The MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS): Current Status

Near-Earth objects (NEOs) represent an ongoing flux of small bodies from elsewhere in the Solar System to near-Earth space. The study of these objects teaches us about the original environment of the Solar System during formation, and the conditions as physical and chemical changes occur throughout Solar System history. The MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS) began in 2004 and has obtained ~1,350 spectral observations of over 1,000 objects. The current phase of the project has three key goals: (1) to improve our understanding of the compositional distribution of NEO spectra with respect to asteroid size via additional IRTF SpeX prism spectra, (2) to examine the distribution of volatiles in the NEO population through an analysis of SpeX LXD 3-micron spectra, and (3) to transition the program from MIT and update our infrastructure. 

We continue a regular cadence of SpeX prism (0.7 - 2.5 microns) observations with a key goal of increasing the sample of small NEOs in our data set. We assign the highest priority to targets with estimated diameters less than 600 meters (H~18.8). Other observational priorities include new discoveries, Potentially Hazardous Asteroids (PHAs), Virtual Impactors (VIs), and low-ΔV objects (< 7 km/s), and asteroids at their most favorable observing geometries. Our efforts to increase the population of small objects observed has been successful (see our progress in Figure 1 ).  Recent research highlights include pre- and post-close approach observations of S-type 2024 MK (McGraw et al. 2024). These spectra showed no evidence of surface refresh at a close approach of 0.76 lunar distance. Ongoing work includes studies of the compositional distribution with respect to size in our sample and an investigation of C-type objects with low MOID (Minimum Orbit Intersection Distance) values as a followup to Binzel et al. (2010).

Observations with SpeX LXD (1.7 - 4.2 microns) are limited to objects with V < 14.0 for our program. We define this limit based on signal-to-noise considerations. Our LXD program consists of two components: (1) a traditional observing program with known targets and (2) a target of opportunity program to observe newly discovered targets. We have successfully obtained LXD spectra of 15 unique targets since the start of this program element in the 2022B semester.

Our presentation will discuss the current status of MITHNEOS including our progress in the new 3-micron effort and our ongoing prism studies.