The Japanese IR sky survey mission IRTS (Infrared Telescope in Space) was
performed successfully in 1995. The IRTS data are now beeing analized.
To date, we have obtained the intensity maps of the so-called UIR emission
bands at 3.3, 6.2, 7.7, 8.6 and 11.3 micron in the galactic plane at around
l=50 deg. The diffuse component emissted from the general interstellar
space without any strong UV sources has been clearly detected in those maps.
The spectral resolution of the IRTS, however, was 20-30, a little bit too
low for an accurate estimation of each UIR band. Therefore, follow-on
observations of the part of the sky area surveyed by the IRTS with a higer
spectral resolution are very valuable. And to check for the consistensy
between the IRTS and the ISO is also important for both missions. We propose
here the spectrophotometric observations of the diffuse UIR band in the
galactic plane region near l=50 deg with the PHT-S.