Developing plug-and-play spacecraft systems: NASA Goddard Space Flight Center's (GSFC) Essential Services Node (ESN)

Abstract

The phrase refers to hardware and software devices that, after being installed (plugged in), can immediately be used (played with). The system can be used for a specific application without requiring additional software programming or hardware design. The Essential Services Node (ESN) takes a big step in moving space systems to the plug and play environment of commercial systems. Systems that use the ESN to interface subsystems to the spacecraft bus (either MILSTD-1553B or MIL-STD-1773) provide a standard interface to both the sub-systems and the spacecraft bus. The ESN is a multi-chip module (MCM) that contains an ASIC, memory devices, and analog circuitry. The ASIC contains a microprocessor, a MIL-STD-1553B/-1773 bus interface, and many industry standard devices. The memory includes program-, data- and shared-RAM. The analog logic includes a 16-channel A/D converter, an 8-channel 1.0 mA current source, and an analog power strobing circuit. The ESN MCM is a low-power ( 100K), industry standard, spacecraft control and data system, which eliminates custom interfaces by choosing a set of industry standard interfaces. This paper describes how the ESN provides a standard interface to the spacecraft's bus and its sub-systems. It also describes the plug-and-play standard, Open Firmware, and our plans to port it to the spacecraft environment.