  The CRyogenic InfraRed Echelle Spectrograph (CRIRES) Upgrade project
CRIRES$^{+}$ extended the capabilities of CRIRES. It transformed this VLT
instrument into a cross-dispersed spectrograph to increase the wavelength range
that is covered simultaneously by up to a factor of ten. In addition, a new
detector focal plane array of three Hawaii 2RG detectors with a 5.3 $\mu$m
cutoff wavelength replaced the existing detectors. Amongst many other
improvements, a new spectropolarimetric unit was added and the calibration
system has been enhanced. The instrument was installed at the VLT on Unit
Telescope 3 at the beginning of 2020 and successfully commissioned and verified
for science operations during 2021, partly remotely from Europe due to the
COVID-19 pandemic. The instrument was subsequently offered to the community
from October 2021 onwards. This article describes the performance and
capabilities of the upgraded instrument and presents on sky results.

Instrumentation and Methods for Astrophysics