  The Airborne Infrared Spectrometer (AIR-Spec) offers an unprecedented
opportunity to explore the Near Infra-Red (NIR) wavelength range. It has been
flown at two total solar eclipses, in 2017 and 2019. The wavelength range of
the much improved instrument on the second flight (July 2, 2019) was shifted to
cover two density sensitive lines from S XI. In this paper we study detailed
diagnostics for temperature, electron density and elemental abundances by
comparing results from AIR-Spec slit positions above the east and the west limb
with those from Hinode/EIS, the PolarCam detector and SDO/AIA. We find very
good agreement in the electron densities obtained from the EIS EUV line ratios,
those from the NIR S XI ratio and those obtained from the polarized brightness
PolarCam measurements. Electron densities ranged from Log Ne [cm$^{-3}]$ = 8.4
near the limb, falling to 7.2 at $R_0=1.3$. EIS spectra indicate that the
temperature distribution above the west limb is near-isothermal at around 1.3
MK, while that on the east has an additional higher-T component. The AIR-Spec
radiances in Si X and S XI as well as the AIA data in the 171, 193, and 211
Angstroms bands are consistent with the EIS results. EIS and AIR-Spec data
indicate that the sulphur abundance (relative to silicon) is photospheric in
both regions, confirming our previous results of the 2017 eclipse. The AIA data
also indicate that the absolute iron abundance is photospheric.
  Our analysis confirms the importance of the diagnostic potential of the NIR
wavelength range, and that this important wavelength range can be used reliably
and independently to determine coronal plasma parameters.
