Performance Benchmarking and Analysis of Prognostic Methods for CMAPSS Datasets

Six years and more than seventy publications later this paper looks back and analyzes the development of prognostic algorithms using C-MAPSS datasets generated and disseminatedby the prognostic center of excellence at NASA Ames Research Center. Among those datasets are five run-to-failure CMAPSS datasets that have been popular due to various characteristicsapplicable to prognostics. The C-MAPSS datasets pose several challenges that are inherent to general prognostics applications. In particular, management of high variability due to sensor noise, effects of operating conditions, and presence of multiple simultaneous fault modes are some factors that have great impact on the generalization capabilities of prognostics algorithms. More than seventy publications have used the C-MAPSS datasets for developing datadriven prognostic algorithms. However, in the absence of performance benchmarking results and due to common misunderstandings in interpreting the relationships between these datasets, it has been difficult for the users to suitably compare their results. In addition to identifying differentiating characteristics in these datasets, this paper also provides performance results for the PHM’08 data challenge wining entries to serve as performance baseline. This paper summarizes various prognostic modeling efforts that used C-MAPSS datasets and provides guidelines and references to further usage of these datasets in a manner that allows clear and consistent comparison between different approaches.

A Teller of Tales

Bradbury’s six-year odyssey to celebrate and explore the history of Halloween opens chapter 3, culminating in the shift from a screen project to the 1972 publication of The Halloween Tree. In 1972 Bradbury also opened the “Cosmic Evolution” lecture series in San Francisco, sponsored in part by the NASA/Ames Research Center. Chapter 3 concludes with Bradbury’s entry into the world of writing conferences, first with Writer’s Community at Squaw Valley and then with the annual Santa Barbara Writers’ Conference, where he would lecture and work with writers for more than thirty years. At the urging of Shel Dorf, Bradbury’s role as a perennial featured presence at the San Diego Comic Con also began in the early 1970s.

Bioinspired Optical Sensor for Remote Measurement of Small Displacements at a Distance

Identifying appropriate sites for landing a spacecraft or building permanent structures is critical for extraterrestrial exploration. By tracking the movement of land masses and structures on a planetary surface, scientists can better predict issues that could affect the integrity of the site or structures. A lightweight, low-cost, low-power bioinspired optical sensor is being developed at the National Aeronautics and Space Administration (NASA) Ames Research Center to remotely measure small displacements of land masses on either side of a fault. This paper describes the sensor, which is inspired by the compound eye vision system found in many insects, and the algorithms developed to estimate displacement. The results are presented for indoor and outdoor tests using the sensor to measure the displacement of a specially designed target that is located 0.35, 6, and 30 m from the sensor and is moved 10 mm to the left and right of a centered position, simulating the displacement of land masses on either side of a fault. Measurement uncertainties estimates were a few tenths of a millimeter when the target was located 0.35 and 6 m from the sensor. At the 30 m distance, corrections were required to obtain accuracies in the order of 1 mm.

A new non-resonant laser-induced fluorescence instrument for the airborne in situ measurement of formaldehyde

A new in situ instrument for gas-phase formaldehyde (HCHO), COmpact Formaldehyde FluorescencE Experiment (COFFEE), is presented. COFFEE utilizes non-resonant laser-induced fluorescence (NR-LIF) to measure HCHO, with 300 mW of 40 kHz 355 nm laser output exciting multiple HCHO absorption features. The resulting HCHO fluorescence is collected at 5 ns resolution, and the fluorescence time profile is fit to yield the ambient HCHO mixing ratio. Typical 1σ precision at ∼ 0 pptv HCHO is 150 pptv for 1 s data. The compact instrument was designed to operate with minimal in-flight operator interaction and infrequent maintenance (1–2 times per year). COFFEE fits in the wing pod of the Alpha Jet stationed at the NASA Ames Research Center and has successfully collected HCHO data on 27 flights through 2017 March. The frequent flights, combined with a potentially long-term data set, makes the Alpha Jet a promising platform for validation of satellite-based column HCHO.

Ontologies to Support Customer Requirement Formulation in Aerospace Design

The major goal of customer requirement formulation is to achieve a common understanding between the project stakeholders and the engineering requirements. Many times, this process can be ambiguous, incomplete, and time consuming especially when more than one engineering discipline is involved. Therefore, adequate requirement formulation tools can be a major contributor to solving these challenges. The use of ontologies provides a standardized way of describing concepts in a domain of interest and the relationships between these concepts to better understand the domain as a whole. This paper describes the methodology used to create an ontology derived from twenty customer requirements of a mid-size, twin-engine, commercial transport-class aircraft provided by NASA Ames Research Center. One key stipulation that NASA had was that this ontology effectively captures the relationships that exist between the hardware and software level of each customer requirement. The final ontology was created using Protégé OWL, an open source ontology editor, which will be used by NASA in order to improve the customer requirement creation phase of future NASA products. The ontology and requirements were further generalized into a set of common patterns for describing requirements in this domain. These pattern templates provide a tool to ensure that common styles of requirements have been considered, and that these common styles are uniform. This research paper fills a gap in the customer requirement research field by introducing the use of ontologies and common patterns to reduce ambiguity and repetition.

A new non-resonant laser-induced fluorescence instrument for the airborne in situ measurement of formaldehyde

A new in situ instrument for gas-phase formaldehyde (HCHO), COmpact Formaldehyde FluorescencE Experiment (COFFEE), is presented. COFFEE utilizes non-resonant laser-induced fluorescence (NR-LIF) to measure HCHO, with 300 mW of 40 kHz 355 nm laser output exciting multiple HCHO absorption features. The resulting HCHO fluorescence is collected at 5 ns resolution, and the fluorescence time profile is fit to yield the ambient HCHO mixing ratio. Typical 1-σ precision at ~ 0 pptv HCHO is 150 pptv for 1 s data. The compact instrument was designed to operate with minimal in-flight operator interaction and infrequent maintenance (1–2 times per year). COFFEE fits in the wing pod of the Alpha Jet stationed at NASA Ames Research Center and has successfully collected HCHO data on 27 flights through 2017 March. The frequent flights, combined with a potentially long-term data set, makes the Alpha Jet a promising platform for validation of satellite-based column HCHO.