  Large-area lithium-drifted silicon (Si(Li)) detectors, operable 150{\deg}C
above liquid nitrogen temperature, have been developed for the General
Antiparticle Spectrometer (GAPS) balloon mission and will form the first such
system to operate in space. These 10 cm-diameter, 2.5 mm-thick multi-strip
detectors have been verified in the lab to provide <4 keV FWHM energy
resolution for X-rays as well as tracking capability for charged particles,
while operating in conditions (~-40{\deg}C and ~1 Pa) achievable on a
long-duration balloon mission with a large detector payload. These
characteristics enable the GAPS silicon tracker system to identify cosmic
antinuclei via a novel technique based on exotic atom formation, de-excitation,
and annihilation. Production and large-scale calibration of ~1000 detectors has
begun for the first GAPS flight, scheduled for late 2021. The detectors
developed for GAPS may also have other applications, for example in heavy
nuclei identification.
