  We are developing an ultra-wideband spectroscopic instrument, DESHIMA (DEep
Spectroscopic HIgh-redshift MApper), based on the technologies of an on-chip
filter-bank and Microwave Kinetic Inductance Detector (MKID) to investigate
dusty star-burst galaxies in the distant universe at millimeter and
submillimeter wavelength. An on-site experiment of DESHIMA was performed using
the ASTE 10-m telescope. We established a responsivity model that converts
frequency responses of the MKIDs to line-of-sight brightness temperature. We
estimated two parameters of the responsivity model using a set of skydip data
taken under various precipitable water vapor (PWV, 0.4-3.0 mm) conditions for
each MKID. The line-of-sight brightness temperature of sky is estimated using
an atmospheric transmission model and the PWVs. As a result, we obtain an
average temperature calibration uncertainty of $1\sigma=4$%, which is smaller
than other photometric biases. In addition, the average forward efficiency of
0.88 in our responsivity model is consistent with the value expected from the
geometrical support structure of the telescope. We also estimate line-of-sight
PWVs of each skydip observation using the frequency response of MKIDs, and
confirm the consistency with PWVs reported by the Atacama Large
Millimeter/submillimeter Array.
