Accessible does not mean exploitable: HiPERCAM reveals the ultra-fast rotation of 2022 OB5

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 s g s r s i s z 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 rot = 1 . 542 ± 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 Δ 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. • First asteroid characterisation with HiPERCAM (GTC). • 2022 OB 5 is confirmed as an ultra-fast rotator with P rot = 1 . 542 ± 0 . 001 min. • Simultaneous five-band photometry supports an X-complex taxonomy. • Extreme rotation limits the exploitability of candidate mission targets.