Continued Operation of COSMIC GPS Radio Occultation Constellation in Support of Research Applications in Atmospheric Sciences

2006年发射的气象学、电离层和气候星座观测系统(COSMIC)是由六颗在低地球轨道上运行的极轨卫星组成的星座。每颗卫星的主要有效载荷是全球定位系统(GPS)接收器(由NASA喷气推进实验室开发)，当GPS发射器卫星相对于宇宙卫星上升和下降时，该接收器接收来自GPS发射器卫星的定位信号。GPS信号在从发射机传输到接收机时被大气折射，在一定程度上取决于低层大气的温度和水蒸气含量以及电离层中的电荷密度。折射导致传输信号的相位延迟，可以通过反转来恢复电子密度(在电离层中)、干燥大气温度和水蒸气(尽管水蒸气需要额外信息)的轮廓。由于这些剖面是从GPS发射机的上升和设置或掩星中提取的，这项技术被称为GPS无线电掩星(GPSRO)，或者更一般地被称为GNSSRO，其中GNSS是全球导航卫星系统。GNSSRO已被证明是一种高效的观测方法，因为测量可以在任何天气条件下进行，不受云层和气溶胶的影响，并且通过支持GPS发射器的时钟系统进行绝对校准(SI可追踪)。该奖项下的基金支持四类与宇宙有关的工作：1)处理、服务和存档供研究界使用的宇宙数据；2)开展研究以改进GNSSRO反演科学和技术；3)开展研究以支持GNSSRO数据的科学应用；以及4)促进使用GNSSRO数据及其在大气研究中的应用的教育和推广活动。项目1是该奖项及其前身的基本活动，这里还为改进轮廓的质量和生成更多的数据产品提供了支助，例如低层和高层大气变量的月平均气候。除宇宙卫星外，GNSSRO的少量“机遇任务”也得到支持。这些是研究卫星，其中添加了全球导航卫星系统接收器作为二次有效载荷(例如GRACE-B)。项目2下的活动继续发挥私营部门在开发新的全球导航卫星系统处理技术方面的领导作用，例如，制定纠正电离层零星E层绕射造成的误差的方法。项目3下的研究开发了新的同化技术，例如使用二维射线追踪法来计算水平折射率梯度。另一项任务是开发长期气候质量数据集，在该数据集中，对不同卫星的轮廓进行最佳组合，以考虑到它们误差特征的差异。由于GNSSRO数据具有SI可追溯性，因此非常适合于生成长期多任务数据集。项目4下的工作解决了全球资源监测和报告组织数据的可获得性与研究界采用数据之间的差距。活动包括接待学术访问者，举办会议和研讨会，举办夏季座谈会和教程。由于宇宙观测对天气、气候和电离层研究具有巨大价值，这项工作具有学术价值。这项工作通过私人投资机构的教育和外联工作产生了更广泛的科学影响，以促进来自几个研究界的科学家采用和使用这些数据。此外，PIS还向世界各地的业务天气预报中心提供宇宙数据，这些数据已被证明对提高天气预报技能非常有用。这一奖项取代了美国国家科学基金会向COSMIC提供资金的先前合作协议AGS-1033112。虽然NSF不再通过早期的CA提供资金，但该奖项仍将有效，因为它包含来自其他机构的资金，以支持后续COSMIC-2任务的发展。该奖项不为COSMIC-2提供资金。

Launched in 2006, the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) is a constellation of six polar-orbiting satellites in Low Earth Orbit. The primary payload of each satellite is a Global Positioning System (GPS) receiver (developed at the NASA Jet Propulsion Laboratory) which receives positioning signals from the GPS transmitter satellites as they rise and set relative to the COSMIC satellite. The GPS signals are refracted by the atmosphere as they travel from the transmitter to the receiver, to an extent which depends on the temperature and water vapor content of the lower atmosphere and the density of electric charge in the ionosphere. The refraction causes a delay in the phase of the transmitted signal which can be inverted to retrieve profiles of electron density (in the ionosphere), dry atmospheric temperature, and water vapor (although water vapor requires additional information). Because the profiles are retrieved from the rising and setting, or occultation, of the GPS transmitters, the technology is referred to as GPS Radio Occultation (GPSRO), or more generally as GNSSRO, where GNSS is the Global Navigation Satellite System. GNSSRO has proven to be a highly effective observing method as the measurements can be made under all weather conditions, are unaffected by clouds and aerosols, and are absolutely calibrated (SI traceable) through the clock system that supports the GPS transmitters.Funds under this award support COSMIC-related work in four categories: 1) processing, serving, and archiving COSMIC data for use by the research community; 2) conducting research to improve GNSSRO inversion science and techniques; 3) conducting research in support of scientific applications of GNSSRO data; and 4) education and outreach activities to promote the use of GNSSRO data and its application to atmospheric research. Item 1 is the bread-and-butter activity of this award and its predecessors, and support is also provided here for improving the quality of the profiles and generating additional data products such as monthly mean climatologies for both lower- and upper-atmospheric variables. In addition to the COSMIC satellites, a small number of GNSSRO "missions of opportunity" are also supported. These are research satellites to which a GNSS receiver has been added as a secondary payload (GRACE-B for example). Activities under item 2 continue the PIs' leadership role in the development of new GNSS processing techniques, for example by developing methods to correct errors caused by diffraction in sporadic E layers in the ionosphere. Research under item 3 develops new assimilation techniques such as the use of 2D ray-tracing methods to account for horizontal refractivity gradients. Another task is to develop long-term climate-quality datasets in which profiles from different satellites are optimally combined to account for differences in their error characteristics. GNSSRO data are well-suited for generating long-term multi-mission datasets given their SI traceability. Work under item 4 addresses a gap between the availability of GPSRO data and its adoption by the research community. Activities include hosting academic visitors, conducting meetings and workshops, and holding summer colloquia and tutorials.The work has intellectual merit due to the great value of the COSMIC observations for weather, climate and ionospheric research. The work has scientific broader impacts through the PIs' education and outreach efforts to promote the adoption and use of the data by scientists from several research communities. In addition, the PIs provide the COSMIC data to operational weather forecasting centers worldwide, and the data has been shown to be quite useful for improving the skill of weather forecasts.This award supercedes AGS-1033112, the previous cooperative agreement under which NSF provided funds to COSMIC. While NSF is no longer providing funds via the earlier CA, that award will remain active as it contains funds from other agencies to support the development of the follow-on COSMIC-2 mission. This award does not provide funds for COSMIC-2.