Minor planets and related objects. IV. Asteroid (1566) Icarus.

Gehrels, T.; Roemer, Elizabeth; Taylor, Ronald C.; Zellner, B.

doi:10.1086/110962

Cited by 52 publications

(30 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Measurements of the polarization of light reflected from the surface of asteroids as a function of phase angle have been made by Lyot (1934), Gehrels et al (1970), Veverka (1970Veverka ( , 19-1a, b, 1973, Dunlap et al (1973), DunlaR (1974), Zellner et al (1974) and Zellner and Gradie (1976a, b). Polarimetric measure ments of laboratory, comparison materials have been used as a basis for interpreting these data by Dollfus (1971), -Dollfus and Geake (1975), Veverka and Noland (1973), Bowell and Zellner (1973) and Zellner and Gradie (1976a) is a function of the albedo of the surface inaterial& Polarime tricly derived asteroid albedos have the same general range (3-30%) as do meteoritic materials.…”

Section: Additional Information Sourcesmentioning

confidence: 99%

Asteroid surface materials: Mineralogical characterizations from reflectance spectra

1978

View full text Add to dashboard Cite

Section: Additional Information Sourcesmentioning

confidence: 99%

Asteroid surface materials: Mineralogical characterizations from reflectance spectra

1978

View full text Add to dashboard Cite

“…llb). These data are taken from Gehrels et al (1970), and are difficult to compare rigorously with our measurements as they were made using wide-band filters. To strengthen the argument, the polarization curve of Icarus is consistent with the curves for Bruderheim (Gehrels et al, 1970).…”

Section: )mentioning

confidence: 99%

“…These data are taken from Gehrels et al (1970), and are difficult to compare rigorously with our measurements as they were made using wide-band filters. To strengthen the argument, the polarization curve of Icarus is consistent with the curves for Bruderheim (Gehrels et al, 1970). As Icarus was only observed over phase angles ranging from 40°to 1000, its negative branch cannot be compared with those of our samples, but at a = 600 the polarization of Icarus is about 3.5% (in the spectral range of our G filter) that compares favorably with the values for the "coated" sample given in Table VI.…”

mentioning

confidence: 99%

Photometric and polarimetric properties of the bruderheim chondritic meteorite

Egan¹,

Veverka

Noland

et al. 1973

Icarus

View full text Add to dashboard Cite

RE -447T.fABSTRACT r Photometric and polarimetric laboratory measurements were made, as a function of phase angle in the U(0.36 im), G(0.541.m) and R(0.67Lm) bands for 0 , 30O and 600 incident illumination on four particle size ranges of Bruderheim, an L6 olivine-hypersthene chondritic meteorite.The four particle size ranges were: 0.25-4.76mm, 0.25-4.76mm coated with <74lm powder, 74-250pm, and < 37pm. In addition, normal reflectance measurments were made in the spectral range from 0.31 to 1.1lm. Comparison with astronomical data reveals that none of the asteroids in the main belt for which adequate observations exist can be matched with Bruderheim, which is representative of the most common meteoritic material encountered by the Earth. However, it appears from the polarization and photometry data that the surface of-the Apollo asteroid Icarus is consistent with an ordinary chondrite composition. ' This suggests the possibility that this material, although common in Earth-crossing orbits, is rare as a surface constituent in the main asteroid belt.ii . I INTRODUCTIONRecently, much astronomical effort has been devoted to the study of the physical properties of asteroid surfaces. This has resulted in an ever growing store of spectral, photometric, and polarimetric data that 'have not been sufficiently complemented by laboratory measurements.Because there are many indirect arguments (Anders, 1964) which indicate that most meteorites are fragments of asteroid bodies, and since McCord, et al. (1970) 'have successfully identified the spectral reflectance curve of one asteroid, Vesta, with that of a basaltic achondrite, laboratory measurments on meteorite samples should prove useful in an intrepretation of asteroid surfaces. We 'have chosen to study the spectral, photometric, and polarimetric properties of the Bruderheim olivine-hypersthene chondrite, which is representative of the most common meteoritic material recovered on Earth (Mason, 1962), and, hence, might also be the most common in interplanetary space. II INSTRUMENTATIONThe Grumman goniometer, designed to measure the polarimetric and photometric properties of samples up to 60mm in diameter, consists of a light source on a 3-meter long arm and a sensor on another 3-meter long arm. The center of rotation of the arms is situated on the average sample surface, and the average normal to the surface lies in the plane defined by the arms.The source is a G-E Type 2331 tungsten lamp, followed by a quartz ground glass diffuser, a Lyot depolarizer, an aperture plate, a 420 cycle, seven 1' bladed chopper, and an 11.4 cm diameter quartz objective lens. This assembly produces a beam collimated to 1°, of uniform brightness to 1 percent or less, with a residual polarization of 0.1 percent or less on the 60mm illuminated sample area. The source arm is ordinarily fixed at an incident illumination angle between 0 and 60 degrees.The sensors used in this investigation were photomultipliers RCA Types 6199 and 7102 with mumetal shields. The sensor arm normally traverses a phase ang...

show abstract

“…For instance, is it possible, as Bell (1917), Stumpff (1948), Widorn (1964) and recently Gehrels et al (1970) have tried to do, to determine the absolute reflectivities of asteroids in this way?…”

Section: ) Introductionmentioning

confidence: 99%

The Physical Meaning of Phase Coefficients

Veverka

1971

International Astronomical Union Colloquium

View full text Add to dashboard Cite

The question of what information about an asteroid's surface is contained in a measurement of the phase coefficient between phase angles of 10° and 30° is examined in detail. Contrary to some past claims it is shown that absolute reflectivities cannot be derived from phase coefficients. Furthermore, typical asteroid phase coefficients cannot be interpreted unambiguously. This is because the observed phase coefficient may depend as much on the photometric properties of an individual surface element as on the degree of large-scale surface roughness, and these two effects are impossible to separate if only disk integrated measurements are available. The wavelength dependence of asteroid phase coefficients should be small and should contain little information about the surface. In the case of irregular asteroids with macroscopically rough surfaces, the importance of large-scale shadowing, and hence the observed phase coefficient, will depend on the aspect of the asteroid. In such cases, therefore, phase coefficients must be carefully defined to be meaningful It should be possible, in some cases, to estimate the relative surface roughness of two quasi-spherical asteroids by combining photometric and polarimetric observations. For example, if the two asteroids have almost identical polarization curves but quite different phase coefficients, it is likely that the asteroid with the larger phase coefficient has a macroscopically rougher surface.

show abstract

Minor planets and related objects. IV. Asteroid (1566) Icarus.

Cited by 52 publications

References 0 publications

Asteroid surface materials: Mineralogical characterizations from reflectance spectra

Asteroid surface materials: Mineralogical characterizations from reflectance spectra

Photometric and polarimetric properties of the bruderheim chondritic meteorite

The Physical Meaning of Phase Coefficients

Contact Info

Product

Resources

About