Environmental assessment in the prelaunch phase of Hayabusa2 for safety declaration of returned samples from the asteroid (162173) Ryugu: background monitoring and risk management during development of the sampler system

Abstract

We report ground-based environmental assessments performed during development of the sampler system until the launch of the Hayabusa2 spacecraft. We conducted static monitoring of potential contaminants to assess the environmental cleanliness during (1) laboratory work performed throughout the development and manufacturing processes of the sampler devices, (2) installation of the sampler system on the spacecraft, and (3) transportation to the launch site at the Japan Aerospace Exploration Agency’s (JAXA’s) Tanegashima Space Center. Major elements and ions detected in our inorganic analyses were sodium (Na), potassium (K), and ionized chloride (Cl ^–); those elements and ions were positively correlated with the total organic content and with exposure duration in the range from 10 ¹ to 10 ³ nanograms per monitor coupon within an ~ 30-mm diameter scale. We confirmed that total deposits on the coupon were below the microgram-scale order during manufacturing, installation, and transportation in the prelaunch phase. The present assessment yields a nominal safety declaration for analysis of the pristine sample (> 5.4 g) returned from asteroid (162173) Ryugu combined with a highly clean environmental background level. We expect that the sample returned from Ryugu by Hayabusa2 will be free of severe and/or unknown contamination and will allow us to provide native profiles recorded for the carbonaceous asteroid history.

Graphical Abstract