  The Near-Infrared Spectrograph (NIRSpec) is one of the four focal plane
instruments on the James Webb Space Telescope. In this paper, we summarize the
in-orbit performance of NIRSpec, as derived from data collected during its
commissioning campaign and the first few months of nominal science operations.
More specifically, we discuss the performance of some critical hardware
components such as the two NIRSpec Hawaii-2RG (H2RG) detectors, wheel
mechanisms, and the micro-shutter array. We also summarize the accuracy of the
two target acquisition procedures used to accurately place science targets into
the slit apertures, discuss the current status of the spectro-photometric and
wavelength calibration of NIRSpec spectra, and provide the as measured
sensitivity in all NIRSpec science modes. Finally, we point out a few important
considerations for the preparation of NIRSpec science programs.
