  The NASA supported High-Altitude Calibration (HiCal)-2 instrument flew as a
companion balloon to the ANITA-4 experiment in December 2016. Based on a HV
discharge pulser producing radio-frequency (RF) calibration pulses, HiCal-2
comprised two payloads, which flew for a combined 18 days, covering 1.5
revolutions of the Antarctic continent. ANITA-4 captured over 10,000 pulses
from HiCal, both direct and reflected from the surface, at distances varying
from 100-800 km, providing a large dataset for surface reflectivity
measurements. Herein we present details on the design, construction and
performance of HiCal-2.
