Nanosatellite optical downlink experiment: design, simulation, and prototyping

The nanosatellite optical downlink experiment (NODE) implements a free-space optical communications (lasercom) capability on a CubeSat platform that can support low earth orbit (LEO) to ground downlink rates>10  Mbps. A primary goal of NODE is to leverage commercially available technologies to provide a scalable and cost-effective alternative to radio-frequency-based communications. The NODE transmitter uses a 200-mW 1550-nm master-oscillator power-amplifier design using power-efficient M-ary pulse position modulation. To facilitate pointing the 0.12-deg downlink beam, NODE augments spacecraft body pointing with a microelectromechanical fast steering mirror (FSM) and uses an 850-nm uplink beacon to an onboard CCD camera. The 30-cm aperture ground telescope uses an infrared camera and FSM for tracking to an avalanche photodiode detector-based receiver. Here, we describe our approach to transition prototype transmitter and receiver designs to a full end-to-end CubeSat-scale system. This includes link budget refinement, drive electronics miniaturization, packaging reduction, improvements to pointing and attitude estimation, implementation of modulation, coding, and interleaving, and ground station receiver design. We capture trades and technology development needs and outline plans for integrated system ground testing.United States. National Aeronautics and Space Administration. Research Fellowship ProgramLincoln Laboratory (Lincoln Scholars)Lincoln Laboratory (Military Fellowship Program)Fundación Obra Social de La Caixa (Fellowship)Samsung FellowshipUnited States. Air Force (Assistant Secretary of Defense for Research & Engineering. Contract FAs872105C0002

Rotary SMA actuator for CubeSat deployable structures

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.Includes bibliographical references (pages 155-158).Over a decade of continuing CubeSat technology improvements are driving the wide adoption of CubeSats for research and commercial missions. Resource constraints onboard CubeSats still limit their ability to support multi-use actuators, but there is a need for a rotary CubeSat actuator that can be actively commanded to different angles. This type of actuator can be implemented in a CubeSat mechanism for differential drag management, increased power generation, and reconfigurable deployable structures. We propose using a shape memory alloy (SMA) actuator to meet this need. A SMA can be annealed at high temperatures to remember a trained shape. Upon cool down, the SMA element transforms to the martensite phase and is easily deformed. When the element is heated above the transformation temperature it transforms to the stiff austenite phase and assumes its remembered shape, driving the mechanism. Two SMA actuators are trained to different shapes and provide bidirectional rotary motion for use as a space mechanism. The actuators are designed by implementing kinematic, thermal, and bending models to size the SMA element. The models also predict the performance, size, weight, and power of the actuator and ensure it can operate in the CubeSat environment. Then, a prototype of the proposed actuator is manufactured, assembled, and ground tested. Testing is used to validate the models and verify the requirements necessary to operate onboard a CubeSat. The prototype meets all requirements and offers a reduced mass, volume, and complexity alternative to current CubeSat electromagnetic actuators. Future work is necessary to improve the mechanical performance and positional control of the SMA actuator.by Maxim O. Khatsenko.S.M