827 research outputs found

    Spacecraft Applications of Compact Optical and Mass Spectrometers

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    Optical spectrometers, and mass spectrometers to a lesser extent, have a long and rich history of use aboard spacecraft. Space mission applications include deep space science spacecraft, earth orbiting satellites, atmospheric probes, and surface landers, rovers, and penetrators. The large size of capable instruments limited their use to large, expensive spacecraft. Because of the novel application of micro-fabrication technologies, compact optical and mass spectrometers are now available. The new compact devices are especially attractive for spacecraft because of their small mass and volume, as well as their low power consumption. Dispersive optical multi-channel analyzers which cover the 0.4-1.1 micrometer wavelength are now commercially available in packages as small as 3 x 6 x 18 mm exclusive of drive and recording electronics. Mass spectrometers as small as 3 x 3 mm, again without electronics, are under development. A variety of compact optical and mass spectrometers are reviewed in this paper. A number of past space applications are described, along with some upcoming opportunities that are likely candidate missions to fly this new class of compact spectrometers

    Design and fabrication of optical filters for long wavelength spectroscopy application

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    The design and fabrication of thin film Fabry-Perot interferometer (FPI) for long wavelength spectroscopy application is demonstrated. The system is designed to be integrated in a small portable spectrometer for the measurement of molecular absorption or emission as well as substance that has an infrared signature. A Fabry-Perot interferometer with dielectric mirrors was fabricated using fabrication process on a silicon substrate. The FPI was made of multi thin layers, deposited on silicon (Si) substrate, alternating between high and low refractive-index (n) layers. Si was used as a substrate due to the high precision of etching achievable using conventional VLSI fabrication techniques. Since the wavelength of interest was in the far infrared (5 to 15 micrometers), the layers were selected carefully to minimize the thickness required to meet the quarter-wave optical-thickness criteria for the interferometer. Another criterion that had to be met is the ratio of the refractive indices (n) between the layers. In this study, we have utilized germanium (Ge), which has n value of ~ 4 in the wavelength range of interest, and zinc oxide (ZnO), which has n value average of ~1.8 in the range of interest. Deposition of the layers was carried out using electron beam deposition for Ge and sputtering for ZnO. First the Si substrate was etched precisely to provide the gap needed for the wavelengths on interest and then the dielectric layers were deposited. For example, using Ge thickness of 0.576 µm, ZnO thickness of 1.22 µm, and a gap of 4.77 µm, we have demonstrated a filter transmitting a wavelength of 9.2 micrometers with a full width at half maximum of ~ 0.5 microns using one stack of Ge/ZnO layers. Simulations, using Freesnell software, were consistent with the experimental results. The tuning of the FPI with different cavity distances was demonstrated by measuring the transmission spectrum of the FPI. The transmission measurement was carried out using Fourier Transform Infrared Spectroscopy (FTIR) while the thickness of the layers was confirmed by scanning electron microscopy (SEM)

    Remote photothermal actuation for calibration of in-phase and quadrature readout in a mechanically amplified Fabry-Pérot accelerometer

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    A mechanically amplified Fabry-Pérot optical accelerometer is reported in which photothermal actuation is used to calibrate the in-phase and quadrature (I&Q) readout. The Fabry-Pérot interferometer (FPI) is formed between a gold-coated silicon mirror, situated in the middle of a V-beam amplifier, and the end surface of a cleaved optical fiber. On the opposite side of the silicon mirror, a further cleaved optical fiber transmits near-infrared laser light (λ = 785 nm), which is absorbed by the uncoated silicon causing heating. The thermal expansion of the V-beam is translated into an amplified change in cavity length of the FPI, large enough for the 2π-phase variation necessary for I&Q calibration. A simple 1D thermal analysis of the structure has been developed to predict the relationship between laser power and change in cavity length. A device having a V-beam of length 1.8 mm, width 20 μm, and angle 2 ° was found to undergo a cavity length change of 785 nm at 30 mW input power. The device response was approximately linear for input accelerations from 0.01 to 15 g. The noise was measured to be ~ 60 μg/√Hz from 100 Hz to 3.0 kHz, whereas the limit of detection was 47.7 mg from dc to 3.0 kHz

    Use of a Novel Infrared Wavelength-tunable Laser Mueller-matrix Polarimetric Scatterometer to Measure Nanostructured Optical Materials

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    Nanostructured optical materials, for example, metamaterials, have unique spectral, directional, and polarimetric properties. Samples designed and fabricated for infrared (IR) wavelengths have been characterized using broadband instruments to measure specular polarimetric transmittance or reflectance as in ellipsometry or integrated hemisphere transmittance or reflectance. We have developed a wavelength-tunable IR Mueller-matrix (Mm) polarimetric scatterometer which uses tunable external-cavity quantum-cascade lasers (EC-QCLs) to tune onto and off of the narrowband spectral resonances of nanostructured optical materials and performed full polarimeteric and directional evaluation to more fully characterize their behavior. Using a series of EC-QCLs, the instrument is tunable over 4.37-6.54 μm wavelengths in the mid-wave IR and 7.41-9.71 μm in the long-wave IR and makes measurements both at specular angles, acting as a Mm polarimeter, and at off-specular angles, acting as a Mm scatterometer. Example measurements of an IR thermal metamaterial are shown

    Advanced Exploration Technologies: Micro and Nano Technologies Enabling Space Missions in the 21st Century

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    Some of the many new and advanced exploration technologies which will enable space missions in the 21st century and specifically the Manned Mars Mission are explored in this presentation. Some of these are the system on a chip, the Computed-Tomography imaging Spectrometer, the digital camera on a chip, and other Micro Electro Mechanical Systems (MEMS) technology for space. Some of these MEMS are the silicon micromachined microgyroscope, a subliming solid micro-thruster, a micro-ion thruster, a silicon seismometer, a dewpoint microhygrometer, a micro laser doppler anemometer, and tunable diode laser (TDL) sensors. The advanced technology insertion is critical for NASA to decrease mass, volume, power and mission costs, and increase functionality, science potential and robustness

    Uncooled Carbon Microbolometer Imager

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    The discovery of infrared radiation two centuries ago and the theory of blackbody radiation one century later have given birth to the field of thermal imaging. Since then, researchers have devised numerous ways to detect infrared radiation. From World War II to the 1980s, semiconductor-based cooled photon detector arrays have reigned over the field of thermal imaging. Albeit limited to expensive, bulky systems used for military applications due to their cooling requirement they have been . The emergence of micromachining techniques in the 1980s however, have allowed for the development of uncooled, thermal detector arrays. Uncooled systems are expected to find more and more applications, especially in the civilian world. Here we present a novel and simple way to fabricate uncooled infrared detectors suitable for integration into large-area arrays. The design is based on carbon obtained by means of polymer pyrolysis. We demonstrate how some electrical and thermal properties can be adjusted by process parameters, and then present the first micromachined carbon uncooled bolometer made of two-layers of self-supporting pyrolyzed-parylene carbon having different process-tuned properties. Finally, based on this unique design and fabrication process, we develop a carbon bolometer array and demonstrate the thermal imaging capability by taking thermal images. Measurements show that the sensitivity to target temperature can be as low as 31mK and 44mK for 100us and 12us electrical signal integration time, respectively. This matches the current state of the art which is very promising considering the fact that this is the first time pyrolytic carbon has been used to fabricate a microbolometer array.</p
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