HEXTE

HEXTE, or High Energy X-ray Timing Experiment, was an instrument aboard NASA's Rossi X-ray Timing Explorer (RXTE). Operational from 1995 to 2012, HEXTE was designed to perform timing and spectroscopy of hard X-rays in the approximate 15 to 250 keV range, complementing the PCA instrument which operated at lower energies.

The instrument consisted of two independent detector clusters, A and B, each built around phoswich scintillation detectors using a NaI(Tl)/CsI(Na) configuration to distinguish photon-induced events from background. HEXTE employed a rocking mechanism to periodically point at the target (on-source) and at nearby blank sky (off-source) to measure and subtract the background, enabling sensitive measurements in a high-background energy regime.

HEXTE contributed to a wide range of high-energy X-ray studies, including timing analyses of X-ray binaries and pulsars, spectroscopy of accreting compact objects, and observations of active galactic nuclei and gamma-ray bursts. The instrument’s data, in conjunction with RXTE's PCA, allowed broad-band spectral studies and detailed investigations of rapid variability.

After the mission ended in 2012, HEXTE data have remained publicly available through HEASARC, supporting continued analysis by the astrophysics community. HEXTE’s design and observational strategy influenced later missions aiming to characterize hard X-ray sources with timing precision.