The JAXA-developed Thermal InfraRed Imager (TIRI) onboard the Hera Spacecraft, the European Space Agency (ESA) binary asteroid explorer, performed the initial checkout from October 10th to 16th, 2024, and the TIRI is now confirmed as healthy.

During the checkout, while the Hera spacecraft was leaving from our planet, the Earth and Moon thermal images were successfully taken by TIRI, looking down obliquely from north compared to the Moon's orbit. The distance between the Earth and the Hera spacecraft was from about 1.4 million km for the first image taken on October 10th, to about 3.8 million km for the last image taken on October 15th. The Moon was moving around the Earth, from "half moon" to "full moon" as seen from the Earth.

Hera will perform a Mars swing-by in March 2025, and arrive at the binary asteroid system of Didymos and Dimorphos in December 2026 to conduct proximity observations for about half a year. Hera will investigate the remanent of the kinetic impact from the NASA DART spacecraft on Dimorphos, and determine the efficiency of impact deflection, as well as perform research to elucidate the planetary formation processes, which is thought to occur through repeated collisional fragmentation and re-accretion of celestial bodies.

TIRI will acquire thermographic images of both asteroids to estimate the porosity and grain size distribution of the surface materials on the global scale. It will also perform multi-band imaging using filters to understand the composition of the surface materials. In addition, TIRI has the capability to image the surface even in the shadowed areas which allows precise shape modeling of asteroids and measurement of their rotation and revolution, contributing to planetary defense. Stay tuned for TIRI's future results.

Thanks all those involved in TIRI development, and Hera launch and operation!

Thermal images of the Earth and Moon taken from October 10 to 15, 2024
(Credit: ESA/JAXA)