Spitzer Space Telescope

Ever since the early days of my PhD thesis, I have been involved in the thermal modeling of thermal-infrared observations of near-Earth objects and other asteroids. Such asteroid thermal models simulate the surface temperature distributions of asteroids utilizing some simplifying assumptions and enabling the estimation of physical properties like size and albedo. In the framework of several large-scale Spitzer Space Telescope observing programs, we have observed more than 2000 near-Earth objects and measured their thermal emission to constrain their diameters and albedos. Now that Spitzer has officially retired, we have finalized our observations and analysis, and compiled all of our results in one large data set. This compilation comprises 2204 diameter and geometric albedo estimates for 2132 different near-Earth objects - the largest homogeneous data set of its kind for this population. The results of these efforts are available GitHub. ...

Little is known about the physical properties of the smallest NEOs with diameters of less than 10 meters. Due to their small sizes, they are usually very faint and hard to observe. Hence, only a small number of asteroids in this size regime are known and for only very few of those physical properties like diameter and albedo have been measured. However, small NEOs are much more frequent than larger NEOs, making some of these objects easily accessible spacecraft targets and potential impactors. Traditionally, people believed that these small NEOs have formed through collisions and that they are individual slabs of rock, i.e,. monolithic bodies. ...

Part of the NEO population is considered to consist of so-called dead comets. Dead comets are comets that have spent a long time as NEOs and have been depleted their volatile inventories in numerous, close encounters with the Sun, i.e., they are extinct comets. They can be identified through their distinctive comet-like orbits and their low, comet-like albedos. The dead comet archetype is NEO (3552) Don Quixote. We observed Don Quixote as part of the ExploreNEOs program, in which ~600 NEOs were observed to derive the diameters and albedos of these objects. Our observations at 3.6 and 4.5 µm were saturated because the target was brighter than expect, revealing something rather unexpected. ...