GPS Space Segment Science & Technology Investment at the Air Force Research Laboratory

Donna Cowell Senft, Kevin Slimak and Lawrence "Robbie” Robertson

Abstract:	The Air Force Research Laboratory Space Vehicles Directorate (AFRL/RV) has a history of developing innovative spacecraft concepts and demonstrating these concepts on-orbit in flight experiments. Currently, AFRL/RV is investing in technologies to provide options for future GPS spacecraft. These technologies have the potential to provide significant savings, resulting in spacecraft that are smaller and cheaper to launch, or alternatively, GPS spacecraft with improved capabilities. As described in solicitations, AFRL/RV is interested in improved radio frequency (RF) components for signal generation, such as: L-band amplifiers; diplexers, triplexers, and quadriplexers; and spacecraft antennas. More efficient RF components can allow reduction in spacecraft power and thermal system mass and size while maintaining GPS signals at legacy levels. Digital payload components such as an on-orbit reprogrammable digital waveform generator and 64-bit radiation-hardened non-volatile memory could result in more flexible methods of signal generation, potentially leading to a capability to broadcast new signals from existing GPS spacecraft, without requiring constellation replenishment with new spacecraft. Investigation into new types of spacecraft clocks is underway. State-of-practice rubidium fountain clocks provide reliable, stable time-keeping, but these clocks operate at nearly theoretical levels of performance, providing little headroom. Developmental clocks could provide improved clock stability, but equally important goals are improving clock robustness to supplier sub-components and reducing cost. Under investigation are cold atom clocks, optical clocks, and space-compatible components for these clocks. Together, these investments promise to provide innovative options for next generation GPS spacecraft, options that can not only reduce operational costs, but could also provide new capabilities for the Global Positioning System. Progress toward new technologies will be described, along with discussion of the capabilities the new components are expected to enable.
Published in:	Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015) September 14 - 18, 2015 Tampa Convention Center Tampa, Florida
Pages:	1924 - 1939
Cite this article:	Senft, Donna Cowell, Slimak, Kevin, Robertson, Lawrence "Robbie”, "GPS Space Segment Science & Technology Investment at the Air Force Research Laboratory," Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015), Tampa, Florida, September 2015, pp. 1924-1939.
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