Progressive development of microsatellite technologies has resulted in increased demand for lightweight electrical power subsystems including solar arrays. The use of thin film photovoltaics has been recognized as a key solution to meet the power needs. The lightweight cells can generate sufficient power and still meet critical mass requirements. Commercially available solar cells produced on lightweight substrates are being studied as an option to fulfill the power needs. The commercially available solar cells are relatively inexpensive and have a high payoff potential. Commercially available thin film solar cells are primarily being produced for terrestrial applications. The need to convert the solar cell from a terrestrial to a space compatible application is the primary challenge. Solar cell contacts, grids and interconnects need to be designed to be atomic oxygen resistant and withstand rapid thermal cycling environments. A mechanically robust solar cell interconnect is also required in order to withstand handling during fabrication and survive during launch. The need to produce the solar cell interconnects has been identified as a primary goal of the PowerSphere program and is the topic of this paper. Details of the trade study leading to the final design involving the solar cell wrap around contact, flex blanket, welding process, and frame will be presented at the conference.
Research Containing: Microsatellite
Satellite formation flight and realignment maneuver demonstration aboard the International Space Station
The Synchronized Position Hold Engage and Reorient Experimental Satellites (SPHERES), developed by the MIT Space Systems Laboratory, enable the maturation of control, estimation, and autonomy algorithms for distributed satellite systems, including the relative control of spacecraft required for satellite formation flight. Three free-flyer microsatellites are currently on board the International Space Station (ISS). By operating under crew supervision and by using replenishable consumables, SPHERES creates a risk-tolerant environment where new high-risk yet high-payoff algorithms can be demonstrated in a microgravity environment. Through multiple test sessions aboard the ISS, the SPHERES team has incrementally demonstrated the ability to perform formation flight maneuvers with two and three satellite formations. The test sessions aboard the Space Station include evaluation of coordinated maneuvers which will be applicable to interferometric spacecraft formation missions. The satellites are deployed as a formation and required to rotate around a common center about a given axis, mimicking an interferometer. Various trajectories are then implemented to point the synthetic aperture in a different orientation by changing the common axis of revolution. Observation-time optimizing synchronization strategies and fuel balancing/fuel optimizing trajectories are discussed, compared and evaluated according to resulting mission duration and potential scientific output.