Zodiacal light (ZL) is sunlight scattered by interplanetary dust particles
(IDPs) at optical wavelengths. The spatial distribution of IDPs in the Solar
System may hold an important key to understanding the evolution of the Solar
System and material transportation within it. The number density of IDPs can be
expressed as n(r)∼r−α, and the exponent α∼1.3 was
obtained by previous observations from interplanetary space by Helios 1/2 and
Pioneer 10/11 in the 1970s and 1980s. However, no direct measurements of
α based on ZL observations from interplanetary space outside Earth's
orbit have been performed since then. Here, we introduce initial results for
the radial profile of the ZL at optical wavelengths observed over the range
0.76-1.06 au by ONC-T aboard the Hayabusa2# mission in 2021-2022. The ZL
brightness we obtained is well reproduced by a model brightness, although there
is a small excess of the observed ZL brightness over the model brightness at
around 0.9 au. The radial power-law index we obtained is α=1.30±0.08, which is consistent with previous results based on ZL observations. The
dominant source of uncertainty arises from the uncertainty in estimating the
diffuse Galactic light (DGL).Comment: 22 pages, 19 figures, 4 tables, accepted for publication by Earth,
Planets and Spac