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R. King

Publications and source records attributed to R. King.

4 recordsLinked to original sources
USGS2008

Ultrahigh resolution topographic mapping of Mars with MRO HiRISE stereo images: Meter-scale slopes of candidate Phoenix landing sites

The objectives of this paper are twofold: first, to report our estimates of the meter‐to‐decameter‐scale topography and slopes of candidate landing sites for the Phoenix mission, based on analysis of Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images with a typical pixel scale of 3 m and Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) images at 0.3 m pixel −1 and, second, to document in detail the geometric calibration, software, and procedures on which the photogrammetric analysis of HiRISE data is based. A combination of optical design modeling, laboratory observations, star images, and Mars images form the basis for software in the U.S. Geological Survey Integrated Software for Imagers and Spectrometers (ISIS) 3 system that corrects the images for a variety of distortions with single‐pixel or subpixel accuracy. Corrected images are analyzed in the commercial photogrammetric software SOCET SET (® BAE Systems), yielding digital topographic models (DTMs) with a grid spacing of 1 m (3–4 pixels) that require minimal interactive editing. Photoclinometry yields DTMs with single‐pixel grid spacing. Slopes from MOC and HiRISE are comparable throughout the latitude zone of interest and compare favorably with those where past missions have landed successfully; only the Mars Exploration Rover (MER) B site in Meridiani Planum is smoother. MOC results at multiple locations have root‐mean‐square (RMS) bidirectional slopes of 0.8–4.5° at baselines of 3–10 m. HiRISE stereopairs (one per final candidate site and one in the former site) yield 1.8–2.8° slopes at 1‐m baseline. Slopes at 1 m from photoclinometry are also in the range 2–3° after correction for image blur. Slopes exceeding the 16° Phoenix safety limit are extremely rare.

Journal of Geophysical Research E: Planets↗
USGS2007

Ultrahigh resolution topographic mapping of Mars with HiRISE stereo images: Methods and first results

The Mars Reconnaissance Orbiter (MRO) arrived at Mars on 10 March 2006 and began its primary science phase in November. The High Resolution Imaging Science Experiment (HiRISE) on MRO is the largest, most complex camera ever flown to another planet. Plans call for this scanner to image roughly 1% of Mars by area at a pixel scale of 0.3 m during the next Mars year. Among the thousands of images will be hundreds of stereopairs that will provide an unprecedented three-dimensional view of the Martian surface at meter scale. These stereopairs will provide a tremendous amount of information for focused scientific studies, landing site selection and validation, and the operation of landers and rovers. In this paper, we describe our approach to generating geodetically controlled digital topographic models (DTMs) from such stereopairs, our early results, and plans for future DTM production. Our approach to the photogrammetric processing of HiRISE images follows that which we have previously described for the MOC and the Mars Express High Resolution Stereo Camera (HRSC). We use the USGS in-house digital cartographic software ISIS to do initial processing, including ingestion, decompression, and radiometric calibration of the images. "Three-dimensional" photogrammetric processing steps, including control and DTM creation and editing, are performed on a photogrammetric workstation running the commercial software SOCET SET (® BAE Systems). Noteworthy departures from past practice are the use of ISIS 3, the object-oriented successor to the older ISIS 2 system, and pre-processing in ISIS to correct geometric complications of the HiRISE images that cannot be modelled in the SOCET sensor model: multiple CCD detectors in the focal plane, optical distortion around an axis far from the detectors, and (ultimately) the small "jitter" motions of spacecraft pointing that distort the images and hence the DTMs. The first HiRISE stereopair analyzed covered the location of the Opportunity rover near the 750-m crater informally named Victoria in Meridiani Planum. This scene was extremely unfavorable for automated stereomatching, with extensive areas that are almost featureless, extremely steep, or both, but these problems were offset by the high quality of the HiRISE imagery, permitting us to obtain a 1 m/post DTM that required only limited interactive editing. Subsequent mapping of the Spirit rover site and a variety of scientifically interesting sites has proven that the greater surface texture found at most places on Mars leads to even better DTMs with even less editing required. We are currently working to refine and streamline our procedures in order to maximize the number of sites that can be mapped and studied in three dimensions with HiRISE.

Conference Paper↗
USGS1997

Southern California Permanent GPS Geodetic Array: Continuous measurements of regional crustal deformation between the 1992 Landers and 1994 Northridge earthquakes

The southern California Permanent GPS Geodetic Array (PGGA) was established in 1990 across the Pacific-North America plate boundary to continuously monitor crustal deformation. We describe the development of the array and the time series of daily positions estimated for its first 10 sites in the 19-month period between the June 28, 1992 ( M w =7.3), Landers and January 17, 1994 ( M w =6.7), Northridge earthquakes. We compare displacement rates at four site locations with those reported by Feigl et al. [1993], which were derived from an independent set of Global Positioning System (GPS) and very long baseline interferometry (VLBI) measurements collected over nearly a decade prior to the Landers earthquake. The velocity differences for three sites 65–100 km from the earthquake's epicenter are of order of 3–5 mm/yr and are systematically coupled with the corresponding directions of coseismic displacement. The fourth site, 300 km from the epicenter, shows no significant velocity difference. These observations suggest large-scale postseismic deformation with a relaxation time of at least 800 days. The statistical significance of our observations is complicated by our incomplete knowledge of the noise properties of the two data sets; two possible noise models fit the PGGA data equally well as described in the companion paper by Zhang et al . [this issue]; the pre-Landers data are too sparse and heterogeneous to derive a reliable noise model. Under a fractal white noise model for the PGGA data we find that the velocity differences for all three sites are statistically different at the 99% significance level. A white noise plus flicker noise model results in significance levels of only 94%, 43%, and 88%. Additional investigations of the pre-Landers data, and analysis of longer spans of PGGA data, could have an important effect on the significance of these results and will be addressed in future work.

Journal of Geophysical Research B: Solid Earth↗