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JAXA宇宙科学研究本部では、将来の月惑星着陸ミッションに欠かせないセンサとして、距離測定と速度測定を行うパルス方式の電波高度速度計(着陸レーダ)の開発を行っている。月や惑星に着陸して本格的な科学観測をするためには、分散誤差100m程度で複雑な地形の中にピンポイントで着陸する技術が要求されている。本研究の着陸レーダは周波数4.3GHzのパルスレーダで、高度と速度を同時に測定する。BBM(Bread Board Model)を試作し、実験用航空機に搭載してフィールド試験を行った。その結果要求精度の5％を達成することができ、また、姿勢が変化した場合や複雑な地形に対しても測定可能であることが確認された。本論文ではBBMと高度測定原理、およびフィールド試験の結果より高度測定精度について報告する。, Institute of Space and Astronautical Science JAXA develops the radio altimeter and velocity meter (landing radar) that is one of mandatory navigation sensor for a planetary lander. The landing radar can measure its relative altitude and speed from planetary surface by C band (4.3 [GHz]) pulse. The BBM (Bread Board Model) with the function which can measure speed and altitude simultaneously was manufactured and the field experiment has been done by using helicopter that carried the BBM radar. From the result of the field experiment, the BBM radar realized the design performance and attained 5 [percent] of the required accuracy from the lander system. It was also able to evaluate the geographical feature dependability of measurement accuracy by comparing a natural surface with an ideal surface at the Airport. This paper introduces the BBM and the algorism of altimeter and describes the result of field experiment., 資料番号: AA0063481017

The nadir ionospheric TEC is retrieved from TOPEX/POSEIDON (T/P) and JASON-1 along track altimetry database. After careful comparison, it is found that the nadir TEC and the zenith TEC from GIM, IRI is identical with each other in large scale, long term variation. Seasonal and 11 year periodical variations of the TEC difference between GIM and T/P can be identified. A difference about 1 to 2 TECU between T/P and Jason-1 TEC is noticed. Where, the IRI is not precise enough to calibrate the satellite altimetry data due to the poor spatial and time resolution. Around Japan Islands, the difference between GEONET TEC and Jason-1 shows both of the biases of Jason-1 and of the failed calibration if GEONET duel frequency GPS observables., 資料番号: AA0047899164