Session
Technical Session IX: Advanced Technologies-Communications
Abstract
Precision time-keeping is a critical requirement of any satellite navigation system, including GPS. Even the most stable space qualified atomic clocks drift over time to the point where they can significantly degrade navigation precision. Periodic re-synchronization of these clocks with respect to terrestrial time standards is therefore required. Time transfer through Earth’s atmosphere using optical frequencies offers improved accuracy due to reduced time delay uncertainties relative to radio frequencies. In this paper we describe the design and laboratory testing of the Optical Precision Time Transfer Instrument, a compact device for real-time terrestrial-to-space clock corrections, using existing satellite laser ranging facilities. This instrument will comprise roughly 1U of a 3U CubeSat mission, sponsored by the Air Force’s University Nanosatellite Program and slated for launch in the 2017 time-frame. The instrument will demonstrate time transfer with a short term accuracy of 100 psec, equivalent to 3 cm of position error, and a long term timing error of 6 nsec over one orbit, limited solely by the frequency stability of the on-board miniature atomic clocks. Future missions using this time transfer technology and equipped with higher stability clocks will enable disaggregated navigation systems, with precision time-keeping components separated from other functionality.
Optical time transfer for future disaggregated small satellite navigation systems
Precision time-keeping is a critical requirement of any satellite navigation system, including GPS. Even the most stable space qualified atomic clocks drift over time to the point where they can significantly degrade navigation precision. Periodic re-synchronization of these clocks with respect to terrestrial time standards is therefore required. Time transfer through Earth’s atmosphere using optical frequencies offers improved accuracy due to reduced time delay uncertainties relative to radio frequencies. In this paper we describe the design and laboratory testing of the Optical Precision Time Transfer Instrument, a compact device for real-time terrestrial-to-space clock corrections, using existing satellite laser ranging facilities. This instrument will comprise roughly 1U of a 3U CubeSat mission, sponsored by the Air Force’s University Nanosatellite Program and slated for launch in the 2017 time-frame. The instrument will demonstrate time transfer with a short term accuracy of 100 psec, equivalent to 3 cm of position error, and a long term timing error of 6 nsec over one orbit, limited solely by the frequency stability of the on-board miniature atomic clocks. Future missions using this time transfer technology and equipped with higher stability clocks will enable disaggregated navigation systems, with precision time-keeping components separated from other functionality.
