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J/A+A/338/340     Asteroids as IR Standards for ISOPHOT   (Mueller+ 1998)

Asteroids as far-infrared photometric standards for ISOPHOT Mueller T.G., Lagerros J.S.V. <Astron. Astrophys. 338, 340 (1998)> =1998A&A...338..340M (SIMBAD/NED BibCode)
ADC_Keywords: Minor planets ; Polarization ; Spectra, infrared Keywords: minor planets, asteroids - radiation mechanisms: thermal - infrared: solar system Abstract: Asteroids are used as far-IR calibrators for the imaging photopolarimeter ISOPHOT on board the Infrared Space Observatory ISO. For the 10 selected objects we compiled a large uniform database of 678 individual observations, ranging from 7-2000µm. Applying a new thermophysical model to the observations we derived thermal properties of the selected asteroids, based on spin-vector solutions, direct size measurements and the HG-magnitude system. Our investigations indicate very rough surfaces, reflected in the beaming effect, and very low levels of heat conduction, expressed in thermal inertias between 5 and 25J/m2/s0.5/K. Due to scattering processes in the porous regolith, the emissivity varies significantly with wavelength. In case of Vesta we find emissivities as low as 0.6 in the far-IR/submillimetre region. By entering the combined results into the thermophysical model we defined new photometric standards for the far-IR. The absolute accuracy for thermal flux or lightcurve predictions is 5-10% for the first category objects and 10-20% for the secondaries. The methods and procedures discussed here are included in the first update of the ISOPHOT calibration in 1998. Description: Thermal emission observations of 10 selected asteroids. Mid- and far-IR data compiled from a number of sources into uniform database. The table consists of 678 individual observations, ranging from 7 to 2000 microns. Inband fluxes have been converted to monochromatic flux densities. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table7.dat 61 678 Thermal emission observations of 10 selected asteroids
See also: II/190 : IRAS Minor Planet Survey (IMPS) (Tedesco 1992) : The JCMT archive Byte-by-byte Description of file: table7.dat
Bytes Format Units Label Explanations
1- 4 I4 --- Asteroid [1/532] Asteroid number. See Note (1) 6- 19 F14.6 d JD Julian Date 21- 27 F7.2 um lambda [7.7,2000] Wavelength 29- 37 F9.4 Jy flux Monochromatic flux 39- 46 F8.4 Jy e_flux Flux error 48- 61 A14 --- Inst Telescope and instrument. See Note (2)
Note (1): The IAU designation (number and name) 1 Ceres 2 Pallas 3 Juno 4 Vesta 10 Hygiea 54 Alexandra 65 Cybele 106 Dione 313 Chaldaea 532 Herculina Note (2): Telescope and instrument: HHT: Heinrich-Hertz-Telescope IRAS: Infrared Astronomical Satellite IRTF: Infrared Telescope Facility ISO/ISOPHOT: Infrared Space Observatory / Imaging-Photopolarimeter JCMT/UKT14: James Clerk Maxwell Telescope / United Kingdom Telescope, Cryostat No. 14-Bolometer UKIRT/MAX: United Kingdom Infrared Telescope / Mid-Infrared Array eXpandable-Camera
Acknowledgements: Johan Lagerros References: Altenhoff W.J., Baars J.W.M., Schrami J.B. et al. 1996A&A...309..953A Lebofsky L.A., Sykes M.V., Tedesco E.F. et al., 1986Icar...68..239L Mueller, T., 1997, Ph.D. thesis, Ruprecht-Karls-Universitat, Heidelberg
(End) Johan Lagerros [Uppsala Astronomical Observatory] 08-Sep-1998
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