A DECam Twilight Survey For Asteroids Interior to Earth’s Orbit

Small asteroids interior to Earth’s orbit are hard to observe in the glare of the Sun. Most large scale surveys observing interior to Earth’s orbit have only used relatively small telescopes. We have begun a survey using the Dark Energy Camera (DECam) on the CTIO Blanco 4 meter telescope in Chile to look for asteroids interior to Earth during twilight time. In our limited survey observations to date, we have already discovered one new rare Atira/Apohele asteroid, 2021 LJ4, which has an orbit completely interior to Earth's orbit. These interior asteroid populations are important to complete the census of asteroids near Earth, including some of the most likely Earth impactors that cannot easily be discovered in other surveys. We will also be able to discover asteroids that are interior to or in resonance with Venus, allowing us to determine if the Venus resonance reservoir is highly populated. Comparing the actual population of asteroids found interior to Earth and Venus with those predicted to exist by interpolating from the known population exterior to Earth is important to better understand the composition and structure of the asteroid population. Various internal stresses on the near Earth objects such as tidal deformation and solar heating will cause more fragile asteroid compositions and structures to erode or break-up as they approach the planets and Sun. Thus the fraction of asteroids interior to the Earth and Venus compared to exterior will give us insights into the strength and make-up of these objects.