Detection of Chelyabinsk-type objects in the thermal infrared

The Chelyabinsk progenitor asteroid approached Earth undetected, because its radiant was close to the Sun. In addition, the 20-m size object was very faint and very fast moving. Visible wavelength observations of such objects also suffer from the high phase angle illumination geometry. We examine this event within the framework of current and forthcoming infrared space initiatives, such as ESA’s planned NEOMIR space mission. We focus on strategies for early detection of similar objects before potential impact.

Infrared (IR) observations from space offer distinct advantages: (i) enhanced Sun-asteroid contrast compared to visible wavelengths, (ii) small, fast-rotating object are (nearly) isothermal which make IR detections at high phase angles easier, (iii) immediate good-quality size estimation upon IR detection, and (iv) feasibility of observations near the Sun.

We scrutinize the IR-detection scenario of a 20-m object on a Chelyabinsk-like orbit, acknowledging challenges such as high background levels from zodiacal light and high apparent sky motion of the targets. Our investigation addresses key questions: (1) optimal IR wavelengths for (theoretical) detection, (2) measurement strategies for high apparent motion targets, (3) practical aspects when searching for NEAs close to the Sun, (4) optimal placement of IR telescopes in space, and (5) estimated lead times for detecting Chelyabinsk-type objects before potential impact for different telescope sizes and detector integration time.