{'fraction_non_alphanumeric': 0.018409425625920472, 'fraction_numerical': 0.005891016200294551, 'mean_word_length': 5.205479452054795, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Improvement of the 1.57-micron laser absorption sensor with chirp modulation to evaluate spatial averaging carbon dioxide density

A 1.57-μm laser remote sensor using differential absorption spectrometory is being developed as a candidate for the next space-based mission to observe atmospheric CO2 and/or other trace gases. In a previous study, the performance of a proto-type system with sinusoidal modulation was evaluated based on ground and airborne measurements. The airborne measurements showed that the LAS with sinusoidal modulation could detect strong CO2 plume, and suppress the impact of an aerosol layer over high surface reflectivity. Based on those results, an outline of LAS system on the space platform such as the International Space Station Japan Experimental Module (ISS-JEM) was desined. However, an elevated layer in the observation path is still remain, which leads to reduce effective observed data as long as current sinusoidal modulation is employed. In order to prevent the impact of elevated layer, different modulation schemes such as random or frequency modulation are capable. We are currently improving the LAS system with a chirp modulation scheme for the purpose. Some of recent airborne measurements using sinusoidal modulation and ground-based measurements using chirp modulation in progress will be shown in this meeting.