planetary probes have
uncovered phenomena such as volcanoes on To and atmo-
spheric circulation on Jupiter that could yield important
geologic and atmospheric information if studied system-
atically from near-Earth orbit. Despite the remarkable
advances of the past decade, however, many of the most
significant questions confronting astronomy today remain
unanswered.
Astronomers have only begun to glimpse how the Milky
Way and other types of galaxies may have appeared at
earlier times. Evolution of some galactic types may
progress much more rapidly than has been believed. De-
spite our most intensive efforts throughout the 1970's,
the age of our Universe and its distance scale remain
uncertain by at least a factor of 2. Determination of
the geometry, scale, and evolutionary fate of the Uni-
verse and its components remains a major challenge to
astronomers during the 1980's.
X-ray, optical/infrared, and radio studies have all
revealed the ubiquity and variety of energetic phenomena
in galactic nuclei.
Quasars, Seyfert galaxies, and BL
Lac objects, as well as less spectacular systems, all
seem to contain enormous energy sources that are not
understood. Many astronomers believe that this galactic
nuclear activity owes its origin to the accretion of
matter by supermassive objects
~ _ (black holes?). It is
still uncertain whether new physics or more conventional
ideas, such as "explosions" of star formation, are
required to explain these phenomena. Much effort in the
1980's will be devoted to the study and interpretation of
active galactic nuclei.
Accretion of matter can also play a significant role
in affecting the evolution and physical state of indi-
vidual stars under special conditions. Accretion of
material onto dense objects such as white dwarfs, neutron
stars, and black holes may be the only signature of these
unseen bodies. ~
Accretion also accounts for the spectacu-
lar outbursts of novae. Physical models of accretion
under various conditions are primitive and await guidance
from new observations.
Astronomers were surprised to learn in the 1970's that
much of the interstellar medium in our Galaxy apparently
consists of hot gas at temperatures of about 1 million
degrees. It is not yet known how much material is in the
form of hot gas, how it is heated, or how it affects the
Representative terms from entire chapter:
black holes
