We deploy a laser absorption-based sensor in the Caltech Hypervelocity Expansion Tube (HET). This sensor employs spectrally-resolved tunable diode laser absorption spectroscopy (TDLAS) to measure gas temperature at 1400 \(\, \pm \,\) 200K and velocity at 3360 \(\, \pm \,\) 80 m/s. Temperature and velocity measurements are subsequently combined to infer total enthalpy at 7.1 \(\, \pm \,\) 0.4 MJ/kg. The sensor targets the D \(_1\) transition of atomic potassium near 770 nm and samples at 5 \(\mu \) s time intervals. Measurements reported here characterize the HET’s MSL1 condition, a Mach 5 CO \(_2\) flow which simulates Mars planetary entry. With these measurements, we evaluate the HET freestream simulations described in Part I. Because we find some disagreement between simulated flow conditions and measurements, we deploy a second, CO \(_2\) -targeting, TDLAS sensor to verify the potassium-targeting velocity measurements—the second sensor agrees with the potassium-targeting sensor, but discrepancies with the simulations remain. This work demonstrates how combining simulations and experiments in hypersonics can improve our understanding of ground-test facilities and hypersonic simulations. Additionally, the measurements characterize temperature and velocity for future experiments in the HET at this condition.