Department of Defense Synchronized Position, Hold, Engage, Reorient, Experimental Satellites – Chip Scale Atomic Clock (DoD SPHERES – CSAC)demonstrates the performance of an atomic clock in the sustained microgravity environment of ISS. Atomic clocks are the most accurate time keepers in the world. An atomic clock is a precision clock that depends for its operation on an electrical oscillation regulated by the natural vibration frequencies of an atomic system.Principal Investigator(s)
Aurora Flight Sciences Corporation, Cambridge, MA, United States
National Aeronautics and Space Administration (NASA)Sponsoring Organization
National Laboratory - Department of Defense (NL-DoD)ISS Expedition Duration:
September 2011 - September 2012
29/30,31/32Previous ISS Missions
Department of Defense Synchronized Position, Hold, Engage, Reorient, Experimental Satellites – Chip Scale Atomic Clock (DoD SPHERES - CSAC)test sessions allow DoD SPHERES - CSAC to synchronize the timing between two clocks using a high precision off-board module. The drift between clocks within each test session and between test sessions is measured. The differences in relative motion between the two clocks may provide useful data relating to motion-induced clock drift, which is not easily observed while the DoD SPHERES - CSAC units are strapped down. Some mechanisms relating to drift may be device dependent, but some are due to relative motion between devices.
For this experiment, the SPHERES platform on ISS is used to demonstrate synchronized timing between multiple free-flying bodies using the Chip Scale Atomic Clock. SPHERES provides a space qualified platform, allowing DoD SPHERES - CSAC to claim flight heritage. This allows DoD SPHERES - CSAC to leverage the existing SPHERES hardware, software, and processes to facilitate safety reviews, crew training, data interfaces, and operations. Part of the DoD SPHERES - CSAC effort will also develop a universal interface for future investigations, as an upgrade to the existing SPHERES expansion port. These interfaces will be left on the SPHERES satellites, for future use by other investigators.
Each of the three 9 in. diameter SPHERES microsatellites on ISS has twelve cold gas (CO2) thrusters, three rate gyros, three accelerometers, and a pseudo-GPS sensing system that permits state estimation relative to the frame of the US Laboratory on ISS to 2 mm and 2 degree accuracy. A typical test session starts with the uplink of algorithms one week before the test session, loading of the algorithms onto the SPHERES through the communication system, cross-linking of real-time data to the ISS laptop, and finally downlinking of the data. This data is analyzed, algorithms are revised, and the next test session is scheduled.
The development of Chip-Scale Atomic Clock enables ultra-miniaturized (wristwatch in size) and ultra low power time and frequency references for high-security UHF communication and jam-resistant GPS receivers. The use of these ultra-miniature time reference units could greatly improve the mobility and robustness of any systems and platforms with sophisticated UHF communication and/or navigation requirements. DoD SPHERES – CSAC may also help in the development of small-scale inertial navigation systems (INS) for use on small satellites (mass 1-10 kg). An INS is a navigation aid that uses a computer, motion sensor, and rotation sensors to continuously calculate via dead reckoning the position, orientation and velocity of a moving object without the need for external references.Earth Applications
DoD SPHERES – CSAC results may help in the development of small-scale inertial navigation systems (INS) for use on vehicles such as ships, aircraft, submarines. The CSAC investigation is part of the Defense Advanced Research Projects Agency (DARPA) InSPIRE program and as such enlists the support and involvement of students and teachers in educational outreach in inspiring the next generation of scientists and engineers with exposure and experience in carrying out meaningful space experimentation.
DoD SPHERES is allocated five test sessions per Increment. This allocation of test sessions is shared between DoD SPHERES - CSAC, VERTIGO, and RINGS; as the facility lead, NASA Ames determines specific test session scheduling based on ongoing planning and research results for the three DoD SPHERES experiments.Operational Protocols
A typical DoD SPHERES-CSAC test session consist of: