leifda

• Hamran, Svein-Erik; Paige, David A.; Allwood, Abigail; Amundsen, Hans E. Foss; Berger, Tor & Brovoll, Sverre [Vis alle 20 forfattere av denne artikkelen] (2022). Ground penetrating radar observations of subsurface structures in the floor of Jezero crater, Mars. Science Advances. 8(34). doi: 10.1126/sciadv.abp8564. Fulltekst i vitenarkiv
• Hamran, Svein-Erik; Paige, David A.; Amundsen, Hans E. Foss; Berger, Tor; Brovoll, Sverre & Carter, Lynn [Vis alle 19 forfattere av denne artikkelen] (2020). Radar imager for Mars’ subsurface experiment—RIMFAX. Space Science Reviews. ISSN 0038-6308. doi: 10.1007/s11214-020-00740-4. Fulltekst i vitenarkiv Vis sammendrag

  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.

• 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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• 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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Mathiassen, Kim; Hanssen, Leif & Hallingstad, Oddvar (2010). A low cost navigation unit for positioning of personnel after loss of GPS position. I Mautz, Rainer; Kunz, Melanie & Ingensand, Hilmar (Red.), Proceedings of the 2010 International Conference on Indoor Positioning and Indoor Navigation. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781424458646. Fulltekst i vitenarkiv

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• Berger, Tor; Hamran, Svein-Erik; Ødegaard, Nina; Øyan, Mats Jørgen & Damsgård, Leif (2015). Stripmap Autofocus of Short Range Ku-band Synthetic Aperture Radar Data. Fulltekst i vitenarkiv
• Singh, S.; Adrat, M.; Antweiler, M.; Ulversøy, Tore; Mjelde, Terje Mikal Olsen & Hanssen, Leif [Vis alle 8 forfattere av denne artikkelen] (2010). NATO RTO/IST RTG on SDR: Acquiring and sharing knowledge for developing SCA-based Waveforms on SDRs. Fulltekst i vitenarkiv
• Hanssen, Leif & Gakkestad, Jakob (2010). Solar Cell Requirement for Powering of Wireless Sensor Network used in Northern Europe. Fulltekst i vitenarkiv
• Mathiassen, Kim; Hanssen, Leif & Hallingstad, Oddvar (2010). A Low Cost Navigation Unit for Positioning of Personnel After Loss of GPS Position. Fulltekst i vitenarkiv

Se alle arbeider i NVA