Speaker
Description
Near-Earth Objects (NEOs) provide a window into the smallest population of asteroids and comets that originated from different regions of the Solar System. As NEO discoveries increase – currently at about 3,000 objects per year – the majority are not followed up with physical characterization, which would provide insights into their formation and evolutionary processes. Such data can also help assess their potential as targets for future mining, exploration, and planetary defense missions.
Anticipating an increase in new discoveries with the start of LSST operations, we initiated a year-long, monthly photometric observation campaign of newly-discovered NEOs visible with the 2.61-m VLT Survey Telescope (VST) at Cerro Paranal, Chile. VST's 1-degree FoV enables the tracking of very fast-moving NEOs and also brings important collateral science: many other Small Solar System Bodies (SSSB) can be observed simultaneously.
The observations were carried out from February to September 2023, with two nights scheduled every month around the full Moon. The targets were observed by cycling through the SDSS r’i’z’g’r’ filters with exposure times of 10 to 30 s depending on the observational conditions. Every target was observed for 1 hour. In total, we acquired 5519 image cubes covering 72 NEAs, and likely 5 to 10 times that number of background SSSBs depending on the pointing region. The magnitude limit is estimated to be r’=21.5 for SNR=3 and exposure time of 20s. The data cubes are radiometrically calibrated in the Astro-WISE environment through the VST pipeline available by ARES cluster at INAF-OACN.
After calibration, the analysis is carried out by procedures in Python3 language and the use of Scikit-image, Astropy, Photutils, and Astroquery libraries. The steps are: 1. Querying SSSBs and Fixed Sources in the Field; 2. Moving Objects Locus Detection; 3. Target Tracking, Cube alignment, image stacking. 4. Aperture Photometry and lightcurve color analysis.
All data has been flux calibrated. To date, reduction and analysis have been completed for 107 SSSBs observed during the first 3 observing months. The obtained colors cluster in the typical bimodality between “S-like” and “C-like” asteroids, depending on the presence or absence of the 1-micron silicate band (i’-z’). Besides such more common asteroid types, we observe a significant diversity in the spectrophotometry of NEOs, suggesting the presence of rarer compositional types (e.g., A/L, Q and B/F) among our targets.
A new volley of monthly observations has been performed from February to September 2025. We focused on scattered monthly observations of newly discovered NEOs, with exposure times of 30s (r’), 40s (i’,g’) 50s (z’), and two 1-hour sequences per target. With this refined strategy, we aim to improve the signal of background stars for better astrometric positioning, and better sampling of phase and rotational curves. Data calibration down to April 2025 has been already carried out.