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Observations of solar system objects

, ; Spoto, F.; Lindegren, Lennart LU ; Hobbs, David LU ; Mcmillan, Paul LU ; MICHALIK, DANIEL LU and Zwitter, Tomaž (2018) In Astronomy and Astrophysics 616.
Abstract
Context. The Gaia spacecraft of the European Space Agency (ESA) has been securing observations of solar system objects (SSOs) since the beginning of its operations. Data Release 2 (DR2) contains the observations of a selected sample of 14,099 SSOs. These asteroids have been already identified and have been numbered by the Minor Planet Center repository. Positions are provided for each Gaia observation at CCD level. As additional information, complementary to astrometry, the apparent brightness of SSOs in the unfiltered G band is also provided for selected observations. Aims. We explain the processing of SSO data, and describe the criteria we used to select the sample published in Gaia DR2. We then explore the data set to assess its... (More)
Context. The Gaia spacecraft of the European Space Agency (ESA) has been securing observations of solar system objects (SSOs) since the beginning of its operations. Data Release 2 (DR2) contains the observations of a selected sample of 14,099 SSOs. These asteroids have been already identified and have been numbered by the Minor Planet Center repository. Positions are provided for each Gaia observation at CCD level. As additional information, complementary to astrometry, the apparent brightness of SSOs in the unfiltered G band is also provided for selected observations. Aims. We explain the processing of SSO data, and describe the criteria we used to select the sample published in Gaia DR2. We then explore the data set to assess its quality. Methods. To exploit the main data product for the solar system in Gaia DR2, which is the epoch astrometry of asteroids, it is necessary to take into account the unusual properties of the uncertainty, as the position information is nearly one-dimensional. When this aspect is handled appropriately, an orbit fit can be obtained with post-fit residuals that are overall consistent with the a-priori error model that was used to define individual values of the astrometric uncertainty. The role of both random and systematic errors is described. The distribution of residuals allowed us to identify possible contaminants in the data set (such as stars). Photometry in the G band was compared to computed values from reference asteroid shapes and to the flux registered at the corresponding epochs by the red and blue photometers (RP and BP). Results. The overall astrometric performance is close to the expectations, with an optimal range of brightness G ∼ 12 - 17. In this range, the typical transit-level accuracy is well below 1 mas. For fainter asteroids, the growing photon noise deteriorates the performance. Asteroids brighter than G ∼ 12 are affected by a lower performance of the processing of their signals. The dramatic improvement brought by Gaia DR2 astrometry of SSOs is demonstrated by comparisons to the archive data and by preliminary tests on the detection of subtle non-gravitational effects. © ESO 2018. (Less)
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author
organization
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type
Contribution to journal
publication status
published
subject
keywords
Asteroids: general, Astrometry, Methods: data analysis, Minor planets, Space vehicles: instruments, Asteroids, Luminance, Orbits, Photometry, Random errors, Solar system, Space flight, Systematic errors, Asteroids: generals, Methods:data analysis, Data handling
in
Astronomy and Astrophysics
volume
616
publisher
EDP Sciences
external identifiers
  • scopus:85051851022
ISSN
1432-0746
DOI
10.1051/0004-6361/201832900
language
English
LU publication?
yes
id
230d5b0a-d2b0-4ff1-8064-6010423f9aad
date added to LUP
2018-09-13 13:38:24
date last changed
2018-10-03 12:10:49
@article{230d5b0a-d2b0-4ff1-8064-6010423f9aad,
  abstract     = {Context. The Gaia spacecraft of the European Space Agency (ESA) has been securing observations of solar system objects (SSOs) since the beginning of its operations. Data Release 2 (DR2) contains the observations of a selected sample of 14,099 SSOs. These asteroids have been already identified and have been numbered by the Minor Planet Center repository. Positions are provided for each Gaia observation at CCD level. As additional information, complementary to astrometry, the apparent brightness of SSOs in the unfiltered G band is also provided for selected observations. Aims. We explain the processing of SSO data, and describe the criteria we used to select the sample published in Gaia DR2. We then explore the data set to assess its quality. Methods. To exploit the main data product for the solar system in Gaia DR2, which is the epoch astrometry of asteroids, it is necessary to take into account the unusual properties of the uncertainty, as the position information is nearly one-dimensional. When this aspect is handled appropriately, an orbit fit can be obtained with post-fit residuals that are overall consistent with the a-priori error model that was used to define individual values of the astrometric uncertainty. The role of both random and systematic errors is described. The distribution of residuals allowed us to identify possible contaminants in the data set (such as stars). Photometry in the G band was compared to computed values from reference asteroid shapes and to the flux registered at the corresponding epochs by the red and blue photometers (RP and BP). Results. The overall astrometric performance is close to the expectations, with an optimal range of brightness G ∼ 12 - 17. In this range, the typical transit-level accuracy is well below 1 mas. For fainter asteroids, the growing photon noise deteriorates the performance. Asteroids brighter than G ∼ 12 are affected by a lower performance of the processing of their signals. The dramatic improvement brought by Gaia DR2 astrometry of SSOs is demonstrated by comparisons to the archive data and by preliminary tests on the detection of subtle non-gravitational effects. © ESO 2018.},
  articleno    = {A13},
  author       = {,  and Spoto, F. and Lindegren, Lennart and Hobbs, David and Mcmillan, Paul and MICHALIK, DANIEL and Zwitter, Tomaž},
  issn         = {1432-0746},
  keyword      = {Asteroids: general,Astrometry,Methods: data analysis,Minor planets,Space vehicles: instruments,Asteroids,Luminance,Orbits,Photometry,Random errors,Solar system,Space flight,Systematic errors,Asteroids: generals,Methods:data analysis,Data handling},
  language     = {eng},
  publisher    = {EDP Sciences},
  series       = {Astronomy and Astrophysics},
  title        = {Observations of solar system objects},
  url          = {http://dx.doi.org/10.1051/0004-6361/201832900},
  volume       = {616},
  year         = {2018},
}