| 1. |
- Tengblad, Olof, 1957, et al.
(författare)
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LaBr3(Ce):LaCl3(Ce) Phoswich with pulse shape analysis for high energy gamma-ray and proton identification
- 2013
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 704:0, s. 19-26
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Tidskriftsartikel (refereegranskat)abstract
- A novel Phoswich design based on new generation scintillator crystals is presented. The detector composed from a combination of a LaBr3(Ce) with a LaCl3(Ce) crystal in one cylinder coupled to a photo multiplier tube has been tested both for incident gamma rays in the range of 0.3–6 MeV, as well as for high energy protons in the range 120–180 MeV. The Phoswich assembly has not significantly deteriorated the energy resolution, which for 662 KeV gamma rays gives a resolution of 4.5%, while for high energy protons (Ep=180 MeV) an energy resolution of 1% was obtained. It is shown that the signals from the two crystals can be separated in an event by event based mode. Using direct digitizing of the detector pulse an off-line pulse-shape analysis was performed built either on a total to tail or total to pulse height method in order to fully identify the incoming radiation. Our aim with this R&D is to in the future build a detector which is able to detect with good efficiency and resolution over a wide energy range; 0.1–30 MeV gamma rays and 20–400 MeV protons. Monte Carlo simulations made in order to design the next prototype are presented.
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| 2. |
- Tengblad, O., et al.
(författare)
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Phoswich scintillator for proton and gamma radiation of high energy
- 2011
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. - 9780735409835 ; 1409, s. 141-144
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Konferensbidrag (refereegranskat)abstract
- We present here a Phoswich scintillator design to achieve both high resolution gamma ray detection, and good efficiency for high energy protons. There are recent developments of new high resolution scintillator materials. Especially the LaBr3(Ce) and LaCl3(Ce) crystals have very good energy resolution in the order of 3% for 662 keV gamma radiation. In addition, these materials exhibit a very good light output (63 and 32 photons/keV respectively). A demonstrator detector in the form of an Al cylinder of 24 mm diameter and a total length of 80 mm with 2 mm wall thickness, containing a LaBr3(Ce) crystal of 20 mm diameter and 30 mm length directly coupled to a LaCl3(Ce) crystal of 50 mm length, and closed with a glass window of 5 mm, was delivered by Saint Gobain. To the glass window a Hamamatsu R5380 Photomultiplier tube (PMT) was coupled using silicon optical grease. © 2011 American Institute of Physics.
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| 3. |
- Blomberg, Erik, 1987, et al.
(författare)
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A polarimetric model of topographic effects on P-band forest backscatter
- 2015
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Ingår i: Proceedings of PolInSAR 2015.
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Konferensbidrag (refereegranskat)abstract
- P-band backscatter from boreal forest is simulated using a fully polarimetric Cylinder-Over-Ground model. Trees are represented by tapered stacks of cylinders placed over lossy dielectric planar ground that is individually fitted to the topography. The results show a strong topographic dependence and also demonstrate the limitations of the odd-, even, and volume-scattering interpretation of the Pauli decomposition. BioSAR 3 SAR images, in-situ data and LiDAR-derived DCM and DTM enable a comparison with real forest backscatter through simulation of complete plots. While many features are reproduced the need for an expansion of the model to include ground and branch scattering is identified. If sufficient agreement is achieved the model will be used to further improve topographic corrections for the retrieval of above ground forest biomass from P-band SAR images.
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| 4. |
- Blomberg, Erik, 1987
(författare)
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Biomass Retrieval in Topographic Boreal Forest using Polarimetric and Tomographic SAR in P- and L-band
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Forests and their associated habitats are an integral part of Earth's biosphere and provide essential environmental services. There is an ever present need for accurate and economic monitoring of forest parameters such as biomass - of great interest both locally, for forest management and resource utilization, and globally as it represents stored atmospheric CO2 and one of the largest uncertainties in climate modelling.Forest monitoring using orbital assets has the benefit of consistent, large scale coverage with short revisit times. Radars have an advantage over optical sensors in that they are active sensors independent of solar illumination and are much less sensitive to weather, with synthetic aperture radar (SAR) providing images comparable to optical data in resolution. The longer wavelengths used by radars interact differently with the forest canopy, with the longest wavelengths able to penetrate down to the ground even in dense forest. Radar backscatter therefore includes information about the forest structure, but may also contain significant contributions from the underlying ground surface.Electromagnetic modelling of these interactions, the focus of the first paper, is important in order to support the retrieval of relevant parameters from the returned signal. It is demonstrated that much of the variations in intensity and polarization seen in P-band SAR images can be attributed to the direct and indirect reflections of vertical stems on sloping ground. The sensitivity of forest backscatter polarization to the geometry and structure of the scene forms the basis of biomass retrieval models such as the one evaluated in the second paper, which includes all linear polarimetric components as well as a ground slope term. This model, previously evaluated for two Swedish boreal forest sites, is here revisited with a new data set and the results are shown to be consistent with previous findings, although a systematic increase in backscatter attributed to varying moisture conditions result in higher biomass estimates. The third and final paper includes the first evaluation of biomass retrieval using tomographic SAR (TomoSAR) data representative of a proposed L-band mission with two formation flying satellites. Tomography can resolve the vertical forest profile and offers a new dimension for forest structure investigation. A linear model using the HH-polarized backscatter is found to retrieve forest biomass with an RMSE of 26-30%, performing better than higher resolution data from an airborne SAR despite only utilizing a single polarization.
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| 5. |
- Blomberg, Erik, 1987, et al.
(författare)
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Evaluating P-Band TomoSAR for Biomass Retrieval in Boreal Forest
- 2021
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Ingår i: IEEE Transactions on Geoscience and Remote Sensing. - 0196-2892 .- 1558-0644. ; 59:5, s. 3793-3804
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Tidskriftsartikel (refereegranskat)abstract
- P-band synthetic aperture radar (SAR) is sensitive to above-ground biomass (AGB) but retrieval accuracy has been shown to deteriorate in topographic areas. In boreal forest, the signal penetrates through the canopy to interact with the ground producing variations in backscatter depending on ground topography, forest structure, and soil moisture. Tomographic processing of multiple SAR images Tomographic SAR (TomoSAR) provides information about the vertical backscatter distribution. This article evaluates the use of P-band TomoSAR data to improve AGB retrievals from backscattered intensity by suppressing the backscattered signal from the ground. This approach can be used even when the tomographic resolution is insufficient to resolve the vertical backscatter profile. The analysis is based on P-band data from two campaigns: BioSAR-1 (2007) in Remingstorp, southern Sweden, and BioSAR-2 (2008) in Krycklan (KR), northern Sweden. BioSAR airborne data were also processed to correspond as closely as possible to future BIOMASS TomoSAR acquisitions, with BioSAR-2-based results shown. A power law AGB model using volumetric HV polarized backscatter performs best in KR, with training residual root mean-squared error (RMSE) of 30%-36% (27-33 t/ha) for airborne data and 38%-39% for simulated BIOMASS data. Airborne TomoSAR data suggest that both vertical and horizontal tomographic resolution are of importance and that it is possible to greatly reduce AGB retrieval bias when compared with airborne P-band SAR backscatter intensity-based retrievals. A lack of significant ground slopes in Remningstorp reduces the benefit of using TomoSAR data which performs similar to retrievals based solely on P-band SAR backscatter intensity.
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| 6. |
- Blomberg, Erik, 1987, et al.
(författare)
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Evaluating spaceborne L-band pol tomo SAR for forest biomass retrieval based on airborne SAR data
- 2018
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Ingår i: Proceedings of the European Conference on Synthetic Aperture Radar, EUSAR. - 2197-4403. ; 2018-June, s. 1405-1407
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Konferensbidrag (refereegranskat)abstract
- This paper presents an evaluation of L-band tomographic synthetic-aperture radar (TomoSAR) data for forest biomass retrievals. Tomograms are processed from multiple synthetic-aperture radar (SAR) data sets from the Krycklan forest site, located in the north and south of Sweden. Tomographic performance is matched to possible future spaceborne SAR configurations such as SAOCOM-CS. Ivol, the integrated volumetric backscatter between 10 m and 30 m, is found to result in improved biomass retrievals compared to those based on slope corrected SAR intensity γ0from the original airborne E-SAR system.
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| 7. |
- Blomberg, Erik, 1987, et al.
(författare)
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Forest Biomass Retrieval from BioSAR 2010 P-band SAR Data using a Regression-Based Model
- 2015
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Ingår i: IEEE International Geoscience and Remote Sensing Symposium. - 2153-6996. - 9781479979295 ; 2015-November, s. 4193-4195
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Konferensbidrag (refereegranskat)abstract
- A model for retrieval of boreal forest biomass from polarimetric P-band SAR images developed using the BioSAR 2007 and BioSAR 2008 data sets is revisited and evaluated using data from BioSAR 2010. Incorporating the HV backscatter component as well as the HH/VV ratio and the ground slope, the model is noteworthy as performing well when retrieving biomass values in Remningstorp using parameters trained in Krycklan. These two Swedish test sites are separated by 720 km and represent two different types of boreal forest as well varying topography. SAR images and biomass estimates obtained from Remningstorp in 2010 provides an opportunity to test the model further. This dataset results in a qualitative reproduction of the previous result, showing the expected changes due to forest management, but with a relative overestimation of biomass. A large part of this can be explained by the timing as the new acquisitions took place during early autumn instead of spring with the associated changes in moisture conditions.
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| 8. |
- Blomberg, Erik, 1987, et al.
(författare)
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Forest Biomass Retrieval from L-Band SAR Using Tomographic Ground Backscatter Removal
- 2018
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Ingår i: IEEE Geoscience and Remote Sensing Letters. - 1558-0571 .- 1545-598X. ; 15:7, s. 1030-1034
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Tidskriftsartikel (refereegranskat)abstract
- A tomographic synthetic aperture radar (TomoSAR) represents a possible route to improved retrievals of forest parameters. Simulated orbital L-band TomoSAR data corresponding to the proposed Satellites for Observation and Communications-Companion Satellite (SAOCOM-CS) mission (1.275 GHz) are evaluated for retrieval of above-ground biomass in boreal forest. L-band data and biomass measurements, collected at the Krycklan test site in northern Sweden as part of the BioSAR 2008 campaign, are used to compare biomass retrievals from SAOCOM-CS to those based on SAOCOM SAR data. Both data sets are in turn compared with the corresponding airborne case, as represented by experimental airborne SAR through processing of the original SAR data. TomoSAR retrievals use a model involving a logarithmic transform of the volumetric backscatter intensity, Ivol, defined as the total backscatter originating between 10 and 30 m above ground. SAR retrievals are obtained with slope-compensated intensity γ0using the same model. It is concluded that tomography using SAOCOM-CS represents an improvement over an airborne SAR imagery, resulting in biomass retrievals from a single polarization (HH) having a 26%-30% root-mean-square error with a little to no impact from the look direction or the local topography.
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| 9. |
- Blomberg, Erik, 1987, et al.
(författare)
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P-band Polarimetric Model of Vertical Tree Stems on Sloping Ground
- 2014
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Ingår i: Joint 2014 IEEE International Geoscience and Remote Sensing Symposium, IGARSS 2014 and the 35th Canadian Symposium on Remote Sensing, CSRS 2014; Quebec Convention CentreQuebec City; Canada; 13 July 2014 through 18 July 2014. - 9781479957750 ; , s. 80-83
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Konferensbidrag (refereegranskat)abstract
- A fully polarimetric model is implemented to simulate backscatter from boreal forest. The aim is to correct for topography on a sub-stand level during the recovery of forest properties from P-band SAR data, specifically directed at the upcoming BIOMASS mission. The model incorporates the direct, double-bounce and triple-bounce scattering from tree stems on a sloping ground. Topography is introduced by assigning an independent and arbitrarily oriented local ground plane to each tree. Simulated SAR images are produced from in-situ measurements and a high resolution digital topography model (DTM) based on LiDAR data. These were obtained during BioSAR 2010 together with the corresponding SAR images, which are used for validation.
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| 10. |
- Blomberg, Erik, 1987, et al.
(författare)
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Simulated biomass retrieval from the spaceborne tomographic Saocom-CS mission at L-band
- 2016
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Ingår i: European Space Agency, (Special Publication) ESA SP. - 0379-6566. - 9789292213053 ; 740
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Konferensbidrag (refereegranskat)abstract
- This paper presents an evaluation of above-ground biomass (ABG) retrieval in boreal forests using simulated tomographic synthetic-aperture radar (SAR) data corresponding to the future SAOCOM-CS (L-band 1.275 GHz) mission. Using forest and radar data from the BioSAR 2008 campaign at the Krycklan test site in northern Sweden the expected performance of SAOCOM-CS is evaluated and compared with the E-SAR airborne Lband SAR (1.300 GHz). It is found that SAOCOM-CS data produce retrievals on par with those obtained with E-SAR, with retrievals having a relative RMSE of 30% or less. This holds true even if the acquisitions are limited to a single polarization, with HH results shown as an example.
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