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RISS 인기검색어
- 검색키워드
- 저자 : Southwick, L M (검색결과 5 건)
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ShadowCam Instrument and Investigation Overview
Mark Southwick Robinson,Scott Michael Brylow,Michael Alan Caplinger,Lynn Marie Carter,Matthew John Clark,Brett Wilcox Denevi,Nicholas Michael Estes,David Carl Humm,Prasun Mahanti,Douglas Arden Peckham 한국우주과학회 2023 Journal of Astronomy and Space Sciences Vol.40 No.4
ShadowCam is a National Aeronautics and Space Administration Advanced Exploration Systems funded instrument hosted onboard the Korea Aerospace Research Institute (KARI) Korea Pathfinder Lunar Orbiter (KPLO) satellite. By collecting high-resolution images of permanently shadowed regions (PSRs), ShadowCam will provide critical information about the distribution and accessibility of water ice and other volatiles at spatial scales (1.7 m/pixel) required to mitigate risks and maximize the results of future exploration activities. The PSRs never see direct sunlight and are illuminated only by light reflected from nearby topographic highs. Since secondary illumination is very dim, ShadowCam was designed to be over 200 times more sensitive than previous imagers like the Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC). ShadowCam images thus allow for unprecedented views into the shadows, but saturate while imaging sunlit terrain.
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Prasun Mahanti,Mark Southwick Robinson,David Carl Humm,Robert Vernon Wagner,Nicholas Michael Estes,Jean-Pierre Williams 한국우주과학회 2023 Journal of Astronomy and Space Sciences Vol.40 No.4
Lunar permanently shadowed regions (PSRs) never see direct sunlight and are illuminated only by secondary illumination - light reflected from nearby topography. The ShadowCam imaging experiment onboard the Korea Pathfinder Lunar Orbiter is acquiring images of these PSRs. We characterize and discuss the nature of secondary illumination for the Shackleton PSR from ShadowCam radiance-calibrated images. We also use modeling to understand the magnitude and direction of the secondary illumination. Results from our analysis highlight the non-homogeneous, dynamic, and complex nature of PSR secondary lighting. Knowledge of the direction of the secondary illumination is crucial for reli-able interpretation of contrasts observed in ShadowCam images. This preliminary analysis of the floor of Shackleton crater from images acquired over multiple secondary illumination conditions does not reveal indications of exposed surface ice, even though temperatures are constantly below 110K.
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Movement of trifluralin , metolachlor and metribuzin in the soil environment
Kim, Jung Ho,Feagley, S E,Southwick, L M,Wills, H W,Bengtson, R L 한국농화학회 1992 Applied Biological Chemistry (Appl Biol Chem) Vol.35 No.4
The objective of this study was to evaluate the runoff behavior and leaching properties in soil environment of trifluralin, metolachlor and metribuzin: herbicides used widely in Louisiana and other states with soybeans. Adsorption-desorption of the these herbicides trifluralin, metolachlor and metribuzin was studied in a selected soil (Clay loam). At a 1: 10 soil/water ratio, the Freundlich constant Kd, for trifluralin metolachlor and metribuzin were 9.97, 1.54 and 1.10 respectively. Leaching and distribution of these herbicides were evaluated in soil columns (id 5.4㎝×26㎝). When the soil columns were leached with three pore volume of water, the distribution of trifluralin in soil and Leachate water was 70.02% and 0.005% of the applied amount respectively. The distribution of metolachlor was 42.93% in soil and 21.33% in leachate water. The distribution of metribuzin was 8.88% in soil and 68.97% in leachate water. Metolachlor and metribuzin were readily leached while trifluralin was strongly adsorbed to the soil. The results of the study illustrate the strong correlation between adsorption-desorption properties and leaching properties. From Louisiana field plot applied 1683 g/㏊ trifluralin 2759 g/㏊ of metolachlor and 609 g/㏊ of metribuzin, half life the field was 0.083∼0.052 ng/㎖. The concentration of metolachlor and metribuzin were 19∼402 ng/㎖ and 1.5∼56.2 ng/㎖ respectively. The trifluralin loss in surface water from the field was 0.0016% (0.0269 g/㏊) of the amount applied on 3 times of run off events. The total in surface water was 12.34% (340.46 g/㏊) and 7.11% (43.29 g/㏊) respectively, for the metolachlor and metribuzin on 7 times of run off events. The concentration of trifluralin in 1 m and 2 m well were the range of 0.04 ng/㎖∼0.08 ng/㎖. This indicated that leaching of trifluralin was very low. The concentration of metolachlor in 1 m well was decreased froth 205.3 ㎎/㎖ during 17∼62 days after application. The concentration of metribuzin in 1 m well also was decreased from 64.2 ng/㎖ to 0.70 ng/㎖, but in 2 m well was increased from 1.9 ng/㎖ to 76.7 ng/㎖. A contamination of metolachlor and metribuzin in ground water were higher than trifluralin.
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David Carl Humm,Mallory Janet Kinczyk,Scott Michael Brylow,Robert Vernon Wagner,Emerson Jacob Speyerer,Nicholas Michael Estes,Prasun Mahanti,Aaron Kyle Boyd,Mark Southwick Robinson 한국우주과학회 2023 Journal of Astronomy and Space Sciences Vol.40 No.4
ShadowCam is a high-sensitivity, high-resolution imager provided by NASA for the Danuri (KPLO) lunar mission. ShadowCam calibration shows that it is well suited for its purpose, to image permanently shadowed regions (PSRs) that occur near the lunar poles. It is 205 times as sensitive as the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC). The signal to noise ratio (SNR) is greater than 100 over a large part of the dynamic range, and the top of the dynamic range is high enough to accommodate most brighter PSR pixels. The optical performance is good enough to take full advantage of the 1.7 meter/pixel image scale, and calibrated images have uniform response. We describe some instrument artifacts that are amenable to future corrections, making it possible to improve performance further. Stray light control is very challenging for this mission. In many cases, ShadowCam can image shadowed areas with directly illuminated terrain in or near the field of view (FOV). We include thorough qualitative descriptions of circumstances under which lunar brightness levels far higher than the top of the dynamic range cause detector or stray light artifacts and the size and extent of the artifact signal under those circumstances.
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