TECHNOLOGY AREAS: Battlespace, Space Platforms
OBJECTIVE: Accurately determine current and future satellite drag with a thermospheric physical model using near real time space weather data and indices.
DESCRIPTION: Orbital drag on spacecraft is a critical factor in providing collision avoidance warnings for manned spaceflight and other high-value assets, accurately cataloging orbiting objects, predicting reentry times, and estimating satellite lifetimes, on-board fuel requirements, and attitude dynamics. Uncertainties in neutral density variations are the major limiting factor for precise low-Earth orbit determination at altitudes below about 700 km. Long-standing shortfalls in satellite drag prediction have been due to the complex thermosphere neutral density and wind response during periods of high geomagnetic activity and inadequate prediction capability for solar EUV and geomagnetic storm variations.
Although thermospheric physical models have been used for research for many years, their technical feasibility for satellite drag forecasting is still not at par with empirical models. A challenging R&D effort is to improve physical model capability so that its 72 hour neutral density forecast could be better than the current empirical Jacchia Bowman 2008 (JB08) neutral density model. The objective of this STTR is to establish technical feasibility of thermospheric physical models that can help improve orbit prediction in a near real time environment.
This R&D effort is enhanced by a recent AFOSR-supported Multi-University Research Initiative “Neutral Atmosphere Density Interdisciplinary Research." It has greatly improved the understanding of the physics of geomagnetic storm response and neutral density profiles under solar and geomagnetic quiet time conditions. Under the MURI various studies have used new data sets from orbital drag, satellite-borne accelerometers, and EUV remote sensors for improving climatological descriptions of thermospheric variability vs altitude, latitude, day of year, local time, and solar-geomagnetic conditions. While near real time data and indices including EUV data, solar flux and geomagnetic indices, solar wind and IMF measurements are now becoming available, thermospheric models have not yet taken advantage of the data for improving neutral density and wind modeling. This topic thus requests innovative approaches to develop a flexible and robust thermospheric physical model satisfying the needs of near real time satellite drag forecast. Successful proposals will help develop innovative algorithms employing new physical concepts and near real time space weather data and indices. The new algorithms will eventually be utilized in the modeling of satellite drag by the Air Force Space Command (AFSPC) and the Joint Space Operations Center (JSpOC).
PHASE I: Develop an initial model module running in a near real time environment. Demonstrate that the proposed new physical processes can achieve satellite drag specification capability equivalent to current empirical model JB08. Validate with historical orbit-averaged CHAMP and GRACE satellite neutral density data.
PHASE II: Incorporate new physical processes into thermospheric physical models. Develop innovative solar and geomagnetic forecast algorithms that use near real time space weather data and indices. Demonstrate that the developed model can improve current 3-day satellite drag forecast capability. Deliverables will be the model and prediction algorithms, validation reports, and any necessary data storage and network hardware.
PHASE III DUAL USE COMMERCIALIZATION:
Military Application: Results of this work can be used to improve AF space catalog accuracy, a critical component for space situational awareness. The developed model can be utilized in the DoD operational centers.
Commercial Application: The new algorithms matured under this grant can be used for high accuracy collision avoidance in commercial software applications.