Jay H. Lieske

Report of the IAU/IAG/COSPAR working group on cartographic coordinates and rotational elements of the planets and satellites: 1991

This paper is the entire report of the IAU Working Group on Cartographic Coordinates and Rotational Elements of the Planets and Satellites, including three annexes. Tables give the recemmended values for the directions of the north poles of rotation and the prime meridians of the planets and satellites. Reference surfaces for mapping these bodies are described. The annexes discuss the guiding principles, given in the body of the report, present explanatory notes, and provide a bibliography of the rotational elements and reference surfaces of the planets and satellites, definitions, and algebraic expressions of relevant parameters.

Icarus and the determination of astronomical constants.

Icarus radar and optical observations analyzed to verify general relativity predictions using Schwarzschild metrics and to estimate solar oblateness, Mercury mass, etc

Astrometry from Mutual Phenomena of the Galilean Satellites in 1990-1992

This paper derives astrometric data for the Galilean satellites from 213 light curves of 86 mutual eclipses and occultations that occurred in 1990–1992. Comparisons of these data with predictions based on the most precise modern ephemeris (E5) generally show good agreement, although it is rather poorer in the case of J1 (Io).

Computer-developed construction of analytic expressions for the coordinates and partial derivatives of Jupiter's Galilean satellites

In his effort to develop series expressions for the coordinates of the Galilean satellites accurate to one are second (Jovicentric), R. A. Sampson was forceda priori to adopt certain numerical values for several constants imbedded in his theory. His final numerical values for the series expressions are not amenable to adjustment of the constants of integration nor of physical constants which affect the motion of the satellites. A method which utilizes computer-based algebraic manipulation software has been developed to reconstruct Sampsons theory, to remove existing errors, to introduce neglected effects and to provide analytical expressions for the coordinates as well as for the partial derivatives with respect to orbital parameters, Jupiter and satellite masses, Jupiters oblateness (J2,J4) and Jupiters pole and period of rotation. The computer-based manipulations enable one to perform, for example, the approximately 108 multiplications required in calculating some perturbations (and their partial derivatives) of Satellite II by Satellite III with ease, and provide algebraic expressions which can readily be adjusted to generate theories corresponding to revised constants of integration and physical parameters.

Simultaneous solution for the masses of the principal planets from analysis of optical, radar, and radio tracking data.

The Jet Propulsion Laboratory has developed a set of computer programs known as the Solar System Data Processing System (SSDPS) which is employed in improving the ephemerides of the major planets and for improving the values of several associated astronomical constants. A group of solutions for the masses of the major planets, together with the AU and radii of Mercury, Venus, and Mars, is presented. These solutions based upon optical, radar, and spacecraft radio tracking data are preliminary. The relative power of radar and radio tracking data vis-à-vis purely optical data in a solution is shown. The problems which could arise by adopting solutions based upon a single data type are demonstrated.

Early eclipses of the Galilean satellites

A brief summary of the development of the theory of motion of the Galilean satellites is presented. Over 7700 eclipse observations have been collected and reduced using the Ephemeris E-2. They are of great potential in improving the ephemerides of the satellites and can yield important information on the evolution of the Galilean system.

DIVISION I-III / WORKING GROUP NATURAL PLANETARY SATELLITES

1. Activities of the Working Group on Natural Planetary Satellites The main goal of the Working Group was to gather astrometric observations made during the triennum as well as old observations not yet published in the data base. The WG encouraged the making of new observations. A Spring School was organized in China in order to teach the observational techniques of natural satellites to students and young astronomers. New theoretical models of the motion of the satellites and fit of the current models to new observations were used in order to make ephemerides of all the planetary satellites with tools useful for observations such as configurations. These ephemerides named MULTISAT are available at or at . Original ephemerides are also available on JPL’s Horizons ephemerides and on MPC ephemerides for irregular satellites. A workshop has been held in Paris in November 2006 for organizing campaigns of observations. The problem of a standard format for the astrometric observations of the natural satellites raised and will have to be solved during the next triennum.

A Collection of Galilean Satellite Eclipses 1652–1982

It is known that early (i.e. 17th–18th century) visual observations of Jupiter’s Galilean satellites are approximately as accurate as modern visually observed eclipses (Lieske 1982). In the early days the clocks were the primary source of error while in present days problems related to the Earth’s and Jupiter’s atmospheres have become the primary limiting factor. The early observations were generally made in local apparent time (i.e. related to the real hour angle of the sun). After the development by Huygens in 1656 of the pendulum clock, these early observations, when reduced to a modern UT system, have been shown to be quite accurate.