Space Science Reviews delivers another Hera-based paper. In vol. 221 (dated 5 Nov.):
Okada, T. Tanaka, S. Sakatani, N. et al. The Thermal InfraRed Imager on Hera art. 104 s11214-025-01227-w
The journal had already posted not one but two papers on the Hera mission to the Didymos-Dimorphos system. But those were on the overall mission, give or take- here’s one on the TIRI (Thermal InfraRed Imager) instrument, now on its way aboard the Hera probe, after DART. TIRI was contributed by the Japanese, derived from the Hayabusa2 TIR instrument and an instrument on the UNFORM2 mission, in Earth orbit. As a derivative design, it just wasn’t that expensive or schedule-limiting, so everyone wins. (Except, maybe, an aerospace firm losing a contract for a brand-new program.)
TIRI is important even after TIR. Hayabusa2 went to a C-type (carbonaceous) body; Didymos (and we assume Dimorphos… ?) are S-type. No thermal imagers have seen S-type asteroids at this level of detail. Hayabusa1 had no instrument reaching this far in the infrared; NEAR Shoemaker, groundbreaking in some ways, was cost-limited and left us wanting more. In any case, Hera will get close-ups of both Didymos and Dimorphos. While Didymos is in a size class like Itokawa, Dimorphos is a different scale entirely. We expect Didymos to have particle sizes on its surface regolith that Dimorphos should not; Dimorphos’ gravity is too low, and finer grains will be lost to space in impact events. These fine grains affect infrared emission- grains actually approach the wavelength.
Also note that some minerals literally emit in some infrared bands. TIRI may see them directly.
Okada et al. gladly report that the launch went without issue, and checkouts are good. TIRI turned around and shot Earth after launch, as a calibration target. During the Mars flyby this Spring, both the planet and its satellites were targeted. One more year to Didymos/Dimorphos, can’t wait!