Potential for observing and discriminating impact craters and comparable volcanic landforms on Magellan radar images
Observations of small terrestrial craters by Seasat synthetic aperture radar (SAR) at high resolution (approx. 25 m) and of comparatively large Venusian craters by Venera 15/16 images at low resolution (1000 to 2000 m) and shorter wavelength show similarities in the radar responses to crater morphol...
Main Author: | |
---|---|
Format: | Other/Unknown Material |
Language: | unknown |
Published: |
1989
|
Subjects: | |
Online Access: | http://ntrs.nasa.gov/search.jsp?R=19900003113 |
id |
ftnasantrs:oai:casi.ntrs.nasa.gov:19900003113 |
---|---|
record_format |
openpolar |
spelling |
ftnasantrs:oai:casi.ntrs.nasa.gov:19900003113 2023-05-15T17:40:01+02:00 Potential for observing and discriminating impact craters and comparable volcanic landforms on Magellan radar images Ford, J. P. Unclassified, Unlimited, Publicly available JAN 1, 1989 http://ntrs.nasa.gov/search.jsp?R=19900003113 unknown http://ntrs.nasa.gov/search.jsp?R=19900003113 Accession ID: 90N12429 No Copyright Other Sources 91 Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 10 1989 ftnasantrs 2012-02-15T18:12:26Z Observations of small terrestrial craters by Seasat synthetic aperture radar (SAR) at high resolution (approx. 25 m) and of comparatively large Venusian craters by Venera 15/16 images at low resolution (1000 to 2000 m) and shorter wavelength show similarities in the radar responses to crater morphology. At low incidence angles, the responses are dominated by large scale slope effects on the order of meters; consequently it is difficult to locate the precise position of crater rims on the images. Abrupt contrasts in radar response to changing slope (hence incidence angle) across a crater produce sharp tonal boundaries normal to the illumination. Crater morphology that is radially symmetrical appears on images to have bilateral symmetry parallel to the illumination vector. Craters are compressed in the distal sector and drawn out in the proximal sector. At higher incidence angles obtained with the viewing geometry of SIR-A, crater morphology appears less compressed on the images. At any radar incidence angle, the distortion of a crater outline is minimal across the medial sector, in a direction normal to the illumination. Radar bright halos surround some craters imaged by SIR-A and Venera 15 and 16. The brightness probably denotes the radar response to small scale surface roughness of the surrounding ejecta blankets. Similarities in the radar responses of small terrestrial impact craters and volcanic craters of comparable dimensions emphasize the difficulties in discriminating an impact origin from a volcanic origin in the images. Similar difficulties will probably apply in discriminating the origin of small Venusian craters, if they exist. Because of orbital considerations, the nominal incidence angel of Magellan radar at the center of the imaging swath will vary from about 45 deg at 10 deg N latitude to about 16 deg at the north pole and at 70 deg S latitude. Impact craters and comparable volcanic landforms will show bilateral symmetry parallel to the illumination vector and will appear increasingly compressed toward higher latitudes. Other/Unknown Material North Pole NASA Technical Reports Server (NTRS) North Pole Venera ENVELOPE(155.572,155.572,63.961,63.961) |
institution |
Open Polar |
collection |
NASA Technical Reports Server (NTRS) |
op_collection_id |
ftnasantrs |
language |
unknown |
topic |
91 |
spellingShingle |
91 Ford, J. P. Potential for observing and discriminating impact craters and comparable volcanic landforms on Magellan radar images |
topic_facet |
91 |
description |
Observations of small terrestrial craters by Seasat synthetic aperture radar (SAR) at high resolution (approx. 25 m) and of comparatively large Venusian craters by Venera 15/16 images at low resolution (1000 to 2000 m) and shorter wavelength show similarities in the radar responses to crater morphology. At low incidence angles, the responses are dominated by large scale slope effects on the order of meters; consequently it is difficult to locate the precise position of crater rims on the images. Abrupt contrasts in radar response to changing slope (hence incidence angle) across a crater produce sharp tonal boundaries normal to the illumination. Crater morphology that is radially symmetrical appears on images to have bilateral symmetry parallel to the illumination vector. Craters are compressed in the distal sector and drawn out in the proximal sector. At higher incidence angles obtained with the viewing geometry of SIR-A, crater morphology appears less compressed on the images. At any radar incidence angle, the distortion of a crater outline is minimal across the medial sector, in a direction normal to the illumination. Radar bright halos surround some craters imaged by SIR-A and Venera 15 and 16. The brightness probably denotes the radar response to small scale surface roughness of the surrounding ejecta blankets. Similarities in the radar responses of small terrestrial impact craters and volcanic craters of comparable dimensions emphasize the difficulties in discriminating an impact origin from a volcanic origin in the images. Similar difficulties will probably apply in discriminating the origin of small Venusian craters, if they exist. Because of orbital considerations, the nominal incidence angel of Magellan radar at the center of the imaging swath will vary from about 45 deg at 10 deg N latitude to about 16 deg at the north pole and at 70 deg S latitude. Impact craters and comparable volcanic landforms will show bilateral symmetry parallel to the illumination vector and will appear increasingly compressed toward higher latitudes. |
format |
Other/Unknown Material |
author |
Ford, J. P. |
author_facet |
Ford, J. P. |
author_sort |
Ford, J. P. |
title |
Potential for observing and discriminating impact craters and comparable volcanic landforms on Magellan radar images |
title_short |
Potential for observing and discriminating impact craters and comparable volcanic landforms on Magellan radar images |
title_full |
Potential for observing and discriminating impact craters and comparable volcanic landforms on Magellan radar images |
title_fullStr |
Potential for observing and discriminating impact craters and comparable volcanic landforms on Magellan radar images |
title_full_unstemmed |
Potential for observing and discriminating impact craters and comparable volcanic landforms on Magellan radar images |
title_sort |
potential for observing and discriminating impact craters and comparable volcanic landforms on magellan radar images |
publishDate |
1989 |
url |
http://ntrs.nasa.gov/search.jsp?R=19900003113 |
op_coverage |
Unclassified, Unlimited, Publicly available |
long_lat |
ENVELOPE(155.572,155.572,63.961,63.961) |
geographic |
North Pole Venera |
geographic_facet |
North Pole Venera |
genre |
North Pole |
genre_facet |
North Pole |
op_source |
Other Sources |
op_relation |
http://ntrs.nasa.gov/search.jsp?R=19900003113 Accession ID: 90N12429 |
op_rights |
No Copyright |
_version_ |
1766140784827957248 |