The Near-Earth Objects Follow-Up Program: First Results

doi:10.1006/icar.1995.1142

Icarus

Volume 117, Issue 1, September 1995, Pages 62-70

https://doi.org/10.1006/icar.1995.1142 Get rights and content

Abstract

In the framework of our project for the establishment of a follow-up station to be integrated into the future European network for the search for near-Earth objects (EUNEASO), we have carried out photometry and astrometry of eight near-Earth asteroids and two Mars crossers. From a total of 42 single-night lightcurves we have determined for the first time accurate rotation periods and amplitudes for eight objects (1981, 2062, 4953, 5653, 5836, 1993 BX₃, 1994 JF₁, and 1994 LC₁). In one case (5797) we have refined the previous determinations. For the asteroid 1994 AW₁ we find an indication for a possible complex rotation state.

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Cited by (71)

Photometry of small asteroids of different families and dynamical groups with a short rotation period
2023, Planetary and Space Science
We present photometric observations of 25 small asteroids from different families (Eos, Erigone, Flora, Maria, Massalia, Phocaea and Zita) and dynamical groups. We derive their synodic periods and lightcurve amplitudes, as well as V–R color indices, and absolute magnitudes. Furthermore, we revise their albedos using the determined absolute magnitudes. Three of the objects are studied for the first time. We also make estimates of the diameters of four asteroids. Many of the observed asteroids have short rotation periods and small amplitudes of the lightcurves, which may be indicative of their potential binary nature. Our photometry in combination with future data can be used in further studies. Analysis of the parameters obtained for the observed asteroids, such as absolute magnitudes, revised albedos, as well as color indices obtained from the SDSS and Sky-Mapper surveys, makes it possible to effectively classify them taxonomically.
Photometry of selected outer main belt asteroids
2021, Planetary and Space Science
Citation Excerpt :
Some observations were also made at other observational sites with the 0.5-m, 1-m and 1.25-m telescopes of the Crimean Astrophysical Observatory, the 0.7-m telescope of the Kharadze Abastumani Astrophysical Observatory in Georgia, and the 1-m telescope of the Observatory of Fesenkov Astrophysical Institute in Kazakhstan, to minimize influence of weather conditions and obtain a good phase angle coverage. The CCD-image data were reduced with the synthetic aperture photometry package (ASTPHOT) developed at the DLR by S. Mottola (Mottola et al., 1995). The absolute calibrations of the comparison stars were performed with the standard star sequences from Landolt (1992) and Skiff (2007).
We present new photometric observations for twelve asteroids ((122) Gerda, (152) Atala, (260) Huberta, (665) Sabine, (692) Hippodamia, (723) Hammonia, (745) Mauritia, (768) Struveana, (863) Benkoela, (1113) Katja, (1175) Margo (2057) Rosemary) from the outer part of the main belt aimed to obtain the magnitude-phase curves and to verify geometric albedo and taxonomic class based on their magnitude-phase behaviors. The measured magnitude-phase relations confirm previously determined composition types of (260) Huberta (C-type), (692) Hippodamia (S-type) and (1175) Margo (S-type). Asteroids (665) Sabine and (768) Struveana previously classified as X-type show phase-curve behavior typical for moderate-albedo asteroids and may belong to the M-type. The phase-curve of (723) Hammonia is typical for the S-type which contradicts the previously determined C-type. We confirmed the moderate-albedo of asteroids (122) Gerda and (152) Atala, but their phase-curves are different from typical for the S-type and may indicate more rare compositional types. Based on magnitude-phase behaviors and V-R colors, (2057) Rosemary most probably belongs to M-type, while asteroids (745) Mauritia and (1113) Katja belong to S-complex. The phase curve of the A-type asteroid (863) Benkoela does not cover the opposition effect range and further observations are needed to understand typical features of the phase-curves of A-type asteroids in comparison with other types. We have also determined lightcurve amplitudes of the observed asteroids and obtained new or improved values of the rotation periods for most of them.
A satellite orbit drift in binary near-Earth asteroids (66391) 1999 KW4 and (88710) 2001 SL9 — Indication of the BYORP effect
2021, Icarus
We obtained thorough photometric observations of two binary near-Earth asteroids (66391) Moshup = 1999 KW4 and (88710) 2001 SL9 taken from 2000 to 2019. We modeled the data and derived physical and dynamical properties of the binary systems. For (66391) 1999 KW4, we derived its mutual orbit's pole, semimajor axis and eccentricity that are in agreement with radar-derived values (Ostro et al., 2006. Science, 314, 1276–1280). However, we found that the data are inconsistent with a constant orbital period and we obtained unique solution with a quadratic drift of the mean anomaly of the satellite of −0.65 ± 0.16 deg./yr² (all quoted uncertainties correspond to 3σ). This means that the semimajor axis of the mutual orbit of the components of this binary system, determined a = 2.548 ± 0.015 km by Ostro et al. (2006), increases in time with a mean rate of 1.2 ± 0.3 cm/yr.
For (88710) 2001 SL9, we determined that the mutual orbit has a pole within 10° of (L, B) = (302^∘, −73^∘) (ecliptic coordinates), and is close to circular (eccentricity < 0.07). The data for this system are also inconsistent with a constant orbital period and we obtained two solutions for the quadratic drift of the mean anomaly: 2.8 ± 0.2 and 5.2 ± 0.2 deg./yr², implying that the semimajor axis of the mutual orbit of the components (estimated a ~ 1.6 km) decreases in time with a mean rate of −2.8 ± 0.2 or −5.1 ± 0.2 cm/yr for the two solutions, respectively.
The expanding orbit of (66391) 1999 KW4 may be explained by mutual tides interplaying with binary YORP (BYORP) effect (McMahon and Scheeres, 2010a. Icarus 209, 494–509). However, a modeling of the BYORP drift using radar-derived shapes of the binary components predicted a much higher value of the orbital drift than the observed one. It suggests that either the radar-derived shape model of the secondary is inadequate for computing the BYORP effect, or the present theory of BYORP overestimates it. It is possible that the BYORP coefficient has instead an opposite sign than predicted; in that case, the system may be moving into an equilibrium between the BYORP and the tides.
In the case of (88710) 2001 SL9, the BYORP effect is the only known physical mechanism that can cause the inward drift of its mutual orbit.
Together with the binary (175706) 1996 FG3 which has a mean anomaly drift consistent with zero, implying a stable equilibrium between the BYORP effect and mutual body tides (Scheirich et al., 2015. Icarus 245, 56-63), we now have three distinct cases of well observed binary asteroid systems with their long-term dynamical models inferred. They indicate a presence of all the three states of the mutual orbit evolution – equilibrium, expanding and contracting – in the population of near-Earth binary asteroids.
Studies of irregular satellites: I. Lightcurves and rotation periods of 25 Saturnian moons from Cassini observations
2019, Icarus
Disk-integrated time-resolved photometric observations have been performed for 25 irregular moons of Saturn with the ISS camera of the Cassini spacecraft in a wide range of solar phase angles. From the derived lightcurves, synodic rotation periods were determined, ranging from ~5.5 h to ~76 h; the fastest observed spin rate is much slower than the disruption rotation barrier of asteroids at ~2 h. The lightcurves show very different structures which indicates that Saturn's irregular moons have a large variety of shapes. All lightcurves except for Phoebe and Paaliaq show 2-maxima/2-minima or 3-maxima/3-minima patterns. The lightcurve amplitudes range between 0.1 mag and > 2 mag, the latter is measured in observations of objects Ymir, Kiviuq, and Siarnaq at phase angles α > 60°. While most lightcurve amplitudes from observations obtained at α < 30° are <0.5 mag, most at α > 50° are >0.5 mag. This campaign marks the first utilization of an interplanetary spacecraft for a systematic photometric survey of irregular moons.
Asteroid observations at low phase angles. IV. Average parameters for the new H, G<inf>1</inf>, G<inf>2</inf> magnitude system
2016, Planetary and Space Science
We present new observational data for selected main-belt asteroids of different compositional types. The detailed magnitude–phase dependences including small phase angles (<1°) were obtained for these asteroids, namely: (10) Hygiea (down to the phase angle of 0.3°, C-type), (176) Iduna (0.2°, G-type), (214) Aschera (0.2°, E-type), (218) Bianca (0.3°, S-type), (250) Bettina (0.3°, M-type), (419) Aurelia (0.1°, F-type), (596) Scheila (0.2°, D-type), (635) Vundtia (0.2°, B-type), (671) Carnegia (0.2°, P-type), (717) Wisibada (0.1°, T-type), (1021) Flammario (0.6°, B-type), and (1279) Uganda (0.5°, E-type). For several asteroids, the dependences of brightness on the phase angle were investigated in the BVRI bands. We found a great diversity in the opposition-effect behavior both in the magnitude and the width of the opposition surges, especially for low-albedo asteroids. Some low-albedo asteroids (e.g., (10) Hygiea) display a broad opposition effect with an amplitude of 0.15–0.20 mag relative to the extrapolation of the linear part of the phase curve. Other asteroids (e.g., (596) Scheila, (1021) Flammario) show linear magnitude–phase dependences down to small phase angles (0.1–0.2°). Using numerous data sets on the magnitude–phase dependences with extensive phase-angle coverage, we examined in more detail the new three-parameter H, G₁, G₂ magnitude system. We determined the values of the G₁ and G₂ parameters for magnitude phase dependences of individual asteroids and obtained the average parameters for main asteroid compositional types. The values obtained can be used for the estimation of the absolute magnitude of an asteroid from a single observed magnitude when the magnitude–phase dependency is unknown and/or to calculate a visible magnitude for the ephemerides.
Surface composition of near-Earth Asteroid (4953) 1990 MU: Possible fragment of (6) Hebe
2014, Icarus
Citation Excerpt :
Hicks et al. (1998) placed 1990 MU into the Q-class, although their visible to very-near-infrared spectrum (0.55–0.95 μm) did not include the critical band center near 1 μm. In 2000 Erikson et al. compared lightcurve measurements acquired in 1992 with those of Mottola et al. (1995), and found that they agreed with the earlier results. Binzel et al. (2002) listed 1990 MU as belonging to the S-class.
Near-Earth asteroids (NEAs) are interesting as both a threat to the Earth and as the immediate parent bodies of most meteorites. We observed NEA (4953) 1990 MU using the NASA Infrared Telescope Facility (IRTF) and University of Hawaii (U.H.) telescopes on Mauna Kea to constrain its surface composition and origin. The surface composition of 1990 MU is similar to ordinary chondrites (H chondrites). The calculated olivine and pyroxene chemistry of 1990 MU (Fa_13.5±1.3 and Fs_12.7±1.4) are consistent with the olivine and pyroxene chemistry ranges for H chondrites (Fa_15–21 and Fs_13–19) (Dunn, T.L., McCoy, T.J., Sunshine, J.M., McSween, H.Y. [2010]. Icarus 208, 789–797), although the estimated Fa value is at the lower end of the H chondrite range. The olivine abundance ratio of 1990 MU (0.57 ± 0.03) is slightly higher but not inconsistent with H chondrites (0.47–0.55 ± 0.03). The radar circular polarization ratio (same circular polarization state or SC/opposite circular polarization state or OC) (Benner, L.A.M., Ostro, S.J., Magri, C., Nolan, M.C., Howell, E.S., Giorgini, J.D., Jurgens, R.F., Margot, J.L., Taylor, P.A., Busch, M.W., Shepard, M.K. [2008]. Icarus, 198, 294–304) of 1990 MU is 0.36 ± 0.03, which is higher than the mean SC/OC ratio for S-type NEAs (0.270 ± 0.079). The 1990 MU SC/OC is also higher than those of (25143) Itokawa (0.27 ± 0.04), (4179) Toutatis (0.29 ± 0.01) and (433) Eros (0.28 ± 0.06) suggesting a rougher surface at decimeter scale (Benner, L.A.M., Ostro, S.J., Magri, C., Nolan, M.C., Howell, E.S., Giorgini, J.D., Jurgens, R.F., Margot, J.L., Taylor, P.A., Busch, M.W., Shepard, M.K. [2008]. Icarus, 198, 294–304). We constrained the diameter of 1990 MU (4.4 km) using the average albedo at 0.55 μm of H chondrites (0.21) and absolute magnitude (H) of 14.1 (Flower, J.W., Chillemi J.R. [1992]. IRAS Asteroid Data Processing: The IRAS Minor Planet Survey, Philips Laboratory Technical Report PL-TR-92-2049. Jet Propulsion Laboratory, Pasadena, California, pp. 17–43). This diameter is higher than the 2.8 km value from Harris et al. (Harris, A.W. et al. [2011]. Astron. J. 141, 10) using an albedo of 0.52 for 1990 MU. This albedo value is unusually high for H chondrites, which have an albedo range of 0.12–0.30. We compared olivine and pyroxene chemistries of 1990 MU with main belt Asteroid (6) Hebe, probable parent body of H chondrite meteorites and IIE irons (Gaffey, M.J., Gilbert, S.L. [1998]. Meteor. Planet. Sci. 33, 1281–1295), and found that 1990 MU has more high-calcium pyroxene than Hebe. Fayalite and ferrosilite values of the two asteroids are consistent with H chondrites but do not overlap each other. The differences could be due to compositional variations observed on Hebe by Gaffey and Gilbert (Gaffey, M.J., Gilbert, S.L. [1998]. Meteor. Planet. Sci. 33, 1281–1295), although the observed rotational variation in spectral parameters does not match well with those of 1990 MU.

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Regular ArticleThe Near-Earth Objects Follow-Up Program: First Results

Abstract

Regular Article
The Near-Earth Objects Follow-Up Program: First Results