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

2006年发射的气象、电离层和气候星座观测系统（COSMIC）是一个由低地球轨道上的六颗极轨道卫星组成的星座。每颗卫星的主要有效载荷是一个全球定位系统（GPS）接收器（由美国航天局喷气推进实验室开发），当GPS发射器卫星相对于COSMIC卫星上升和下降时，接收来自GPS发射器卫星的定位信号。全球定位系统信号在从发射机传播到接收机时会受到大气层的折射，折射的程度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，可以将其反转以检索电子密度（电离层中），干燥大气温度和水蒸气（尽管水蒸气需要额外的信息）的分布。由于轮廓是从GPS发射机的上升和设置或掩星中检索的，因此该技术被称为GPS无线电掩星（GPSRO），或更一般地称为GNSSRO，其中GNSS是全球导航卫星系统。 全球卫星定位系统天文台已证明是一种非常有效的观测方法，因为测量可以在所有天气条件下进行，不受云和气溶胶的影响，并且绝对经过校准（SI可追溯）。该奖项的基金支持四个类别的COSMIC相关工作：1）处理、服务和存档COSMIC数据，供研究界使用; 2）开展研究，以改进全球导航卫星系统RO反演科学和技术; 3）开展研究，支持全球导航卫星系统RO数据的科学应用;以及4）开展教育和外联活动，以促进全球导航卫星系统RO数据的使用及其在大气研究中的应用。 第1项是该奖项及其前身的基础活动，在此还为提高廓线质量和生成更多数据产品提供支持，例如低层和高层大气变量的月平均气候学。除了COSMIC卫星外，还支持少量全球卫星导航卫星系统研究组织的“机遇飞行任务”。 这些卫星是研究卫星，其上增加了一个全球导航卫星系统接收器作为辅助有效载荷（例如GRACE-B）。 项目2下的活动继续发挥了专业人员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，通过开发方法来纠正电离层中零星E层衍射造成的误差。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方法来计算水平的放射性活动梯度。 另一项任务是开发长期的气候质量数据集，其中将不同卫星的剖面最佳地结合起来，以考虑其误差特征的差异。全球导航卫星系统研究组织的数据非常适合于生成长期多任务数据集，因为它们具有SI可追踪性。 项目4下的工作涉及全球地球观测系统研究组织数据的可得性与研究界对其采用之间的差距。 活动包括接待学术访问者，举办会议和讲习班，举办夏季座谈会和辅导班，由于COSMIC观测对天气、气候和电离层研究的巨大价值，这项工作具有智力价值。 通过PI的教育和推广工作，这项工作具有更广泛的科学影响，以促进来自几个研究社区的科学家采用和使用数据。 此外，美国国家科学基金会还向世界各地的气象预报中心提供COSMIC的数据，这些数据对提高气象预报水平有很大的帮助。该项目是美国国家科学基金会资助COSMIC的合作协议AGS-1033112的后续项目。 虽然NSF不再通过早期的CA提供资金，但该奖项将继续有效，因为它包含来自其他机构的资金，以支持后续COSMIC-2使命的发展。 该合同不为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.