Research indicates that atomized liquid seed particles will be small enough to accurately track the flow dynamics of rarefied supersonic nozzles. However, the accuracy of the particle tracking must be quantified. This article describes the process used to determine the accuracy of particle based velocimetry measurements. Measurements taken with seed particle based tracking techniques are compared to a molecular tracer technique called molecular tagging velocimetry to confirm if the particles accurately track the flow. Particle based velocity measurements are confirmed to track the mean flow features to within 5% of the molecular tracer based velocimetry technique, however the particle based measurements do not accurately track shocks.