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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Minor planets and related objects. XXIX - Asteroid 29 Amphitrite

UBV photometry and lightcurves of asteroid 29 Amphitrite from all observed apparitions (March 1956-May 1977) are combined to obtain a phase function having a linear phase coefficient of 0.030 + or - 0.002 mag/deg and a mean absolute magnitude of 6.19 + or - 0.04. Amphitrite displays a reddening of its B - V color index with increasing solar phase angle: 0.816 + or - 0.004 at a phase angle of 2 deg and 0.848 + or - 0.004 at 23 deg. Since Amphitrite's orbital inclination is low (6 deg) and its lightcurve amplitudes range between 0.06 and 0.11 mag, and are well distributed in longitude, it is concluded that the obliquity of its pole is significantly different from zero. During some apparitions Amphitrite's light curves display only one maximum and minimum per 5.3904 + or - 0.007-hr rotation period while in others as many as five of each are present. This is interpreted to mean that Amphitrite has a quasi-spherical shape with a highly irregular and/or variegated surface.

Tedesco, E. F.↗
NASA NTRS1984

Minor planet 1983TB - A dead comet?

IDS spectra of the Apollo asteroid 1983TB wer obtained at McDonald Observatory on Dec. 2, 1983 UT. These spectra were examined for cometary-type emissions and none were found. The reflectance of 1983TB was found to be similar to an S-type asteroid.

Cochran, A. L.↗
NASA NTRS1991

Minor planet 1566 Icarus: Asteroid or comet?

By employing a cometary nongravitational force model, based on the outgassing of a water ice nucleus, the orbital fits to the optical and radar astrometric data are improved for both Apollo and Icarus. A reliable value for the magnitude of these nongravitational effects can be determined for Icarus, but not Apollo. Because Icarus is less than a kilometer in extent, the small amount of outgassing required to explain its anomalous orbital behavior would probably not be sufficient to create an easily visible coma. While these results do not prove that 1566 Icarus is an active comet masquerading as an asteroid, this object certainly deserves future scrutiny to determine its true identity. A near-Earth asteroid showing cometary activity must represent only the tip of a much larger cometary iceburg. For such an object whose aphelion is well inside Jupiter's orbit, the time scale for losing its volatiles is much shorter than the time scale for evolving out of the inner solar system. Thus, for each active member of the near-Earth asteroid population, there must be many more that are temporarily or permanently inactive.

Yeomans, Donald K.↗
NASA NTRS1988

Astrometric observations of comets and asteroids and subsequent orbital investigations

The 155-cm reflector was used for observations of comets and minor planets on 28 nights during April-October. Twenty-two of the observations refer to comets, 62 to numbered minor planets (numbered, that is, by the end of the semester: only nine of them refer to minor planets already numbered at the time of the last report), and the remainer to unnumbered minor planets. Observations were made of four new comets discovered during the semester and a fifth discovered in January. Observations of Wilson (19861), P/Tempel 2 and two other returning short-period comets are also continuing. Among the odd numbered minor planets observed were the earth-approaching objects (1685) Toro and (1980) Tezcatlipoca. The Earth approacher 1980 PA was numbered (3908).

Mccroskey, Richard E.↗
NASA NTRS1989

Astrometric observations of comets and asteroids and subsequent orbital investigations

Observations were made with the 155-cm reflector at the Oak Ridge Observatory. Since the last semiannual report (issued in November 1988) there have been 20 observations of comets, 146 of numbered minor planets and 135 of minor planets that were unnumbered at the time of observation. The orbit computations made during this period mainly applied to new discoveries, which have recently been exceptionally numerous. 1989 has already produced five new Apollo objects, and the new-moon period in early January produced a record six new comets.

Mccrosky, Richard E.↗
NASA NTRS1986

Astrometric observations of comets and asteroids and subsequent orbital investigations

The 155-cm reflector was used for observations of comets and minor planets on 32 nights during April-October. The distribution was fairly uniform, ranging from 45 in June and September to 28 in July: on September 1 a total of 17 observations was made. A table is included which lists the 230 measurements published during the semester. These include six additional measurements going back to 1984 and the republication of a previously misidentified 1976 observation as a new discovery. Thirty-two of the observations refer to comets, 83 to numbered minor planets, and the remainder to unnumbered minor planets. Among the older-numbered minor planets observed were the Earth-approaching objects (3103) 1982 BB, (3199) 1982 RA (Nefertiti), (3361) 1982 HR and (3362) 1984 QA (Khufu), some of which were of interest for radar experiments. Unnumbered Earth-approaching objects observed were 1963 RH, 1983 RD, 1985 TB and 1986 DA, as well as the new discoveries 1986 JK, 1986 LA and 1986 PA.

Mccrosky, R. E.↗
NASA NTRS1992

The mass of (1) Ceres from perturbations on (348) May

The most promising ground-based technique for determining the mass of a minor planet is the observation of the perturbations it induces in the motion of another minor planet. This method requires careful observation of both minor planets over extended periods of time. The mass of (1) Ceres has been determined from the perturbations on (348) May, which made three close approaches to Ceres at intervals of 46 years between 1891 and 1984. The motion of May is clearly influenced by Ceres, and by using different test masses for Ceres, a search was made to determine the mass of Ceres that minimizes the residuals in the observations of May.

Williams, Gareth V.↗
NASA NTRS1987

Astrometric observations of comets and asteroids and subsequent orbital investigations

The 155-cm reflector of the Smithsonian Astrophysical Observatory was used for observations of comets and minor planets on 35 nights during October l986- April l987. The distrubution was fairly uniform November-February, but poor weather permitted only 21 observations during March. Table I lists the 423 measurements published (in the MPCs) since the last report, two of them actually made at the very beginning of May l987. Forty-six of the observations refer to comets, 193 to numbered minor planets (numbered, that is, by the end of the semester; only 11 of them refer to minor planets already numbered at the time of the last report), and the remainder to unnumbered minor planets.

Mccrosky, Richard E.↗
NASA NTRS1979

The discovery and orbit of /2060/ Chiron

'Slow-moving Object Kowal' was discovered as an asteroidal object of photographic magnitude about 18 on photographic plates made on October 18 and 19, 1977 with the 122-cm Schmidt telescope at Palomar Observatory. It was determined that the object was located between 14 and 17 AU from the earth in a low-inclination, near-circular orbit. Examination of subsequent plates and earlier observations of the area allowed a more exact calculation of the orbital elements, which suggest the object to be in 3:5 resonance with Saturn at a perihelion of 8.5 AU. The object's orbital behavior suggests that of an inactive comet perturbed by Saturn from a previous orbit, however its magnitude is uncharacteristically large for a comet. It is proposed that object Kowal was once an ordinary minor planet that was deflected into its present orbit by collisions with other minor planets and a series of encounters with Jupiter and Saturn. The object has received the minor planet number (2060) and the name of Chiron has been proposed.

Kowal, C. T.↗
NASA NTRS1992

Minor satellites and the Gaspra encounter

Observational evidence, especially from occultations and radar, indicate that satellites of minor planets are numerous and commonplace. This leads to the prediction that the Galileo spacecraft will find many such 'minor satellites' at the upcoming close encounter with minor planet 951 Gaspra. If such objects are found, this argues strongly against the current theory of minor planet origin from the primeval solar nebula.

Vanflandern, Thomas C.↗
NASA NTRS1982

Reconnaissance and recovery of the brighter asteroids. Brief summary of the entire project

An inexpensive method of baking large (8- by 10-inch) IIIa-J plates in 2 percent forming gas was found and successfully tested. The large storage capacity and fine grain structure of the emulsion made the sky fog negligible on plates of one-hour exposure at Link. Plates were taken through the end of October 18, 1981 on various asteroids from the recent critical lists published in the Minor Planet Circulars and the Russian Ephemeris of Minor Planets.

Edmonson, F. K.↗
NASA NTRS1991

Asteroid absolute magnitudes and slope parameters

A new listing of absolute magnitudes (H) and slope parameters (G) has been created and published in the Minor Planet Circulars; this same listing will appear in the 1992 Ephemerides of Minor Planets. Unlike previous listings, the values of the current list were derived from fits of data at the V band. All observations were reduced in the same fashion using, where appropriate, a single basis default value of 0.15 for the slope parameter. Distances and phase angles were computed for each observation. The data for 113 asteroids was of sufficiently high quality to permit derivation of their H and G. These improved absolute magnitudes and slope parameters will be used to deduce the most reliable bias-corrected asteroid size-frequency distribution yet made.

Tedesco, Edward F.↗
NASA NTRS1989

Discovery and follow up of asteroids

After a summary of the increasing activity in steroid discovery during the past few years, the importance of carefully thought out observing strategy is discussed, in particular with regard to target selection, observing frequency, and the time distribution of observations. Problems of cataloging and orbit linkage are outlined, inasmuch as they affect individual observers and orbit computers, as well as the work of the Minor Planet Center. There is some discussion of appropriate two-way communication between observers and the Minor Planet Center.

Bowell, E.↗
NASA NTRS1984

The astrometry programme at Mt. John Observatory

The comet (and minor planet) astrometry program uses one of two 0.6 meter (24 in.) Cassegrain telescopes at Mt. John University Observatory. For astrometric photographs of comets and minor planets a simple guide probe camera is attached to the Cassegrain. Frequently the Cassegrain field does not include sufficient cataloged stars for a satisfactory reduction. In these cases the comet position is transferred to an astrograph plate. Ephemeris data are calculated to the tenth of a day nearest the meridian transit of the object or for dusk or dawn twilight for low objects. Star measurement and identification are checked by reducing positions of cataloged stars.

Gilmore, A. C.↗
NASA NTRS1985

How many Earth-approaching asteroids are there?

The discovery process of Earth-approaching asteroids is formulated as a periodic sampling problem from an urn with replacement. It presumes as unchanging number of such objects over recent historical times, a fixed limiting magnitude/angular speed combination for detection probability, and allows for the possibility of the lack of detection or the lack of sufficient observations to refine an orbit at the first noticed apparition. While simple, the model is sufficiently powerful to show that an estimate of the number of Earth-approaching minor planets is impossible. This conclusion is insensitive to uncertainties in perturbing influences, celestial mechanics, or a model for the distribution of the orbital element sets of these minor planets.

Taff, L. G.↗