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 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)
http://cadcwww.dao.nrc.ca/jcmt : 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 1996A&A...309..953A
Lebofsky L.A., Sykes M.V., Tedesco E.F. et al., 1986Icar...68..239L 1986Icar...68..239L
Mueller, T., 1997, Ph.D. thesis, Ruprecht-Karls-Universitat, Heidelberg
(End) Johan Lagerros [Uppsala Astronomical Observatory] 08-Sep-1998