학술논문
Antarctic Surface Reflectivity Calculations and Measurements from the ANITA-4 and HiCal-2 Experiments
Document Type
Working Paper
Author
Prohira, S.; Novikov, A.; Dasgupta, P.; Jain, P.; Nande, S.; Allison, P.; Banerjee, O.; Batten, L.; Beatty, J. J.; Belov, K.; Besson, D. Z.; Binns, W. R.; Bugaev, V.; Cao, P.; Chen, C.; Chen, P.; Clem, J. M.; Connolly, A.; Cremonesi, L.; Dailey, B.; Deaconu, C.; Dowkontt, P. F.; Fox, B. D.; Gordon, J.; Gorham, P. W.; Hast, C.; Hill, B.; Hupe, R.; Israel, M. H.; Lam, J.; Liu, T. C.; Ludwig, A.; Matsuno, S.; Miki, C.; Mottram, M.; Mulrey, K.; Nam, J.; Nichol, R. J.; Oberla, E.; Ratzlaff, K.; Rauch, B. F.; Romero-Wolf, A.; Rotter, B.; Russell, J.; Saltzberg, D.; Seckel, D.; Schoorlemmer, H.; Stafford, S.; Stockham, J.; Stockham, M.; Strutt, B.; Tatem, K.; Varner, G. S.; Vieregg, A. G.; Wissel, S. A.; Wu, F.; Young, R.
Source
Phys. Rev. D 98, 042004 (2018)
Subject
Language
Abstract
The balloon-borne HiCal radio-frequency (RF) transmitter, in concert with the ANITA radio-frequency receiver array, is designed to measure the Antarctic surface reflectivity in the RF wavelength regime. The amplitude of surface-reflected transmissions from HiCal, registered as triggered events by ANITA, can be compared with the direct transmissions preceding them by O(10) microseconds, to infer the surface power reflection coefficient $\cal{R}$. The first HiCal mission (HiCal-1, Jan. 2015) yielded a sample of 100 such pairs, resulting in estimates of $\cal{R}$ at highly-glancing angles (i.e., zenith angles approaching $90^\circ$), with measured reflectivity for those events which exceeded extant calculations. The HiCal-2 experiment, flying from Dec., 2016-Jan., 2017, provided an improvement by nearly two orders of magnitude in our event statistics, allowing a considerably more precise mapping of the reflectivity over a wider range of incidence angles. We find general agreement between the HiCal-2 reflectivity results and those obtained with the earlier HiCal-1 mission, as well as estimates from Solar reflections in the radio-frequency regime. In parallel, our calculations of expected reflectivity have matured; herein, we use a plane-wave expansion to estimate the reflectivity R from both a flat, smooth surface (and, in so doing, recover the Fresnel reflectivity equations) and also a curved surface. Multiplying our flat-smooth reflectivity by improved Earth curvature and surface roughness corrections now provides significantly better agreement between theory and the HiCal 2a/2b measurements.
Comment: submitted to Astropart. Phys
Comment: submitted to Astropart. Phys