Accessible does not mean exploitable: HiPERCAM reveals the ultra-fast rotation of 2022 OB$_5$

Abstract

2022 OB$_5$ is a sub-10-metre Apollo-type near-Earth asteroid whose orbital configuration placed it among the most dynamically accessible small bodies in near-Earth space, motivating its selection as the target of the first commercial asteroid-prospecting mission. We present its first photometric characterisation, based on high-cadence simultaneous five-band $u_sg_sr_si_sz_s$ observations obtained with HiPERCAM at the 10.4-m Gran Telescopio Canarias (GTC). Analysis of the light curves yields a rotation period of $P_{\rm rot} = 1.542 \pm 0.001$ min, independently confirmed with observations taken by the Two-meter Twin Telescope, establishing 2022 OB$_5$ as an ultra-fast rotator. The reflectance spectrum derived from the simultaneous multiband photometry is featureless and moderately red, consistent with the X-complex. Despite its good orbital accessibility, the ultra-fast rotation of 2022 OB$_5$ poses severe practical challenges for any surface operation with current technology, regardless of compositional interest. This illustrates a population-level challenge: at the sizes and $\Delta v$ values most favourable for in-situ missions, fast rotation is the dominant spin state, and rotation period measurement is therefore an indispensable prerequisite for evaluating the resource potential of asteroid mission candidates.