Abstract
Context
. Near-infrared (NIR) sky brightness is a fundamental parameter for evaluating the performance of ground-based infrared observatories.
Aims
. Dome A on the Antarctic plateau offers exceptional atmospheric conditions, yet its NIR sky background has not been continuously monitored. We present the first continuous
J
- and
H
-band measurements of the sky background at Dome A from polar day to polar night and characterize their median levels and temporal variability.
Methods
. The Antarctic Infrared Binocular Telescope (AIRBT), operating in the
J
and
H
bands, obtained continuous fixed-pointing observations from February to May 2024, which were used to measure the NIR sky background.
Results
. The median sky brightness is 5.2/2.9 and 15.3/13.4 mag arcsec
−2
in the
J
and
H
bands during daytime and nighttime, respectively. The twilight-nighttime boundaries occur at solar elevations of −9.3° in
J
and −7.4° in
H
. At the same solar elevation, the NIR sky background during the polar night is darker by about 0.1 and 0.4 mag arcsec
−2
in the
J
and
H
bands compared to the regular day–night alternation period. During the polar-night period, the nighttime sky brightness in the
H
band shows a more evident association with the sunspot number, while the corresponding trend in the
J
band is weaker.
Conclusions
. These results reveal systematic differences in the sky background between the polar and nonpolar environments and between polar night and regular day–night cycles. The measured sky brightness may be elevated, as the observations were conducted near solar maximum, highlighting the importance of long-term monitoring across the solar cycle.