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Radio Interferometric Observation of an Asteroid Occultation
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- Harju, Jorma (author)
- Department of Physics, University of Helsinki, Finland. Max-Planck-Institut für extraterrestrische Physik, Garching, Germany
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- Lehtinen, Kimmo (author)
- Finnish Geospatial Research Institute FGI, Masala, Finland
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- Romney, Jonathan (author)
- Long Baseline Observatory, Socorro, USA
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- Department of Physics, University of Helsinki, Finland Max-Planck-Institut für extraterrestrische Physik, Garching, Germany Finnish Geospatial Research Institute FGI, Masala, Finland (creator_code:org_t)
- 2018-09-14
- 2018
- English.
- In: Astronomical Journal. - : University of Chicago Press. - 0004-6256 .- 1538-3881. ; 156:4, s. 1-10
- Journal article (peer-reviewed)
Abstract
Subject headings
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- The occultation of the radio galaxy 0141+268 by the asteroid(372)Palma on 2017 May 15 was observed using sixantennas of the Very Long Baseline Array(VLBA). The shadow of Palma crossed the VLBA station at Brewster,Washington. Owing to the wavelength used, and the size and the distance of the asteroid, a diffraction pattern in theFraunhofer regime was observed. The measurement retrieves both the amplitude and the phase of the diffractedelectromagnetic wave. This is thefirst astronomical measurement of the phase shift caused by diffraction. Themaximum phase shift is sensitive to the effective diameter of the asteroid. The bright spot at the shadow’s center,the so called Arago–Poisson spot, is clearly detected in the amplitude time-series, and its strength is a goodindicator of the closest angular distance between the center of the asteroid and the radio source. A sample ofrandom shapes constructed using a Markov chain Monte Carlo algorithm suggests that the silhouette of Palmadeviates from a perfect circle by 26±13%. The best-fitting random shapes resemble each other, and we suggesttheir average approximates the shape of the silhouette at the time of the occultation. The effective diameterobtained for Palma, 192.1±4.8 km, is in excellent agreement with recent estimates from thermal modeling ofmid-infrared photometry. Finally, our computations show that because of the high positional accuracy, a singleradio interferometric occultation measurement can reduce the long-term ephemeris uncertainty by an order ofmagnitude.
Subject headings
- TEKNIK OCH TEKNOLOGIER -- Elektroteknik och elektronik -- Annan elektroteknik och elektronik (hsv//swe)
- ENGINEERING AND TECHNOLOGY -- Electrical Engineering, Electronic Engineering, Information Engineering -- Other Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)
Keyword
- minor planets
- asteroids: general
- minor planets
- asteroids: individual (372 Palma)
- techniques: interferometric
- Onboard space systems
- Rymdtekniska system
Publication and Content Type
- ref (subject category)
- art (subject category)
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- Poutanen, Markku
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