  We used the reparameterized Near-Earth Asteroid Thermal Model to model
observations of a curated set of over 4000 asteroids from the Wide-field
Infrared Survey Explorer in two wavelength bands (W2-3 or W3-4) and compared
the results to previous results from all four wavelength bands (W1-4). This
comparison was done with the goal of elucidating unique aspects of modeling
two-band observations so that any potential biases or shortcomings for planned
two-band surveys (e.g., the NASA Near-Earth Object Surveyor Mission) can be
anticipated and quantified. The W2-3 two-band fits usually yielded slightly
smaller diameters than the four-band fits, with a median diameter difference of
-10%, with the 5% and 95% quantiles of the distribution at -32% and -1.5%,
respectively. We conducted similar comparisons for W3-4, in part because the
longest wavelength bands are expected to provide the best two-band results. We
found that the W3-4 two-band diameters are slightly larger than the four-band
results, with a median diameter difference of 11% and the 5% and 95% quantiles
of the distribution at -2.1% and 26%, respectively. The diameter uncertainty,
obtained with bootstrap analysis, is larger by 30% and 35% (median values) for
the W2-3 and W3-4 fits, respectively, than for the corresponding four-band
fits. Using 23 high-quality stellar occultation diameters as a benchmark, we
found that the median errors of W2-3 and W3-4 diameter estimates are -15% and
+12%, respectively, whereas the median error of the four-band fits is 9.3%.
Although the W2-3 and W3-4 diameters appear to have greater systematic errors
and uncertainties than their four-band counterparts, two-band estimates remain
useful because they improve upon diameter estimates obtained from visible
photometry alone.
