Asgeir J. Sørensen

Dr. Asgeir J. Sørensen

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Research Focus & Metrics

Academic Career Length

23Years (2004-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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5 January 2018 in Science Advances
Verified
Journal Article
Open access
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MLMartin Ludvigsen
Martin Ludvigsen
JBJørgen Berge
Jørgen Berge
MGMaxime Geoffroy
Maxime Geoffroy
JCJonathan H. Cohen
Jonathan H. Cohen
PTPedro R. De La Torre
Pedro R. De La Torre
GJGeir Johnsen
Geir Johnsen
Using new enabling technologies, we document behavioral patterns and susceptibility to light pollution never previously seen.

28 January 2023 in Remote Sensing
Verified
Journal Article
Open access
PDF file
Sivert BakkenSivert Bakken
Sivert Bakken
MHMarie B. Henriksen
Marie B. Henriksen
RBRoger Birkeland
Roger Birkeland
DLDennis David Langer
Dennis David Langer
AOAdrienne Oudijk
Adrienne Oudijk
TJTor Arne Johansen
Tor Arne Johansen
The HYPSO-1 satellite, a 6U CubeSat carrying a hyperspectral imager, was launched on 13 January 2022, with the Goal of imaging ocean color in support of marine research. This article describes the development and current status of the mission and payload operations, including examples of agile planning, captures with low revisit time and time series acquired during a campaign. The in-orbit performance of the hyperspectral instrument is also characterized. The usable spectral range of the instrument is in the range of 430 nm to 800 nm over 120 bands after binning during nominal captures. The spatial resolvability is found empirically to be below 2.2 pixels in terms of Full-Width at Half-Maximum (FWHM) at 565 nm. This measure corresponds to an inherent ground resolvable resolution of 142 m across-track for close to nadir capture. In the across-track direction, there are 1216 pixels available, which gives a swath width of 70 km. However, the 684 center pixels are used for nominal captures. With the nominal pixels used in the across-track direction, the nadir swath-width is 40 km. The spectral resolution in terms of FWHM is estimated to be close to 5 nm at the center wavelength of 600 nm, and the Signal-to-Noise Ratio (SNR) is evaluated to be greater than 300 at 450 nm to 500 nm for Top-of-Atmosphere (ToA) signals. Examples of images from the first months of operations are also shown.

28 March 2006 in Journal of Offshore Mechanics and Arctic Engineering
Verified
Journal Article
Closed access
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RPR. Pascoal
R. Pascoal
Carlos Guedes SoaresCarlos Guedes Soares
Carlos Guedes Soares
ASAsgeir J. Sørensen
Asgeir J. Sørensen
Wave spectra are estimated from wave frequency motions of a vessel at zero or low advance speed. Minimization of a cost functional that indicates how well the estimated spectrum results in the measured motion spectra was based on sequential quadratic programming and a genetic algorithm. Two procedures have been developed and applied to numerically simulated motions of a 59 m length offshore supply vessel.

19 March 2020 in Remote Sensing
Verified
Journal Article
Open access
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AMAksel Alstad Mogstad
Aksel Alstad Mogstad
Øyvind ØdegårdØyvind Ødegård
Øyvind Ødegård
SNStein M. Nornes
Stein M. Nornes
MLMartin Ludvigsen
Martin Ludvigsen
GJGeir Johnsen
Geir Johnsen
JBJørgen Berge
Jørgen Berge
In 2007, a possible wreck site was discovered in Trygghamna, Isfjorden, Svalbard by the Norwegian Hydrographic Service. Using (1) a REMUS 100 autonomous underwater vehicle (AUV) equipped with a sidescan sonar (SSS) and (2) a Seabotix LBV 200 mini-remotely operated vehicle (ROV) with a high-definition (HD) camera, the wreck was in 2015 identified as the Figaro: a floating whalery that sank in 1908. The Figaro is to our knowledge currently the northernmost wreck in the world to be investigated by archaeologists. As the wreck is protected by law as an underwater cultural heritage (UCH) site, only non-intrusive methods could be used during surveys. In this study, we demonstrate how using multiple complementary remote sensing techniques can be advantageous with respect to acquiring a holistic overview of a recently discovered wreck site. In January 2016, the wreck was revisited, and a full photogrammetric survey of the site was conducted with a Sperre Subfighter 7500 medium class ROV. In addition to stereo camera images, HD-video and underwater hyperspectral imagery was also obtained from the wreck site. In terms of data analysis and interpretation, the emphasis was in the current study put on the photogrammetric 3D model and the underwater hyperspectral imagery. The former provided an excellent general overview of the Figaro wreck site, whereas the latter supplied detailed information from a 14.65-m2 sub-area situated on the top of the wreck. By analyzing classified underwater hyperspectral imagery in context with supplementary information from the 3D model, the levels of biofouling associated with different marine archaeological substrate types were assessed. Our findings suggest that strongly protruding archaeological objects support significantly higher levels of biofouling than their surroundings, and consequently that high-density biological assemblages could serve as proxies for identifying human-made artifacts on the seafloor.

1 January 2019 in Ocean Engineering
Verified
Journal Article
Open access
SVS.A. Vilsen
S.A. Vilsen
TSThomas Sauder
Thomas Sauder
ASAsgeir J. Sørensen
Asgeir J. Sørensen
MFM. Føre
M. Føre

24 November 2023 in Ocean Engineering
Verified
Journal Article
Open access
RMRenan Guedes Maidana
Renan Guedes Maidana
SKSusanna Dybwad Kristensen
Susanna Dybwad Kristensen
IUIngrid Bouwer Utne
Ingrid Bouwer Utne
ASAsgeir J. Sørensen
Asgeir J. Sørensen