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4. Discussion

The theory parameters which result from the analysis of these data are listed in Table 6 (click here), which will produce coordinates in the B1950 frame when used with the galsat software. A future paper will document how they, and any other set of galsat parameters, can be transformed to the J2000 system in a manner such that the galsat software will directly produce J2000 coordinates. In Table 6 (click here), the uncertainties listed for the tex2html_wrap_inline1572 and tex2html_wrap_inline1720 parameters are the formal errors obtained in the estimation process. By comparing the coordinates of ephemerides E3 with those of E5 and interpreting those differences to represent a 1-tex2html_wrap_inline1722 error, we obtain a scale factor which should be applied for the formal uncertainties listed in the table. That scale factor ranges between 2.5 and 3, so we recommend that the formal errors be multiplied by 3. The derived values of the angular variables for E5 are given in Table 7 (click here). The series coefficients for satellite coordinates tex2html_wrap_inline1724 and tex2html_wrap_inline1726 are summarized in Table 8 (click here) for the E5 ephemerides.

Representing the Jupiter-equatorial projection of the orbital radius by tex2html_wrap_inline2174, and the true and mean longitudes by tex2html_wrap_inline2176 and tex2html_wrap_inline2178, respectively, then the equatorial radial component tex2html_wrap_inline2180 consists of cosine terms tex2html_wrap_inline2182 while the longitude component tex2html_wrap_inline2184 consists of sine terms tex2html_wrap_inline2186 and the latitude component tex2html_wrap_inline2188 consists of sine terms tex2html_wrap_inline2190 As developed by Sampson (1921, pp. 229-230), the "time-completed'' tex2html_wrap_inline2192 may be defined as
equation537
where t is "ephemeris time'' (TDB). One can employ the time-completed to compute the latitude quantity tex2html_wrap_inline2196 from the shorter series for tex2html_wrap_inline2198 via the relationship tex2html_wrap_inline2200 It effectively amounts to calculating the latitude perturbations as a function of true longitude rather than as a function of mean longitude.

The Jupiter equatorial coordinates tex2html_wrap_inline2202 are computed from the orbital components tex2html_wrap_inline2204 using the equations
 eqnarray542

The Earth-equatorial coordinates tex2html_wrap_inline2206 are then computed from the Jupiter-equatorial coordinates via the rotation matrices
equation546

It is these Earth-equatorial coordinates tex2html_wrap_inline2208 that are provided by the galsat software.

As described in Theory, the Earth-equatorial coordinates are constructed from the series for tex2html_wrap_inline1724 and tex2html_wrap_inline1726 by the relationship


 eqnarray552

where the right-hand sides are the result of computing the series given in Table 8 (click here). The third equation for s(t) employs the time-completed tex2html_wrap_inline2216 to evaluate the series for tex2html_wrap_inline2218 and thus to obtain s(t).

The adjustable parameters tex2html_wrap_inline1572 and tex2html_wrap_inline1720 for ephemerides E5 in the B1950 frame are given in Table 6 (click here). The derived values of the angular variables for E5 are given in Table 7 (click here).

Acknowledgements

This paper represents the results of one phase of research conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The CCD observations were made by D. and A. Monet of the USNO Flagstaff Station and were processed into right-ascension and declination normal-point residuals on a fixed ephemeris by W.M. Owen Jr at JPL.

   

Table 6: Values of theory parameters tex2html_wrap_inline1572 and tex2html_wrap_inline1720 for E5 in B1950 frame [see also Tables 2 and 3]

   

Table 7: Derived variables for ephemeris E5

  figure168 figure175 figure180 figure186

Table 8: Series coefficients for E5

 figure191 figure197 figure202 figure208

Table 8: continued


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