The mission aims to design and implement a CubeSat-based trusted-node Quantum Key Distribution testbed in LEO. The purpose of which is to demonstrate the feasibility of QKD from LEO with a CubeSat to an optical ground station consisting primarily commercial off the shelf (COTS) components.The QKD payload will use polarization encoding of weak coherent pulse sources, coupled to fore optics, that can be used to downlink quantum keys to an optical ground station. The optical ground station will make use of a commercially available reflector telescope for the quantum channel and a tracking S-band communications station for a classical, unsecured, channel. The classical channel will also handle downlinking of housekeeping telemetry from the satellite.
The University Nanosatellite Program (UNP) funds U.S. university students and programs to design, build, launch, and operate small satellites. UNP is funded by the Air Force Office of Scientific Research (AFOSR) and managed from the Air Force Research Laboratory’s (AFRL) Space Vehicles Directorate (RV) located on Kirtland Air Force Base, NM. UNP is nationally recognized with its own funding line on the President’s Portfolio of Science, Technology, Engineering, and Math.
UNP’s objective is to train the next generation of space professionals by providing a rigorous concept-to-flight-ready spacecraft development process centered on systems engineering principles and practices. UNP provides AFRL and DoD parties the option to leverage technologies and platforms in research areas of interest to AFRL. Finally, UNP provides AFRL and industry a work force pipeline made up of students who have been trained in small satellite development.
The generation of entangled photon pairs for polarization encoding are ultimately desirable, however, it is possible to implement QKD protocols with weak coherent laser sources. The generation of truly entangled photon pairs would require nonlinear optional elements, e.g.. BBO crystals, which have low entangled pair production rates and are complex to practically implement. We have chosen to emulate the Micius mission in implementing a scaled-down version of a weak coherent pulse system. This is already a proven method, both terrestrially and on orbit, and is straightforward to implement with COTS components.This is equally true for the required optical ground station component of the mission. The technology readiness level (TRL) of our payload is estimated to be TRL 3, due to the fact that we have yet to build it, although we do have a lab demonstration model, on a table-top scale.
The beacon tracking and tilt mirror scheme for fine pointing have been used by previous CubeSat missions. This experience can be leverage for our system, but the TRL level is still relatively low (TRL 3) due to it not being built for our specific mission needs and tested.The beacon tracking and QKD send/receive system will all need to be tested in the lab environment. The goal is to advance the payload to at least TRL 5 by the flight selection review.
No specific military customers have been identified, however, some examples of potential military customers, with interest in quantum communications, are Army Space and Missile Defense Command (SMDC) Technology Center and Air Force Research Laboratory Information Directorate (RI). More generally, the capacity to utilize QKD for secure messaging to distant and/or mobile end stations has operational impacts to various military branches. The issues of vulnerability to math-based encryption are just as impactful, if not more, to military communications as any other communications. The current mission contributes to the ability to establish a low-cost network of satellite QKD systems and mobile optical ground stations deployable to ground locations, ships, land vehicles and aircraft.
(1) LEOPS- Launch and Early Orbit Phase
During this phase the satellite is deployed from the launch vehicle and enters Deployment Mode. In this mode the satellite will activate its subsystems, deploy the panels and antennas, detumble, charge, and establish communications. The satellite will transition into Default Mode and perform systems checkouts and a Post Launch Assessment Review. It is estimated to take 1 to 3 months until we begin Nominal Operations.
(2) Nominal Operations- During this phase the satellite will spend the majority of the time in Default Mode. In this mode the satellite will be conducting basic operations such as suntracking, transmitting/receiving and dumping momentum. When the stringent orbital and weather requirement are met, the satellite will transition to Experiment Mode. The operations of Experiment Mode are described in detail below. Safe Mode places the satellite in a near comatose state in which only the most essential systems are active. This mode is used to keep the satellite alive when it encounters anomalies on orbit.
(3) End of Life- During this phase the satellite will end Nominal Operations and deploy deorbiters. The satellite will reenter the atmosphere and burnup within 25 years.
(1) The satellite slews to the optical ground station and begins tracking.
(2) Ground station tracks the satellite with a beacon laser. The optical payload onboard the satellite uses the uplink beacon to direct the pointing of the downlink laser.
(3) The optical payload downlinks the weak coherent pulse to the optical ground station.
(4) Beacon tracking and QKD downlink ended,
(5) Mission data is transmitted to the ground station and the satellite exits experiment mode.