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  • (near-)real-time orbit determination for gnss radio occultation processing

    جزئیات بیشتر مقاله
    • تاریخ ارائه: 1392/07/24
    • تاریخ انتشار در تی پی بین: 1392/07/24
    • تعداد بازدید: 1427
    • تعداد پرسش و پاسخ ها: 0
    • شماره تماس دبیرخانه رویداد: -
     the processing of gps radio occultation measurements for use in numerical weather predictions requires a precise orbit determination (pod) of the host satellite in near-real-time. making use of data from the gras instrument on metop-a, the performance of different gps ephemeris products and processing concepts for near-real-time and real-time pod is compared. while previous analyses have focused on the achievable along-track velocity accuracy, this study contributes a systematic comparison of the resulting estimated bending angles. this enables a more rigorous trade-off of different orbit determination methodologies in relation to the end-user needs for atmospheric science products. it is demonstrated that near-real-time gps orbit and clock products have reached a sufficient quality to determine the metop-a along-track velocity with an accuracy of better than 0.05 mm/s that was formerly only accessible in post-processing. the resulting bending angles are shown to exhibit standard deviation and bias differences of less than 0.3 % compared with post-processed products up to altitudes of at least 40 km, which is notably better than 1 % accuracy typically assumed for numerical weather predictions in this height regime. complementary to the analysis of ground-based processing schemes, the potential of autonomous on-board orbit determination is investigated for the first time. using actual gras flight data, it is shown that a 0.5 m 3d rms position accuracy and a 0.2 mm/s along-track velocity accuracy can in fact be obtained in real-time with the currently available gps broadcast ephemeris quality. bending angles derived from the simulated real-time processing exhibit a minor performance degradation above tangent point heights of 40 km but negligible differences with respect to ground-based products below this altitude. onboard orbit determination and, if desired, bending angle computation, can thus enable a further simplification of the ground segment in future radio occultation missions and contribute to reduced product latencies for radio occultation data assimilation in numerical weather predictions.

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