CASPER (Concordia Atmospheric SPectroscopy of Emitted Radiation)
is a spectrometer proposed for installation at Dome C, devoted to
measurements of atmospheric emission in the spectral region
between 180 μm and 3 mm (3–55 cm-1). This
instrument will be able to perform continuous spectral sampling at
different altitudes at angular scales of ~1°. From the
recorded data it is possible to extract atmospheric transmittance
within 1% in the whole wide operating band, together with water
vapour content and O2 and O3 concentrations. CASPER will
allow us to characterize the site for future FIR/mm telescopes.
Atmospheric data recorded by CASPER will allow for correction of
astrophysical and cosmological observations without the need for
telescope-specific procedures and further loss of observation time
with more precision in the observations themselves. Calibration of
ground-based telescopes on known sky sources is strongly affected
by atmospheric absorption. CASPER has this as its primary goal.
The spectrometer is based on a Martin-Puplett interferometer. Two
data sampling solutions will be performed: phase modulation &
fast scan strategy. Sky radiation is collected towards the
interferometer by an optical setup that allows the field of view,
to explore the full 0° ÷ 90° range of elevation angles. With
a low spurious polarization instrument, monitoring of polarized
atmospheric contribution will be possible.