Great 2003 Mars Coming (05)

Great 2003 Mars Coming

The Astronomical Almanac for the Year 2003


  Some elements associated with Mars employed in The Astronomical Almanac for the year 2003 are revised from those employed in 2002, and hence we should note there are several discontinuations between 31 December 2002 and 1 January 2003.
  The Mean Equatorial Radius of Mars in the 2002 edition was 3397 km, while in the new edition the value 3396.2 km was employed. The Geometric Flattening was formerly fixed as 0.006476, while in the new 2003 edition, since they employed the recent result that the Northern Polar Radius Rn is different from the Southern Polar Radius Rs (due to P K SEIDELMANN et al), the Flattening was defined in two ways.

Let Re denote the Equatorial Radius, and then the Flattenings are given by
      Fn=(Re - Rn)/Re=0.006772
      Fs=(Re - Rs)/Re=0.005000

That implies

And hence Rs is slightly larger. In the previous editions, the Flattening was Rs=Rn=0.993524Re. Since the symmetry was broken, we can easily suppose the central latitude φ should be affected.
  Another alteration of constant is employed concerning the Sidereal Period of Rotation of Mars: In the former editions it was defined 1.025 956 75 day, while in the new 2003 edition, it was altered to 1.025 956 76 day. The little amount of difference is however effective to the Latitude ω of CM or to an employment of the first period.
The values in the Ephemeris for 00:00 TDT of 28 December 2002 and 1 January 2003 are different in the following ways:

The 2002 Edition shows
                ω         φ          λ         δ e    δ p      ι      Ds
28 December  123.63°W  14.82°N   114.59°Ls    4.50"  4.47"    27.3°  23.04°N
01 January    84.80°W  13.86°N   116.44°Ls    4.57"  4.54"    28.0°  22.67°N

while the 2003 Edition does
28 December  123.36°W  14.81°N   114.59°Ls    4.49"  4.47"    27.3°  23.01°N
01 January    84.53°W  13.84°N   116.44°Ls    4.57"  4.54"    28.0°  22.64°N
where λ denote the season in Ls. Revision of elements concerning the orbit was not made, and so no discontinuation is thereabout Ls and others. We follow the present alteration of The Almanac, but even the case of ω there does nearly occur no misleading if we shall follow our tradition to round off ω to no decimal.
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