NASA Psyche Mission: Charting a Metallic World_ for information

In this artist’s rendition, we explore a metallic world named Psyche, an asteroid that offers a unique window into the building blocks of planet formation. The NASA Psyche mission launches in 2023 and will arrive at the asteroid Psyche, which orbits the Sun between Mars and Jupiter, in 2026. The spacecraft, also named Psyche, will spend 21 months orbiting the asteroid, mapping it and studying its properties. The mission is led by Principal Investigator Lindy Elkins-Tanton of Arizona State University. NASA’s Jet Propulsion Laboratory is responsible for the mission’s overall management, system engineering, integration and test, and mission operations. Maxar Technologies is providing a high-power solar electric propulsion spacecraft chassis.
Size
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The first size estimate of Psyche was 253 kilometres (157 mi) and came from IRAS thermal infrared emission observations.This is 15% larger than the currently accepted mean value, but was later found to be an accurate estimate for the IRAS viewing aspect because Psyche was viewed pole-on at the time of the measurement.

Psyche has been observed to occult a star on nine occasions. Four of these, 2004, 2010,2014,and 2019,

generated multi-chord data sets[16] and have been used along with adaptive optics imaging and three-dimensional modeling to estimate Psyche's mean diameter, with recent models all converging to an equivalent-volume mean diameter of 222±3 km.

Multiple views of 16 Psyche imaged by the Very Large Telescope
Mass and bulk density
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Psyche is massive enough that its gravitational perturbations on other asteroids can be observed, which enables a mass measurement. Historical values for its mass have ranged from 1.6×1019 kg to 6.7×1019 kg. However, most recent mass estimates have begun to converge to values of (2.287±0.070)×1019 kg. Assuming the mean volume of (5.75±0.19)×106 km3, this equates to a bulk density of 3.977±0.253 g/cm3.