No abstract

A unified approach to improved usability can be identified in the works of Gilb (1981, 1984), Shackel (1984), Bennett (1984), Carroll and Rosson (1985), and Butler (1985). We term this approach “usability engineering,” and seek to contribute to it by showing, via a product development case study, how user-derived estimates of the impact of design activities on engineering goals may be made. 1

Autonomy is required for manned spacecraft missions distant enough that light-time communication delays make ground-based mission control infeasible. Presently, ground controllers develop a complete schedule of power modes for all spacecraft components based on a large number of factors. The proposed architecture is an early attempt to formalize and automate this process using on-vehicle computation resources. In order to demonstrate this architecture, an autonomous electrical power system controller and vehicle Mission Manager are constructed. These two components are designed to work together in order to plan upcoming load use as well as respond to unanticipated deviations from the plan. The communication protocol was developed using "paper" simulations prior to formally encoding the messages and developing software to implement the required functionality. These software routines exchange data via TCP/IP sockets with the Mission Manager operating at NASA Ames Research Center and the autonomous power controller running at NASA Glenn Research Center. The interconnected systems are tested and shown to be effective at planning the operation of a simulated quasi-steady state spacecraft power system and responding to unexpected disturbances.

At the last IEEE-PVSC, the new stretched lens array (SLA) concept was introduced. Since that conference, the SLA team has made significant advances in the SLA technology, including component-level improvements, array-level optimization, space environment exposure testing, and prototype hardware fabrication and evaluation. This paper will describe the evolved version of the SLA, highlighting the improvements in the lens, solar cell, rigid panel structure, and complete solar array wing. The near-term SLA will provide outstanding wing-level performance: >180 W/kg specific power, >300 W/sq.m. power density, >300 V operational voltage, and excellent durability in the space environment.

A unified approach to improved usability can be identified in the works of Gilb (1981, 1984), Shackel (1984, Bennett (1984), Carroll and Rosson (1985), and Butler (1985). We term this approach "usability engineering," and seek to contribute to it by showing, via a product development case study, how userderived estimates of the impact of design activities on engineering goals may be made.'