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Aeronomy and Astrophysics  

Aeronomy and Astrophysics
The polar regions have been called Earth's window to outer space. Originally, this term applied to aurora and other dynamic events staged as incoming solar plasmas encountered the Earth's geomagnetic fields. Because of its unique properties, the polar upper atmosphere becomes a virtual screen on which the results of such interactions can be viewed (and through which evidence of other processes can pass). More recently, this concept has been extended to refer to the "ozone hole" in the polar atmosphere. As scientists have verified an annual loss of ozone in the polar stratosphere, a window previously thought "closed" (stratified ozone blocking the sun's ultraviolet rays) is now known to "open" in certain seasons.

For astronomers and astrophysicists, the South Pole presents unique opportunities. Thanks to the relative lack of environmental pollution and anthropogenic "noise," the unique pattern of light and darkness, and the geomagnetic force field properties, scientists staging their instruments here can probe the structure of the sun and the universe with unprecedented precision. Studies supported by the Aeronomy and Astrophysics program probe three regions:

• The stratosphere and the mesosphere: In these lower regions, current research focuses on stratospheric chemistry and aerosols, particularly those implicated in the ozone cycle.

• The thermosphere, the ionosphere, and the magnetosphere: These higher regions derive many characteristics from the interplay between energetically-charged particles (ionized plasmas in particular) and geomagnetic/geoelectric fields. The upper atmosphere, particularly the ionosphere, is the ultimate sink of solar wind energy transported into the magnetosphere just above it. This region is energetically dynamic, with resonant wave-particle interactions, and Joule heating from currents driven by electric fields.

• The universe beyond, for astronomical and astrophysical studies: Many scientific questions extend outside the magnetosphere, including a particular interest in the sun and cosmic rays. Astrophysical studies are primarily conducted at Amundsen-Scott South Pole Station or on long-duration balloon flights launched from McMurdo.

Virtually all research projects sponsored by this program benefit from (indeed most require) the unique physical conditions found only in the high latitudes, yet their ramifications extend far beyond Antarctica. High-latitude astrophysical research contributes to the understanding of Antarctica's role in global environmental change, promotes interdisciplinary study of geosphere/biosphere interactions in the middle and upper atmosphere, and improves understanding of the critical processes of solar energy in these regions. Life exists on earth in a balance – not only because of the critical distance from the sun – but also because of numerous chemical and atmospheric phenomena peculiar to our atmosphere. The 20th century expansion of traditional astronomy to the science of astrophysics, coupled with the emerging discipline of atmospheric science (See also the Ocean and Climate Systems program), is nowhere better exemplified than in Antarctica.

AMANDA—Antarctic Muon and Neutrino Detector Array.
Robert Morse, University of Wisconsin.

Neutrinos are elementary particles: With no electrical charge, and believed to have very little or no mass, they can take any of three forms. Coursing through the universe, they interact only rarely with other particles. AMANDA's primary objective is to discover the sources – both within our galaxy and beyond – of the shower of very-high-energy neutrinos descending on (and usually passing through) the Earth. AMANDA uses an array of photomultiplier tubes embedded between 1 and 2 kilometers in the ice near the South Pole to create a Cherenkov detector out of the natural ice. This system will detect high-energy neutrinos originating off the planet that have passed through Earth. Such sources of origin could be diffuse, made up of contributions from many active galactic nuclei (AGNI); or they could be point sources of neutrinos – coming from supernova remnants (SNRs), rapidly rotating pulsars, neutron stars, individual blazars, or other extragalactic point sources.

Recently, new sources of high-energy gamma rays have been discovered, such as the source Mrk-421 discovered by NASA's Compton Gamma-Ray Observatory (CGRO) and Mt. Hopkins Observatory. AMANDA is designed to study just such objects, which are believed to emit high-energy neutrinos copiously. To date, neutrino astronomy has been limited to the detection of solar neutrinos, plus one brief, spectacular burst from the supernova that appeared in the Large Magellanic Cloud in February 1987 (SN-1987a). Only now is it becoming technically feasible to build large neutrino telescopes. As one of the first-generation detectors, AMANDA promises to make seminal contributions to this new branch of neutrino astronomy. (AA-130-O)

South Pole Air Shower Experiment–2.
Thomas Gaisser, University of Delaware.

As cosmic rays from space arrive at the Earth's upper atmosphere, molecules begin to feel the impact. The South Pole Air Shower Experiment-2 (SPASE-2) deploys a sparsely filled array of 120 scintillation detectors over 15,000 square meters at South Pole. This instrument array detects energetic charged particles (primarily electrons) that are produced in the upper atmosphere by cosmic rays. To detect the Cherenkov radiation produced in the high atmosphere by the same showers, a subarray called VULCAN has been constructed of nine photodetectors. The SPASE array is located less than half a kilometer from the top of AMANDA; this low-energy collector is designed to complement AMANDA's neutrino detecting capacity. [Described in the previous project summary (AA-130-O)]

SPASE-2 has two goals:

• To investigate the high-energy primary cosmic radiation, by determining the relative contribution of different groups of nuclei at energies above approximately 100 teraelectronvolts. This can be done by analyzing coincidences between SPASE and AMANDA. Such coincident events are produced by high energy cosmic-ray showers with trajectories that pass through SPASE (on the surface) and AMANDA (buried 1.5 to 2 kilometers beneath it). AMANDA detects the high energy, penetrating muons in those same showers for which SPASE detects the low energy electrons arriving at the surface. This is meaningful because the ratio of muons to electrons depends on the mass of the original primary cosmic ray nucleus. VULCAN adds two other ratios that also depend on primary mass in readings from the showers it detects.

• To use the coincident events as a tagged beam, which will permit investigation and calibration of certain aspects of the AMANDA response. This project cooperates with the University of Leeds in the United Kingdom. (AO-109-O)

Magnetometer data acquisition at McMurdo and Amundsen-Scott South Pole Stations.
Louis Lanzerotti, AT&T Bell Laboratories, and Alan Wolfe, New York City Technical College.

The magnetosphere is that region of space surrounding a celestial object (such as the Earth or the Sun) where the object's magnetic field is strong enough to trap charged particles. Magnetometers have been installed at selected sites in both polar regions to measure changes in the magnitude and direction of Earth's magnetic field (in the frequency range from 0 to about 0.1 hertz). The unique climatic conditions in Antarctica also permit scientists to view the atmosphere optically and to correlate such hydromagnetic-wave phenomena with particle-precipitation measurements.

In this project we are measuring such variations with magnetometers installed at conjugate sites in both hemispheres; at McMurdo and Amundsen-Scott South Pole Stations, Antarctica, and at Iqaluit, in the Northwest Territories in Canada. Our data are also being analyzed and associated with similar data acquired from several automatic geophysical observatories comprising the PENGUIN program [polar experiment network for geophysical upper-atmosphere investigations, (AO-112-O)].

Using all of these systems, we are deriving information about the causes and propagation of low-frequency hydromagnetic waves in the magnetosphere, as well as the coupling of the interplanetary medium into the dayside magnetosphere. (AO-101-O)

An investigation of magnetospheric boundaries using ground-based induction magnetometers operated at manned stations as part of an extensive ground array.
Roger Arnoldy, University of New Hampshire.

The poles of the Earth – the points marking the axis around which the planet rotates – experience unique magnetic phenomena.

By measuring magnetic pulsations at these high geomagnetic latitudes, scientists can study the plasma physics of some of the important boundaries of the magnetosphere. Geophysicists refer to the continuous stream of highly-charged particles emitted by the Sun as the solar wind. Two of the important areas of the magnetosphere are the area through which the solar wind enters and the area where its energy is transferred to the Earth's atmosphere in the form of aurora and similar phenomena.

This study employs an array of induction-coil magnetometers located at high geomagnetic latitudes in both north and south polar regions; in the Arctic at Sondre Stromfjord, Greenland, and Iqaluit, Northwest Territories, Canada, and in the Antarctic at Amundsen-Scott South Pole and McMurdo Stations. The data collected here is also being analyzed in the context of that from similar magnetometers in the U.S. and British automatic geophysical observatory (AGO) networks and the MACCS array in Canada. (The project is jointly supported by the U.S. Arctic and Antarctic Programs.) (AO-102-O)

Antarctic auroral imaging.
Stephen Mende, Lockheed Palo Alto Research Laboratory.

Scientists are only beginning to try to perform quantitative studies on the dynamic behavior of the magnetosphere. In the past, detail-oriented explorations by space satellites have enabled them to map the average distribution of magnetospheric energetic particle plasma content. But the dynamics of auroral phenomena – when particles from the magnetosphere precipitate into the atmosphere, producing fluorescence – have been hard to quantify through optical means. Amundsen-Scott South Pole Station is uniquely situated to observe aurora because the darkness of polar winter permits continuous optical monitoring; in most other sites, the sky becomes too bright near local mid-day.

The aurora can actually be regarded as a two-dimensional projection of the three-dimensional magnetosphere because particles tend to travel along the magnetic field line. By observing the dynamics and the morphology of the aurora, scientists get a reliable glimpse into the dynamics of the region of the three-dimensional magnetosphere associated directly with it. This method relies on knowledge relating the type of aurora to specific energies of precipitation and to specific regions of the magnetosphere.

In this study, an intensified optical, all-sky imager, operating in two parallel wavelength channels – 4,278 and 6,300 Ångstroms – will be used to record digital and video images of aurora. These wavelength bands allow us to discriminate between more- and less-energetic electron auroras and other precipitation. The South Pole Station observations of the polar cap and cleft regions entail measuring auroral-precipitation patterns and then interpreting the results in terms of the coordinated observations of (magnetic) radio-wave absorption images as well as (high-frequency) coherent-scatter radar measurements.

This work should provide insight into the sources and energization mechanisms of auroral particles in the magnetosphere, as well as other forms of energy inputs into the high-latitude atmosphere. (AO-104-O)

A study of very high latitude geomagnetic phenomena.
Vladimir Papitashvili, University of Michigan.

This project continues a joint U.S./Russian program to operate an Antarctica-based array of automated magnetometers. As the only land mass at very high latitudes, the antarctic continent is uniquely suited to these instruments, providing an excellent and stable location for magnetometric investigations of the polar cap current systems in the Earth's magnetosphere.

Such studies are particularly important to the understanding of how the energy and momentum from the solar wind becomes coupled to the magnetosphere, ionosphere, and upper atmosphere. They also provide an excellent point of reference for other satellite-based experiments (both currently in progress and planned for the near future).

The specific tasks to be undertaken include design improvements in the digital geomagnetic data-acquisition systems at Vostok and Mirnyy, as well as continued operation and maintenance of autonomous stations along the Russian traverse route to Vostok. One aspect of the study that should enhance our results is the new satellite data-transmission capability at Vostok. This will provide a near-real-time polar cap magnetic index for space, weather and research applications. (AO-105-O)

Global thunderstorm activity and its effects on the radiation belts and the lower ionosphere.
Umran Inan, Stanford University.

Tracking dynamic storms is a challenge, but lightning associated with thunderstorms can provide scientists an indirect way of monitoring global weather. This project employs very-low-frequency (VLF) radio receivers at Palmer Station, Antarctica, operated in collaboration with the British and Brazilian Antarctic Programs, both of which operate similar receivers. All are contributors to the Global Change Initiative.

The VLF receivers measure changes in the amplitude and phase of signals received from several distant VLF transmitters. These changes follow lightning strokes because radio (whistler) waves from the lightning can cause very energetic electrons from the Van Allen radiation belts to precipitate into the upper atmosphere. This particle precipitation then increases ionization in the ionosphere, through which the propagating VLF radio waves must travel. Because the orientations to the VLF transmitters are known, it is possible to triangulate the lightning sources that caused the changes, and thus to track remotely the path of the thunderstorms. (AO-106-O)

Study of polar stratospheric clouds by lidar.
Guido Di Donfrancesco, Instituto De Fisica Dell'Atmosfere, Rome, Italy.

The appearance each spring of the stratospheric ozone hole above Antarctica is driven by chlorine compounds interacting on the surfaces of polar stratospheric clouds (PSCs) that formed the previous polar winter. This is one explanation for why ozone depletion is much more severe in polar regions than elsewhere.

This project uses light detection and range finding (lidar) to study the polar stratospheric clouds (PSCs), stratospheric aerosol, and the thermal behavior and dynamics of the atmosphere above McMurdo Station. Continuous lidar observations provide insight on PSC formation, evolution, and other peculiar characteristics. These data will provide a complement to the information gained from balloon-borne instruments in project AO-131-O, and thus collaborative activities will be coordinated with the University of Wyoming. (AO-107-O)

Extremely-low-frequency/very-low-frequency (ELF/VLF) waves at the South Pole.
Umran S. Inan, Stanford University.

Atmospheric scientists orient their studies around different strata, or regions, and the boundaries and interactions between these regions are of particular interest. How are the upper atmospheric regions coupled electrodynamically? What can we learn by measuring the energy that is being transported between the magnetosphere and the ionosphere? These are but two of the questions the U.S. Antarctic Program's automatic geophysical observatory program is designed to explore.

Plasmas occur in the magnetosphere and the ionosphere, and can be transported and accelerated by a variety of different wave-particle interactions. One important dynamic in this system is particle precipitation that is driven by extra-low-frequency/very-low-frequency (ELF/VLF) waves. Thus, measuring ELF/VLF waves from multiple sites provides a powerful tool for remote observations of magnetosphere processes.

This project maintains a system at Amundsen-Scott South Pole Station to measure magnetospheric ELF/VLF phenomena, and to correlate the data with measurements made by the automatic geophysical observatory system. (AO-108-O)

High-latitude antarctic neutral mesospheric and thermospheric dynamics and thermodynamics.
Gonzalo Hernandez, University of Washington.

The antarctic region attracts atmospheric scientists for a number of reasons; a basic one is that measurements taken at the Earth's rotational axis are largely unaffected by planetary magnetic waves. This simplifies the study of the large-scale dynamics of the atmosphere.

For example, how do scientists measure the temperature and windspeed of the atmosphere? One primary method is by deduction, based on the emission spectra of certain trace gases as they are borne along in currents at predictable heights. Hydroxyl radicals (OH), for example, are confined to a fairly narrow band near 90 kilometers altitude.

This study uses a Fabry-Perot infrared interferometer (located at Amundsen-Scott South Pole Station, Antarctica) to make orthogonal observations of the band spectra of several trace species – most importantly the hydroxyl radical (OH). The doppler shift of the band lines provides an algorithm for researchers to measure the windspeed. The brightness and line ratios within the bands provide density and temperature information. (AO-110-O)

Riometry in Antarctica and conjugate regions.
Theodore J. Rosenberg and Allan T. Weatherwax, University of Maryland at College Park.

The University of Maryland continues to conduct research into upper atmospheric processes; using photometry to take auroral luminosity measurements and riometry to make high-frequency cosmic noise absorption measurements. A primary focus of our analysis activities over the next several years will include coordinated ground- and satellite-based studies and Sun-Earth comparisons.

The latest work also involves extensive collaboration with other investigators using complementary data sets. Continuation of science activities into the 1998-2001 time frame will enable us to participate in, and contribute to, several major science initiatives, including the GEM, CEDAR, ISTP/GGS, and National Space Weather programs as we enter the next solar maximum period.

Riometers measure the relative opacity of the ionosphere. This work employs a new imaging riometer system called IRIS (imaging riometer for ionospheric studies). The first two IRISs were installed at Amundsen-Scott South Pole Station and Sondre Stromfjord, Greenland.

A third IRIS has been installed at Iqiluit, Northwest Territories, Canada – the magnetic conjugate to South Pole. Broadbeam riometers also operate at several frequencies at South Pole, McMurdo, and Iqiluit; auroral photometers operate at South Pole and McMurdo. This array of instruments constitutes a unique network for the simultaneous study of auroral effects in both magnetic hemispheres.

The focus of all of this work is to enhance understanding of the relevant physical processes and forces that drive the observed phenomena; this includes both internal (such as magnetospheric/ionospheric instabilities) and external forces, such as solar wind/IMF variations. From such knowledge may emerge an enhanced capability to forecast; many atmospheric events can have negative technological or societal impact, and accurate forecasting could ameliorate these impacts. (AO-111-O)

Polar experiment network for geophysical upper-atmosphere investigations (PENGUIN).
Theodore Rosenberg, University of Maryland at College Park.

The data obtained from automatic geophysical observatories (AGOs) help researchers understand the Sun's influence on the structure and dynamics of the Earth's upper atmosphere. The ultimate objective of this research into how the solar wind couples with the Earth's magnetosphere, ionosphere, and thermosphere is to be able to predict solar-terrestrial interactions that can interfere with long-distance phone lines, power grids, and satellite communications.

A consortium of U.S. and Japanese scientists will use a network of six AGOs, established on the east antarctic polar plateau and equipped with suites of instruments to measure magnetic, auroral, and radiowave phenomena. The AGOs are totally autonomous, operate year round and require only annual austral summer service visits.

When combined with measurements made at select manned stations, these arrays facilitate studies on the energetics and dynamics of the high-latitude magnetosphere on both large and small scales. The research will be carried out along with in situ observations of the geospace environment by spacecraft, in close cooperation with other nations working in Antarctica and in cooperation with conjugate studies performed in the Northern Hemisphere. (AO-112-O)

All-sky-camera measurements of the aurora australis from Amundsen-Scott South Pole Station.
Masaki Ejiri, National Institute of Polar Research, Japan.

Amundsen-Scott South Pole Station, located at the south geographic pole, is a unique platform from which to undertake measurements of the polar ionosphere, situated in such a way that dayside auroras can be viewed for several hours each day. Research has shown these auroras come from the precipitation of low-energy particles entering the magnetosphere in the solar wind.

Since 1965, data have been acquired at the South Pole using a film-based, all-sky-camera system. Using advanced technology, we can now digitize photographic images and process large amounts of information automatically. As this project continues to acquire 35-millimeter photographic images, American and Japanese researchers will collaborate in deploying a new all-sky-camera processing system developed at Japan's National Institute of Polar Research. This system displays data in a geophysical coordinate framework, and analyzes series of images over short and long intervals thus enhancing observations over discrete, individual photographs.

These studies should provide further insight into the physics of the magnetosphere, the convection of plasma in the polar cap, and solar winds in the thermosphere; specifically dayside auroral structure, nightside substorm effects, and polar-cap arcs. (AO-117-O)

Solar and heliosphere studies with antarctic cosmic-ray observations.
John Bieber, University of Delaware.

Cosmic rays – penetrating atomic nuclei from outer space that move at nearly the speed of light – continuously bombard the Earth. Neutron monitors deployed in Antarctica provide a vital three-dimensional perspective on this shower and how it varies along all three axes. Accumulated neutron-monitor records (begun in 1960 at McMurdo Station and in 1964 at South Pole Station) provide a long-term historical record that supports efforts to understand the nature and causes of cosmic-ray and solar-terrestrial variations occurring over the 11-year sunspot cycle, the 22-year Hale cycle, and even longer timescales.

This project continues a series of year-round observations at McMurdo and Amundsen-Scott South Pole Stations, recording cosmic rays with energies in excess of 1 billion electronvolts. These data will advance our understanding of a number of fundamental plasma processes occurring on the Sun and in interplanetary space. At the other extreme, we will study high time-resolution (10-second) cosmic-ray data to determine the three-dimensional structure of turbulence in space, and to elucidate the mechanism by which energetic charged particles scatter in this turbulence. (AO-120-O)

Rayleigh and sodium lidar studies of the troposphere, stratosphere, and mesosphere at McMurdo and Amundsen-Scott South Pole Stations.
Jim Abshire, National Aeronautics and Space Administration, Goddard Space Flight Center.

Each austral winter, polar stratospheric clouds (PSCs) form in the extremely cold polar stratosphere. Each spring, as the stratospheric ozone begins to degrade, one particular form of these PSCs, the Type 1, appear to have a particular role. This project's primary science mission is to detect, monitor and profile these Type 1 PSCs with the automated geophysical observatory (AGO) lidar. This is an ongoing, National Aeronautics and Space Administration (NASA)-funded project to develop and demonstrate a compact, low-power, and autonomous atmospheric lidar system for operation throughout the AGOs that have been established in Antarctica by the U.S. Antarctic Program.

Type 1 PSCs depolarize incident radiation. Because the laser transmitters in AGO lidar produce light that is highly linearly polarized, they can generate a depolarization signal of up to several percent. These data are stored in the lidar instruments and, at least once a day, AGO lidar transmits an atmospheric profile back to NASA's Goddard Space Flight Center in Greenbelt, Maryland.

This project also conducts continuous, long-term monitoring of atmospheric transmission and backscatter from the surface. These data are being compiled for use by the Geoscience Laser Altimeter System (GLAS), which produces specialized information on atmospheric conditions. (AO-126-O)

Rayleigh and sodium lidar studies of the troposphere, stratosphere, and mesosphere at the Amundsen-Scott South Pole Station.
George Papen, University of Illinois.

The Earth's atmosphere is described by several stratified layers, each with distinctive structure, dynamics and characteristics. The stratosphere begins about 11 kilometers (km) above the surface; the mesosphere runs from about 50 km to its upper boundary, the menopause, where atmospheric temperature reaches its lowest point (about –80°C), before beginning to rise with increasing altitude through the outer layer, the thermosphere, which runs from 80 km to outer space.

This research deploys a sodium-resonance lidar at the South Pole to study the atmosphere's vertical structure and dynamics, from the lower stratosphere up to the menopause. As the project enters its third year, scientists will add an iron-resonance lidar, extending their ability to measure the air dynamics and temperature structure even higher, to about 100 kilometers. Another addition, an airglow imaging camera, will be used to study horizontal structure.

This final complement of instrumentation, used in conjunction with the normal balloon-borne radiosondes flown regularly from South Pole, will provide extensive data on:

• the temperature structure from the surface to 100 kilometers altitude;

• the nature of the polar stratospheric clouds (PSCs), which are important to ozone chemistry;

• the variability and frequency of occurrence of metallic layers in the mesosphere, which play roles in communications as well as atmospheric chemistry;

• atmospheric gravity waves; and

• many other phenomena, some of which are unique to the South Pole.


High-latitude electromagnetic wave studies using antarctic automatic geophysical observatories.
James LaBelle, Dartmouth College.

Aurora are light shows (streamers and arches of light) created when electrons accelerated along Earth's magnetic field lines excite atoms in the atmosphere; they occur at the poles because of the peculiar magnetic flux generated there. The energy associated with this phenomenon is significant and complex; one small but distinctive aspect of that energy are radio emissions detectable at frequencies between 0.05 and 5.0 megahertz (MHz).

Scientists understand the phenomenon of auroral hiss that causes broadband noise at frequencies below 1 MHz. But two other radio phenomena attributable to auroras remain unexplained: Narrowband emissions near 2.8 and 4.2 MHz, and broadband noise bursts in the frequency range of 1.4 to 4.0 MHz.

Although these radio emissions constitute a small fraction of the total energy of the aurora, they may provide important clues to the more energetic processes; this possibility would mirror the use of radio emissions from the Sun to infer processes taking place in the solar corona.

Taking advantage of radio-quiet antarctic conditions, this project uses low-frequency/middle-frequency/high-frequency receivers in hopes of developing insights about these emissions from antarctic auroral zone and polar cap sites. The receivers will be installed at Amundsen-Scott South Pole Station, in three U.S. automatic geophysical observatories and in two British automatic geophysical observatories. (AO-128-O)

In situ measurements of polar stratospheric clouds spanning the austral winter and of ozone from late winter to early spring.
Terry Deshler, University of Wyoming.

The appearance each spring of the stratospheric ozone hole above Antarctica is driven by chlorine compounds interacting on the surfaces of polar stratospheric clouds (PSCs) that formed the previous polar winter. This is one explanation for why ozone depletion is much more severe in polar regions than elsewhere.

This project uses balloon-borne instruments to provide detailed information on the clouds' particles, their distribution, and on ozone changes. Our measurements will provide vertical profiles of both the PSCs and ozone, size distributions of the PSC particles, and some information on their composition and physical state (liquid or solid). Our project is enhanced by a lidar system at McMurdo Station operated by the Instituto De Fisica Dell'Atmosfere [(Rome), see project AO-107-O]. The results contribute to the World Meteorological Organization/UNEP Network for the Detection of Stratospheric Change as well as to the Global Change Initiative. (AO-131-O)

Trace gas measurements over the South Pole using millimeter-wave spectroscopy.
Robert L. de Zafra, State University of New York at Stony Brook.

Many atmospheric gases radiate millimeter-length radio waves, but each species has its own unique spectrum. These fingerprints not only identify the gas, but also provide information on its temperature and pressure. These properties enable scientists to use the millimeter-wave spectrum of the atmosphere to determine how abundantly and at what altitudes a number of trace species can be found.

This research uses a millimeter spectroscope to monitor the atmosphere above South Pole, Antarctica, for ozone, carbon monoxide, nitrous oxide, nitric acid, water vapor, and nitrogen dioxide, over the course of a year. Several of these gases have important roles in the formation of the annual antarctic ozone hole. Others – particularly water vapor and carbon monoxide – can provide information about the vertical transport and other dynamics of the upper stratosphere and the mesosphere. (AO-138-O)

Cosmology from Dome-C in Antarctica.
Lucio Piccirillo, Bartol Research Institute, University of Delaware.

When the universe was created some 15 billion years ago in the Big Bang, matter began coursing outward. The general flux of that movement was discovered in 1965, and is known as thermal cosmic microwave background radiation (CMBR). Measurements of the CMBR provide the only direct evidence on the distribution of matter in the very early Universe.

Concordia is one of the highest and coldest sites presently occupied in Antarctica. These conditions minimize water vapor in the atmosphere, which can hinder accurate measurements of the CMBR, which is anisotropic; that is, its readings vary along the different axes. Thus the new French/Italian station on Dome C in Antarctica (Concordia Station) is a potentially superb place from which to make anisotropic CMBR measurements. This project involves an international collaboration between the United States, Italy, and France. We will also evaluate the site for other future uses. (AO-140-O)

An optical investigation of the genesis of solar activity.
David M. Rust, Johns Hopkins University.

Energy stored in the Sun's magnetic fields is released in a number of dynamic phenomena, such as flares and coronal mass ejections. Scientists trying to model and understand these events face several hurdles: The Sun must be observed for long, continual periods, but the Earth's rotation limits unbroken observation from any fixed telescope to the length of a day; further, the required resolution can be achieved only by a telescope situated above most of the atmosphere. Thus far, only two solutions have been found. You can build a large, special purpose spacecraft for hundreds of millions of dollars, or launch a long distance balloon (LDB) from a polar site.

This study, The Flare Genesis Experiment, uses a high-altitude, long-duration balloon flying around the antarctic continent to deploy an 80-centimeter telescope that captures images and magnetograms of the solar photosphere and chromosphere; this instrument produces an unprecedented resolution of 0.2 arc-sec. The project is jointly sponsored by the National Science Foundation, the National Aeronautics and Space Administration, and the Air Force. (AB-146-O)

Center for Astrophysical Research in Antarctica (CARA).
Stephan Meyer, University of Chicago.

Astronomers probe the infrared (IR) spectrum at submillimeter scales in search of data that could suggest answers to some of the seminal questions about the formation of the Universe; such as:

• How do stars form from interstellar gas?

• How did the planets form?

• What was the nature of primeval galaxies?

• How were matter and energy distributed in the early Universe?

Antarctica is an ideal spot for such research: The cold temperatures and lack of water vapor in the atmosphere above the polar plateau makes the infrared spectrum of sky in that region consistently clearer and darker than anywhere else on Earth. These conditions enable scientists to collect measurements that would be extremely difficult or impossible from other sites.

To capitalize on these advantages, the University of Chicago and several collaborating institutions in 1991 established the Center for Astrophysical Research in Antarctica (CARA), one of 23 Science and Technology Centers funded by the National Science Foundation. CARA's scientific mission is to investigate the conditions for astronomy at the South Pole and other sites on the polar plateau, and to establish an observatory at the South Pole. Currently, CARA supports research using three major telescope facilities:

• The Astronomical Submillimeter Telescope/Remote Observatory (AST/RO) project uses a 1.7-meter (m) diameter telescope to survey interstellar gas in the galactic plane, the galactic center, and the Magellanic Clouds.

• The South Pole Infrared Explorer (SPIREX) project uses a 0.6-m diameter telescope to observe distant galaxies, cool stars, and heavily obscured star-forming regions.

• The Cosmic Background Radiation Anisotropy (COBRA) project helps researchers test current theories of the origin of the Universe.

In addition to projects using these three telescopes, CARA's Advanced Telescopes Project collects data on the quality of polar plateau sites for astronomical observations, and configures plans for future telescopes and facilities. The following projects and principal investigators are currently part of CARA:

CARA-wide operations and activities.
Stephan Meyer, University of Chicago. (AC-370-O)

The Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) project develops studies on atomic and molecular gas in the Milky Way and nearby galaxies. Proposals to use their 1.7-m diameter telescope are invited from the astronomical community. Antony Stark, Smithsonian Institution. (AC-371-O)

The Advanced Telescopes Project (in addition to gathering measurements of "seeing" quality using the SPIREX telescope) also supports a number of other efforts including wide-field cameras, a near-IR sky brightness monitor (in collaboration with the University of New South Wales), and an instrument for monitoring mid-IR sky brightness and transmission (in collaboration with the National Aeronautics and Space Administration's Goddard Space Flight Center). Bob Lowenstein, University of Chicago. (AC-372-O)

The Degree Angular Scale Interferometer (DASI) is a 13-element interferometer designed to measure anisotropies in the Cosmic Microwave Background (CMB). Now in its final phase of construction, DASI will capture radiation readings over a large range of scales with very high sensitivity, and should be collecting data by Feb 2000. The instrument uses cooled HEMT amplifiers running between 26 and 36GHz, in five 2-GHz channels and will operate from the South Pole. John Carlstrom, University of Chicago. (AC-373-O)

The South Pole Infrared Explorer (SPIREX) project is ideal for extensive large-scale infrared and submillimeter surveys of star-forming regions in the Milky Way and Magellanic Clouds. The SPIREX telescope (60 centimeters in diameter) was built to exploit the unique observing conditions at the South Pole and to develop and demonstrate the technology needed to operate IR telescopes during the antarctic winter.

The telescope has been enhanced to lower total telescope emissivity to just 5 percent. The Abu camera is based on an Aladdin 1024x1024 pixel indium antimonide focal plane array and a set of broad- and narrow-band filters spanning the range between 2.4 and 5 millimeter (mm). It was developed at NOAO to test advanced focal-plane arrays. Combining this camera with the telescope permits wide-field (10.2 arc-minutes) astronomical imaging at wavelengths of 3-5 microns (m); this region of the spectrum is where the advantages of the South Pole over temperate sites are greatest.

The Abu/SPIREX project is the result of unique collaboration: The National Optical Astronomy Observatories (NOAO) contributes the Abu, the best existing 3-5 micron camera; the United States Naval Observatory (USNO) and CARA commit to operating the SPIREX and conducting the science at the world's darkest 3-5 micron site, the South Pole. In addition to researchers at NOAO and USNO, the effort includes collaborators from Boston University (BU), Goddard Space Flight Center (GSFC), Ohio State University (OSU), Rochester Institute of Technology (RIT), the University of Chicago (UC), the University of New South Wales (UNSW), and the Universities Space Research Association (USRA). Bob Lowenstein, University of Chicago. (AC-374-O)

The Viper telescope is a 2-meter class telescope that will extend the observations (now being made with the 0.75-meter Python telescope) to structures in the cosmic microwave background having smaller angular scales.

The primary goal of the Viper project is to determine the power spectrum of the CMBR anisotropy over the range of angular scales where cosmological models most differ in their predictions. Viper data should permit scientists to better discriminate among these models. Viper images will also be used to search for cosmological defect-imprints on the CMBR. Jeffrey Peterson, Carnegie-Mellon University. (AC-375-O)

The Submillimeter Polarimeter for Antarctic Remote Observing (SPARO), operating on the Viper 2-meter telescope is newly deployed to the Pole in 1999. SPARO is a 9-pixel, 450-micron polarimetric imager, which requires only infrequent cryogen refills, making maintenance easier during the winterover.

The South Pole offers superb conditions for SPARO observations, extending submillimeter polarimetry (measurement of the polarization of thermal emission from magnetically aligned dust grains) to regions of low-column density that cannot be studied from other sites. SPARO is similar to polarimeters in the University of Chicago array designed for other telescopes; but those instruments (for example, at the Caltech Submillimeter Observatory and the Owens Valley Radio Observatory) provide much better angular resolution. SPARO's geographic advantage, however, results in a much enhanced submillimeter sensitivity to extended emission.

The primary goal for the 1999-2000 phase of the project is to reveal the large-scale magnetic field in the nucleus of our Galaxy. Giles Novak, Northwestern University. (AC-376-O)

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