The Longwave Infrared Camera (LIR), which mounts an uncooled
micro-bolometer array (UMBA), is under development for the Japanese
Venus orbiter mission, PLANET-C.
LIR detects thermal emission from the top of the sulfur
dioxide cloud in a wavelength region 8--12 μm to map the
cloud-top temperature which is typically as low as 230 K.
The requirement for the noise equivalent temperature difference (NETD)
is 0.3 K.
Images of blackbody targets in room temperature (~300 K) and low
temperature (~230 K) have been acquired in a vacuum environment
using a prototype model of LIR, showing that the NETD of 0.2 K and 0.8
K are achieved in ~300 K and ~230 K, respectively.
We expect that the requirement of NETD<0.3 K for ~230 K
targets will be achieved by averaging several tens of images which are
acquired within a few minutes.
The vibration test for the UMBA was also carried out and the result
showed the UMBA survived without any pixel defects or malfunctions.
The tolerance to high-energy protons was tested and verified using a
commercial camera in which a same type of UMBA is mounted.
Based on these results, a flight model is now being manufactured with minor
modifications from the prototype.
Using the third version of tunable diode laser heterodyne spectrometers developed by the Tohoku University optical group, infrared absorption spectra of atmospheric O3, N2O, CH4, and HNO3 were observed at Syowa station from August 1994 to January 1995. This portable spectrometer has an ultra high spectral resolution of 0.0013 cm-1 and a signal-to-noise ratio of 500 for 10-min scan time. From ozone absorption spectra obtained in early spring, the height profiles of ozone concentration up to 30 km were retrieved at intervals of ten minutes. These profiles showed extremely low ozone concentration in the altitude range of 15-20 km, which is a typical feature of the antarctic ozone hole. Furthermore, these profiles demonstrated the existence of rapid variations of ozone concentration in the altitude range of 20-30 km. From the potential vorticity analysis using the objective analysis data provided by the Japanese meteorological agency, it was concluded that these variations wee caused by a passage of westward traveling waves produced at the polar vortex boundary.
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