Engineering topics

Lindenmayer, Kelly

Publications and source records attributed to Lindenmayer, Kelly.

4 records

NASA NTRS1988

Knowledge based tools for Hubble Space Telescope planning and scheduling: Constraints and strategies

The Hubble Space Telescope (HST) presents an especially challenging scheduling problem since a year's observing program encompasses tens of thousands of exposures facing numerous coupled constraints. Recent progress in the development of planning and scheduling tools is discussed which augment the existing HST ground system. General methods for representing activities, constraints, and constraint satisfaction, and time segmentation were implemented in a scheduling testbed. The testbed permits planners to evaluate optimal scheduling time intervals, calculate resource usage, and to generate long and medium range plans. Graphical displays of activities, constraints, and plans are an important feature of the system. High-level scheduling strategies using rule based and neural net approaches were implemented.

Miller, Glenn↗

NASA NTRS1988

The proposal entry processor: Telescience applications for Hubble Space Telescope science operations

The Proposal Entry Processor (PEP) System supports the submission, entry, technical evaluation review, selection and implementation of Hubble Space Telescope (HST) observing proposals. The PEP system is described concentrating on features which illustrate principles of telescience as applied to the HST. These principles are applicable to other observatories, both space and ground based. The PEP proposal forms allow a scientist to specify scientific objectives without becoming needlessly involved in implementation details. The Remote Proposal Submission System (RPSS) allows proposers to submit proposals electronically via Telenet, SPAN, and other networks. The RPSS performs syntax and sematic checks on proposals. The PEP uses a fourth generation database system to store proposal information and to allow general queries and reports. The Transformation subsystem uses an expert system written in OPS5 to cast a scientific description of an observing program into parameters used by the planning and scheduling system. The TACOS system is a natural language database which supports the proposal selection process. Technical evaluations for resource usage and duplicate science are performed using rulebased systems.

Jackson, Robert↗

NASA NTRS1988

Verification and validation of rulebased systems for Hubble Space Telescope ground support

As rulebase systems become more widely used in operational environments, the focus is on the problems and concerns of maintaining expert systems. In the conventional software model, the verification and validation of a system have two separate and distinct meanings. To validate a system means to demonstrate that the system does what is advertised. The verification process refers to investigating the actual code to identify inconsistencies and redundancies within the logic path. In current literature regarding maintaining rulebased systems, little distinction is made between these two terms. In fact, often the two terms are used interchangeably. Verification and validation of rulebased systems are discussed as separate but equally important aspects of the maintenance phase. Also described are some of the tools and methods that were developed at the Space Telescope Science Institute to aid in the maintenance of the rulebased system.

Vick, Shon↗

NASA NTRS1987

Maintaining an expert system for the Hubble Space Telescope ground support

The transformation portion of the Hubble Space Telescope (HST) Proposal Entry Processor System converts astronomer-oriented description of a scientific observing program into a detailed description of the parameters needed for planning and scheduling. The transformation system is one of a very few rulebased expert systems that has ever entered an operational phase. The day to day operations of the system and its rulebase are no longer the responsibility of the original developer. As a result, software engineering properties of the rulebased approach become more important. Maintenance issues associated with the coupling of rules within a rulebased system are discussed and a method is offered for partitioning a rulebase so that the amount of knowledge needed to modify the rulebase is minimized. This method is also used to develop a measure of the coupling strength of the rulebase.

Lindenmayer, Kelly↗