J. Hanley

Ralph: A Visible/Infrared Imager for the New Horizons Pluto/Kuiper Belt Mission

The New Horizons instrument named Ralph is a visible/near infrared multi-spectral imager and a short wavelength infrared spectral imager. It is one of the core instruments on New Horizons, NASA’s first mission to the Pluto/Charon system and the Kuiper Belt. Ralph combines panchromatic and color imaging capabilities with SWIR imaging spectroscopy. Its primary purpose is to map the surface geology and composition of these objects, but it will also be used for atmospheric studies and to map the surface temperature. It is a compact, low-mass (10.5 kg) power efficient (7.1 W peak), and robust instrument with good sensitivity and excellent imaging characteristics. Other than a door opened once in flight, it has no moving parts. These characteristics and its high degree of redundancy make Ralph ideally suited to this long-duration flyby reconnaissance mission.

The Solar Wind Around Pluto (SWAP) Instrument Aboard New Horizons

Abstract The Solar Wind Around Pluto (SWAP) instrument on New Horizons will measure the interaction between the solar wind and ions created by atmospheric loss from Pluto. These measurements provide a characterization of the total loss rate and allow us to examine the complex plasma interactions at Pluto for the first time. Constrained to fit within minimal resources, SWAP is optimized to make plasma-ion measurements at all rotation angles as the New Horizons spacecraft scans to image Pluto and Charon during the flyby. To meet these unique requirements, we combined a cylindrically symmetric retarding potential analyzer with small deflectors, a top-hat analyzer, and a redundant/coincidence detection scheme. This configuration allows for highly sensitive measurements and a controllable energy passband at all scan angles of the spacecraft.

Effects of tensile loading on the properties of elastic-wave propagation in a strand

Effects of tensile loading on the properties of longitudinal-mode elastic-wave propagation in a 1.52-cm-diam, seven-wire strand used for prestressed concrete structures were investigated experimentally. In an unloaded state, the wave propagation properties in strand matched those seen in individual wires comprising the strand, namely, straight center wire and helical outer wires. In the strand, however, extraneous signals were found to be produced from the propagating wave due to physical interactions between the adjacent wires. Under tensile loading, it was observed that a certain portion of the frequency components of the wave became highly attenuative and, thus, absent in the frequency spectrum of the wave. The center frequency of this missing portion, called notch frequency, was found to increase linearly with log N, where N is the applied tensile load. In addition, on both sides of the notch frequency, the wave exhibited a large dispersion in a manner similar to the behavior near a cutoff frequency. ...

The Rosetta Ion and Electron Sensor (IES) measurement of the development of pickup ions from comet 67P/Churyumov‐Gerasimenko

The Rosetta Ion and Electron Sensor (IES) has been measuring solar wind ions intermittently since exiting from hibernation in May 2014. On 19 August, when Rosetta was ~80 km from the comet 67P/Churyumov-Gerasimenko, which was ~3.5 AU from the Sun, IES began to see ions at its lowest energy range, ~4–10 eV. We identify these as ions created from neutral species emitted by the comet nucleus, photoionized by solar UV radiation in the neighborhood of the Rosetta spacecraft (S/C), and attracted by the small negative potential of the S/C resulting from the population of thermal electrons. Later, IES began to see higher-energy ions that we identify as having been picked up and accelerated by the solar wind. IES continues to measure changes in the solar wind and the development of the pickup ion structure.

Detection of corrosion in pipe using the magnetostrictive sensor technique

A technique for inspecting steel pipes or tubes using magnetostrictive sensors (MsSs) is described. Signals acquired from approximately 6.6-m-long, 164-mm-diameter, 5-mm-wall steel pipes before and after inducing a simulated corrosion defect are given. The data show that the MsS technique is very sensitive to corrosion-type defects and can be used for 100% volumetric inspection of a long segment of piping from a single sensor location. Also, the ability to operate the sensor with a substantial gap to the outside surface of pipe makes the MsS technique suitable for inspection of piping under thermal insulation or lagging.

Magnetostrictive sensors for the characterization of corrosion in rebars and prestressing strands

The feasibility of characterizing the severity of corrosion in reinforcing bars and prestressing strands was investigated using the magnetostrictive sensor (MsS) technique and time-frequency analysis. Relatively high bandwidth elastic waves were generated and detected in these steel members using the MsS technique. The detected signals wee then analyzed for their dispersion characteristics and attenuation with time-frequency analysis. In both rebars and strands, the wave attenuation was found to increase with an increased degree of corrosion. Wave attenuation was found to increase significantly when strands and rebar were cast in concrete. Initial studies showed that low frequencies will be needed to operate over a significant distance in concrete.

Recent developments in nondestructive evaluation of steel strands and cables using magnetostrictive sensors

Recent developments in magnetostrictive sensor (MsS) technology and its application to nondestructive evaluation (NDE) and monitoring of steel strands and cables are described. Areas of development include sensor design, instrumentation, signal processing, and NDE techniques. Examples of MsS application to NDE of steel strands are given, including monitoring of wire fracture events, inspection for fractured wires, and measurement of the applied load.

Simulators, software and small satellites: Testing in tight spaces

In the world of spacecraft integration and test, “Test As You Fly” (TAYF) is the mantra. This is sometimes easier said than done since methods to stimulate the various sensors can be difficult, and commanding many flight actuators while the spacecraft is sitting on the ground is impractical. As such, a mixture of sensor stimulation, sensor emulation and other environment simulations are used to dupe the spacecraft into believing it is flying, thus enabling the flight software (FSW) and control algorithms to be tested in their final flight configurations. When building and testing very small satellites, some additional obstacles are present. For example, installing external simulators and emulators necessary for activities such as attitude determination and control (AD&C) testing and mission simulations late in the integration schedule may be precluded due to a lack of physical access. Using special electrical ground support equipment (EGSE) interfaces to stimulate the spacecraft may introduce other challenges - no one wants to stand before a launch readiness review board and say that one set of FSW was used during final mission tests and simulations, but that another version will be loaded just prior to launch! The Cyclone Global Navigation Satellite System (CYGNSS) mission is a constellation of eight microsatellites that is currently in the integration and test phase. The CYGNSS payload is comprised of a set of Global Positioning System (GPS) receivers, which compare direct and ocean-reflected signals to measure surface wind speeds. Each microsat has a suite of AD&C sensors and actuators that must be simulated or stimulated during test. Designing a simulation and test environment that was cost-effective for a NASA Class D mission and dealt with the limitations of size, while maintaining a TAYF philosophy, presented significant challenges. This paper discusses how satellite size translated into challenges in the design of the FSW and EGSE, and how this impacted the overall test and simulation approach. Unique and creative solutions developed will be described, such as the use of “man-in-the-middle attack” techniques (commonly used by cyber hackers) to allow the FSW to execute normally even while communicating over non-flight interfaces. Finally, the pros and cons of the various design choices will be discussed.