Duncan M. Kahle

Simulation of a Miniature, Low-Power Time-of-Flight Mass Spectrometer for In Situ Analysis of Planetary Atmospheres

We are implementing nano- and micro-technologies to develop a miniaturized electron impact ionization mass spectrometer for planetary science. Microfabrication technology is used to fabricate the ion and electron optics, and a carbon nanotube (CNT) cathode is used to generate the ionizing electron beam. Future NASA planetary science missions demand miniaturized, low power mass spectrometers that exhibit high resolution and sensitivity to search for evidence of past and present habitability on the surface and in the atmosphere of priority targets such as Mars, Titan, Enceladus, Venus, Europa, and short-period comets. Toward this objective, we are developing a miniature, high resolution reflectron time-of-flight mass spectrometer (Mini TOF-MS) that features a low-power CNT field emission electron impact ionization source and microfabricated ion optics and reflectron mass analyzer in a parallel-plate geometry that is scalable. Charged particle electrodynamic modeling (SIMION 8.0.4) is employed to guide the iterative design of electron and ion optic components and to characterize the overall performance of the Mini TOF-MS device via simulation. Miniature (< 1000 cm3) TOF-MS designs (ion source, mass analyzer, detector only) demonstrate simulated mass resolutions > 600 at sensitivity levels on the order of 10-3 cps/molecule N2/cc while consuming 1.3 W of power and are comparable to current spaceflight mass spectrometers. Higher performance designs have also been simulated and indicate mass resolutions ~1000, though at the expense of sensitivity and instrument volume.

A miniature MEMS and NEMS enabled time-of-flight mass spectrometer for investigations in planetary science

Solar system exploration and the anticipated discovery of biomarker molecules is driving the development of a new miniature time-of-flight (TOF) mass spectrometer (MS). Space flight science investigations become more feasible through instrument miniaturization, which reduces size, mass, and power consumption. However, miniaturization of space flight mass spectrometers is increasingly difficult using current component technology. Micro electro mechanical systems (MEMS) and nano electro mechanical systems (NEMS) technologies offer the potential of reducing size by orders of magnitude, providing significant system requirement benefits as well. Historically, TOF mass spectrometry has been limited to large separation distances as ion mass analysis depends upon the ion flight path. Increased TOF MS system miniaturization may be realized employing newly available high speed computing electronics, coupled with MEMS and NEMS components. Recent efforts at NASA Goddard Space Flight Center in the development of a miniaturized TOF mass spectrometer with integral MEMS and NEMS components are presented. A systems overview, design and prototype, MEMS silicon ion lenses, a carbon nanotube electron gun, ionization methods, as well as performance data and relevant applications are discussed.

Performance of the QWIP focal plane arrays for NASA's Landsat Data Continuity Mission

The focal plane assembly for the Thermal Infrared Sensor (TIRS) instrument on NASAs Landsat Data Continuity Mission (LDCM) consists of three 512 x 640 GaAs Quantum Well Infrared Photodetector (QWIP) arrays. The three arrays are precisely mounted and aligned on a silicon carrier substrate to provide a continuous viewing swath of 1850 pixels in two spectral bands defined by filters placed in close proximity to the detector surfaces. The QWIP arrays are hybridized to Indigo ISC9803 readout integrated circuits (ROICs). QWIP arrays were evaluated from four laboratories; QmagiQ, (Nashua, NH), Army Research Laboratory, (Adelphi, MD), NASA/ Goddard Space Flight Center, (Greenbelt, MD) and Thales, (Palaiseau, France). All were found to be suitable. The final discriminating parameter was the spectral uniformity of individual pixels relative to each other. The performance of the QWIP arrays and the fully assembled, NASA flight-qualified, focal plane assembly will be reviewed. An overview of the focal plane assembly including the construction and test requirements of the focal plane will also be described.

Mechanisms and Temperature Dependence of Single Event Latchup Observed in a CMOS Readout Integrated Circuit From 16–300 K

Heavy ion-induced single event latchup (SEL) is characterized in a commercially available CMOS readout integrated circuit operating at cryogenic temperatures. SEL observed at 24 K and below is believed to be possible when free carriers produced by an ion strike initiate an exponential increase in the free carrier density via shallow-level impact ionization (SLII). This results in a large current increase that proceeds to a sustained latched state, even though the classic condition for parasitic bipolar gain product is not met since it is much less than unity. The LET threshold for SEL is significantly lower at 20 K as compared to 300 K although the saturated cross section is 2-3 times higher at 300 K. The temperature dependence of the SEL cross section is characterized from 16-300 K. SEL behavior attributed to the classical cross-coupled parasitic bipolar model is observed from ~135-300 K, and the reduction in the SEL cross section is remarkably modest as the temperature is lowered from room temperature to ~200 K. Temperature dependent electrical latchup characterization of a 130 nm pnpn test structure also indicates a change in the latchup behavior at ~50 K consistent with the SLII mechanism.

Wide field instrument preliminary design for the Wide Field InfraRed Survey Telescope

We present the Wide Field Infra-Red Survey Telescope (WFIRST) wide field instrument concept based on the reuse of a 2.4m telescope recently made available to NASA. Two instrument channels are described, a wide field channel (~0.8x0.4degrees, 300Mpix, imaging and spectroscopy over 0.76-2.0um), and an integral field unit (3x3 arcsec, 1Mpix, R{2pixel} ~100 over 0.6-2.0um). For this mission concept, the telescope, instruments, and spacecraft are in a geosynchronous orbit and are designed for serviceability. This instrument can accomplish not only the baseline exoplanet microlensing, dark energy, and infrared surveys for WFIRST, but can perform at higher angular resolution and with deeper observations. This enables significant opportunities for more capable general observer programs. The emphasis on achieving very good imaging stability is maintained from the previous work.

An advanced airborne multisensor imaging system for fast mapping and change detection applications

The advanced airborne multisensor imaging system (AAMIS) has been developed for a light fixed wing aircraft. It integrates a suite of state-of-the-art electro-optical (EO), thermal, hyperspectral, and Lidar imaging instrument packages for simultaneous active ranging and passive imaging that covers the electromagnetic (EM) spectrum of the visible and near infrared range and the long-wave infrared range. AAMIS has been tested for todays fast mapping and change detection needs. It demonstrates leading performance in providing comprehensive geometric and geophysical aerial image products with high spatial, spectral, radiometric, temporal and range resolutions. High resolution innovative data products collected by AAMIS sensors are presented. These include 3.5 cm resolution orthomosaics for a complete 15 km times 25 km large area coverage, 1 ft resolution hyperspectral images with contiguous 10 nm spectral resolution for the 410-820 nm range, 0.02 K resolution thermal images in a large 1 k by 1 k frame video format, and 20 cm range accuracy 3D Lidar mapping products.

ACCESS: design and preliminary performance

ACCESS, Absolute Color Calibration Experiment for Standard Stars, is a series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35.1.7μm bandpass. Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant to many astrophysical problems. Systematic errors associated with problems such as dark energy now compete with the statistical errors and thus limit our ability to answer fundamental questions in astrophysics. The ACCESS design, calibration strategy, and an updated preliminary performance estimate are discussed.

Performance overview of the Euclid infrared focal plane detector subsystems

In support of the European space agency (ESA) Euclid mission, NASA is responsible for the evaluation of the H2RG mercury cadmium telluride (MCT) detectors and electronics assemblies fabricated by Teledyne imaging systems. The detector evaluation is performed in the detector characterization laboratory (DCL) at the NASA Goddard space flight center (GSFC) in close collaboration with engineers and scientists from the jet propulsion laboratory (JPL) and the Euclid project. The Euclid near infrared spectrometer and imaging photometer (NISP) will perform large area optical and spectroscopic sky surveys in the 0.9-2.02 μm infrared (IR) region. The NISP instrument will contain sixteen detector arrays each coupled to a Teledyne SIDECAR application specific integrated circuit (ASIC). The focal plane will operate at 100K and the SIDECAR ASIC will be in close proximity operating at a slightly higher temperature of 137K. This paper will describe the test configuration, performance tests and results of the latest engineering run, also known as pilot run 3 (PR3), consisting of four H2RG detectors operating simultaneously. Performance data will be presented on; noise, spectral quantum efficiency, dark current, persistence, pixel yield, pixel to pixel uniformity, linearity, inter pixel crosstalk, full well and dynamic range, power dissipation, thermal response and unit cell input sensitivity.

ACCESS: design and sub-system performance

Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant to many astrophysical problems. ACCESS, “Absolute Color Calibration Experiment for Standard Stars”, is a series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35-1.7µm bandpass.

Modeling effects of common molecular contaminants on the Euclid infrared detectors

Cleanliness specifications for infrared detector arrays are usually so stringent that effects are neglibile. However, the specifications determine only the level of particulates and areal density of molecular layer on the surface, but the chemical composition of these contaminants are not specified. Here, we use a model to assess the impact on system quantum efficiency from possible contaminants that could accidentally transfer or cryopump to the detector during instrument or spacecraft testing and on orbit operation. Contaminant layers thin enough to meet typical specifications, < 0.5μgram/cm2, have a negligible effect on the net quantum efficiency of the detector, provided that the contaminant does not react with the detector surface, Performance impacts from these contaminant plating onto the surface become important for thicknesses 5 - 50μgram/cm2. Importantly, detectable change in the ”ripple” of the anti reflection coating occurs at these coverages and can enhance the system quantum efficiency. This is a factor 10 less coverage for which loss from molecular absorption lines is important. Thus, should contamination be suspected during instrument test or flight, detailed modelling of the layer on the detector and response to very well known calibrations sources would be useful to determine the impact on detector performance.