Planetary Ephemerides Research Articles

The Occultation of BD -17° 4388 by Neptune: I. Determination of Neptune’s position

The possibility of the occultation by Neptune of a star of similar apparent magnitude to itself was first pointed out by the amateur astronomer Ross A. Shuart. It was clear that such an event would provide data on Neptune’s position which would be of value to the observatories which produce the planetary ephemerides. The existing ephemeris of Neptune is known to contain small errors which have been accumulating over many years.

Astronomical constants and planetary ephemerides deduced from radar and optical observations

Astronomical constants and planetary ephemerides deduced from radar and optical observations

Current status of special planetary and lunar theories and ephemerides

An examination of some specialized lunar and planetary ephemerides has revealed inconsistencies in the adopted planetary masses, the presence of non-gravitational terms, and some outright numerical errors. They should be considered of temporary usefulness only, subject to subsequent amendment as required for the interpretation of observational data.

Planetary position-velocity ephemerides obtained by special perturbations

Description of position-velocity ephemerides of venus and the earth-moon system generated by using special perturbation methods

Some Astronomical and Geophysical Considerations for Space Navigation

This paper deals with astronomical and geophysical considerations applicable to optical measurements made with selfcontained equipment in a space vehicle in order to determine its position and/or velocity. Various measurements made from the earth, their temporal variations and their accuracy as applied to space navigation are discussed. Information regarding stellar positions, magnitudes, spectra and frequency distribution is presented. A discussion of planetary positional ephemerides, diameters, phase curves, albedos and spectral characteristics is given. The advantages of using asteroids vis-à-vis planets are discussed. There are several problems in observing terrestrial occultations of stars from a satellite due to the presence of the earth's atmosphere. Pertinent atmospheric characteristics, such as cloudiness, absorption, scattering and emission of radiation are discussed in the above context.

A radar investigation of Venus

Radar measurements of Venus carried out by the Millstone radar of the Massachusetts Institute of Technology Lincoln Laboratory from 6 March to 18 May 1961 are reported. Range measurements reduced with the help of Duncombe's elements for the orbits of the earth and Venus lead to a value for the astro- nomical unit of 149 597 850+400 km. Reduced with 6378.388 km for the earth's equatorial radius, this yields for the solar parallax irO = 8'.' +0'.'000024. Small residual systematic errors in the planetary ephemerides are disclosed. Measurements of the signal intensity and range dispersion are compatible with a relatively smooth rocky surface as the reflecting agency. The observed frequency broadening is com- patible with a sidereal rotational period of 225 (+275, -110) days, which suggests that the period of rotation equals the period of revolution.

The astronomical unit determined by radar reflections from Venus

view Abstract Citations (23) References (4) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The astronomical unit determined by radar reflections from Venus Muhleman, D. O. ; Holdridge, D. B. ; Block, N. Abstract Radar reflections from the surface of the planet Venus at a wavelength of 12.5 cm yielded a value of the astronomical unit of 149 598 845+250 (p.e.) km, or a solar parallax of 8"7940976+147 based on an earth radius of 6378 145 m. The computations were accomplished utilizing Doppler-frequency-shift and time-of- flight observations (range measurements) in conjunction with the "best" available planetary ephemerides of the earth and Venus. The investigations yielded proof of the transparency of the Venus atmosphere at 12.5 cm and some information on the radius of Venus. Systematic errors in the published ephemerides are also discussed. Publication: The Astronomical Journal Pub Date: May 1962 DOI: 10.1086/108693 Bibcode: 1962AJ.....67..191M full text sources ADS |

Present and Future Requirements for Planetary Ephemerides

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