The size-frequency distribution of H>13 NEOs and ARM targets detected by Pan-STARRS1

Abstract

We determine the absolute magnitude (H) distribution (or size-frequency distribution, SFD; $N(H) \propto 10^{\alpha H}$ where $\alpha$ is the slope of the distribution) for near-Earth objects (NEO) with $13 22$. There is also another change in slope from steep to shallow around H=27. The three ARM target candidates detected by Pan-STARRS1 in one year of surveying have a corrected SFD with slope $\alpha = 0.40^{+0.33}_{-0.45}$. We also show that the window for follow up observations of small (H$\gtrsim$22) NEOs with the NASA IRTF telescope and Arecibo and Goldstone radars are extremely short - on order of days, and procedures for fast response must be implemented in order to measure physical characteristics of small Earth-approaching objects. CFHT's MegaCam and Pan-STARRS1 have longer observing windows and are capable of following-up more NEOs due to their deeper limiting magnitudes and wider fields of view.