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Статті в журналах з теми "Occultation de la violence"

Автор: Grafiati

Опубліковано: 23 вересня 2022

Оновлено: 28 січня 2023

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1

Luis, Ballester Brage, Rosario Pozo Gordaliza, and Carmen Orte Socías. "Delocalized Prostitution: Occultation of the New Modalities of Violence." Procedia - Social and Behavioral Sciences 161 (December 2014): 90–95. http://dx.doi.org/10.1016/j.sbspro.2014.12.015.

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2

Lacombe, Delphine. "Visibilité et occultation des violences masculines envers les femmes au Nicaragua (1979-1996)." Problèmes d'Amérique latine 84, no. 2 (2012): 13. http://dx.doi.org/10.3917/pal.084.0013.

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3

Stahl, Don. "The Occultation." Chicago Review 40, no. 4 (1994): 19. http://dx.doi.org/10.2307/25305877.

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4

Dyson, Freeman J. "Occultation Astronomy." International Astronomical Union Colloquium 123 (1990): 413–15. http://dx.doi.org/10.1017/s0252921100077368.

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Анотація:

The era of occultation astronomy, studying dark objects by observing occultations of bright ones, has begun. The paper of Duncan, Quinn and Tremarne, “The Origin of Short-Period Comets”, Astrophys. J. Letters, 328, 69-73 (1988), greatly improved the prospects for occultation astronomy by demonstrating the existence of a second comet reservoir, the Kuiper Belt, much closer to us than the Oort Cloud and concentrated toward the ecliptic plane. Charles Alcock at Livermore (private communication) has begun work on a practical system of small telescopes to observe occultations of stars by comets. I here propose a system similar in concept of Alcock’s but using different hardware. We need to try various systems on a small scale to find out which are most cost-effective. My proposal is based on the Multiple Telescope Robotic Observatory (MTRO) developed by Boyd and Genet at Fairborn Observatory in Arizona. See Russell M. Genet, “Multiple-Telescope Robotic Observatories in Space”, submitted to P.A.S.P. (1990).

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5

Kammarti, Adrian. "La double occultation." Critique 901, no. 6 (May 24, 2022): 577–87. http://dx.doi.org/10.3917/criti.901.0577.

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6

Stagliano, J. J. "Dynamical occultation correction." Physics and Chemistry of the Earth, Part B: Hydrology, Oceans and Atmosphere 25, no. 10-12 (January 2000): 833–35. http://dx.doi.org/10.1016/s1464-1909(00)00111-8.

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7

Schaefer, Bradley E., Henk J. J. Bulder, and Jean Bourgeois. "Lunar occultation visibility." Icarus 100, no. 1 (November 1992): 60–72. http://dx.doi.org/10.1016/0019-1035(92)90018-3.

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8

Agol, Eric. "Occultation and Microlensing." Astrophysical Journal 579, no. 1 (November 2002): 430–36. http://dx.doi.org/10.1086/342880.

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9

Liu, Congliang, Gottfried Kirchengast, Yueqiang Sun, Veronika Proschek, Xin Wang, Longfei Tian, Qifei Du, et al. "Impacts of Orbital and Constellation Parameters on the Number and Spatiotemporal Coverage of LEO-LEO Occultation Events." Remote Sensing 13, no. 23 (November 29, 2021): 4849. http://dx.doi.org/10.3390/rs13234849.

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Анотація:

The development of small-satellite technologies allows the low Earth orbit intersatellite link (LEO-LEO) occultation method to observe the Earth’s atmosphere with global coverage and acceptable costs using electromagnetic signals, in which the L/X/K/M band and short-wave infrared band signals have been well demonstrated to be suitable. We hence need to investigate the impacts of orbital and constellation parameters on the number and spatiotemporal distribution of LEO-LEO occultation events for best-possible LEO-LEO occultation mission design and optimization at the targeted mission size. In this study, firstly, an occultation events location simulation model accounting for the right ascension of the ascending node (RAAN) precession was set up and the concept of a time-dependent global coverage fraction of occultation events was defined. Secondly, numerical experiments were designed to investigate the orbital parameters’ impacts and to assess the performance of LEO-LEO occultation constellations, in which the Earth is divided into 5° × 5° latitude and longitude cells. Finally, the number, timeliness, and global coverage fraction of occultation events for two-orbit and multi-orbit LEO-LEO constellations were calculated and analyzed. The results show that: ① the orbit inclination and RAAN are the main impacting parameters followed by orbital height, while the RAAN precession is a relevant modulation factor; ② co-planar counter-rotating receiving and transmitting satellite orbits are confirmed to be ideal for a two-satellite LEO-LEO constellation; ③ polar and near-polar orbit constellations most readily achieve global coverage of occultation events; near-equator orbit constellations with supplementary receiving and transmitting satellite orbit planes also readily form the occultation event geometry, though the occultation events are mainly distributed over low and low-to-middle latitude zones; and ④ a well-designed larger LEO-LEO occultation constellation, composed of 36–72 satellites, can meet the basic requirements of global numerical weather prediction for occultation numbers and timeliness, yielding 23,000–38,000 occultation events per day and achieving 100% global coverage in 12–18 h.

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10

Zhu, Qinglin, Mingchen Sun, Xiang Dong, and Pengfei Zhu. "Design and Simulation of Stellar Occultation Infrared Band Constellation." Remote Sensing 14, no. 14 (July 10, 2022): 3327. http://dx.doi.org/10.3390/rs14143327.

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Анотація:

This study provides an in-depth analysis of the characteristics of stellar occultation events. Using 10 target star sources, the influence of orbital elements on the number, duration, and distribution of stellar occultation events was simulated and analyzed, and the constellation configuration was designed. The results showed the following points: (1) the orbital inclination had the greatest influence on the number of occultation events, with obvious upward and downward trends in the range of 10–40° and 150–180°, and the amount of occultation data remained at about 303 times under the other angle conditions. The orbital height had an effect on the number of occultations, but the amplitude was small. (2) The use of four orbits had an impact on the occultation duration. The duration decreased with an increase in the orbit height and inclination, the distribution was symmetrical with the perigee angular distance, and it increased with an increase in the ascending intersection right ascension. (3) The higher the orbital height, the less comprehensive the longitudinal and latitudinal distribution of occultation events. With an orbital inclination of less than 150°, the greatest occultation event was covered to encompass the entire world. The other two orbital elements had negligible effects on the longitudinal and latitudinal distribution of occultation events. (4) The elevation of the occultation event increased with an increase in the orbital altitude, but the azimuth showed no obvious change trends. A considerable number of normal occultations can be obtained with an orbital inclination of less than 120°. The other two orbital elements had a negligible effect on the distribution of altitude and azimuth of occultation events. A stellar occultation constellation configuration was designed based on the simulation results, and the results showed that the following parameters of satellites can be used to realize the global distribution of occultation events: orbital height of 500 km, orbital inclination of 97.3771°, perigee angular distance of 40°, and ascending node right ascension steps of 40°. This configuration will ensure that an adequate number of normal occultations are obtained, which will ensure the quality of data inversion under the condition of 152 infrared target star sources.

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11

Trigano, Shmuel. "La raison d'une occultation." Pardès 34, no. 1 (2003): 16. http://dx.doi.org/10.3917/parde.034.0016.

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12

Russell, James M., Larry L. Gordley, Jae H. Park, S. Roland Drayson, W. Donald Hesketh, Ralph J. Cicerone, Adrian F. Tuck, John E. Frederick, John E. Harries, and Paul J. Crutzen. "The Halogen Occultation Experiment." Journal of Geophysical Research 98, no. D6 (1993): 10777. http://dx.doi.org/10.1029/93jd00799.

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13

Fraser, Wesley C., Stephen Gwyn, Chad Trujillo, Andrew W. Stephens, J. J. Kavelaars, Michael E. Brown, Federica B. Bianco, et al. "Kuiper Belt Occultation Predictions." Publications of the Astronomical Society of the Pacific 125, no. 930 (August 2013): 1000–1014. http://dx.doi.org/10.1086/672001.

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14

Martin-Neira, Manuel. "GNSS Interferometric Radio Occultation." IEEE Transactions on Geoscience and Remote Sensing 54, no. 9 (September 2016): 5285–300. http://dx.doi.org/10.1109/tgrs.2016.2559944.

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15

Han, Cheongho, Vijay K. Narayanan, and Andrew Gould. "Lunar Occultation of MACHOs." Astrophysical Journal 461 (April 1996): 587. http://dx.doi.org/10.1086/177086.

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16

Gorbanev, Yu M., V. V. Kleshchonok, and S. R. Kimakovsky. "OBSERVATION OF AN OCCULTATION OF THE UCAC4 488-082551 STAR BY ASTEROID (76228) 2000 EH 75 ON 31 MAY 2022." Odessa Astronomical Publications 35 (December 14, 2022): 71–73. http://dx.doi.org/10.18524/1810-4215.2022.35.268213.

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Анотація:

Observations of an occultation of the UCAC4 488-082551 star by asteroid (76228) 2000 EH 75 were carried out on 31 May 2022 at Kryzhanivka observation station of Odesa I. I. Mechnykov National University (the observatory code A85). A set of instruments, which included a Schmidt telescope (the primary mirror diameter D = 271.25 mm; the corrector plate diameter D k = 223.9 mm; the focal length F = 440 mm), a GPS receiver and Videoscan-415-2001 CCD camera, was used to perform observations. The observing conditions were as follows: clear sky, the star’s altitude 49 0 south, the Moon was below the local horizon. The target star from the UCAC4 catalogue (Zacharias et al. 2013) has the following photometric parameters: m B = 14.008; m V = 12.720; m r = 12.284; m i = 11.813. The diameter of the star has not been determined. Asteroid (76228) is a Main Belt asteroid with an orbital period of 4.17178 years. It has an absolute magnitude of 14.93, the visible geometric albedo of 0.123±0.013 and diameter of 5.00±0.23 km (Masiero et al. 2011). The time of occultation predicted using ephemerides was 23:52:44±4 sec. The maximum duration of the occultation was 0.4 sec, provided that the observing site was located at the centre of the occultation track (strip). A drop in the star’s brightness observed during occultation was about 8 m . The occultation event was recorded as a sequence of GIF images with the exposure time of 0.5 sec per frame. The system clock of the computer used for the occultation recording was controlled with a GPS receiver in a fashion similar to that described in the paper by Karbovsky et al. (2017). The data processing yielded an estimate of the occultation duration of 0.46±0.04 sec. The uncertainty of the occultation start time within exposure results in the total estimate of accuracy in timing the maximum phase of occultation 23:52:44.06±0.10 sec. The chord length across the asteroid estimated by timing the occultation is L = 9.2±0.8. This chord length is close to the estimates of the asteroid diameter reported in the paper by Masiero et al. (2011).

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17

Azam, F., K. Bramstedt, A. Rozanov, K. Weigel, H. Bovensmann, G. P. Stiller, and J. P. Burrows. "SCIAMACHY lunar occultation water vapor measurements: retrieval and validation results." Atmospheric Measurement Techniques 5, no. 10 (October 24, 2012): 2499–513. http://dx.doi.org/10.5194/amt-5-2499-2012.

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Abstract. SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) lunar occultation measurements have been used to derive vertical profiles of stratospheric water vapor for the Southern Hemisphere in the near infrared (NIR) spectral range of 1350–1420 nm. The focus of this study is to present the retrieval methodology including the sensitivity studies and optimizations for the implementation of the radiative transfer model on SCIAMACHY lunar occultation measurements. The study also includes the validation of the data product with the collocated measurements from two satellite occultation instruments and two instruments measuring in limb geometry. The SCIAMACHY lunar occultation water vapor measurement comparisons with the ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer) instrument have shown an agreement of 5% on the average that is well within the reported biases of ACE in the stratosphere. The comparisons with HALOE (Halogen Occultation Experiment) have also shown good results where the agreement between the instruments is within 5%. The validations of the lunar occultation water vapor measurements with MLS (Microwave Limb Sounder) instrument are exceptionally good, varying between 1.5 to around 4%. The validations with MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) are in the range of 10%. A validated dataset of water vapor vertical distributions from SCIAMACHY lunar occultation measurements is expected to facilitate the understanding of physical and chemical processes in the southern mid-latitudes and the dynamical processes related to the polar vortex.

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18

Straus, Paul. "Ionospheric climatology derived from gps occultation observations made by the ionospheric occultation experiment." GPS Solutions 9, no. 2 (June 9, 2005): 164–73. http://dx.doi.org/10.1007/s10291-005-0145-7.

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19

Chen, Sihe, Eliot F. Young, Leslie A. Young, Tanguy Bertrand, François Forget, and Yuk L. Yung. "Global climate model occultation lightcurves tested by August 2018 ground-based stellar occultation." Icarus 356 (March 2021): 113976. http://dx.doi.org/10.1016/j.icarus.2020.113976.

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20

Azam, F., K. Bramstedt, A. Rozanov, K. Weigel, H. Bovensmann, G. P. Stiller, and J. P. Burrows. "SCIAMACHY lunar occultation water vapor measurements: retrieval and validation results." Atmospheric Measurement Techniques Discussions 5, no. 1 (February 3, 2012): 1029–73. http://dx.doi.org/10.5194/amtd-5-1029-2012.

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Анотація:

Abstract. SCIAMACHY lunar occultation measurements have been used to derive vertical profiles of stratospheric water vapor for the Southern Hemisphere in the near infrared (NIR) spectral range of 1350–1420 nm. The focus of this study is to present the retrieval methodology including the sensitivity studies and optimizations for the implementation of the radiative transfer model on SCIAMACHY lunar occultation measurements. The study also includes the validation of the data product with the collocated measurements from two satellite occultation instruments and two instruments measuring in limb geometry. The SCIAMACHY lunar occultation water vapor measurements comparisons with the ACE-FTS instrument have shown an agreement of 5% on the average that is well within the reported biases of ACE in the stratosphere. The comparisons with HALOE have also shown good results where the agreement between the instruments is within 5%. The validations of the lunar occultation water vapor measurements with MLS instrument are exceptionally good varying between 1.5 to around 4%. The validations with MIPAS are in the range of 10%. A validated dataset of water vapor vertical distributions from SCIAMACHY lunar occultation measurements is expected to facilitate the understanding of physical and chemical processes in the southern mid-latitudes and the dynamical processes related to polar vortex.

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21

Cheng, Wei, Youping Xu, Zhiwu Deng, and Chunli Gu. "GPS Radio Occultation Data Assimilation in the AREM Regional Numerical Weather Prediction Model for Flood Forecasts." Advances in Meteorology 2018 (November 11, 2018): 1–9. http://dx.doi.org/10.1155/2018/1376235.

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Based on the Backward Four-Dimensional Variational Data Assimilation (Backward-4DVar) system with the Advanced Regional Eta-coordinate Model (AREM), which is capable of assimilating radio occultation data, a heavy rainfall case study is performed using GPS radio occultation (GPS RO) data and routine GTS data on July 5, 2007. The case study results indicate that the use of radio occultation data after quality control can improve the quality of the analysis to be similar to that of the observations and, thus, have a positive effect when improving 24-hour rainfall forecasts. Batch tests for 119 days from May to August during the flood season in 2009 show that only the use of GPS RO data can make positive improvements in both 24-hour and 48-hour regional rainfall forecasts and obtain a better B score for 24-hour forecasts and better TS score for 48-hour forecasts. When using radio occultation refractivity data and conventional radiosonde data, the results indicate that radio occultation refractivity data can achieve a better performance for 48-hour forecasts of light rain and heavy rain.

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22

Li, Junhai, and Shuanggen Jin. "High-order ionospheric effects on electron density estimation from Fengyun-3C GPS radio occultation." Annales Geophysicae 35, no. 3 (March 15, 2017): 403–11. http://dx.doi.org/10.5194/angeo-35-403-2017.

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Abstract. GPS radio occultation can estimate ionospheric electron density and total electron content (TEC) with high spatial resolution, e.g., China's recent Fengyun-3C GPS radio occultation. However, high-order ionospheric delays are normally ignored. In this paper, the high-order ionospheric effects on electron density estimation from the Fengyun-3C GPS radio occultation data are estimated and investigated using the NeQuick2 ionosphere model and the IGRF12 (International Geomagnetic Reference Field, 12th generation) geomagnetic model. Results show that the high-order ionospheric delays have large effects on electron density estimation with up to 800 el cm−3, which should be corrected in high-precision ionospheric density estimation and applications. The second-order ionospheric effects are more significant, particularly at 250–300 km, while third-order ionospheric effects are much smaller. Furthermore, the high-order ionospheric effects are related to the location, the local time, the radio occultation azimuth and the solar activity. The large high-order ionospheric effects are found in the low-latitude area and in the daytime as well as during strong solar activities. The second-order ionospheric effects have a maximum positive value when the radio occultation azimuth is around 0–20°, and a maximum negative value when the radio occultation azimuth is around −180 to −160°. Moreover, the geomagnetic storm also affects the high-order ionospheric delay, which should be carefully corrected.

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23

Bai, W. H., Y. Q. Sun, Q. F. Du, G. L. Yang, Z. D. Yang, P. Zhang, Y. M. Bi, X. Y. Wang, C. Cheng, and Y. Han. "An introduction to the FY3 GNOS instrument and mountain-top tests." Atmospheric Measurement Techniques 7, no. 6 (June 24, 2014): 1817–23. http://dx.doi.org/10.5194/amt-7-1817-2014.

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Abstract. The FY3 (Feng-Yun-3) GNOS (GNSS Occultation Sounder) mission is a GNSS (Global Navigation Satellite System) radio occultation mission of China for remote sensing of Earth's neutral atmosphere and the ionosphere. GNOS will use both the global positioning system (GPS) and the Beidou navigation satellite systems on the China Feng-Yun-3 (FY3) series satellites. The first FY3-C was launched at 03:07 UTC on 23 September 2013. GNOS was developed by the Center for Space Science and Applied Research, Chinese Academy of Sciences (CSSAR). It will provide vertical profiles of atmospheric temperature, pressure, and humidity, as well as ionospheric electron density profiles on a global basis. These data will be used for numerical weather prediction, climate research, and ionospheric research and space weather. This paper describes the FY3 GNOS mission and the GNOS instrument characteristics. It presents simulation results of the number and distribution of GNOS occultation events with the regional Beidou constellation and the full GPS constellation, under the limitation of the GNOS instrument occultation channel number. This paper presents the instrument performance as derived from analysis of measurement data in laboratory and mountain-based occultation validation experiments at Mt. Wuling in Hebei Province. The mountain-based GNSS occultation validation tests show that GNOS can acquire or track low-elevation radio signal for rising or setting occultation events. The refractivity profiles of GNOS obtained during the mountain-based experiment were compared with those from radiosondes. The results show that the refractivity profiles obtained by GNOS are consistent with those from the radiosonde. The rms of the differences between the GNOS and radiosonde refractivities is less than 3%.

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24

Bai, W., Y. Sun, Q. Du, G. Yang, Z. Yang, P. Zhang, Y. Bi, X. Wang, C. Cheng, and Y. Han. "An introduction to FY3 GNOS instrument and its performace tested on ground." Atmospheric Measurement Techniques Discussions 7, no. 1 (January 27, 2014): 703–26. http://dx.doi.org/10.5194/amtd-7-703-2014.

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Анотація:

Abstract. The FY3 GNOS (GNSS Occultation Sounder) mission is a GNSS (Global Navigation Satellite System) radio occultation mission of China for remote sensing of Earth's neutral atmosphere and the ionosphere. GNOS will use both the Global Positioning System (GPS) and the Beidou navigation satellite systems on the China Feng-Yun-3 (FY3) series satellites. The first FY3-C was launched at 03:03 UTC, 23 September 2013. GNOS was developed by Center for Space Science and Applied Research, Chinese Academy of Sciences (CSSAR). It will provide vertical profiles of atmospheric temperature, pressure, and humidity, as well as ionospheric electron density profiles on a global basis. These data will be used for numerical weather prediction, climate research, and ionospheric research and space weather. This paper describes the FY3 GNOS mission and the GNOS instrument characteristics. It presents simulation results of the number and distribution of GNOS occultation events with the Regional Beidou constellation and the full GPS constellation, under the limitation of the GNOS instrument occultation channel number. This paper presents the instrument performance as derived from analysis of measurement data in laboratory and mountain-based occultation validation experiments at Mt. Wuling in Hebei Province. The mountain-based GNSS occultation validation tests show that GNOS can acquire or track lower elevation radio signal for rising or setting occultation events. The refractivity profiles of GNOS obtained during the mountain-based experiment were compared with those from radiosondes. The results show that the refractivity profiles obtained by GNOS are consistent with those from the radiosonde. The RMS of the differences between the GNOS and radiosonde refractivities is less than 3%.

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25

Benzon, Hans-Henrik, and Stig Syndergaard. "Simulation of radio occultation measurements." Space Communications 22, no. 2-4 (2013): 179–87. http://dx.doi.org/10.3233/sc-130013.

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26

Kursinski, E. Robert, George A. Hajj, Stephen S. Leroy, and Benjamin Herman. "The GPS Radio Occultation Technique." Terrestrial, Atmospheric and Oceanic Sciences 11, no. 1 (2000): 053. http://dx.doi.org/10.3319/tao.2000.11.1.53(cosmic).

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27

Schmidtke, Paul C., John L. Africano, and Rob Quigley. "KPNO lunar occultation summary. II." Astronomical Journal 97 (March 1989): 909. http://dx.doi.org/10.1086/115037.

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28

Schmidtke, P. C., and J. L. Africano. "KPNO LUNAR OCCULTATION SUMMARY. III." Astronomical Journal 141, no. 1 (December 7, 2010): 10. http://dx.doi.org/10.1088/0004-6256/141/1/10.

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29

Millis, Robert L. "Occultation studies with small telescopes." Symposium - International Astronomical Union 118 (1986): 199–211. http://dx.doi.org/10.1017/s0074180900151332.

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Various types of occultations and eclipses offer individuals with access to small telescopes the opportunity to contribute significantly to modern solar system research. In fact, often it is only through the cooperation of several such observers that the desired scientific objectives can be realized. This review discusses three classes of occultations which are of high current interest and which are particularly suitable for investigation with small telescopes.

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30

French, Linda M., Guarionex Morales, Steven L. Gaiser, and Jay A. Frogel. "Photometry of occultation candidate stars." Icarus 67, no. 3 (September 1986): 540–42. http://dx.doi.org/10.1016/0019-1035(86)90130-2.

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31

Cordier, Bertrand, Jacques Paul, Pierre Mandrou, and Jean-Pierre Roques. "Earth occultation or coded mask?" Nature 368, no. 6473 (April 1994): 698. http://dx.doi.org/10.1038/368698a0.

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32

Zhang, Shuang-Nan, Gerald J. Fishman, B. Alan Harmon, and William S. Paciesas. "Earth occultation or coded mask?" Nature 368, no. 6473 (April 1994): 698. http://dx.doi.org/10.1038/368698b0.

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33

Shaw, John H. "Atmospheric winds from occultation spectra." Applied Optics 24, no. 15 (August 1, 1985): 2433. http://dx.doi.org/10.1364/ao.24.002433.

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34

Bus, Schelte J., Marc W. Buie, David G. Schleicher, William B. Hubbard, Robert L. Marcialis, Richard Hill, Lawrence H. Wasserman, et al. "Stellar Occultation by 2060 Chiron." Icarus 123, no. 2 (October 1996): 478–90. http://dx.doi.org/10.1006/icar.1996.0173.

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35

Simons, D. A., E. E. Becklin, and K. W. Hodapp. "High Resolution Near-Infrared Imaging and Computer Simulations of a Lunar Occultation of the Galactic Center." Symposium - International Astronomical Union 136 (1989): 509–12. http://dx.doi.org/10.1017/s007418090018698x.

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A high resolution K-band (2.2 μm) image of the Galactic center was acquired as part of an effort to develop computer simulations of a lunar occultation of the IRS 16 region that was previously observed in 1986 September. Through our computer simulations and recent observations of another occultation that occurred in 1988 September, confident identifications of the objects detected during the 1986 September occultation were acquired. In particular, IRS 16C, 16SW, and 16NE were all identified and found to be unresolved (<0.05″ in angular extent).

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36

Buie, Marc W., and John M. Keller. "THE RESEARCH AND EDUCATION COLLABORATIVE OCCULTATION NETWORK: A SYSTEM FOR COORDINATED TNO OCCULTATION OBSERVATIONS." Astronomical Journal 151, no. 3 (February 23, 2016): 73. http://dx.doi.org/10.3847/0004-6256/151/3/73.

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37

Straus, P. R. "RETRACTED: Ionospheric climatology derived from GPS occultation observations made by the ionospheric occultation experiment." Advances in Space Research 39, no. 5 (2007): 793–802. http://dx.doi.org/10.1016/j.asr.2006.08.009.

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38

Bai, Weihua, Guojun Wang, Yueqiang Sun, Jiankui Shi, Guanglin Yang, Xiangguang Meng, Dongwei Wang, et al. "Application of the Fengyun 3 C GNSS occultation sounder for assessing the global ionospheric response to a magnetic storm event." Atmospheric Measurement Techniques 12, no. 3 (March 7, 2019): 1483–93. http://dx.doi.org/10.5194/amt-12-1483-2019.

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Abstract. The rapid advancement of global navigation satellite system (GNSS) occultation technology in recent years has made it one of the most advanced space-based remote sensing technologies of the 21st century. GNSS radio occultation has many advantages, including all-weather operation, global coverage, high vertical resolution, high precision, long-term stability, and self-calibration. Data products from GNSS occultation sounding can greatly enhance ionospheric observations and contribute to space weather monitoring, forecasting, modeling, and research. In this study, GNSS occultation sounder (GNOS) results from a radio occultation sounding payload aboard the Fengyun 3 C (FY3-C) satellite were compared with ground-based ionosonde observations. Correlation coefficients for peak electron density (NmF2) derived from GNOS Global Position System (GPS) and Beidou navigation system (BDS) products with ionosonde data were higher than 0.9, and standard deviations were less than 20 %. Global ionospheric effects of the strong magnetic storm event in March 2015 were analyzed using GNOS results supported by ionosonde observations. The magnetic storm caused a significant disturbance in NmF2 level. Suppressed daytime and nighttime NmF2 levels indicated mainly negative storm conditions. In two longitude section zones of geomagnetic inclination between 40 and 80∘, the results of average NmF2 observed by GNOS and ground-based ionosondes showed the same basic trends during the geomagnetic storm and confirmed the negative effect of this storm event on the ionosphere. The analysis demonstrates the reliability of the GNSS radio occultation sounding instrument GNOS aboard the FY3-C satellite and confirms the utility of ionosphere products from GNOS for statistical and event-specific ionospheric physical analyses. Future FY3 series satellites and increasing numbers of Beidou navigation satellites will provide increasing GNOS occultation data on the ionosphere, which will contribute to ionosphere research and forecasting applications.

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39

Marzano, F. S., and D. Cimini. "Flower elliptical-orbit constellation exploiting millimetre-wave radiometry and radio occultation for meteo-climatological applications." Advances in Geosciences 25 (July 13, 2010): 167–77. http://dx.doi.org/10.5194/adgeo-25-167-2010.

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Abstract. This paper reports on the potential of combining elliptical-orbit Flower constellations with millimeter-wave radiometry and radio-occultation, a mission concept briefly named FloRad2. The advantages of flower constellation with respect to conventional orbits are discussed, including the flexibility ensuring increasing coverage with separate launches. Millimeter-wave radiometry and radio-occultation receivers provide the advantage to design fairly compact payloads that comply well with current technology of mini-satellites. Millimeter-wave radiometry and radio-occultation techniques are somewhat complementary and an optimal combination of these observations results in atmospheric products with enhanced vertical and horizontal resolutions. Thus, the combination of small, light payloads employing millimeter-wave radiometry and radio-occultation with Flower elliptical-orbit constellations may result in an optimal compromise between retrieval performances and system complexity that is ideal for continued long-term missions with meteorological and climatological applications.

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40

Javadov, N. H., R. A. Eminov, and N. Ya Ismailov. "Optimum prediction of atmospheric temperature using GPS radio occultation measurements." Geodesy and Cartography 919, no. 1 (February 20, 2017): 48–51. http://dx.doi.org/10.22389/0016-7126-2017-919-1-48-51.

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The matters of optimum forecasting atmospheric temperature using GPS radio occultation measurements are considered. The analysis of the available data regarding to the comparison of temperature measurements using radio occultation method and radiosondes was made. As a result it was concluded that the mean value of those results’ difference and also the mean quadratic deviation of these difference increases in common by increase of the forecasting time. In order to prevent surplus loading of telemetry channels and broadcasting inaccurate forecast values via them the optimization of general procedure of radio occultation temperature measurements are carried out using fine functions method. For optimization the concurrent parameters, changing on antiphase order are determined. It is found out that utilization of fine function method taking into account the applied optimization criterion and some limitation conditions make it possible to optimize the whole procedure of forecasting atmospheric temperature using the GPS radio occultation measurements.

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41

Meyer, J., A. Bracher, A. Rozanov, A. C. Schlesier, H. Bovensmann, and J. P. Burrows. "Solar occultation with SCIAMACHY: algorithm description and first validation." Atmospheric Chemistry and Physics Discussions 5, no. 1 (January 10, 2005): 17–66. http://dx.doi.org/10.5194/acpd-5-17-2005.

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Abstract. This presentation concentrates on solar occultation measurements with the spaceborne spectrometer SCIAMACHY in the UV-Vis wavelength range. Solar occultation measurements provide unique information about the vertical distribution of atmospheric constituents. For retrieval of vertical trace gas concentration profiles, an algorithm has been developed based on the optimal estimation method. The forward model is capable to simulate the extinction signals of different species as they occur in atmospheric transmission spectra obtained from occultation measurements. Furthermore, correction algorithms have been implemented to address shortcomings of the tangent height pre-processing and inhomogeneities of measured solar spectra. First results of O3 and NO2 vertical profile retrievals have been validated with data from ozone sondes and satellite based occultation instruments. The validation shows very promising results for SCIAMACHY O3 and NO2 values between 15 to 35 km with errors in the order of 10% and 15%, respectively.

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42

Meyer, J., A. Bracher, A. Rozanov, A. C. Schlesier, H. Bovensmann, and J. P. Burrows. "Solar occultation with SCIAMACHY: algorithm description and first validation." Atmospheric Chemistry and Physics 5, no. 6 (June 22, 2005): 1589–604. http://dx.doi.org/10.5194/acp-5-1589-2005.

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Abstract. This presentation concentrates on solar occultation measurements with the spaceborne spectrometer SCIAMACHY in the UV-Vis wavelength range. Solar occultation measurements provide unique information about the vertical distribution of atmospheric constituents. For retrieval of vertical trace gas concentration profiles, an algorithm has been developed based on the optimal estimation method. The forward model is capable of simulating the extinction signals of different species as they occur in atmospheric transmission spectra obtained from occultation measurements. Furthermore, correction algorithms have been implemented to address shortcomings of the tangent height pre-processing and inhomogeneities of measured solar spectra. First results of O3 and NO2 vertical profile retrievals have been validated with data from ozone sondes and satellite based occultation instruments. The validation shows very promising results for SCIAMACHY O3 and NO2 values between 15 to 35km with errors of the order of 10% and 15%, respectively.

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43

Xue, Wang-Chen, Xiao-Bo Li, Shao-Lin Xiong, Yong Chen, Shuang-Nan Zhang, Li-Ming Song, Shu Zhang, et al. "Neutral Atmospheric Density Measurement Using Insight-HXMT Data by the Earth Occultation Technique." Astrophysical Journal Supplement Series 264, no. 1 (December 14, 2022): 5. http://dx.doi.org/10.3847/1538-4365/ac9f16.

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Abstract The Earth occultation technique has broad applications in both astronomy and atmospheric density measurements. We construct the background model during the occultation of the Crab Nebula observed by the Insight-Hard X-ray Modulation Telescope (Insight-HXMT) at energies between 6 and 100 keV. We propose a Bayesian atmospheric density retrieval method based on the Earth occultation technique, combining Poisson and Gaussian statistics. By modeling the atmospheric attenuation of X-ray photons during the occultation, we simultaneously retrieved the neutral densities of the atmosphere at different altitude ranges. Our method considers the correlation of densities between neighboring atmospheric layers and reduces the potential systematic bias to which previous work may be subject. Previous analyses based on light-curve fitting or spectral fitting also lost some spectral or temporal information of the data. In contrast to previous work, the occultation data observed by the three telescopes on board Insight-HXMT is fully used in our analysis, further reducing the statistical error in density retrieval. We apply our method to cross-check the (semi)empirical atmospheric models, using 115 sets of occultation data of the Crab Nebula observed by Insight-HXMT. We find that the retrieved neutral density is ∼10%, ∼20%, and ∼25% less than the values of the widely used atmospheric model NRLMSISE-00, in the altitude range of 55–80 km, 80–90 km, and 90–100 km, respectively. We also show that the newly released atmospheric model NRLMSIS 2.0 is generally consistent with our density measurements.

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44

Kissling, W. M., G. L. Blow, W. H. Allen, J. Priestley, P. Riley, P. Daalder, and M. George. "The Diameter of (9) Metis from the Occultation of SAO 190531." Publications of the Astronomical Society of Australia 9, no. 1 (1991): 150–52. http://dx.doi.org/10.1017/s1323358000025352.

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AbstractThe observations in this paper were carried out as part of a program co-ordinated by the Occultation Section of the Royal Astronomical Society of New Zealand.On 6 August 1989 minor planet (9) Metis occulted the magnitude 8.7 star SAO 190531. The occultation was observed by two visual observers in Tasmania, and at one photoelectric and two visual sites in New Zealand. From the five chords obtained we have deduced an average cross-sectional diameter for this minor planet of 173.5 km at the time of the occultation. This is in good agreement with previous radiometric and polarimetric results.

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45

Xia, Pengfei, Shirong Ye, Kecai Jiang, and Dezhong Chen. "Estimation and evaluation of COSMIC radio occultation excess phase using undifferenced measurements." Atmospheric Measurement Techniques 10, no. 5 (May 16, 2017): 1813–21. http://dx.doi.org/10.5194/amt-10-1813-2017.

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Abstract. In the GPS radio occultation technique, the atmospheric excess phase (AEP) can be used to derive the refractivity, which is an important quantity in numerical weather prediction. The AEP is conventionally estimated based on GPS double-difference or single-difference techniques. These two techniques, however, rely on the reference data in the data processing, increasing the complexity of computation. In this study, an undifferenced (ND) processing strategy is proposed to estimate the AEP. To begin with, we use PANDA (Positioning and Navigation Data Analyst) software to perform the precise orbit determination (POD) for the purpose of acquiring the position and velocity of the mass centre of the COSMIC (The Constellation Observing System for Meteorology, Ionosphere and Climate) satellites and the corresponding receiver clock offset. The bending angles, refractivity and dry temperature profiles are derived from the estimated AEP using Radio Occultation Processing Package (ROPP) software. The ND method is validated by the COSMIC products in typical rising and setting occultation events. Results indicate that rms (root mean square) errors of relative refractivity differences between undifferenced and atmospheric profiles (atmPrf) provided by UCAR/CDAAC (University Corporation for Atmospheric Research/COSMIC Data Analysis and Archive Centre) are better than 4 and 3 % in rising and setting occultation events respectively. In addition, we also compare the relative refractivity bias between ND-derived methods and atmPrf profiles of globally distributed 200 COSMIC occultation events on 12 December 2013. The statistical results indicate that the average rms relative refractivity deviation between ND-derived and COSMIC profiles is better than 2 % in the rising occultation event and better than 1.7 % in the setting occultation event. Moreover, the observed COSMIC refractivity profiles from ND processing strategy are further validated using European Centre for Medium-Range Weather Forecasts (ECMWF) analysis data, and the results indicate that the undifferenced method reduces the noise level on the excess phase paths in the lower troposphere compared to the single-difference processing strategy.

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46

Hu, Xiong, Xiaocheng Wu, Shuli Song, Maoli Ma, Weili Zhou, Qingchen Xu, Lei Li, et al. "First Observations of Mars Atmosphere and Ionosphere with Tianwen-1 Radio-Occultation Technique on 5 August 2021." Remote Sensing 14, no. 11 (June 6, 2022): 2718. http://dx.doi.org/10.3390/rs14112718.

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The radio-occultation technique can provide vertical profiles of planetary ionospheric and atmospheric parameters, which merit the planetary-climate and space-weather scientific research so far. The Tianwen-1 one-way single-frequency radio-occultation technique was developed to retrieve Mars ionospheric and atmospheric parameters. The first radio-occultation event observation experiment was conducted on 5 August 2021. The retrieved excess Doppler frequency, bending angle, refractivity, electron density, neutral mass density, pressure and temperature profiles are presented. The Mars ionosphere M1 (M2) layer peak height is at 140 km (105 km) with a peak density of about 3.7 × 1010 el/m3 (5.3 × 1010 el/m3) in the retrieved electron-density profile. A planetary boundary layer (−2.35 km~5 km), a troposphere (temperature decreases with height) and a stratosphere (24 km–40 km) clearly appear in the retrieved temperature profile below 50 km. Results show that Tianwen-1 radio occultation data are scientifically reliable and useful for further Mars climate and space-weather studies.

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47

Clark, B. J. M., D. R. Anderson, N. Madhusudhan, C. Hellier, A. M. S. Smith, and A. Collier Cameron. "Thermal emission of WASP-48b in the Ks-band." Astronomy & Astrophysics 615 (July 2018): A86. http://dx.doi.org/10.1051/0004-6361/201527071.

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We report a detection of thermal emission from the hot Jupiter WASP-48b in the Ks-band. We used the Wide-field Infra-red Camera on the 3.6-m Canada-France Hawaii Telescope to observe an occultation of the planet by its host star. From the resulting occultation lightcurve we find a planet-to-star contrast ratio in the Ks-band of 0.136 ± 0.014%, in agreement with the value of 0.109 ± 0.027% previously determined. We fit the two Ks-band occultation lightcurves simultaneously with occultation lightcurves in the H-band and the Spitzer 3.6- and 4.5-μm bandpasses, radial velocity data, and transit lightcurves. From this, we revise the system parameters and construct the spectral energy distribution (SED) of the dayside atmosphere. By comparing the SED with atmospheric models, we find that both models with and without a thermal inversion are consistent with the data. We find the planet’s orbit to be consistent with circular (e < 0.072 at 3σ).

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48

Bauer, Peter, Gábor Radnóti, Sean Healy, and Carla Cardinali. "GNSS Radio Occultation Constellation Observing System Experiments." Monthly Weather Review 142, no. 2 (January 24, 2014): 555–72. http://dx.doi.org/10.1175/mwr-d-13-00130.1.

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Abstract Observing system experiments within the operational ECMWF data assimilation framework have been performed for summer 2008 when the largest recorded number of Global Navigation Satellite System (GNSS) radio occultation observations from both operational and experimental satellites were available. Constellations with 0%, 5%, 33%, 67%, and 100% data volume were assimilated to quantify the sensitivity of analysis and forecast quality to radio occultation data volume. These observations mostly constrain upper-tropospheric and stratospheric temperatures and correct an apparent model bias that changes sign across the upper-troposphere–lower-stratosphere boundary. This correction effect does not saturate with increasing data volume, even if more data are assimilated than available in today’s analyses. Another important function of radio occultation data, namely, the anchoring of variational radiance bias corrections, is demonstrated in this study. This effect also does not saturate with increasing data volume. In the stratosphere, the anchoring by radio occultation data is stronger than provided by radiosonde and aircraft observations.

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49

Stecklum, B., R. R. Howell, A. Eckart, and A. Richichi. "High Angular Resolution Observations of Her 36." Symposium - International Astronomical Union 158 (1994): 364–66. http://dx.doi.org/10.1017/s0074180900107934.

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The star Herschel 36 (Her 36) which ionizes most of the Hourglass nebula has been observed during a lunar occultation as well as by speckle interferometry in the near infrared (NIR). From the lunar occultation data the strip brightness profile has been extracted which shows that in the L′ band Her 36 is extended with a FWHM of 0.45″. Subsequent speckle interferometry revealed 11 sources in a 6′ × 6′ area at a level of 0.15″ resolution. From the comparison of the brightness profile obtained by the occultation and the strip brightness profile synthesized from the speckle image, we conclude that Her 36 is surrounded by a very young infrared cluster.

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50

Fong, C. J., D. Whiteley, E. Yang, K. Cook, V. Chu, B. Schreiner, D. Ector, P. Wilczynski, T. Y. Liu, and N. Yen. "Space and ground segment performance of the FORMOSAT-3/COSMIC mission: four years in orbit." Atmospheric Measurement Techniques Discussions 4, no. 1 (January 24, 2011): 599–638. http://dx.doi.org/10.5194/amtd-4-599-2011.

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Abstract. The FORMOSAT-3/COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) mission consisting of six Low-Earth-Orbit (LEO) satellites is the world's first demonstration constellation using radio occultation signals from Global Positioning System (GPS) satellites. The radio occultation signals are retrieved in near real-time for global weather/climate monitoring, numerical weather prediction, and space weather research. The mission has processed on average 1400 to 1800 high-quality atmospheric sounding profiles per day. The atmospheric radio occultation soundings data are assimilated into operational numerical weather prediction models for global weather prediction, including typhoon/hurricane/cyclone forecasts. The radio occultation data has shown a positive impact on weather predictions at many national weather forecast centers. A proposed follow-on mission transitions the program from the current experimental research system to a significantly improved real-time operational system, which will reliably provide 8000 radio occultation soundings per day. The follow-on mission as planned will consist of 12 satellites with a data latency of 45 min, which will provide greatly enhanced opportunities for operational forecasts and scientific research. This paper will address the FORMOSAT-3/COSMIC system and mission overview, the spacecraft and ground system performance after four years in orbit, the lessons learned from the encountered technical challenges and observations, and the expected design improvements for the new spacecraft and ground system.

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