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Jennifer E Donaldson

Publications and source records attributed to Jennifer E Donaldson.

3 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

Architecture and Operations of the OSIRIS-REx Independent Navigation Team

The Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) GoddardSpace Flight Center (GSFC) Independent Navigation Team (INT) performs center-finding and landmark-basedOptical Navigation (OpNav), Orbit Determination (OD), maneuver verification, and additional analyses in support ofnavigation operations motivated by a stringent set of science requirements. The INT has adopted a streamlined andagile approach to navigation operations support via a virtual operations environment, known as "OREX-NAV",which leverages existing capabilities of the Space Science Mission Operations (SSMO) virtual Multi-MissionOperations Center (vMMOC). The virtual environment architecture of OREX-NAV enables the INT to perform dailyoperational tasks and seamlessly interface with external mission networks, regardless of physical location. Throughthe automation and process adopted, the INT is able to keep pace with the rapid cadence of required deliverables.

OSIRIS-REx↗
NASA NTRS2020

Characterization of On-Orbit GPS Transmit Antenna Patterns for Space Users

The GPS Antenna Characterization Experiment (GPS ACE) has made extensive observations of GPS L1 signals received at geosynchronous (GEO) altitude, with the objective of developing comprehensive models of the signal levels and signal performance in the GPS transmit antenna side lobes. The experiment was originally motivated by the fact that data on the characteristics and performance of the GPS signals available in GEO and other high Earth orbits was limited. The lack of knowledge of the power and accuracy of the side lobe signals on-orbit added risk to missions seeking to employ the side lobes to meet navigation requirements or improve performance. The GPS ACE Project lled that knowledge gap through a collaboration between The Aerospace Corporation and NASA Goddard Space Fight Center to collect and analyze observations from GPS side lobe transmissions to a satellite at GEO using a highly-sensitive GPS receiver installed at the ground station. The GPS ACE architecture has been in place collecting observations of the GPS constellation with extreme sensitivity for several years. This sensitivity combined with around-the-clock, all-in-view processing enabled full azimuthal coverage of the GPS transmit gain patterns over time to angles beyond 90 degrees o -boresight. Results discussed in this paper include the reconstructed transmit gain patterns, with comparisons to available pre-fight gain measurements from the GPS vehicle contractors. For GPS blocks with extensive ground measurements, the GPS ACE results show remarkable agreement with ground based measurements. For blocks without extensive ground measurements, the GPS ACE results provide the only existing assessments of the full transmit gain patterns. The paper also includes results of pseudorange deviation analysis to assess systematic errors associated with GPS side lobe signals.

Jennifer E Donaldson↗