  We develop a shape model of asteroid 16 Psyche using observations acquired in
a wide range of wavelengths: Arecibo S-band delay-Doppler imaging, Atacama
Large Millimeter Array (ALMA) plane-of-sky imaging, adaptive optics (AO) images
from Keck and the Very Large Telescope (VLT), and a recent stellar occultation.
Our shape model has dimensions 278 (-4/+8) km x 238 (-4/+6) km x 171 (-1/+5)
km, an effective spherical diameter Deff = 222 -1/+4 km, and a spin axis
(ecliptic lon, lat) of (36 deg, -8 deg) +/- 2 deg. We survey all the features
previously reported to exist, tentatively identify several new features, and
produce a global map of Psyche. Using 30 calibrated radar echoes, we find
Psyche's overall radar albedo to be 0.34 +/- 0.08 suggesting that the upper
meter of regolith has a significant metal (i.e., Fe-Ni) content. We find four
regions of enhanced or complex radar albedo, one of which correlates well with
a previously identified feature on Psyche, and all of which appear to correlate
with patches of relatively high optical albedo. Based on these findings, we
cannot rule out a model of Psyche as a remnant core, but our preferred
interpretation is that Psyche is a differentiated world with a regolith
composition analogous to enstatite or CH/CB chondrites and peppered with
localized regions of high metal concentrations. The most credible formation
mechanism for these regions is ferrovolcanism as proposed by Johnson et al.
(Nature Astronomy vol 4, January 2020, 41-44).
