The EU-ESA Workshop on Size Determination of Potentially Hazardous Near-Earth Objects continues. For Tuesday, 11/12/24, we continued phase curves, but after that it was thermal infrared observations and polarimetry:
https://indico.esa.int/event/530/contributions/
Absolute magnitudes and photometry from the MPC catalog
Peter Vereš (Minor Planet Center, Harvard – Smithsonian Center for Astrophysics), 9:00 AM
The Minor Planet Center (MPC) collects astrometric and photometric data on minor planets, with its catalog currently containing over 450 million data points for nearly 1.4 million objects. Photometric measurements are submitted in various bands & converted to the Johnson-Cousins V-band using band-specific conversion constants. The absolute magnitude H, a proxy for object size, is calculated…
Systematic issues in the photometry of MPC observations leading to erroneous size estimates Tobias Hoffmann, 9:25 AM
Most Potentially Hazardous and Near-Earth Objects are not observed by specific photometric follow-up telescopes. The only estimate on their physical parameters is therefore made based on the discovery observations and their follow-up submitted to the MPC. Those observations usually only include low-accuracy photometry.
Recent studies show that these observations also contain systematic…
A New Statistical Approach to Refining the H-G Model for Near-Earth Asteroids
Marco Fenucci (ESA NEOCC), 9:50 AM
The NEOCC Aegis Orbit Determination & Impact Monitoring system currently uses the H-G model by Bowell et al. 1989 to determine the absolute magnitude H from photometry data. Typically, it is not possible to determine both the absolute magnitude H & the slope parameter G, therefore G is often fixed to a nominal value of 0.15. However, several studies have shown that the slope parameter may…
Thermophysical observations
NEOs in the thermal infrared Thomas Müller (MPE), 11:00 AM
Asteroids reflect only a small fraction of solar radiation, with the majority being emitted at thermal infrared (IR) wavelengths. This high infrared-to-visible flux ratio is especially advantageous for observing near-Earth objects (NEOs), which are often viewed at large phase angles and in close proximity to the Sun. Visible observations are hindered by straylight and rotational variations of…
Determination of Sizes and Other Physical Properties of Near-Earth Objects through Thermophysical Modeling: A Review Marco Delbo (Observatoire de la côte d’Azur), 11:25
The radiometric method has proven highly effective in determining the sizes & albedo of asteroids and near-Earth objects (NEOs). This technique involves measuring the heat flux from these objects in the thermal infrared using telescopes, and modeling these observations as a function of size & other physical parameters. The values of these parameters are constrained by achieving the best…
Polarimetric observations
The Calern Asteroid Polarimetric Survey version 2.0
Philippe Bendjoya (Universit ́e de la Côte d’Azur, Observatoire de la Côte d’Azur, CNRS), 11:50
Polarimetric observations of NEOs are important for a number of reasons:
• Determination of the geometric albedo and hence possible derivation of diameter
• Determination of some surface regolith properties
• For taxonomic classification purposes
• Because it is useful to identify special classes of objects having anomalous compositions
• Because it is useful to identify objects…
Thermophysical observations
From NEOWISE to NEO Surveyor: Recent Results and Future Plans
Amy Mainzer (UCLA), 1:15 PM
The WISE/NEOWISE mission detected ~3000 near-Earth objects (NEOs) over the course its survey from late 2009 to July 2024. From these data, it is possible to obtain measurements of their physical properties, including effective spherical diameter & visible geometric albedo. Roughly 2000 objects in the sample were detected by the automated moving object pipeline, enabling a robust estimate of…
NEO Surveyor: Survey cadence and expected initial knowledge of newly discovered NEOs Joe Masiero (Caltech), 1:40 PM
The Near Earth Object Surveyor mission will survey the sky at infrared wavelengths in order to detect and discover ~100,000 NEOs, with sizes down to 25 m. The mission survey cadence is designed to provide sufficient self-followup to constrain the orbits and sizes of all detected NEOs. However, additional characterization of physical properties such as albedo and spectral taxonomy will…
NEOMIR: ESA’s space-based infrared mission for NEO detection and early warning
Luca Conversi (ESA NEOCC), 2:05 PM
Most current and planned NEO surveys are ground-based and carried out in the visible wavelength range. However, this approach has some limitations, such as (1) weather dependency, (2) that only a portion of the night sky is visible from any given location on Earth, (3) NEOs are difficult to detect at low galactic latitudes and (4) that visible-light surveys can only determine the motion and…
Thermophysical Modeling of (1566) Icarus from Ground-Based Infrared Observations Eric M. MacLennan (University of Helsinki), 2:50 PM
The thermal emission from an asteroid is a consequence of its surface temperatures, and the object’s size can be directly estimated from observations in the infrared. Accurately estimating the surface temperature distribution, which depends on several factors, can improve the precision of these size measurements. Key factors include the asteroid’s shape, spin, and thermophysical properties…
Characterizing Small Recently Discovered NEOs: Diameter, Albedo, and Color Measurements (REMOTE) Andy Lopez-Oquendo (NASA Goddard), 3:15 PM
Rapidly estimating recently discovered hazardous asteroids’ physical properties, such as rotation rate, surface composition, size, and albedo, provides a suitable practice for improving planetary defense techniques by acquiring these measurements hours or days after their discoveries. In this talk, we will present simultaneous optical and mid-infrared observations of recently discovered…
Thermal infrared observations of near-Earth asteroids with the TAO 6.5-m telescope
Jin Beniyama (Observatoire de la Côte d’Azur), 3:40 PM
The Institute of Astronomy, School of Science, University of Tokyo, is promoting the TAO (The University of Tokyo Atacama Observatory) project to construct a 6.5-m telescope at an altitude of 5,640 m in Atacama, Chile. This will be the highest astronomical observatory on Earth, providing exceptionally clear skies for infrared observations at wavelengths up to 38 μm. Scientific observations are…
Polarimetric observations
Study of near-Earth asteroids by polarimetric technique (REMOTE)
Irina Belskaya (Institute of Astronomy, V. N. Karazin Kharkiv National University, Ukraine), 4:50
Polarimetry is an effective tool for remote sensing of asteroid surfaces, mainly for assessing their albedo & surface texture, and searching for surface peculiarities. The main advantage of the polarimetric method of albedo determination is that albedo can be derived directly from polarimetric measurements using simple empirical relationships between polarimetric parameters and albedos….
Capability of the FoReRo2 instrument and the 2m RCC Telescope at the Bulgarian National Astronomical Observatory Rozhen for polarimetric observations of small solar system bodies Galin Biserov Borisov (Inst. of Astronomy and Natl. Astronomical Observatory), 10:35 AM
The Two-Channel-Focal-Reducer Rozhen (FoReRo2) was delivered to the Bulgarian National Astronomical Observatory (BNAO) Rozhen based on a contract between the Max-Planck Institute for Solar System Research and the Institute of Astronomy and National Astronomical Observatory (IA and NAO) in 2004. Since then, the FoReRo2 has been used at the f/8 Ritchey-Chrétien focus of the 2m…
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We started the day with Big Data- if you can’t handle coding and dbases, or don’t have a small army of grad students to filter and parse, look elsewhere. The issue will only multiply when Vera Rubin, SPHEREx, and then NEOSM begin adding their datasets to the heap.
Then we turned to thermal infrared obs- as I said, NEOSM (NEO Surveyor Mission), and likely Europe’s NEOMIR. NEOSM is progressing, not much news if you were already keeping up. If anything, the presentation gave updates on observing cadences and postprocessing. Based on revisits, it does not appear that ground-based telescopes will need do too much follow-up of NEOSM detections, which is the point. (Note, though, that follow-up will happen anyway, since both Vera Rubin and ZTF have twilight observing capability, as do some European assets.)
What is new is NEOMIR progress- Europe’s (proposed) complement to NEOSM. The space mission views in a ’doughnut’ around the Sun and inside NEOSM’s targeted zone. Though the NEOMIR project and viewing zone are still under study, it currently appears that the notional NEOMIR will be able to spot Chelyabinsk-type, Chelyabinsk-sized impactors, and with a few days’ warning at that. Good luck to the project, I hope they get selected and funded.
Then we turned to asteroid (1566) Icarus. Per se, it’s not an exceptional NEO, but it made a good case study. Between all our follow-up telescopes and processes and techniques, we can see what works, what is complementary, and what is contradictory or ambiguous. Great exercise.
And that took us to ground telescopes, even ones that work in nontrivial infrared wavelengths. A. Lopez-Oquendo and J. Beniyama spoke of IRTF and TAO, respectively. These are surprisingly capable, due to their very high mountaintop sites with very dry air. IRTF-MIRSI is now a flexible asteroid follow-up resource; TAO is still under tests and commissioning, but will be a large, valued asset in our toolbox. Can’t wait.
And now for something (mostly) different. Polarimetry can be used to determine asteroid albedo, and therefore, size and threat levels. The polarimetry observations are shorter and faster than phase curves (discussed Monday). Examples were presented. There is some question of the underlying physics, and our resulting confidence in the conclusions, but again this will be something in our toolbox we will be using in at least some capacity. At the very least, polarization instruments and telescopes don’t have to be very expensive.
…more to be shown…