Probing the Firn Refractive Index Profile and Borehole Closure Using Antenna Response

Agarwal, S.; Karg, Timo; Schluter, F.; Hughes, K.; Hanson, J. C.; Vieregg, A. G.; Toscano, S.; Seckel, D.; Oberla, E.; Hallgren, A.; Korntheuer, M.; Botner, O.; Nelles, A.; Karle, A.; Mulrey, K.; Novikov, A.; Hallmann, S.; Heyer, N.; de Vries, K. D.; van Eijndhoven, N.; Wissel, S.; Hornhuber, C.; Couberly, K.; Bouma, S.; Allison, P.; Krebs, R.; Coleman, A.; Oeyen, B.; Welling, C.; Tosi, D.; Aguilar, J. A.; Punsuebsay, N.; Hendricks, B.; Glaser, C.; de Kockere, S.; Kravchenko, I.; Marsee, M. J.; Stoffels, J.; Ryckbosch, D.; Bishop, A.; Muzio, M.; Lahmann, R.; Camphyn, R.; Clark, B. A.; Vijai, A.; Huesca Santiago, Enrique; Van Den Broeck, D. J.; Buitink, S.; Ravn, M.; Pyras, L.; Seikh, M. F. H.; Tutt, J.; Besson, D.; Scholten, O.; Betts, M.; Nozdrina, A.; Chiche, S.; Liu, C. H.; Stachurska, J.; Zink, A.; Windischhofer, P.; Kelley, J. L.; Alden, N.; Ali, S.; Henrichs-Schuhegger, Jakob; Deaconu, C.; Kowalski, Marek; McLennan, C.; Mikhailova, M.; Williams, D. R.; Giri, P.; Glusenkamp, T.; Young, R.

Preprint

PUBDB-2025-05578

Probing the Firn Refractive Index Profile and Borehole Closure Using Antenna Response

Agarwal, S. ; Aguilar, J. A. ; Alden, N. ; Ali, S. ; Allison, P. ; Betts, M. ; Besson, D. ; Bishop, A. ; Botner, O. ; Bouma, S. ; Buitink, S. ; Camphyn, R. ; Chiche, S. ; Clark, B. A. ; Coleman, A. ; Couberly, K. ; de Kockere, S. ; de Vries, K. D. ; Deaconu, C. ; Giri, P. ; Glaser, C. ; Glusenkamp, T. ; Hallgren, A. ; Hallmann, S. ; Hanson, J. C. ; Hendricks, B. ; Henrichs-Schuhegger, J.DESY* ; Heyer, N. ; Hornhuber, C. ; Huesca Santiago, E.DESY* ; Hughes, K. ; Karg, T.DESY* ; Karle, A. ; Kelley, J. L. ; Korntheuer, M. ; Kowalski, M.DESY* ; Kravchenko, I. ; Krebs, R. ; Lahmann, R. ; Liu, C. H. ; Marsee, M. J. ; McLennan, C. ; Mikhailova, M. ; Mulrey, K. ; Muzio, M. ; Nelles, A. ; Novikov, A. ; Nozdrina, A. ; Oberla, E. ; Oeyen, B. ; Punsuebsay, N. ; Pyras, L. ; Ravn, M. ; Ryckbosch, D. ; Schluter, F. ; Scholten, O. ; Seckel, D. ; Seikh, M. F. H. ; Stachurska, J. ; Stoffels, J. ; Toscano, S. ; Tosi, D. ; Tutt, J. ; Van Den Broeck, D. J. ; van Eijndhoven, N. ; Vieregg, A. G. ; Vijai, A. ; Welling, C. ; Williams, D. R. ; Windischhofer, P. ; Wissel, S. ; Young, R. ; Zink, A.

2025

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Report No.: arXiv:2504.03862

Abstract: We present a methodology for extracting firn ice properties using S-parameter reflection coefficients (`$S_{11}$') of antennas lowered into boreholes. Coupled with Finite-Difference Time Domain (FDTD) simulations and calculations, a depth-dependent $S_{11}$ profile can be translated into a refractive index profile. Since the response of an antenna deployed into a dry borehole depends on the diameter of the hole, multi-year $S_{11}$ measurements also permit an estimate of borehole closure complementary to estimates based on calipers or other dedicated mechanical loggers. We present first results, based on data taken in August, 2024 from boreholes at Summit Station, Greenland. We estimate borehole closure resolution of $\mathbf{\sim 2}$mm and also derive an index of refraction profile consistent with previous measurements.

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