Constraining the Physical Properties of Near-Earth Object 2009 Bd

Abstract

We report on Spitzer Space Telescope IRAC observations of near-Earth object (NEO) 2009 BD that were carried out in support of the NASA Asteroid Robotic Retrieval Mission (ARRM) concept. We did not detect 2009 BD in 25 hrs of integration at 4.5 µm. Based on an upper-limit flux density determination from our data, we present a probabilistic derivation of the physical properties of this object. The analysis is based on the combination of a thermophysical model with an orbital model accounting for the non-gravitational forces acting upon the body. We find two physically possible solutions. The first solution shows 2009 BD as a 2.9 ± 0.3 m diameter rocky body (ρ = 2.9 ± 0.5 g cm −3) with an extremely high albedo of 0.85 +0.20 −0.10 that is covered with regolith-like material, causing it to exhibit a low thermal inertia (Γ = 30 +20 −10 SI units). The second solution suggests 2009 BD to be a 4 ± 1 m diameter asteroid with p V = 0.45 +0.35 −0.15 that consists of a collection of individual bare rock slabs (Γ = 2000±1000 SI units, ρ = 1.7 +0.7 −0.4 g cm −3). We are unable to rule out either solution based on physical reasoning. 2009 BD is the smallest asteroid for which physical properties have been constrained, in this case using an indirect method and based on a detection limit, providing unique information on the physical properties of objects in the size range smaller than 10 m.

Neosurvey 1: Initial Results From the Warm Spitzer Exploration Science Survey of Near-Earth Object Properties

“…We have empirically measured the Warm Spitzer CH2 sensitivity (5σ) for faint moving objects to be 2.2 μJy in 5 hr and 1.8 μJy in 10 hr, scaling roughly as the square root of integration time for shorter integrations (Mommert et al 2014b). This is less sensitive than predicted by SENS-PET due to contamination from background sources that cannot be completely subtracted out in the moving frame.…”

“…Our technical approach has been honed through observations of more than 600NEOs with Spitzer in our Cycle6+7 ExploreNEOs program (Trilling et al 2010Harris et al 2011;Mueller et al 2011;Thomas et al 2011;Mommert et al 2015), as well as through a number of Spitzer programs to study individual NEOs of interest (e.g., Mueller et al 2007;Mommert et al 2014aMommert et al , 2014b. The observation design has been proven to deliver high-quality photometry.…”

“…The data processing is performed in a manner similar to our previous reductions for ExploreNEOs (Trilling et al 2010) and our other observations of NEOs (Mommert et al 2014a(Mommert et al , 2014b. The BCDs are downloaded from the Spitzer archive, and we use IRACproc/mopex in the moving object mode to mosaic the frames relative to the NEO position.…”

Trajectory and physical properties of near-Earth asteroid 2009 BD

“…We selected the observation window according to Spitzer observability, the predicted flux density of the asteroid, and we chose the IRAC channel 2 to maximize our chances of detecting 2009 BD (Mommert et al 2014).…”

“…In this paper we combine the constraints coming from nongravitational perturbations and observations from the Spitzer Space Telescope (Werner et al 2004) to estimate the physical properties of 2009 BD. For more details see Mommert et al (2014).…”