Engineering topics

Lesh, F.

Publications and source records attributed to Lesh, F..

3 records

NASA NTRS1977

A continuous/discrete simulation for interplanetary spacecraft

The paper gives a general description of a continuous/discrete simulator of the telemetry flow from an unmanned interplanetary spacecraft in flight. The real time simulation method is based on the trigger method, where a trigger is a set of control words which describe a condition and an action to be taken upon satisfaction of the condition. Simulation consists of finding the points at which the given condition is satisfied and taking the specified action. The paper describes the four kinds of triggers and how they are called. The calculational algorithm used to advance time in the simulator is briefly described.

Lesh, F.↗

NASA NTRS1976

Software techniques for a distributed real-time processing system

The paper describes software techniques developed for the Unified Data System (UDS), a distributed processor network for control and data handling onboard a planetary spacecraft. These techniques include a structured language for specifying the programs contained in each module, and a small executive program in each module which performs scheduling and implements the module task.

Lesh, F.↗

NASA NTRS1976

Distributed microprocessors for spacecraft control and data handling

The Unified Data System (UDS) group at JPL is attempting to reduce total mission costs by designing a spacecraft data system which takes advantage of the natural and historical partitioning of a spacecraft into subsystems. Each subsystem is assigned a microprocessor which needs just enough capability to control the sensors and actuators of that subsystem, collect its data and maintain time synchronization with the rest of the spacecraft. The resulting distributed system avoids many of the overhead costs of a single centralized multi-processing system. To minimize complexity and therefore minimize total mission costs, a variety of standards and restrictions are imposed on the design of hardware, software, and communications. Articulation of these standards and restrictions is a major benefit deriving from the UDS program.

Lesh, F.↗