Advancing Thermospheric Density Quantification: Applying Energy Dissipation Rate GNSS Accelerometry to the Eccentric C/NOFS Satellite

The increase in the number of objects in Low-Earth Orbit (LEO) has heightened the demand for high-accuracy orbital prediction models driven by dependable measurements of thermospheric neutral mass density. Historically, these measurements have been predominantly sourced from advanced accelerometers integrated into satellites like CHAMP or GRACE from past decades or, more recently, the GOCE and Swarm missions. However, incorporating high-performance accelerometers into satellite missions is often infeasible, especially considering the associated escalation in costs and complexity tied to the integration of such hardware enhancements. Given that most satellites include onboard Global Navigation Satellite System (GNSS) receivers, recent attention has focused on alternative techniques for observing neutral density through atmospheric drag such as “GNSS accelerometry,” which involves harnessing spacecraft as instruments themselves to quantify thermospheric density vis-à-vis orbital decay.

This work demonstrates how the Energy Dissipation Rate (EDR) technique utilizes the change in spacecraft orbital energy to recover thermospheric density profiles at cadences ranging from a single orbital period down to as small as a quarter of such periods. After presenting a framework for applying the EDR method to the elliptical orbit of the Communications / Navigation Outage Forecasting System (C/NOFS) satellite, “effective” neutral density profiles integrated over some continuous portion of the orbit called an “orbit arc” are recovered by applying the EDR method to the University Corporation for Atmospheric Research precise orbit determination data product for C/NOFS during January 2011. The merits of the EDR method, especially in its heightened sensitivity to solar/geomagnetic activity, are underscored by investigating a minor geomagnetic storm on 7 January 2011. This significance is further accentuated by a comparative analysis, where the EDR output is contrasted with results obtained from analogous approaches based on processing Two-Line Element sets or the output from semiempirical models such as NRLMSISE-00. Furthermore, this study introduces the novel application of suborbital-average EDR integration tailored for satellites with eccentric orbits, demonstrating its efficacy in offering nuanced insights into thermospheric conditions that would otherwise be obscured by averaging across the entire orbit. The results demonstrate the ability of physics-based techniques and readily accessible data sets to estimate neutral density and provide insight into aeronomy and space weather science. Not only are such methods widely applicable to objects in LEO, but they also have the potential to enhance the science returns of future NASA missions such as GDC and DYNAMIC through supplementary neutral density observations.