In this proposal, we will explore the feasibility of multiple geosynchronous gnss remote sensing observations using on-orbit data from the goes-16 and goes-17 GPS navigation receivers: scintillation…

This is a $500,898 grant awarded by the National Aeronautics and Space Administration (NASA) to the University Corporation for Atmospheric Research (UCAR), a nonprofit consortium of over 115 universities. The grant will fund a project to explore the feasibility of using data from the GOES-16 and GOES-17 geostationary weather satellites to perform new atmospheric remote sensing observations, including detecting scintillation, performing radio occultation profiling, and detecting surface reflections. The project will also conduct trade studies on the optimal configurations for future GNSS remote sensing instruments in geostationary orbit. The work will be performed at UCAR's National Center for Atmospheric Research (NCAR) facilities in Boulder, Colorado. This grant does not have a set-aside designation.

In this proposal, we will explore the feasibility of multiple geosynchronous gnss remote sensing observations using on-orbit data from the goes-16 and goes-17 GPS navigation receivers: scintillation detection, RO profiling and surface reflections. Additionally, we will perform trade space studies assessing the on-orbit receiver requirements for making useful observations of the earth's atmosphere and surface using gnss signals from a geosynchronous (GEO) satellite platform for the benefit of future gnss remote sensing missions. We believe that the most promising new science are the atmospheric measurements possible with the goes GPS receivers. Radio occultation (RO) from geosynchronous orbit holds the potential to provide unique temporal and spatial atmospheric measurements not possible from ground and low earth orbit (LEO) space based receivers, including new observations of the upper atmosphere. This project will explore the potential of GEO gnss receivers to generate new observations both above existing gnss-RO LEO satellites as well as attempt to generate unique GEO RO profiles through the atmosphere. We will analyze archived and future goes data sets to develop atmospheric scintillation detection algorithms using several techniques tailored to the known limitations of the goes data set. Notably, both amplitude and phase measurements from GPS signals tracked by the goes receivers will be used for observing upper and lower atmospheric scintillations. Initial modeling has been performed that indicates that the large distance between the GPS transmitters and the goes receivers may present an advantage over LEO satellites. Additionally, we will develop techniques to generate RO bending angle profiles from goes observations, and explore methods to invert these profiles to refractivity and subsequent estimations of temperature, pressure and (potentially) water vapor in the traversed atmospheric column. Evidence indicates that the goes receivers regularly track signals through the ionosphere and into the troposphere, thus enabling the retrieval of these long duration occultation events with custom processing algorithms to generate new atmospheric observations. Additionally, IT has been demonstrated that coherent grazing angle surface reflections are detectable by LEO RO GPS receivers. The presence of surface reflections in the goes data will be explored as part of this project, particularly over the greenland ICE sheet, where a convergence of goes measurements and historic evidence of reflections in LEO RO data make the possibility of detection most likely. Finally, we will perform a trade space study into the enhanced and/or optimal gnss remote sensing instrument configurations for a) future standard geosynchronous gnss instruments (or missions above the gnss constellations, such as MMS) and b) custom gnss remote sensing mission designs with dedicated gnss remote sensing instruments. Data from the cosmic-2 RO and the cygnss gnss-reflection missions will be used to "anchor" this analysis to reality and provide increased confidence in their predictions of the gnss performance achievable at higher altitudes for various instrument configurations. In summary, this proposed work will enable new atmospheric measurements using the existing goes navigation receiver data sets and make a significant step forward in the understanding of the feasibility of performing gnss remote sensing in geoscynchronous orbits for future missions.