Rising and setting GPS occultations by use of open-loop tracking
Rising and setting GPS occultations by use of open-loop tracking
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DOI：
10.1029/2008jd010483
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发表时间：
2009-02-18
影响因子：
4.4
通讯作者：
Kursinski, E. R.
中科院分区：
文献类型：
--
作者：
Ao, C. O.;Hajj, G. A.;Kursinski, E. R.
GPS掩星的成功已经在包括GPS/MET、CHAMP、SAC-C、GRACE和COSMIC在内的几个任务中得到了证明。然而，在低对流层跟踪GPS信号或获得准确的卫星活动已被证明特别具有挑战性。第一个具有开环（OL）跟踪能力的接收机软件最近在SAC-C上进行了测试并成功实施。除了提高更深入探测对流层低层和行星边界层的能力外，光学跟踪还首次能够获取上升的全球定位系统信号，从而使同一仪器的掩星次数增加一倍。本文介绍了SAC-C和COSMICOL跟踪软件中使用的大气多普勒和延迟模型。我们讨论了SAC-C上进行的测试，并提出了一些OL处理的例子。我们表明，OL数据提供了巨大的改善采样的最低部分的大气。SAC-C OL剖面中80%以上的剖面现在在热带达到2公里以下的高度，而在闭环跟踪下只有50%。
The success of GPS occultations has been demonstrated by several missions including GPS/MET, CHAMP, SAC-C, GRACE, and COSMIC. However, tracking the GPS signal in the lower troposphere or obtaining accurate refractivity there has proven particularly challenging. The first receiver software with open-loop (OL) tracking capability was recently tested and successfully implemented on SAC-C. Besides improving the ability to probe deeper into the lower troposphere and planetary boundary layer, OL tracking also enables the acquisition of rising GPS signals for the first time, thereby doubling the number of occultations from the same instrument. In this paper, we describe the atmospheric Doppler and delay models used in the SAC-C and COSMIC OL tracking software. We discuss the testing carried out on SAC-C and present some examples of OL processing. We show that OL data give vast improvements in sampling the lowest part of the atmosphere. Over 80% of the SAC-C OL profiles now reach below 2 km altitude in the tropics, compared to only 50% achieved under closed-loop tracking.