Session
Session IX: Advanced Technologies I
Location
Utah State University, Logan, UT
Abstract
The University of Colorado Boulder has developed an experiment to characterize the behavior of a chip-scale atomic clock (CSAC) in space, conducted on the MAXWELL CubeSat mission. This experiment integrates a CSAC as an external oscillator to the onboard GPS receiver, enabling clock characterization through real-time estimates of clock bias, GPS pseudorange, and carrier phase measurements. These data will demonstrate the CSAC's short and long-term stability and its sensitivity to the space environment.
This paper evaluates the observation of CSAC performance using GPS within the constraints of the MAXWELL mission. The results, derived from tests with realistic orbit and spacecraft pointing scenarios modeled with an RF signal simulator and ground-based live-sky test data, show that poor GPS visibility limits CSAC observation accuracy and can result in data gaps. We demonstrate a gap-filling algorithm to effectively address these gaps. To mitigate the effects from poor visibility, GPS measurements from live-sky tests are processed with the GipsyX software suite to achieve the most accurate clock stability information. Since the MAXWELL receiver operates at a single frequency and is susceptible to ionospheric effects, we apply the Group and Phase Ionospheric Correction (GRAPHIC) technique to mitigate first-order ionospheric effects for GPS-based clock characterization in Low Earth Orbit (LEO).
SSC24-IX-01-Presentation
Characterizing a Chip Scale Atomic Clock in Low Earth Orbit
Utah State University, Logan, UT
The University of Colorado Boulder has developed an experiment to characterize the behavior of a chip-scale atomic clock (CSAC) in space, conducted on the MAXWELL CubeSat mission. This experiment integrates a CSAC as an external oscillator to the onboard GPS receiver, enabling clock characterization through real-time estimates of clock bias, GPS pseudorange, and carrier phase measurements. These data will demonstrate the CSAC's short and long-term stability and its sensitivity to the space environment.
This paper evaluates the observation of CSAC performance using GPS within the constraints of the MAXWELL mission. The results, derived from tests with realistic orbit and spacecraft pointing scenarios modeled with an RF signal simulator and ground-based live-sky test data, show that poor GPS visibility limits CSAC observation accuracy and can result in data gaps. We demonstrate a gap-filling algorithm to effectively address these gaps. To mitigate the effects from poor visibility, GPS measurements from live-sky tests are processed with the GipsyX software suite to achieve the most accurate clock stability information. Since the MAXWELL receiver operates at a single frequency and is susceptible to ionospheric effects, we apply the Group and Phase Ionospheric Correction (GRAPHIC) technique to mitigate first-order ionospheric effects for GPS-based clock characterization in Low Earth Orbit (LEO).
