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Title: NEOWISE Reactivation Mission Year Three: Asteroid Diameters and Albedos

Abstract

The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) reactivation mission has completed its third year of surveying the sky in the thermal infrared for near-Earth asteroids and comets. NEOWISE collects simultaneous observations at 3.4 and 4.6  μ m of solar system objects passing through its field of regard. These data allow for the determination of total thermal emission from bodies in the inner solar system, and thus the sizes of these objects. In this paper, we present thermal model fits of asteroid diameters for 170 NEOs and 6110 Main Belt asteroids (MBAs) detected during the third year of the survey, as well as the associated optical geometric albedos. We compare our results with previous thermal model results from NEOWISE for overlapping sample sets, as well as diameters determined through other independent methods, and find that our diameter measurements for NEOs agree to within 26% (1 σ ) of previously measured values. Diameters for the MBAs are within 17% (1 σ ). This brings the total number of unique near-Earth objects characterized by the NEOWISE survey to 541, surpassing the number observed during the fully cryogenic mission in 2010.

Authors:
; ;  [1]; ;  [2];  [3];  [4]; ;  [5]
  1. Jet Propulsion Laboratory/California Institute of Technology, 4800 Oak Grove Drive, MS 183-301, Pasadena, CA 91109 (United States)
  2. California Institute of Technology, Infrared Processing and Analysis Center, 1200 California Boulevard, Pasadena, CA 91125 (United States)
  3. University of California, Los Angeles, CA 90095 (United States)
  4. University of Maryland, College Park, MD 20742 (United States)
  5. Planetary Science Institute, 1700 E Fort Lowell Road #106, Tucson, AZ 85719 (United States)
Publication Date:
OSTI Identifier:
22663137
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (Online); Journal Volume: 154; Journal Issue: 4; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALBEDO; ASTEROIDS; COMETS; COMPARATIVE EVALUATIONS; CRYOGENICS; EMISSION; INFRARED SURVEYS; PLANETS; REGENERATION; SKY; SOLAR SYSTEM

Citation Formats

Masiero, Joseph R., Mainzer, A. K., Kramer, E., Nugent, C., Cutri, R. M., Wright, E. L., Bauer, J. M., Grav, T., and Sonnett, S., E-mail: Joseph.Masiero@jpl.nasa.gov. NEOWISE Reactivation Mission Year Three: Asteroid Diameters and Albedos. United States: N. p., 2017. Web. doi:10.3847/1538-3881/AA89EC.
Masiero, Joseph R., Mainzer, A. K., Kramer, E., Nugent, C., Cutri, R. M., Wright, E. L., Bauer, J. M., Grav, T., & Sonnett, S., E-mail: Joseph.Masiero@jpl.nasa.gov. NEOWISE Reactivation Mission Year Three: Asteroid Diameters and Albedos. United States. doi:10.3847/1538-3881/AA89EC.
Masiero, Joseph R., Mainzer, A. K., Kramer, E., Nugent, C., Cutri, R. M., Wright, E. L., Bauer, J. M., Grav, T., and Sonnett, S., E-mail: Joseph.Masiero@jpl.nasa.gov. Sun . "NEOWISE Reactivation Mission Year Three: Asteroid Diameters and Albedos". United States. doi:10.3847/1538-3881/AA89EC.
@article{osti_22663137,
title = {NEOWISE Reactivation Mission Year Three: Asteroid Diameters and Albedos},
author = {Masiero, Joseph R. and Mainzer, A. K. and Kramer, E. and Nugent, C. and Cutri, R. M. and Wright, E. L. and Bauer, J. M. and Grav, T. and Sonnett, S., E-mail: Joseph.Masiero@jpl.nasa.gov},
abstractNote = {The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) reactivation mission has completed its third year of surveying the sky in the thermal infrared for near-Earth asteroids and comets. NEOWISE collects simultaneous observations at 3.4 and 4.6  μ m of solar system objects passing through its field of regard. These data allow for the determination of total thermal emission from bodies in the inner solar system, and thus the sizes of these objects. In this paper, we present thermal model fits of asteroid diameters for 170 NEOs and 6110 Main Belt asteroids (MBAs) detected during the third year of the survey, as well as the associated optical geometric albedos. We compare our results with previous thermal model results from NEOWISE for overlapping sample sets, as well as diameters determined through other independent methods, and find that our diameter measurements for NEOs agree to within 26% (1 σ ) of previously measured values. Diameters for the MBAs are within 17% (1 σ ). This brings the total number of unique near-Earth objects characterized by the NEOWISE survey to 541, surpassing the number observed during the fully cryogenic mission in 2010.},
doi = {10.3847/1538-3881/AA89EC},
journal = {Astronomical Journal (Online)},
number = 4,
volume = 154,
place = {United States},
year = {Sun Oct 01 00:00:00 EDT 2017},
month = {Sun Oct 01 00:00:00 EDT 2017}
}
  • We present preliminary diameters and albedos for 7956 asteroids detected in the first year of the NEOWISE Reactivation mission. Of those, 201 are near-Earth asteroids and 7755 are Main Belt or Mars-crossing asteroids. 17% of these objects have not been previously characterized using the Near-Earth Object Wide-field Infrared Survey Explorer, or “NEOWISE” thermal measurements. Diameters are determined to an accuracy of ∼20% or better. If good-quality H magnitudes are available, albedos can be determined to within ∼40% or better.
  • The Near-Earth Object Wide-Field Infrared Survey Explorer (NEOWISE) mission continues to detect, track, and characterize minor planets. We present diameters and albedos calculated from observations taken during the second year since the spacecraft was reactivated in late 2013. These include 207 near-Earth asteroids (NEAs) and 8885 other asteroids. Of the NEAs, 84% NEAs did not have previously measured diameters and albedos by the NEOWISE mission. Comparison of sizes and albedos calculated from NEOWISE measurements with those measured by occultations, spacecraft, and radar-derived shapes shows accuracy consistent with previous NEOWISE publications. Diameters and albedos fall within ±∼20% and ±∼40%, 1-sigma, respectively,more » of those measured by these alternate techniques. NEOWISE continues to preferentially discover near-Earth objects which are large (>100 m), and have low albedos.« less
  • We present initial results from the Wide-field Infrared Survey Explorer (WISE), a four-band all-sky thermal infrared survey that produces data well suited for measuring the physical properties of asteroids, and the NEOWISE enhancement to the WISE mission allowing for detailed study of solar system objects. Using a NEATM thermal model fitting routine, we compute diameters for over 100,000 Main Belt asteroids from their IR thermal flux, with errors better than 10%. We then incorporate literature values of visible measurements (in the form of the H absolute magnitude) to determine albedos. Using these data we investigate the albedo and diameter distributionsmore » of the Main Belt. As observed previously, we find a change in the average albedo when comparing the inner, middle, and outer portions of the Main Belt. We also confirm that the albedo distribution of each region is strongly bimodal. We observe groupings of objects with similar albedos in regions of the Main Belt associated with dynamical breakup families. Asteroid families typically show a characteristic albedo for all members, but there are notable exceptions to this. This paper is the first look at the Main Belt asteroids in the WISE data, and only represents the preliminary, observed raw size, and albedo distributions for the populations considered. These distributions are subject to survey biases inherent to the NEOWISE data set and cannot yet be interpreted as describing the true populations; the debiased size and albedo distributions will be the subject of the next paper in this series.« less
  • Rectified diameters and albedo estimates of 1517 main-belt asteroids selected from IRAS and the Mid-Course Space Experiment asteroid photometry catalogs are derived from updated infrared thermal models, the Standard Thermal Model and the Near-Earth Asteroid Thermal Model (NEATM), and Monte Carlo simulations, using new Minor Planet Center compilations of absolute magnitudes (H values) constrained by occultation- and radar-derived parameters. The NEATM approach produces a more robust estimate of albedos and diameters, yielding albedos of p{sub v} (NEATM mean) =0.081 {+-} 0.064. The asteroid beaming parameter ({eta}) for the selected asteroids has a mean value of 1.07 {+-} 0.27, and themore » smooth distribution of {eta} suggests that this parameter is independent of asteroid properties such as composition. No trends in {eta} due to size-dependent rotation rates are evident. Comparison of derived values of {eta} as a function of taxonomic type indicates that the beaming parameter values for S- and C-type asteroids are identical within the standard deviation of the population of beaming parameters.« less
  • NASA's Wide-field Infrared Survey Explorer (WISE) spacecraft has been brought out of hibernation and has resumed surveying the sky at 3.4 and 4.6 μm. The scientific objectives of the NEOWISE reactivation mission are to detect, track, and characterize near-Earth asteroids and comets. The search for minor planets resumed on 2013 December 23, and the first new near-Earth object (NEO) was discovered 6 days later. As an infrared survey, NEOWISE detects asteroids based on their thermal emission and is equally sensitive to high and low albedo objects; consequently, NEOWISE-discovered NEOs tend to be large and dark. Over the course of itsmore » three-year mission, NEOWISE will determine radiometrically derived diameters and albedos for ∼2000 NEOs and tens of thousands of Main Belt asteroids. The 32 months of hibernation have had no significant effect on the mission's performance. Image quality, sensitivity, photometric and astrometric accuracy, completeness, and the rate of minor planet detections are all essentially unchanged from the prime mission's post-cryogenic phase.« less