Description
Fast X-ray timing of transient sources has historically been the domain of large, monolithic space
observatories. Here we show that, for the first time, sub-millisecond timing can be achieved with
a wide-field nanosatellite instrument operating without collimation. Using data from the HERMES
X/γ-ray spectrometer on board the SpIRIT CubeSat, we demonstrate sub-millisecond timing
capabilities in the keV range.
This performance is enabled by an algorithmic framework based on cross-correlation techniques
applied to photon Time-of-Arrival (ToA) data, combined with adaptive binning and Monte Carlo
methods to robustly recover fast variability in the low-count regime typical of CubeSat observations.
These results establish CubeSats as a viable platform for fast X-ray photometry, opening
new opportunities for timing studies of both transient and persistent high-energy sources.
This methodology naturally enables cross-band lag measurements and delay studies between optical
and high-energy emission, as targeted by the Optical GEMS project.