Svein-Erik Hamran

• Retselis, Anastasios-Faidon; Knutsen, Elise Wright; Holdcroft, Sam; Viet, Shayla; Wahlén, Rebecka & Virdis, Mario [Show all 19 contributors for this article] (2026). CENSSAT-1: A space weather mission and an educational platform. In Detrell, Gisela; Alarcia, Ramón María García; Messina, Vincenzo & Kinnaird, Alexander (Ed.), Proceedings of the 5th Symposium on Space Educational Activities (SSEA). Technical University of Munich. p. 852–857. doi: 10.14459/2026MD1857465. Full text in Research Archive Show summary

  The Symposium on Space Educational Activities (SSEA), organised by the European Space Agency’s Education Office, provides a forum for university students, professionals working in education, and other professionals in industry or agencies to present and discuss their experiences organising, running and/or participating in Educational Activities related to Space. After successful past events in Padova (2015), Budapest (2018), Leicester (2019), and Barcelona (2022), the 5th SSEA was held in April 2026 (the 8th, 9th, and 10th) in the TUM Aerospace Campus in Willy-Messerschmitt-Strasse 5, Taufkirchen, Germany. The local organisation team was led by the Technical University of Munich (TUM), involving Professors, PostDocs, PhD Candidates, and Master’s and Bachelor’s students, in close collaboration with the Bavarian aerospace ecosystem partners.

• Jones, Alexander J.; Barnes, Robert; Gupta, Sanjeev; Paar, Gerhard; Hurowitz, Joel & Wogsland, Brittan V. [Show all 32 contributors for this article] (2026). A Fluvio-Lacustrine Environment Preserved in the Jezero Crater Inlet Channel, Neretva Vallis, Mars. Journal of Geophysical Research (JGR): Planets. ISSN 2169-9097. 131(1). doi: 10.1029/2025JE009420. Full text in Research Archive Show summary

  Martian fluvial valleys provide evidence for the surface flow of liquid water, making them a key target for rover-based investigations of ancient habitability. The Mars 2020 Perseverance rover spent ∼85 sols exploring the Bright Angel formation, exposed across the floor of Neretva Vallis: the western inlet channel of Jezero crater. This study documents the sedimentology and stratigraphy of the Bright Angel formation to reconstruct its depositional setting. The unit preserves a concave-up bedding structure consistent with a young channel-fill deposit, rather than an older unit exposed by incision of Neretva Vallis. The lower stratigraphy displays a fining-up sequence from coarse-grained sediments up to pebble-conglomerates (the Tuff Cliff member) into a ≥10-m-thick succession of laminated mudstone (the Walhalla Glades member), interpreted as a transgressive sequence recording the onset of lacustrine conditions in Neretva Vallis. Lenses of matrix-supported granule-conglomerate adjacent to the valley wall (the Fern Glen Rapids member) may preserve locally derived debris flows entering the lake. These are overlain by a polymict, matrix-supported, boulder-conglomerate (the Mount Spoonhead member), interpreted as a high-energy debrite derived from the watershed. The sequence is capped by cross-stratified sediments (the Serpentine Rapids member), preserving lake margin deposits. The Bright Angel lacustrine sequence occurs ∼10–50 m higher in elevation than the lake level anticipated for the Jezero western delta, requiring an additional period of lacustrine activity. The structure and spatial distribution of the unit leads us to propose that a late-stage blockage of Neretva Vallis may have facilitated the formation of a perched, valley-confined lake upstream.

• Barnes, Robert; Gupta, Sanjeev; Treiman, Allan; Sholes, Steven; Paar, Gerhard & Tate, Christian [Show all 28 contributors for this article] (2026). Intrusion-Induced Forced Folding Model for the Origin of Séítah Formation Domes on the Jezero Crater Floor, Mars. Journal of Geophysical Research (JGR): Planets. ISSN 2169-9097. 131(3). doi: 10.1029/2025JE009463. Full text in Research Archive
• Cardarelli, Emily L.; Árting, Uni; Paige, David A.; Hamran, Svein-Erik; Russell, Patrick & Andersson, Fredrik [Show all 11 contributors for this article] (2026). Ground penetrating radar observations of ancient large-scale deltaic structures in Jezero crater, Mars. Science Advances. 12(12), p. 1–13. doi: 10.1126/sciadv.adz6095. Full text in Research Archive
• Kolvenbach, Hendrik; Mittelholz, Anna; Stähler, Simon C.; Arm, Philip; Bickel, Valentin T. & Fuhrer, Adrian [Show all 20 contributors for this article] (2025). LunarLeaper—A mission concept to explore the lunar subsurface with a small-scale legged robot. Acta Astronautica. ISSN 0094-5765. 240, p. 63–75. doi: 10.1016/j.actaastro.2025.11.039. Full text in Research Archive Show summary

  We present the LunarLeaper mission concept, which aims to robotically investigate volcanic pits on the lunar surface. Volcanic pits, or skylights, are collapse features that may provide access to subsurface lava tubes, which could serve as shelters for future human explorers and offer insight into the volcanic history of the Moon by exposing ancient lava flows. The existence and extent of large caves are still debated today and require in situ analysis. The Marius Hills site in particular offers a potential entry point to a cave system in a volcanic region on the lunar nearside. Our mission aims to deploy a payload-equipped 15 kg-class legged robot that can approach a pit, such as the Marius Hills pit, while taking measurements during the traverse. During the mission, measurements from a ground-penetrating radar (GPR) and a gravimeter will allow us to survey the subsurface and map any underlying lava tube, if present. The mission will investigate key questions regarding lunar volcanism, such as the existence and geometry of subsurface caves and the magnitude and timing of lava flows, while assessing the site’s suitability for future human utilization and habitation. Furthermore, the mission will demonstrate key enabling technologies such as legged robots, serving as building blocks for the next generation of planetary missions.

• Hurowitz, Joel A.; Tice, M. M.; Allwood, A. C.; Cable, M. L.; Hand, K. P. & Murphy, A. E. [Show all 89 contributors for this article] (2025). Redox-driven mineral and organic associations in Jezero Crater, Mars. Nature. ISSN 0028-0836. 645(8080), p. 332–340. doi: 10.1038/s41586-025-09413-0. Full text in Research Archive Show summary

  The Perseverance rover has explored and sampled igneous and sedimentary rocks within Jezero Crater to characterize early Martian geological processes and habitability and search for potential biosignatures. Upon entering Neretva Vallis, on Jezero Crater’s western edge8, Perseverance investigated distinctive mudstone and conglomerate outcrops of the Bright Angel formation. Here we report a detailed geological, petrographic and geochemical survey of these rocks and show that organic-carbon-bearing mudstones in the Bright Angel formation contain submillimetre-scale nodules and millimetre-scale reaction fronts enriched in ferrous iron phosphate and sulfide minerals, likely vivianite and greigite, respectively. This organic carbon appears to have participated in post-depositional redox reactions that produced the observed iron-phosphate and iron-sulfide minerals. Geological context and petrography indicate that these reactions occurred at low temperatures. Within this context, we review the various pathways by which redox reactions that involve organic matter can produce the observed suite of iron-, sulfur- and phosphorus-bearing minerals in laboratory and natural environments on Earth. Ultimately, we conclude that analysis of the core sample collected from this unit using high-sensitivity instrumentation on Earth will enable the measurements required to determine the origin of the minerals, organics and textures it contains.

• Skartlien, Roar; Finden, Erlend; Knudsen, Kenneth Dahl; Loshelder, Julia; Le, Thi Minh Hue & Tavakoli, Saman [Show all 9 contributors for this article] (2025). Analysis of sensitive clays from the Gjerdrum landslide in Norway: Dielectric spectroscopy with modeled TEM IP-responses, and x-ray diffraction analysis. Journal of Applied Geophysics. ISSN 0926-9851. 242. doi: 10.1016/j.jappgeo.2025.105871. Full text in Research Archive
• Finden, Erlend; Skartlien, Roar; Holm, Sverre & Hamran, Svein-Erik (2024). Induced polarization in the transient electromagnetic method for detection of subsurface ice on Earth, Mars, and the Moon. Planetary and Space Science. ISSN 0032-0633. 254. doi: 10.1016/j.pss.2024.106007. Full text in Research Archive Show summary

  The transient electromagnetic method (TEM) can capture an induced polarization (IP) signature of subsurface ice. Using numerical modeling of a horizontally layered earth, we investigate how IP in TEM can be exploited for subsurface ice detection on Earth, Mars, and the Moon. In the model we implement electrical parameters from laboratory measurements of ice, planetary regolith simulants, and terrestrial soil from the literature. In contrast to currently applied forward models, we include two Cole–Cole relaxation terms to model the dielectric relaxation of adsorbed water or salt hydrate in addition to the relaxation of ice. On Earth, IP signals of shallow layers of silt mixed with 44–100 vol% ice embedded in resistive host layers of 3 km can be detected. Both at mid (45 N) and lower (35 N) latitudes on Mars, meter thick layers of massive ice can be detected at 10 m depth if the ice contains salts. Corresponding layers of 60 vol% ice mixed with Martian regolith simulant show similar detectability. For IP signals of lunar ice to be detected in ice volume fractions of 7.4%–46%, a development in TEM technology is required, including mitigation of early time interference, or enhancing the signal to noise level.

• Paige, David A.; Hamran, Svein-Erik; Amundsen, Hans E. Foss; Russell, Patrick; Kakaria, Reva & Mellon, Michael T. [Show all 16 contributors for this article] (2024). Ground penetrating radar observations of the contact between the western delta and the crater floor of Jezero crater, Mars. Science Advances. 10(4). doi: 10.1126/sciadv.adi8339. Full text in Research Archive
• Casademont, Titus; Dypvik, Henning; Eide, Sigurd; Berger, Tor & Hamran, Svein-Erik (2024). Martian Ground Penetrating Radar: Toward Automated Diffraction Detection for Dielectric Permittivity. IEEE Transactions on Geoscience and Remote Sensing. ISSN 0196-2892. 62. doi: 10.1109/TGRS.2024.3424948. Full text in Research Archive
• Virdis, Mario; Knutsen, Elise Wright; Kohfeldt, Anja; Jebali, Ramsey Al; Teodoro, Luis Filipe Alves & Skauli, Torbjørn [Show all 12 contributors for this article] (2024). University of Oslo CENSSAT-1 mission concept. Proceedings of the International Astronautical Congress. ISSN 0074-1795. Full text in Research Archive
• Ölçek, Deniz; Jebali, Ramsey Al; Meier, Dirk; Haavik, Andreas Fagerland; Gheorghe, Codin & Gjennestad, Magne Sødal [Show all 9 contributors for this article] (2024). Development of a compact scintillator-based gamma-ray neutron detector for terrestrial and space applications. Journal of Instrumentation (JINST). 19. doi: 10.1088/1748-0221/19/01/C01030. Full text in Research Archive
• Stack, K.M.; Ives, L.R.W.; Gupta, S.; Lamb, M.P.; Tebolt, M. & Caravaca, G. [Show all 43 contributors for this article] (2024). Sedimentology and Stratigraphy of the Shenandoah Formation, Western Fan, Jezero Crater, Mars. Journal of Geophysical Research (JGR): Planets. ISSN 2169-9097. 129(2). doi: 10.1029/2023JE008187. Full text in Research Archive
• Raguso, M.C.; Nunes, D.C.; Shoemaker, E.S.; Russell, P.; Paige, D.A. & Hamran, Svein-Erik (2024). Analysis of Orbital Sounding in Context With In-Situ Ground Penetrating Radar at Jezero Crater, Mars. Geophysical Research Letters. ISSN 0094-8276. 51(19). doi: 10.1029/2024GL109027. Full text in Research Archive
• Shoemaker, Emileigh S.; Casademont, Titus; Carter, Lynn M.; Russell, Patrick; Dypvik, Henning & Alwmark, Sanna [Show all 16 contributors for this article] (2024). Observations of Igneous Subsurface Stratigraphy during the Jezero Crater Floor Rapid Traverse from the RIMFAX Ground-penetrating Radar. The Planetary Science Journal (PSJ). 5(8). doi: 10.3847/PSJ/ad6445. Full text in Research Archive
• Eide, Sigurd; Casademont, Titus; Shoemaker, Emileigh S.; Brovoll, Sverre; Berger, Tor & Dypvik, Henning [Show all 7 contributors for this article] (2024). Assessing Radar Attenuation in RIMFAX Soundings at the Jezero Western Fan Front, Mars. Geophysical Research Letters. ISSN 0094-8276. doi: 10.1029/2023GL106471. Full text in Research Archive Show summary

  Estimates of radar attenuation in the shallow Martian subsurface are retrieved from RIMFAX soundings along the Perseverance rover traverse. Specifically, analyzed data is from the Hawksbill Gap area during the rover's first drives onto the Jezero Western Fan Front. The centroid frequency-shift method is employed to quantify attenuation in terms of the constant-Q approximation. Results are then compared with the amplitude decay method, which—in order to calculate attenuation—requires propagation velocities retrieved from radargram analysis. By verifying that results from two separate analyses are consistent, we ensure that quantified radar properties are well constrained. First estimate of constant-Q is 78.8 ± 11.6. For a subsurface propagation velocity of 0.113 m/ns, that equals an attenuation of −2.1 ± 0.4 dB/m at the RIMFAX 675 MHz center frequency. Results are consistent with dry sedimentary rocks, and are distinguishable from the magmatic lithologies on Jezero Crater Floor.

• Horgan, Briony; Udry, Arya; Rice, Melissa; Alwmark, Sanna; Amundsen, Hans E. Foss & Bell, James F. [Show all 45 contributors for this article] (2023). Mineralogy, Morphology, and Emplacement History of the Maaz Formation on the Jezero Crater Floor From Orbital and Rover Observations. Journal of Geophysical Research (JGR): Planets. ISSN 2169-9097. 128(8). doi: 10.1029/2022JE007612. Full text in Research Archive Show summary

  The first samples collected by the Perseverance rover on the Mars 2020 mission were from the Maaz formation, a lava plain that covers most of the floor of Jezero crater. Laboratory analysis of these samples back on Earth would provide important constraints on the petrologic history, aqueous processes, and timing of key events in Jezero crater. However, interpreting these samples requires a detailed understanding of the emplacement and modification history of the Maaz formation. Here we synthesize rover and orbital remote sensing data to link outcrop-scale interpretations to the broader history of the crater, including Mastcam-Z mosaics and multispectral images, SuperCam chemistry and reflectance point spectra, Radar Imager for Mars' subsurface eXperiment ground penetrating radar, and orbital hyperspectral reflectance and high-resolution images. We show that the Maaz formation is composed of a series of distinct members corresponding to basaltic to basaltic-andesite lava flows. The members exhibit variable spectral signatures dominated by high-Ca pyroxene, Fe-bearing feldspar, and hematite, which can be tied directly to igneous grains and altered matrix in abrasion patches. Spectral variations correlate with morphological variations, from recessive layers that produce a regolith lag in lower Maaz, to weathered polygonally fractured paleosurfaces and crater-retaining massive blocky hummocks in upper Maaz. The Maaz members were likely separated by one or more extended periods of time, and were subjected to variable erosion, burial, exhumation, weathering, and tectonic modification. The two unique samples from the Maaz formation are representative of this diversity, and together will provide an important geochronological framework for the history of Jezero crater.

• Simon, J.I.; Hickman-Lewis, K.; Cohen, B.A.; Mayhew, L.E.; Shuster, D.L. & Debaille, V. [Show all 68 contributors for this article] (2023). Samples Collected From the Floor of Jezero Crater With the Mars 2020 Perseverance Rover. Journal of Geophysical Research (JGR): Planets. ISSN 2169-9097. 128(6). doi: 10.1029/2022JE007474. Full text in Research Archive Show summary

  The first samples collected by the Mars 2020 mission represent units exposed on the Jezero Crater floor, from the potentially oldest Séítah formation outcrops to the potentially youngest rocks of the heavily cratered Máaz formation. Surface investigations reveal landscape-to-microscopic textural, mineralogical, and geochemical evidence for igneous lithologies, some possibly emplaced as lava flows. The samples contain major rock-forming minerals such as pyroxene, olivine, and feldspar, accessory minerals including oxides and phosphates, and evidence for various degrees of aqueous activity in the form of water-soluble salt, carbonate, sulfate, iron oxide, and iron silicate minerals. Following sample return, the compositions and ages of these variably altered igneous rocks are expected to reveal the geophysical and geochemical nature of the planet's interior at the time of emplacement, characterize martian magmatism, and place timing constraints on geologic processes, both in Jezero Crater and more widely on Mars. Petrographic observations and geochemical analyses, coupled with geochronology of secondary minerals, can also reveal the timing of aqueous activity as well as constrain the chemical and physical conditions of the environments in which these minerals precipitated, and the nature and composition of organic compounds preserved in association with these phases. Returned samples from these units will help constrain the crater chronology of Mars and the global evolution of the planet's interior, for understanding the processes that formed Jezero Crater floor units, and for constraining the style and duration of aqueous activity in Jezero Crater, past habitability, and cycling of organic elements in Jezero Crater.

• Crumpler, L.S.; Horgan, B.H.N.; Simon, J.I.; Stack, K.M.; Alwmark, S. & Dromart, G. [Show all 24 contributors for this article] (2023). In Situ Geologic Context Mapping Transect on the Floor of Jezero Crater From Mars 2020 Perseverance Rover Observations. Journal of Geophysical Research (JGR): Planets. ISSN 2169-9097. 128(10). doi: 10.1029/2022JE007444. Full text in Research Archive Show summary

  In situ geologic context mapping based on rover and helicopter observations provides documentation of a nearly continuous record of geology and exposed surface structure over a 120 m-wide corridor along the traverse of the Mars 2020/Perseverance rover. The results record the geologic context of Mars 2020 campaign sites and sample sites, including the local extent of bedrock outcrops, stratigraphy, attitude, and structure from imaging and rover-based remote sensing, and outcrop lithology based on in situ proximity science. Mapping identifies a sequence of igneous lithologies including (a) early mafic, possibly intrusive, rocks; (b) pervasively fractured and deeply altered massive bedrock of undetermined protolith; (c) buried and exhumed lava flows with pahoehoe and aa textures; (d) several varieties of regolith; and (e) small impact craters

• Casademont, Titus; Eide, Sigurd; Shoemaker, E.S.; Liu, Y.; Nunes, D.C. & Russell, P. [Show all 10 contributors for this article] (2023). RIMFAX Ground Penetrating Radar Reveals Dielectric Permittivity and Rock Density of Shallow Martian Subsurface. Journal of Geophysical Research (JGR): Planets. ISSN 2169-9097. doi: 10.1029/2022JE007598. Full text in Research Archive Show summary

  The Mars 2020 Perseverance Rover is equipped with the RIMFAX ground penetrating radar instrument which has been continuously surveying the shallow subsurface during the rover's journey. Within the first 379 mission days, we identify hyperbolic patterns in the data, which are thought to be caused by objects such as buried boulders or cavities located in the upper 5 m of the subsurface. To obtain the first detailed estimates of radar wave propagation velocity, we match these scatterer-generated patterns with theoretical traveltime hyperbolas, which take into account the refraction at the surface. We employ these estimates to derive the average dielectric permittivity and bulk rock density of the volume above the scatterer source. The parameters compare well with those obtained through orbital radar measurements and those measured by other instruments onboard the Perseverance Rover. Our findings are consistent with a subsurface dominated by solid rock and mafic material.

• Eide, Sigurd; Casademont, Titus; Berger, Tor; Dypvik, Henning; Hamran, Svein-Erik & Shoemaker, Emileigh S. (2023). Radar Attenuation in the Shallow Martian Subsurface: RIMFAX Time-Frequency Analysis and Constant-Q Characterization Over Jezero Crater Floor. Geophysical Research Letters. ISSN 0094-8276. 50(23). doi: 10.1029/2022GL101429. Full text in Research Archive Show summary

  Attenuation of radar waves in the subsurface can be quantified with a constant-Q approximation through time-frequency analysis. We implement the centroid frequency-shift method and study Radar Imager for Mars' Subsurface Exploration (RIMFAX) data acquired along the Mars 2020 Perseverance rover traverse. Attenuation is among key media properties, but quantified estimates need to account for instrument characteristics and limitations in the analysis technique. We ensure accurate constant-Q characterization and present the first estimates of radar attenuation in the upper 5 m of the shallow Martian subsurface. Over Jezero Crater Floor, constant-Q is on average 70.4 ± 7.7, which equals an attenuation of −2.6 ± 0.3 dB/m at RIMFAX’ 675 MHz center frequency. Regions comprising the Máaz or Séítah formations have similar attenuation properties that are consistent with magmatic lithologies.

• Hamran, Svein-Erik; Paige, David A.; Allwood, Abigail; Amundsen, Hans E. Foss; Berger, Tor & Brovoll, Sverre [Show all 20 contributors for this article] (2022). Ground penetrating radar observations of subsurface structures in the floor of Jezero crater, Mars. Science Advances. 8(34). doi: 10.1126/sciadv.abp8564. Full text in Research Archive
• Farley, K.A.; Stack, K.M.; Shuster, D.L.; Horgan, B.H.N.; Hurowitz, J.A. & Tarnas, J.D. [Show all 114 contributors for this article] (2022). Aqueously altered igneous rocks sampled on the floor of Jezero crater, Mars. Science. ISSN 0036-8075. 377(6614). doi: 10.1126/science.abo2196. Full text in Research Archive
• Eide, Sigurd; Casademont, Titus; Aardal, Øyvind Lund & Hamran, Svein-Erik (2022). Modeling FMCW Radar for Subsurface Analysis. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. ISSN 1939-1404. doi: 10.1109/JSTARS.2022.3165135. Full text in Research Archive Show summary

  Determining subsurface properties through ground penetrating radar sounding can be challenging, especially in planetary exploration, where little is known about the terrain and additional observations are limited. Analysis and interpretation of data acquired with the Radar Imager for Mars’ Subsurface Experiment (RIMFAX) could therefore be improved by in-detail comparison with forward modeling. RIMFAX transmits a frequency modulated continuous waveform and utilizes a stretch processing receiver, and we demonstrate how accurate modeling can be achieved through finite-difference time-domain simulations. As the simulation scheme do not allow for direct implementation of such radar system, this study presents the necessary steps in order to replicate the same transmitter and receiver characteristics. In particular, we investigate how the method holds for modeling sounding in a realistic subsurface medium with attenuating and dispersive properties, by comparing the results with analytical estimates. The modeling approach is also assessed through comparison with RIMFAX field test measurements.

• Eide, Sigurd; Hamran, Svein-Erik; Dypvik, Henning & Amundsen, Hans E. F. (2021). Ground-Penetrating Radar Modeling across the Jezero Crater Floor. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. ISSN 1939-1404. 14, p. 2484–2493. doi: 10.1109/JSTARS.2021.3055944. Full text in Research Archive Show summary

  This article assesses how the ground-penetrating radar RIMFAX will image the crater floor at the Mars 2020 landing site, where lithological compositions and stratigraphic relationships are under discussion prior to mission operation. A putative mafic unit (lava flow, volcanic ash, or volcaniclastic deposit) on the crater floor will be crucial in piecing together the chronology of deposition and for understanding the volcanic history in the region. In order to see how lithological properties and subsurface geometries affect radar sounding, a synthetic radargram is generated through forward modeling with a finite-difference time-domain method. The acquisition is simulated across the mafic unit as a succession of lava flows, exploring detection of internal structures and contacts to adjacent lithologies. To compare modeling results with the alternative formation scenarios, a discussion about sounding over a tephra or volcaniclastic material is presented. Similarities and differences between Martian and terrestrial lithologies can be related to electromagnetic properties relevant for radar sounding. This article, therefore, evaluates potential scientific insights gained from acquisition across the disputed mafic unit, in light of proposed hypotheses of lithological generation.

• Farley, Kenneth A.; Williford, Kenneth H.; Stack, Kathryn M.; Bhartia, Rohit; Chen, Al & Torre, Manuel de la [Show all 30 contributors for this article] (2020). Mars 2020 mission overview. Space Science Reviews. ISSN 0038-6308. 216:142(8), p. 1–41. doi: 10.1007/s11214-020-00762-y. Full text in Research Archive
• Stack, Kathryn M.; Williams, Nathan R; III, Fred Calef; Sun, Vivian Z; Williford, Kenneth H & Farley, Kenneth A. [Show all 67 contributors for this article] (2020). Photogeologic Map of the Perseverance Rover Field Site in Jezero Crater Constructed by the Mars 2020 Science Team. Space Science Reviews. ISSN 0038-6308. 216. doi: 10.1007/s11214-020-00739-x. Full text in Research Archive
• Eriksrød, Jon Håvard; Burkhart, John; Lande, Tor Sverre & Hamran, Svein-Erik (2020). Bistatic SAR Radar for Long-Term Snow Pack Monitoring. IEEE Transactions on Geoscience and Remote Sensing. ISSN 0196-2892. 58(1), p. 218–226. doi: 10.1109/TGRS.2019.2935781. Full text in Research Archive
• Hamran, Svein-Erik; Paige, David A.; Amundsen, Hans E. Foss; Berger, Tor; Brovoll, Sverre & Carter, Lynn [Show all 19 contributors for this article] (2020). Radar imager for Mars’ subsurface experiment—RIMFAX. Space Science Reviews. ISSN 0038-6308. doi: 10.1007/s11214-020-00740-4. Full text in Research Archive Show summary

  The Radar Imager for Mars’ Subsurface Experiment (RIMFAX) is a Ground Penetrating Radar on the Mars 2020 mission’s Perseverance rover, which is planned to land near a deltaic landform in Jezero crater. RIMFAX will add a new dimension to rover investigations of Mars by providing the capability to image the shallow subsurface beneath the rover. The principal goals of the RIMFAX investigation are to image subsurface structure, and to provide information regarding subsurface composition. Data provided by RIMFAX will aid Perseverance’s mission to explore the ancient habitability of its field area and to select a set of promising geologic samples for analysis, caching, and eventual return to Earth. RIMFAX is a Frequency Modulated Continuous Wave (FMCW) radar, which transmits a signal swept through a range of frequencies, rather than a single wide-band pulse. The operating frequency range of 150–1200 MHz covers the typical frequencies of GPR used in geology. In general, the full bandwidth (with effective center frequency of 675 MHz) will be used for shallow imaging down to several meters, and a reduced bandwidth of the lower frequencies (center frequency 375 MHz) will be used for imaging deeper structures. The majority of data will be collected at regular distance intervals whenever the rover is driving, in each of the deep, shallow, and surface modes. Stationary measurements with extended integration times will improve depth range and SNR at select locations. The RIMFAX instrument consists of an electronic unit housed inside the rover body and an antenna mounted externally at the rear of the rover. Several instrument prototypes have been field tested in different geological settings, including glaciers, permafrost sediments, bioherme mound structures in limestone, and sedimentary features in sand dunes. Numerical modelling has provided a first assessment of RIMFAX’s imaging potential using parameters simulated for the Jezero crater landing site.

• Gonzales, Edward; Cordoba, Elizabeth & Hamran, Svein-Erik (2017). Compatibility tests between the mars vehicle system test bed and RIMFAX radar antenna prototype for the mars 2020 mission. IEEE International Symposium on Electromagnetic Compatibility. ISSN 1077-4076. p. 44–50. doi: 10.1109/ISEMC.2017.8077839. Full text in Research Archive
• Aardal, Øyvind; Brovoll, Sverre; Berger, Tor; Balasingham, Ilangko & Hamran, Svein-Erik (2017). Phase distortions in radar respiration monitoring, 2017 First IEEE MTT-S International Microwave Bio Conference (IMBIOC). IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781538617137. doi: 10.1109/IMBIOC.2017.7965778. Full text in Research Archive
• Bjørndal, Øystein; Hamran, Svein-Erik & Lande, Tor Sverre (2017). Bitstream radar waveforms for generic single-chip radar. International Journal of Microwave and Wireless Technologies (IJMWT). ISSN 1759-0787. doi: 10.1017/S1759078717000782. Full text in Research Archive Show summary

  A Digital-to-Time converter (DTC) based on static CMOS multiplexers is presented, achieving a time resolution of 65 ps consuming 0.5 mW. The DTC relies on gate delay for programmability, ensuring robustness, linearity and wide delay range. Details of the transistor implementation (with sizes) is given, together with a detailed discussion on critical design points. Post layout simulations with Monte Carlo, voltage and temperature variations are presented with measurements from two different chip realizations in 90 nm CMOS.

• Ciarletti, Valérie; Clifford, Stephen; Plettemeier, Dirk; Gall, Alice Le; Herve, Yann & Dorizon, Sophie [Show all 16 contributors for this article] (2017). The WISDOM Radar: Unveiling the Subsurface Beneath the ExoMars Rover and Identifying the Best Locations for Drilling. Astrobiology. ISSN 1531-1074. doi: 10.1089/ast.2016.1532. Full text in Research Archive Show summary

  The search for evidence of past or present life on Mars is the principal objective of the 2020 ESA-Roscosmos ExoMars Rover mission. If such evidence is to be found anywhere, it will most likely be in the subsurface, where organic molecules are shielded from the destructive effects of ionizing radiation and atmospheric oxidants. For this reason, the ExoMars Rover mission has been optimized to investigate the subsurface to identify, understand, and sample those locations where conditions for the preservation of evidence of past life are most likely to be found. The Water Ice Subsurface Deposit Observation on Mars (WISDOM) ground-penetrating radar has been designed to provide information about the nature of the shallow subsurface over depth ranging from 3 to 10 m (with a vertical resolution of up to 3 cm), depending on the dielectric properties of the regolith. This depth range is critical to understanding the geologic evolution stratigraphy and distribution and state of subsurface H2O, which provide important clues in the search for life and the identification of optimal drilling sites for investigation and sampling by the Rover's 2-m drill. WISDOM will help ensure the safety and success of drilling operations by identification of potential hazards that might interfere with retrieval of subsurface samples. Key Words: Ground penetrating radar—Martian shallow subsurface—ExoMars.

• García-Pardo, Concepción; Chavez-Santiago, Raul; Fornes-Leal, Alejandro; Brovoll, Sverre; Aardal, Øyvind & Bergsland, Jacob [Show all 10 contributors for this article] (2016). Experimental Ultra Wideband Path Loss Models for Implant Communications, 2016 IEEE 27th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), 4-8 September 2016. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781509032549. doi: 10.1109/PIMRC.2016.7794780. Full text in Research Archive
• Bjørndal, Øystein; Hamran, Svein-Erik & Lande, Tor Sverre (2016). Square wave architectures for radar-on-chip. In Gibson, Andrew (Eds.), 2016 46th European Microwave Conference (EuMC). IEEE (Institute of Electrical and Electronics Engineers). ISSN 9782874870439. p. 1485–1488. doi: 10.1109/EuMC.2016.7824636. Full text in Research Archive
• Bjørndal, Øystein; Hamran, Svein-Erik & Lande, Tor Sverre (2015). UWB waveform generator for digital CMOS radar. In Almeida, Teresa Mendes de (Eds.), Circuits and Systems (ISCAS), 2015 IEEE International Symposium on. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781479983919. p. 1510–1513. doi: 10.1109/ISCAS.2015.7168932. Full text in Research Archive
• Solberg, Lars Erik; Aardal, Øyvind; Berger, Tor; Balasingham, Ilangko; Fosse, Erik & Hamran, Svein-Erik (2015). Experimental investigation into radar-based central blood pressure estimation. IET Radar, Sonar & Navigation. ISSN 1751-8784. 9(2). doi: 10.1049/iet-rsn.2014.0206. Full text in Research Archive Show summary

  To assess whether radar technology can be used for monitoring blood pressure via information from the aorta, two experiments were performed: (i) measurements on a phantom model and (ii) acquisitions on a human subject for in vivo experiments. A linear dependency of phase on radius in the radar echoes in the phantom model showed that the information regarding the radius of a circular, cylindrical object depended on the clutter environment: in a low-clutter case two distinct reflections were identified, whereas in the high-clutter case it was possible to extract a proxy. Radar echoes from antennas strapped to the back of a human subject showed a clear signature from a discernible, distinct reflector believed to be the aorta. However, as for the high-clutter case, only a proxy for aortic radius is available as basis for estimation, which is most likely coupled with aortic displacements.

• Aardal, Øyvind; Brovoll, Sverre; Paichard, Yoann; Berger, Tor; Lande, Tor Sverre & Hamran, Svein-Erik (2015). Radar sensitivity to human heartbeats and respiration. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. doi: 10.1117/12.2180924. Full text in Research Archive Show summary

  Human heartbeats and respiration can be detected from a distance using radar. This can be used for medical applications and human being detection. It is useful to have a system independent measure of how detectable the vital signs are. In radar applications, the Radar Cross Section (RCS) is normally used to characterize the detectability of an object. Since the human vital signs are seen by the radar as movements of the torso, the modulations in the person RCS can be used as a system independent measure of the vital signs detectability. In this paper, measurements of persons seated in an anechoic chamber are presented. The measurements were calibrated using empty room and a metallic calibration sphere. A narrowband radar operating at frequencies from 500 MHz to 18 GHz in discrete steps was used. A turntable provided measurements at precise aspect angles all around the person under test. In an I & Q receiver, the heartbeat and respiration modulation is a combination of amplitude and phase mod- modulations. The measurements were filtered, leaving the modulations from the vital signs in the radar recordings. The procedure for RCS computation was applied to these filtered data, capturing the complex signatures. It was found that both the heartbeat and respiration detectability increase with increasing frequency. The heartbeat signatures are almost equal from the front and the back, while being almost undetectable from the sides of the person. The respiration signatures are slightly higher from the front than from the back, and smaller from the sides. The signature measurements presented in this paper provide an objective system independent measure of the detectability of human vital signs as a function of frequency and aspect angle. These measures are useful for example in system design and in assessing real measurement scenarios. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

• Berger, Tor & Hamran, Svein-Erik (2015). Harmonic Synthetic Aperture Radar Processing. IEEE Geoscience and Remote Sensing Letters. ISSN 1545-598X. doi: 10.1109/LGRS.2015.2447517. Full text in Research Archive Show summary

  We review the basic concept of frequency-modulated continuous wave (FMCW) and describe how such a radar system can be used in a harmonic radar concept. It is argued that synthetic aperture radar (SAR) for FMCW harmonic radar can be implemented by carefully choosing the wavenumbers in the mixing part of the FMCW concept. It is also argued that the following SAR processing is an extension of conventional SAR processing when applied to a harmonic FMCW system.

• Floor, Pål Anders; Chavez-Santiago, Raul; Brovoll, Sverre; Aardal, Øyvind; Bergsland, Jacob & Grymyr, Ole-Johannes [Show all 12 contributors for this article] (2015). In-Body to On-Body Ultrawideband Propagation Model Derived from Measurements in Living Animals. IEEE Journal of Biomedical and Health Informatics. ISSN 2168-2194. 19(3). doi: 10.1109/JBHI.2015.2417805. Full text in Research Archive Show summary

  Ultra wideband (UWB) radio technology for wireless implants has gained significant attention. UWB enables the fabrication of faster and smaller transceivers with ultra low power consumption, which may be integrated into more sophisticated implantable biomedical sensors and actuators. Nevertheless, the large path loss suffered by UWB signals propagating through inhomogeneous layers of biological tissues is a major hindering factor. For the optimal design of implantable transceivers, the accurate characterization of the UWB radio propagation in living biological tissues is indispensable. Channel measurements in phantoms and numerical simulations with digital anatomical models provide good initial insight into the expected path loss in complex propagation media like the human body, but they often fail to capture the effects of blood circulation, respiration, and temperature gradients of a living subject. Therefore, we performed UWB channel measurements within 1-6 GHz on two living porcine subjects because of the anatomical resemblance with an average human torso. We present for the first time a path loss model derived from these invivo measurements, which includes the frequency-dependent attenuation. The use of multiple on-body receiving antennas to combat the high propagation losses in implant radio channels was also investigated.

• Langley, Kirsty A; Kohler, Jack; Sinisalo, Anna Katariina; Øyan, Mats Jørgen; Hamran, Svein-Erik & Hattermann, Tore [Show all 9 contributors for this article] (2014). Low melt rates with seasonal variability at the base of Fimbul Ice Shelf, East Antarctica, revealed by in situ interferometric radar measurements. Geophysical Research Letters. ISSN 0094-8276. 41(22), p. 8138–8146. doi: 10.1002/2014GL061782. Full text in Research Archive
• Brovoll, Sverre; Berger, Tor; Paichard, Yoann; Aardal, Øyvind; Lande, Tor Sverre & Hamran, Svein-Erik (2014). Time-lapse imaging of human heart motion with switched array UWB radar. IEEE Transactions on Biomedical Circuits and Systems. ISSN 1932-4545. doi: 10.1109/TBCAS.2014.2359995. Full text in Research Archive Show summary

  Radar systems for detection of human heartbeats have mostly been single-channel systems with limited spatial resolution. In this paper, a radar system for ultra-wideband (UWB) imaging of the human heart is presented. To make the radar waves penetrate the human tissue the antenna is placed very close to the body. The antenna is an array with eight elements, and an antenna switch system connects the radar to the individual elements in sequence to form an image. Successive images are used to build up time-lapse movies of the beating heart. Measurements on a human test subject are presented and the heart motion is estimated at different locations inside the body. The movies show rhythmic motion consistent with the beating heart, and the location and shape of the reflections correspond well with the expected response form the heart wall. The spatial dependent heart motion is compared to ECG recordings, and it is confirmed that heartbeat modulations are seen in the radar data. This work shows that radar imaging of the human heart may provide valuable information on the mechanical movement of the heart.

• Øyan, Mats Jørgen; Hamran, Svein-Erik; Damsgård, Leif & Berger, Tor (2014). Compact airborne C-band radar sounder. IEEE Transactions on Geoscience and Remote Sensing. ISSN 0196-2892. doi: 10.1109/TGRS.2013.2296074. Full text in Research Archive Show summary

  We describe a lightweight wideband C-band radar sounder, which is designed for use in a small unmanned aerial vehicle, primarily for measuring snow and ice. The waveform used is a gated frequency modulated continuous wave, which enables transmission at low power with relatively high energy in the compressed pulse. Gating allows use of a single antenna, reducing the influence of the direct wave on the systems' dynamic range. The radar operates at 5.3-GHz center frequency and has a bandwidth of 1 GHz, for a nominal range resolution of 15 cm in air or 12 cm in snow. Laboratory testing and airborne acquisition of data over the glacier Hardangerjøkulen show that the radar appears to work well for the intended purpose of measuring snow layer thickness.

• Sinisalo, Anna Katariina; Anschütz, Helgard; Aasen, Anne Tårånd; Langley, Kirsty A; Deschwanden, Angela von & Kohler, Jack [Show all 13 contributors for this article] (2013). Surface mass balance on Fimbul ice shelf, East Antarctica: Comparison of field measurements and large-scale studies. Journal of Geophysical Research (JGR): Atmospheres. ISSN 2169-897X. 118(20), p. 11625–11635. doi: 10.1002/jgrd.50875. Full text in Research Archive
• Aardal, Øyvind; Paichard, Yoann; Brovoll, Sverre; Berger, Tor; Lande, Tor Sverre & Hamran, Svein-Erik (2013). Physical Working Principles of Medical Radar. IEEE Transactions on Biomedical Engineering. ISSN 0018-9294. doi: 10.1109/TBME.2012.2228263. Full text in Research Archive Show summary

  There has been research interest in using radar for contactless measurements of the human heartbeat for several years. While many systems have been demonstrated, not much attention have been given to the actual physical causes of why this work. The consensus seems to be that the radar senses small body movements correlated with heartbeats, but whether only the movements of the body surface or reflections from internal organs are also monitored have not been answered definitely. There has recently been proposed another theory that blood perfusion in the skin could be the main reason radars are able to detect heartbeats. In this paper, an experimental approach is given to determine the physical causes. The measurement results show that it is the body surface reflections that dominate radar measurements of human heartbeats.

• Vu, Tuan Anh; Sudalaiyandi, Shanthi; Hjortland, Håkon André; Næss, Øivind; Lande, Tor Sverre & Hamran, Svein-Erik (2012). A Variable-Gain Single-Bit Ultra-Wideband Quantizer for Baseband Receiver Front-End. In Wang, C (Eds.), 2012 IEEE Asia Pacific Conference on Circuits and Systems. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781457717284. p. 483–486. doi: 10.1109/apccas.2012.6419077. Full text in Research Archive
• Lecomte, Isabelle; Juliussen, Håvard; Støren, Eivind Wilhelm Nagel; Sauvin, Guillaume Cédric; Hamran, Svein-Erik & Lavrientiev, Ivan [Show all 9 contributors for this article] (2012). Geophysical Investigations of Unstable Mountain Slopes in Jotunheimen, Norway. In Several, Authors (Eds.), Near Surface Geoscience 2012. European Association of Geoscientists and Engineers (EAGE). ISSN 9789073834347. doi: 10.3997/2214-4609.20143461. Full text in Research Archive
• Berger, Tor & Hamran, Svein-Erik (2012). Experiments with autofocus for strip map synthetic aperture radar data. IEEE International Conference on Radar (RADAR). ISSN 1097-5764. doi: 10.1109/RADAR.2012.6212108. Full text in Research Archive
• Øyan, Mats Jørgen; Hamran, Svein-Erik; Hanssen, Leif; Berger, Tor & Plettemeier, Dirk (2012). Ultrawideband Gated Step Frequency Ground-Penetrating Radar. IEEE Transactions on Geoscience and Remote Sensing. ISSN 0196-2892. doi: 10.1109/TGRS.2011.2160069. Full text in Research Archive Show summary

  We describe a prototype ultrawideband radar. We show how the system was designed and how the hardware was developed for the radar prototype. Waveform generation, radar parameters, and signal processing for the stepped frequency waveform are discussed. The radar operates from 500 MHz to 3 GHz with a nominal resolution of 6 cm in air. The advantage of the stepped frequency approach over an impulse radar is better matching between the transmitted waveform and the receiver. We use range gating to improve the system dynamic range. The advantages are illustrated with laboratory measurements and field measurements from glacial ice and permafrost in Svalbard, showing penetration depths of 11 m. Antennas which do not require contact with the ground were developed and used in the experiments.

• Solberg, Lars Erik; Hamran, Svein-Erik & Balasingham, Ilangko (2011). Realistic Simulations of Aorta Radius Estimation. In Marchetti, Nicola & Frattasi, Luigi (Ed.), 4th International Symposium on Applied Sciences in Biomedical and Communication Technologies. ACM Publications. ISSN 9781450309134. doi: 10.1145/2093698.2093745. Full text in Research Archive
• Ciarletti, Valerie; Corbel, Charlotte; Plettemeier, Dirk; Cais, Philippe; Clifford, Stephen M. & Hamran, Svein-Erik (2011). WISDOM GPR Designed for Shallow and High-Resolution Sounding of the Martian Subsurface. Proceedings of the IEEE. ISSN 0018-9219. 99(5), p. 824–836. doi: 10.1109/JPROC.2010.2100790. Full text in Research Archive
• Anschütz, Helgard; Sinisalo, Anna Katariina; Isaksson, Elisabeth; McConnell, Joseph R.; Hamran, Svein-Erik & Bisiaux, M. M. [Show all 9 contributors for this article] (2011). Variation of accumulation rates over the last eight centuries on the East Antarctic Plateau derived from volcanic signals in ice cores. Journal of Geophysical Research (JGR): Atmospheres. ISSN 2169-897X. 116. doi: 10.1029/2011JD015753. Full text in Research Archive
• Aardal, Øyvind; Hamran, Svein-Erik; Berger, Tor; Paichard, Yoann & Lande, Tor Sverre (2011). Chest movement estimation from radar modulation caused by heartbeats. In Cauwenberghs, G. (Eds.), IEEE Biomedical Circuits and Systems Conference 2011. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781457714696. p. 422–425. doi: 10.1109/biocas.2011.6107825. Full text in Research Archive
• Müller, Karsten; Hamran, Svein-Erik; Sinisalo, Anna Katariina & Hagen, Jon Ove Methlie (2011). Phase Center of L-Band Radar in Polar Snow and Ice. IEEE Transactions on Geoscience and Remote Sensing. ISSN 0196-2892. 49(11), p. 4572–4579. doi: 10.1109/TGRS.2011.2140376. Full text in Research Archive
• Vu, Tuan Anh; Sudalaiyandi, Shanthi; Hjortland, Håkon André; Næss, Øivind; Lande, Tor Sverre & Hamran, Svein-Erik (2011). A 70-dB, 3.1-10.6-GHz CMOS Amplifier in Low-Power 90 nm CMOS. The Midwest Symposium on Circuits and Systems conference proceedings. ISSN 1548-3746. p. 1–4. doi: 10.1109/MWSCAS.2011.6026639. Full text in Research Archive
• Vu, Tuan Anh; Sudalaiyandi, Shanthi; Hjortland, Håkon André; Næss, Øivind; Lande, Tor Sverre & Hamran, Svein-Erik (2011). An ultra-wideband, continuous-time, differential, single-bit quantizer in 90 nm CMOS. In Nooshabadi, Saeid (Eds.), Circuits and Systems (MWSCAS), 2011 IEEE 54th International Midwest Symposium on. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781612848563. p. 1–4. doi: 10.1109/mwscas.2011.6026680. Full text in Research Archive
• Vu, Tuan Anh; Sudalaiyandi, Shanthi; Hjortland, Håkon André; Næss, Øivind; Lande, Tor Sverre & Hamran, Svein-Erik (2011). An Ultra-Wideband, Continuous-Time, Differential, Single-Bit Quantizer in 90 nm CMOS. The Midwest Symposium on Circuits and Systems conference proceedings. ISSN 1548-3746. doi: 10.1109/MWSCAS.2011.6026680. Full text in Research Archive
• Aardal, Øyvind; Hamran, Svein-Erik; Berger, Tor; Hammerstad, Jan & Lande, Tor Sverre (2011). Radar cross section of the human heartbeat and respiration in the 500MHz to 3GHz band. In Ponchak, George E. (Eds.), Radio and Wireless Symposium (RWS), 2011 IEEE. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781424476879. p. 422–425. doi: 10.1109/rws.2011.5725466. Full text in Research Archive
• Berger, Tor; Tollisen, Steffen & Hamran, Svein-Erik (2011). Comparison of two methods for automatic range alignment in ISAR imaging. IEEE International Conference on Radar (RADAR). ISSN 1097-5764. doi: 10.1109/RADAR.2011.5960489. Full text in Research Archive Show summary

  A maximum likelihood algorithm for translational motion estimation (TME) in ISAR imaging is described and compared with prominent point processing (PPP). It is suggested that the kurtosis (fourth order central moment) of averaged range profiles can be used to decide on which of the two methods that gives the best results in terms of image sharpness. Experimental data of a small aircraft is collected and processed in short intervals. Results from the PPP and the TME algorithms are compared, automatically in terms of a sharpness measure, and also by user inspection. The results indicate that for low kurtosis regions the TME method should be used, while for high kurtosis regions, the PPP method is preferred.

• Solberg, Lars Erik; Balasingham, Ilangko & Hamran, Svein-Erik (2010). Candidate Estimators for Aorta Diameter Estimation Using Monostatic Radar. In Leung, Victor & Vasilakos, Athanasios (Ed.), 5th International ICST Conference on Body Area Networks. The Institute for Computer Sciences, Social Informatics and Telecommunications Engineering (ICST). ISSN 9789639995017. Full text in Research Archive
• Aardal, Øyvind; Hamran, Svein-Erik; Berger, Tor; Hammerstad, Jan & Lande, Tor Sverre (2010). Radar Cross Section of the Human Heartbeat and Respiration. In Georgiou, Julius (Eds.), Proceedings of BioCAS 2010. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781424472680. Full text in Research Archive
• Vu, Tuan Anh; Sudalaiyandi, Shanthi; Dooghabadi, Malihe Zarre; Hjortland, Håkon André; Næss, Øivind & Lande, Tor Sverre [Show all 7 contributors for this article] (2010). Continuous-Time CMOS Quantizer for Ultra-Wideband Applications. IEEE International Symposium on Circuits and Systems proceedings. ISSN 0271-4302. p. 3757–3760. Full text in Research Archive
• Müller, Karsten; Sinisalo, Anna Katariina; Anschütz, Helgard; Hamran, Svein-Erik; Hagen, Jon Ove Methlie & McConnell, Joseph [Show all 7 contributors for this article] (2010). An 860 km surface mass-balance profile on the East Antarctic plateau derived by GPR. Annals of Glaciology. ISSN 0260-3055. 51(55), p. 1–8. Full text in Research Archive
• Berger, Tor & Hamran, Svein-Erik (2010). An efficient scaled maximum likelihood algorithm for translational motion estimation in ISAR imaging. IEEE International Conference on Radar (RADAR). ISSN 1097-5764. p. 75–80. Full text in Research Archive
• Tuan, Anh Vu; Sudalaiyandi, Shanthi; Dooghabadi, Malihe Zarre; Hjortland, Håkon André; Næss, Øivind & Lande, Tor Sverre [Show all 7 contributors for this article] (2010). Continuous-time CMOS quantizer for ultra-wideband applications. In Serdijn, Wouter A. (Eds.), Circuits and Systems (ISCAS), Proceedings of 2010 IEEE International Symposium on. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781424453085. p. 3757–3761. Full text in Research Archive
• Sudalaiyandi, Shanthi; Dooghabadi, Malihe Zarre; Tuan, Anh Vu; Hjortland, Håkon André; Næss, Øivind & Lande, Tor Sverre [Show all 7 contributors for this article] (2010). Power-efficient CTBV symbol detector for UWB applications. In Hong, Wei (Eds.), Proceedings of IEEE International Conference on Ultra Wideband. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781424453054. p. 1–4. Full text in Research Archive
• Solberg, Lars Erik; Hamran, Svein-Erik; Berger, Tor & Balasingham, Ilangko (2010). Minimum Variance Signal Selection for Aorta Radius Estimation Using Radar. EURASIP Journal on Advances in Signal Processing. ISSN 1687-6172. doi: 10.1155/2010/682037. Full text in Research Archive Show summary

  This paper studies the optimum signal choice for the estimation of the aortic blood pressure via aorta radius, using a monostatic radar configuration. The method involves developing the Cramér-Rao lower bound (CRLB) for a simplified model. The CRLB for model parameters are compared with simulation results using a grid-based approach for estimation. The CRLBs are within the 99% confidence intervals for all chosen parameter values. The CRLBs show an optimal region within an ellipsoid centered at 1 GHz center frequency and 1.25 GHz bandwidth with axes of 0.5 GHz and 1 GHz, respectively. Calculations show that emitted signal energy to received noise spectral density should exceed for a precision of approximately 0.1 mm for a large range of model parameters. This implies a minimum average power of 0.4  . These values are based on optimistic assumptions. Reflections, improved propagation model, true receiver noise, and parameter ranges should be considered in a practical implementation.

• Solberg, Lars Erik; Balasingham, Ilangko; Hamran, Svein-Erik & Fosse, Erik (2009). A Feasibility Study on Aortic Pressure Estimation Using UWB Radar. In Beaulieu, Norman & Milstein, Laurence (Ed.), Ultra-Wideband, 2009. ICUWB 2009. IEEE International Conference on. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781424429301. p. 464–468. Full text in Research Archive
• Brandt, Ola; Langley, Kirsty; Giannopoulos, Antonios; Hamran, Svein-Erik & Kohler, Jack (2009). Radar Response of Firn Exposed to Seasonal Percolation, Validation Using Cores and FDTD Modeling. IEEE Transactions on Geoscience and Remote Sensing. ISSN 0196-2892. 47(8), p. 2773–2786. doi: 10.1109/TGRS.2009.2016555. Full text in Research Archive
• Dooghabadi, Malihe Zarre; Vu, Anh Tuan; Sudalaiyandi, Shanthi; Hjortland, Håkon André; Lande, Tor Sverre & Næss, Øivind [Show all 7 contributors for this article] (2009). Electromagnetic Impulse Radio Camera. In Ytterdal, Trond & Aunet, Snorre (Ed.), Proceedings of the 27th Norchip Conference, Trondheim, 16.-17. November, 2009. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781424443116. Full text in Research Archive
• Soldovieri, F; Prisco, G & Hamran, Svein-Erik (2009). A preparatory study on subsurface exploration on Mars using GPR and microwave tomography. Planetary and Space Science. ISSN 0032-0633. 57(8-9), p. 1076–1084. doi: 10.1016/j.pss.2008.11.014. Full text in Research Archive
• Langley, Kirsty A; Lacroix, P; Hamran, Svein-Erik & Brandt, O (2009). Sources of backscatter at 5.3 GHz from a superimposed ice and firn area revealed by multi-frequency GPR and cores. Journal of Glaciology. ISSN 0022-1430. 55(190), p. 373–383. Full text in Research Archive
• Vu, Anh Tuan; Dooghabadi, Malihe Zarre; Sudalaiyandi, Shanthi; Hjortland, Håkon André; Næss, Øivind & Lande, Tor Sverre [Show all 7 contributors for this article] (2009). UWB Vivaldi Antenna for Beamforming. In Ytterdal, Trond & Aunet, Snorre (Ed.), Proceedings of the 27th Norchip Conference, Trondheim, 16.-17. November, 2009. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781424443116. Full text in Research Archive
• Brandt, Ola; Langley, Kirsty; Giannopoulos, Antonios; Hamran, Svein Erik & Kohler, Jack (2009). Radar Response of Firn Exposed to Seasonal Percolation, Validation Using Cores and FDTD Modeling. IEEE Transactions on Geoscience and Remote Sensing. ISSN 0196-2892. 47(8), p. 2773–2786. doi: 10.1109/TGRS.2009.2016555. Full text in Research Archive Show summary

  We use ground-penetrating radars (GPRs), firn cores, and electromagnetic finite-difference time-domain (FDTD) numerical modeling to characterize the GPR response to a frozen high-arctic firn pack. As a result of extensive summertime percolation, the firn pack comprises a high fraction of ice layers, lenses, and vertical glands. We show that the GPR response on the firn pack mainly depends on the following: 1) the thickness of the ice layers; 2) the distance between layers; 3) the layer roughness; and 4) the presence or absence of elliptical ice lenses. Using 3-D FDTD modeling, we show that the GPR is not sensitive to typical ice glands, which implies that the GPR underestimates firn heterogeneity, such that firn stratigraphy in percolation and wet-snow zones could be incorrectly interpreted as being better preserved than it actually is. We find that thin ice layers (< 0.05 m) or multiple thin ice layers give a strong response. Thicker ice layers typically give a weaker backscatter per unit area, mainly due to the lack of interference of the reflections from the upper and lower interfaces, but are, due to their continuity, easily trackable. Ice layers with a thickness comparable to the GPR wavelength give 180. phase-shifted upper and lower reflections and are, in general, separated by a band of low GPR response, due to the lack of permittivity contrast within the ice layers. Despite the ice lenses' relatively short horizontal correlation length, as inferred from cores, bands of high-amplitude clutter caused by these features can be traced over several kilometers in GPR profiles.

• Langley, Kirsty; Hamran, Svein-Erik; Høgda, Kjell Arild; Hogda, KA; Storvold, Rune & Brandt, Ola [Show all 8 contributors for this article] (2008). From glacier facies to SAR backscatter zones via GPR. IEEE Transactions on Geoscience and Remote Sensing. ISSN 0196-2892. 46(9), p. 2506–2516. doi: 10.1109/TGRS.2008.918648. Full text in Research Archive
• Lacroix, P; Legresy, B; Langley, Kirsty A; Hamran, Svein-Erik; Kohler, Jack & Roques, S [Show all 8 contributors for this article] (2008). In situ measurements of snow surface roughness using a laser profiler. Journal of Glaciology. ISSN 0022-1430. 54(187), p. 753–762. Full text in Research Archive
• Langley, Kirsty A; Hamran, Svein-Erik; Hogda, KA; Storvold, R; Brandt, O & Hagen, Jon Ove Methlie [Show all 7 contributors for this article] (2007). Use of C-band ground penetrating radar to determine backscatter sources within glaciers. IEEE Transactions on Geoscience and Remote Sensing. ISSN 0196-2892. 45(5), p. 1236–1246. doi: 10.1109/TGRS.2007.892600. Full text in Research Archive
• Brandt, O; Langley, Kirsty; Kohler, Jack & Hamran, Svein-Erik (2007). Detection of buried ice and sediment layers in permafrost using multi-frequency Ground Penetrating Radar: A case examination on Svalbard. Remote Sensing of Environment. ISSN 0034-4257. 111(2-3), p. 212–227. doi: 10.1016/j.rse.2007.03.025. Full text in Research Archive
• Lecomte, Isabelle; Hamran, Svein-Erik & Gelius, Leiv-J. (2005). Improving Kirchhoff migration with repeated local plane-wave imaging? A SAR-inspired signal-processing approach. Geophysical Prospecting. ISSN 0016-8025. 53, p. 767–785. Full text in Research Archive
• Hamran, Svein-Erik; Lecomte, Isabelle & Gelius, Leiv-J. (2003). Local Plane-Wave Imaging of GPR Data. Journal of Environmental & Engineering Geophysics. ISSN 1083-1363. 8, p. 115–121. Full text in Research Archive
• Lecomte, I.; Gelius, Leiv-J. & Hamran, Svein-Erik (2002). Local imaging approach and applications. In EAGE, . (Eds.), Extended Abstracts Book: 64th EAGE Conference and Technical Exhibition, Florence, Italy. EAGE. ISSN 9789073781207. Full text in Research Archive

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• Holdcroft, Sam; Bocci, Alessio; Scholtz, Laura-Kristin; Retselis, Anastasios-Faidon; Knutsen, Elise Wright & Jebali, Ramsey Al [Show all 20 contributors for this article] (2025). CENSSAT-1 mission concept: a CubeSat for space weather monitoring. doi: 10.5281/ZENODO.17036544. Full text in Research Archive Show summary

  This paper presents an introduction to the CENSSAT-1 mission, an 8U CubeSat, which aims to study space situational awareness. It will investigate the effects of space weather on Earth from a 500 km orbit, using a camera, multi-purpose particle detector, and a Langmuir probe. It will additionally monitor space debris using a radar instrument, and conduct experiments on optimal control and drag based manoeuvring. CENSSAT-1 is aiming for launch in 2027.

• Aardal, Øyvind; Brovoll, Sverre; Berger, Tor; Balasingham, Ilangko & Hamran, Svein-Erik (2017). Phase distortions in radar respiration monitoring. Full text in Research Archive
• Hamran, Svein-Erik; Øyan, Mats Jørgen & Skaugvoll, Grethe (2016). FFI lager Mars-radar for Nasa. Full text in Research Archive Show summary

  I denne podcasten har vi tatt en prat med tre radarforskere som alle jobber for fullt for å få ferdig Rimfax, radaren som skal hjelpe Nasa lete etter liv på Mars.

• Berger, Tor; Hamran, Svein-Erik; Ødegaard, Nina; Øyan, Mats Jørgen & Damsgård, Leif (2015). Stripmap Autofocus of Short Range Ku-band Synthetic Aperture Radar Data. Full text in Research Archive
• Brovoll, Sverre; Berger, Tor; Aardal, Øyvind; Lande, Tor Sverre & Hamran, Svein-Erik (2014). Distortion effects in a switch array UWB radar for time-lapse imaging of human heartbeats. Full text in Research Archive
• Brovoll, Sverre; Aardal, Øyvind; Paichard, Yoann; Berger, Tor; Lande, Tor Sverre & Hamran, Svein-Erik (2013). Optimal frequency range for medical radar measurements of human heartbeats using body-contact radar. Full text in Research Archive
• Brovoll, Sverre; Berger, Tor; Paichard, Yoann; Aardal, Øyvind; Lande, Tor Sverre & Hamran, Svein-Erik (2013). Time-lapse imaging of human heartbeats using UWB radar. Full text in Research Archive
• Aardal, Øyvind; Brovoll, Sverre; Paichard, Yoann; Berger, Tor; Lande, Tor Sverre & Hamran, Svein-Erik (2013). Detecting changes in the human heartbeat with on-body radar. Full text in Research Archive
• Klaveness, Dag; Dypvik, Henning & Hamran, Svein-Erik (2012). The Ål stucture. Full text in Research Archive
• Langley, K.; Sinisalo, A.; Kohler, Jack; Hamran, Svein-Erik; Øyan, Mats Jørgen & Smedsrud, Lars Henrik [Show all 10 contributors for this article] (2011). A look at the basal mass balance ofthe Fimbul ice shelf using ice penetrating radar andoceanographic borehole data. Full text in Research Archive
• Berger, Tor & Hamran, Svein-Erik (2010). An efficient scaled maximum likelihood algorithm for translational motion estimation in ISAR imaging. Full text in Research Archive Show summary

  In ISAR imaging, the relative motion between the target and the radar must be known precisely to produce focused radar images. The translational motion of the target must be compensated for to use only the rotational motion around a fixed centre point for the imaging of the target. An efficient implementation of a maximum likelihood (ML) algorithm for translational motion estimation based on the Chirp-Z transform is described. If the line of sight vector from the radar to the target is not within the rotational plane of the object, or the rotational plane changes during the observation time, and strong reflectors tend to bias the estimate of translational motion. A scaling of range profiles is shown to reduce the bias. The shear average algorithm is similar to the algorithm described here, but it only estimates translational motion to within half the carrier wavelength. Simulated and experimental data are used to show the effectiveness of the algorithm. An image sharpness measure is used to indicate the effects of scaling as a preprocessing step on experimental data. All results are compared to those obtained by shear average and prominent point processing techniques.

• Berger, Tor; Tollisen, Steffen & Hamran, Svein Erik (2010). ISAR imaging of small aircraft. Full text in Research Archive Show summary

  In ISAR imaging, the relative motion between the target and the radar must be known precisely to produce focused radar images. The translational motion of the target must be compensated for in order to use only the rotational motion around a fixed centre point for the imaging of the target. Different methods for range alignment can be used, and the success depends much on the nature of the data. If strong reflectors are dominant throughout the observation period, a prominent point processing (PPP) method may produce good results. If not, other methods may apply. The advantage of using PPP is simplicity in concept and its processing speed. Another method, in general slower than PPP, is based on maximum likelihood estimation of translational motion. An maximum likelihood algorithm for translational motion estimation (TME) is described. Data from the German research radar TIRA at FGAN-FHR is processed to show the potential of the algorithms. Also, after range alignment, the kurtosis (fourth order central moment) of averaged range profiles gives an indication of which of the two methods that gives the best results in terms of image sharpness. Data from TIRA of a small aircraft is collected over a period of minutes and are processed in five second intervals with 80 % overlap. The results from the PPP and the TME algorithms are compared, automatically in terms of a sharpness measure, and also by user inspection. The results indicate that for low kurtosis regions the TME method should be used, while for high kurtosis regions, the PPP method is preferred. In this way the total processing time can be reduced for multi image sequences, as we use the PPP method whenever we can and the TME method whenever we have to.

• Müller, Karsten; Sinisalo, Anna Katariina; Anschütz, Helgard; Hamran, Svein-Erik; Hagen, Jon Ove Methlie & McConnell, Joseph [Show all 7 contributors for this article] (2009). An 860km accumulation rate profile on the East Antarctic plateau derived by GPR. Full text in Research Archive
• Müller, Karsten; Anschütz, Helgard; Sinisalo, Anna Katariina; Hamran, Svein-Erik; Hagen, Jon Ove Methlie & McConnell, Joseph [Show all 8 contributors for this article] (2009). Surface mass balance along the Norwegian/U.S. scientific traverse across East Antarctica. Full text in Research Archive
• Hamran, Svein-Erik; Klaveness, Dag & Dypvik, Henning (2008). GPR Reveals a Sub Bottom Anomaly Inside a Circular Basin in a Small Lake. Full text in Research Archive
• Müller, Karsten; Albert, Mary; Hamran, Svein-Erik & Hagen, Jon Ove Methlie (2008). Radar Scattering Zones across Dronning Maud Land, East Antarctica. Full text in Research Archive
• Müller, Karsten; Hamran, Svein-Erik; Hagen, Jon Ove Methlie & Sinisalo, Anna Katariina (2008). Relation between GPR, SAR and accumulation rate in the dry-snow zone of East Antarctica. Full text in Research Archive
• Hovland, Harald; Hamran, Svein-Erik & Skauli, Torbjørn (2015). Tomographic scanning imager. Akademika forlag. Full text in Research Archive
• Aardal, Øyvind; Hamran, Svein-Erik; Lande, Tor Sverre & Berger, Tor (2013). Radar monitoring of heartbeats and respiration. Universitetet i Oslo. Full text in Research Archive Show summary

  This thesis addresses the use of radar for heartbeat and respiration monitoring. Medical radar can be used for detecting vital signs at distances up to several meters. A medical radar works by transmitting electromagnetic waves towards a person, and receiving echoes reflected off the person. Vital signs appear as modulations in the radar data in period with the heartbeats and respiration. We have measured and analyzed these modulations.<br> The ability to detect human heartbeats from a distance can be used for monitoring patients’ heartbeats without the need of attaching the measurement equipment to the patient. A radar system can be placed over a bed, integrated in a mattress or chair or used for non-intrusive home monitoring. It could also be used as an alternative to the diagnostic monitoring tools of today. In this thesis, the understanding of radar heartbeat detection is explored.<br> Although heartbeats and respiration monitoring using radar have been reported many times before, the optimal frequencies, waveforms and aspect angle of detection were not known. We have described the vital signs modulations as functions of frequency and aspect angle, and found both narrowband and ultra wideband radar to be suited for the task. In addition to quantizing the modulations, an experimental approach to understanding why heartbeat and respiration detection with radar is possible was made. We found that small body surface movements are the cause of the observed heartbeat modulations in radar data, discarding the theory that reflections from internal body organs are seen. On-body radar have been used as well, and a closer connection between the actual movements of the heart and the radar recordings were found than what is achievable using remote radar. With on-body radar and the processing presented in this thesis, details of the heart mechanics can be identified using radar. It is also possible to see changes in the measured waveform when the pulse and blood pressure of the person changes.

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