The South Pole Site
Since 1991 the Center for Astrophysical Research in Antarctica (CARA),
a NSF Science and Technology Center, has supported South Pole research
in infrared, submillimeter, and millimeter astronomy. Infrastructure
developed through 1998 includes a 60-cm infrared telescope, a 1.7-m
submillimeter telescope, a 2-m millimeter wave cosmic background
telescope, and two laboratory buildings. These facilities operate
continuously all year round.
CARA's mission is to exploit the unique conditions at the geographic
South Pole and ultimately to establish a permanent national
observatory. The prototype user-facility instrument Abu/SPIREX
has now demonstrated that very sensitive imaging in
the thermal infrared can be routinely performed at the South Pole.
Our experience with Abu/SPIREX tells us that the South Pole site
should be further developed. We therefore plan to establish
AIRO and construct a larger, more sensitive, automated 2.3 - 5.6 micron
thermal infrared telescope as its first instrument. AIRO will be
a true national observatory at the South Pole. It will be
the culmination of the NSF Office of Polar Programs' scientific
investment and of CARA's efforts.
One of CARA's goals was to characterize the properties of the South
Pole as an infrared wavelength observing site. Briefly, compared with
other ground-based infrared sites, the South Pole is much colder and
much darker, but has only modest seeing at visible wavelengths (1".7
at V). This will not, however, compromise the diffraction limited
infrared performance of AIRO: specifically, the observed atmospheric
structure at the South Pole is such that tip-tilt correction at the
secondary mirror will likely deliver ideal performance across AIRO's
entire wide field at infrared wavelengths (see below).
Sky emission measured across the H, K, and L-band at Siding Spring
Observatory in Australia and at the South Pole. The conditions
at Siding Spring are similar to those at Kitt Peak; Mauna Kea
is only slightly better (see Table 2). Note the substantial
advantage of the South Pole site. From Phillips
et al (1999).
Comparison of sky emission spectra taken in clear conditions from
Canberra and Mauna Kea (Smith & Harper 1998) with the South
Pole. From Chamberlain et al (1999).
MODTRAN atmospheric model for South Pole sky
brightness (Jy arcsec^-2) between 2
and 10 micron. The model assumes an Antarctic temperature and pressure
atmosphere profile, 200 micron of precipitable water vapor (PWV), and
100 km visibility in the `aerosol' layer. These conditions match
the best 10% of our mid-IR measurements. From the JACARA web page:
http://newt.phys.unsw.edu.au/~mgb/jacara.html
Seeing as a function of height of the telescope above the surface.
The solid line represents average results from balloon launches
at the South Pole, while the dashed line is a summary of a similar
experiment performed at the ESO-VLT site at Cerro Paranal in Chile.
From Marks et al (1999).
jackson@bu.edu