The Psyche Gamma-Ray and Neutron Spectrometer

Area of Science:

• Planetary Science
• Astrogeology
• Nuclear Astrophysics

Background:

• Asteroid (16) Psyche is a unique M-class asteroid, potentially a metal-rich planetary core.
• Understanding its composition is key to comprehending planetary formation and differentiation.

Purpose of the Study:

• To detail the Gamma-Ray and Neutron Spectrometer (GRNS) instrument for NASA's Psyche mission.
• To outline the instrument's capability in determining Psyche's elemental and metal-to-silicate composition.
• To explain how GRNS data addresses key mission objectives regarding Psyche's origin and nature.

Main Methods:

• Utilizing a Gamma-Ray Spectrometer (GRS) with a high-purity Germanium (HPGe) sensor for gamma-ray detection (60-9000 keV).
• Employing an anticoincidence shield for background rejection, fast neutron measurements, and cosmic ray flux monitoring.
• Using a Neutron Spectrometer (NS) with 3He proportional sensors to measure neutrons across thermal and epithermal energy ranges.

Main Results:

• The GRNS is designed to measure near-surface abundances of key elements (Ni, Fe, Si, K, S, Al, Ca).
• The instrument will map Psyche's metal fraction, crucial for understanding its internal structure.
• Pre-launch and initial in-space performance data confirm instrument readiness.

Conclusions:

• The GRNS instrument is a critical component for investigating the origin of asteroid Psyche.
• Its measurements will directly address whether Psyche is a planetary core and its formation conditions.
• The paper provides a comprehensive overview of the GRNS, its data products, and operational plan.