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21.
The first 8.5m infrared heterodyne spectrometer has been constructed using tuneable semiconductor (PbSe) diode lasers and was used to measure absorption line profiles of N2O in the laboratory and black body emission from the Moon and from Mars. Spectral information was recorded over a 200 MHz bandwidth using an 8-channel filter bank. The resolution was 25 MHz (6 × 10–6
m) and the minimum detectable (black-body) power was 1 × 10–16 W for 8 min of integration. The results demonstrate the usefulness of heterodyne spectroscopy for the study of remote and local sources in the infrared.We wish to thank Dr Jack Butler and Craig Simpson (Arthur D. Little, Inc.) for their continuing (and successful) efforts to grow better diode lasers during the course of this experiment. We thank the National Radio Astronomy Observatory for the loan of a 40-channel filter bank and associated mini-computer.We thank en masse the dozens of people who loaned equipment to us for the duration of this experiment, and the commercial firms (especially Harshaw, Inc.) which expedited orders for crucial equipment. We thank Dr Bertram Donn, Dr Norman Ness, and Dr George Pieper for administrative, scientific, and financial support; and we thank Mr James Faris for technical assistance and Dr Sol Glicker for preparation of sample gas cells. We thank Dr Thomas Clark for providing the Kohoutek ephemeris, sighting printout, and predicted molecular line positions and for advice and the loan of some equipment. Finally, we wish to acknowledge the strong support accorded us by our wives and families who scarcely saw us during this period. 相似文献
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A pulse compression matched filter is analyzed so that the response may be computed when the pulse width, FM rate, and center frequency simultaneously differ from design conditions. Unilateral and bilateral time domain amplitude weighting for sidelobe reduction is included. A general cross-ambiguity function is defined to include these effects and some basic computed results are presented for the peak envelope response with various degrees of Hamming weighting. Computer evaluation of this cross-ambiguity function allows one to choose a combination of mismatches for signal design trade-off between resolution and detection performance. Since no restrictions are placed upon the mismatch parameters, this analysis may also be used to evaluate the filter discrimination against various interfering signals. 相似文献
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Christoph Noeldeke Maximilian Boettcher Ulrich Mohr Steffen Gaisser Mikel Alvarez Rua Jens Eickhoff Mike Leslie Matt Von Thun Sabine Klinkner Renuganth Varatharajoo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(6):2000-2009
The radiation effects in electronic parts are called single-event effects, which are deemed to be critical for space missions. This paper presents the Single Event Upsets that were observed in an onboard memory device of the Low Earth Orbit “Flying Laptop” satellite mission during its in-orbit operation. The Single Event Upsets were carefully mapped on the satellite orbital space itself and their root causes were investigated together with their rates of occurrence. Subsequently, the events were traced to show several root cause sources such as (i) trapped energetic protons leaking to low altitudes within the South Atlantic Anomaly, (ii) Solar Energetic Particles emitted by an impulsive event on 10 September 2017, and (iii) Galactic Cosmic Rays. A profound analysis was carried out on the observed flight data, and its corresponding results are actually in agreement with the standard energetic particle models. The presented results provide another important insight on the Single Event Upsets for future Low Earth Orbit satellite missions. 相似文献
24.
T. Joseph W. Lazio R.J. MacDowall Jack O. Burns D.L. Jones K.W. Weiler L. Demaio A. Cohen N. Paravastu Dalal E. Polisensky K. Stewart S. Bale N. Gopalswamy M. Kaiser J. Kasper 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The Radio Observatory on the Lunar Surface for Solar studies (ROLSS) is a concept for a near-side low radio frequency imaging interferometric array designed to study particle acceleration at the Sun and in the inner heliosphere. The prime science mission is to image the radio emission generated by Type II and III solar radio burst processes with the aim of determining the sites at and mechanisms by which the radiating particles are accelerated. Specific questions to be addressed include the following: (1) Isolating the sites of electron acceleration responsible for Type II and III solar radio bursts during coronal mass ejections (CMEs); and (2) Determining if and the mechanism(s) by which multiple, successive CMEs produce unusually efficient particle acceleration and intense radio emission. Secondary science goals include constraining the density of the lunar ionosphere by searching for a low radio frequency cutoff to solar radio emission and constraining the low energy electron population in astrophysical sources. Key design requirements on ROLSS include the operational frequency and angular resolution. The electron densities in the solar corona and inner heliosphere are such that the relevant emission occurs at frequencies below 10 MHz. Second, resolving the potential sites of particle acceleration requires an instrument with an angular resolution of at least 2°, equivalent to a linear array size of approximately 1000 m. Operations would consist of data acquisition during the lunar day, with regular data downlinks. No operations would occur during lunar night. 相似文献
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26.
International Space Station power reinitialization 总被引:1,自引:0,他引:1
27.
Bilik I. Tabrikian J. Cohen A. 《IEEE transactions on aerospace and electronic systems》2006,42(1):267-278
An automatic target recognition (ATR) algorithm, based on greedy learning of Gaussian mixture model (GMM) is developed. The GMMs were obtained for a wide range of ground surveillance radar targets such as walking person(s), tracked or wheeled vehicles, animals, and clutter. Maximum-likelihood (ML) and majority-voting decision schemes were applied to these models for target classification. The corresponding classifiers were trained and tested using distinct databases of target echoes, recorded by ground surveillance radar. ML and majority-voting classifiers obtained classification rates of 88% and 96%, correspondingly. Both classifiers outperform trained human operators. 相似文献
28.
Andrew S. Rivkin Jian-Yang Li Ralph E. Milliken Lucy F. Lim Amy J. Lovell Britney E. Schmidt Lucy A. McFadden Barbara A. Cohen 《Space Science Reviews》2011,163(1-4):95-116
Our understanding of the composition of Ceres is driven by remote sensing of its surface. We review spectral observations of Ceres over wavelengths from the ultraviolet to the radio, as well as non-spectral data such as thermal inertia, photometric properties, radar experiments, and surface variability. We also discuss the closest likely meteorite analogs to Ceres and consider the likelihood that material from Ceres could be delivered to Earth. 相似文献
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R. A. Mewaldt C. M. S. Cohen G. M. Mason A. C. Cummings M. I. Desai R. A. Leske J. Raines E. C. Stone M. E. Wiedenbeck T. T. von Rosenvinge T. H. Zurbuchen 《Space Science Reviews》2007,130(1-4):207-219
Although the average composition of solar energetic particles (SEPs) and the bulk solar wind are similar in a number of ways,
there are key differences which imply that solar wind is not the principal seed population for SEPs accelerated by coronal
mass ejection (CME) driven shocks. This paper reviews these composition differences and considers the composition of other
possible seed populations, including coronal material, impulsive flare material, and interplanetary CME material. 相似文献