Projects
DART (Double Asteroid Redirection Test)
DART is NASA's first Planetary Defense Mission. It is the first test of a kinetic impactor, a hazard mitigation method where an asteroid's trajectory is changed following an impact from a spacecraft. We launched in November 2021 and impacted the moon (Dimorphos) of the near-Earth asteroid Didymos on 26 September 2022.
I am the lead of the DART Observations Working Group. We are tasked with determining the characteristics of the Didymos system prior to the impact of DART into the satellite (Dimorphos) and measuring the change in the orbital period of the satellite following the impact. We can use lightcurves (observations of the Didymos system's brightness over time) to study the key features of the system. Thomas et al. (submitted) will present the first orbit period change results.
Observing Asteroids with JWST
I am a member of the JWST Guaranteed Time Observations (GTO) group led by PI Heidi Hammel and Stefanie Milam. I lead the observations of near-Earth objects in the program. Before joining this group, many of us led studies of the capabilities of JWST with respect to our target objects. Thomas et al. (2016) investigated the observability of near-Earth objects. One requirement of the observatory is that non-sidereal rates remain below 30 milliarcseconds per second. We showed that in any given year ~75% of all NEOs could be observed.
Due to our work planning observations of the NEO Didymos, the JWST non-sidereal tracking rate has been increased to 75 milliarcseconds per second. Test observations of fast NEOs have shown a true tracking limit at ~110 mas/sec.
I am also Co-I on a number of accepted Cycle 1 proposals including a ToO to observe a newly discovered Interstellar Object and a parallel program to search for hydration signatures in asteroids.
Space Weathering in Asteroid Families
Space weathering affects our spectroscopic interpretations of near-Earth and Main Belt asteroids. We started our investigations of space weathering in the Koronis family (Thomas et al. 2011, 2012). Our results demonstrated that the spectrophotometric slope increased as size increased. The key assumption in our analysis is that the surface age is correlated with the object size due to our understanding of collisional lifetimes. Therefore, we expect a smaller object to (on average) have a younger surface age and be less space weathered. In addition to the slope trend, we found evidence of a decrease in band depth.
We have expanded this analysis to include all known asteroid families and data from the SDSS Moving Object Catalog 4 to investigate the different slope trends seen in various asteroid compositions. The C-type trends were published in Thomas et al. 2021 and we are working on determining space weathering timescales for the S-type families.