Observation apparatus and atmospheric state determination method

An atmospheric state determination method executed by an observation apparatus including a deep ultraviolet light source configured to transmit pulse light having a wavelength belonging to an ultraviolet region of a solar blind band and a photodetector configured to output a pulse of which a wave height changes according to the number of photons of reflected light of the pulse light received within a response period, the method comprising:

• a wave height determination step of determining and outputting a pulse having a wave height equal to or more than a noise determination threshold among pulses output from the photodetector;
• a wave height detection step of detecting the wave height of the pulse output from the photodetector every time the photodetector outputs the pulse;
• a time of flight measurement step of measuring a time of flight every time a wave height determinator outputs the pulse;
• a data recording step of recording the wave height and the time of flight in association with each other for each pulse output from the wave height determinator;
• a LiDAR data generation step of generating LiDAR data in which the number of pulses having a wave height equal to or more than the pulse determination threshold is aggregated for each distance for each of different pulse determination thresholds after end of the measurement period on the basis of the wave height and the time of flight recorded for each pulse output from the wave height determinator;
• a pulse number integration step of integrating a total number of pulses within a predetermined distance range in the LiDAR data for each piece of the LiDAR data;
• a threshold distribution generation step of generating a threshold distribution obtained by aggregating, for each threshold, the total number of pulses integrated for each piece of the LiDAR data;
• and
• an atmospheric state determination step of determining an atmospheric state by comparing the threshold distribution with a reference threshold distribution.

An observation apparatus comprising:

• a deep ultraviolet light source configured to transmit pulse light having a wavelength belonging to an ultraviolet region of a solar blind band;
• a photodetector configured to output a pulse of which a wave height changes according to the number of photons of reflected light of the pulse light received within a response period;
• and
• a LiDAR data generation unit, a pulse number integration unit, a threshold distribution generation unit, and an atmospheric state determination unit, wherein
• the LiDAR data generation unit generates LiDAR data in which the number of pulses having a wave height equal to or more than each pulse determination threshold is aggregated for each distance for each of a plurality of different pulse determination thresholds,
• the pulse number integration unit integrates a total number of pulses within a predetermined distance range in the LiDAR data for each piece of LiDAR data,
• the threshold distribution generation unit generates a threshold distribution obtained by aggregating, for each threshold, the total number of pulses integrated for each piece of the LiDAR data, and
• the atmospheric state determination unit determines an atmospheric state by comparing the threshold distribution with a reference threshold distribution.