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Astronomical Applications Department, U.S. Naval Observatory - NOVAS 2004 Overview (Page 11)

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Astronomical Applications Department, U.S. Naval Observatory - NOVAS 2004 Overview
EARTH = 332,946.050895
MARS = 3,098,708
JUPITER = 1,047.3486
SATURN = 3,497.898
URANUS = 22,902.98
NEPTUNE = 19,412.24
PLUTO = 135,200,000
EARTH-MOON BARYCENTER = 328,900.561400
DE-405 values are used for many of these, which are in TDB (T
) units. NOVAS output is
practically insensitive to changes in low-order digits of the above constants; they are mostly used
for relatively small corrections, such as the gravitational deflection of light. Probably the light-
time for 1 AU is the most important, because it is used for the light-time correction. The constants
that really matter in NOVAS are the coefficients to the series expansions in the individual
subroutines, i.e., the constants that are embedded in the models for precession, nutation, etc.
ASPLAN ­ now are simply "front-ends" to specific calls to PLACE. All substantive apparent
place calculations of various kinds are now done only in PLACE. The following changes in the
basic algorithms were made:
(1) Calls to FRAME were added in appropriate places to transform between the ICRS and the
dynamical system.
(2) In updating a star's position for proper motion, there is now a correction to the epoch of
interest for the difference in light-time between the solar system barycenter (the reference point for
the input catalog data) and the Earth itself. (This affects only stars with the greatest proper
motions, and then only at the 0.1 mas level). Uses the new subroutine DLIGHT to compute the
epoch offset.
(3) The "Doppler factor", k, is included in the computation of stars' space motion vectors (see
note on VECTRS).
(4) Modifications were made related to the change in gravitational deflection algorithms from
SUNFLD to the more-general GRVDEF (see note on GRVDEF).
(5) Code has been introduced that allows a place to be expressed in the celestial intermediate
system (equator of date with CEO as right ascension origin).
(6) Code has been added that allows the input of an observer's instantaneous geocentric position
and velocity vectors (with respect to the true equator and equinox of date) for a topocentric place
calculation; this is included to support satellite observations.
TERCEL, SOLSYS ­ calls to FRAME added at appropriate places. (In SOLSYS, the call to FRAME
is commented out for DE-405 and later JPL ephemerides, since DE-405 is in ICRS.)
CATRAN, GETHIP, VECTRS ­ code adjusted for new proper motion and parallax units.
CATRAN ­ code added to call FRAME for new IT=4 and IT=5 options that rotate data between
dynamical J2000.0 system and ICRS.
VECTRS, CATRAN ­ 1/(sin(parallax)) now used to compute distance rather than 1/parallax; an
inconsequential change, just to make the expression formally correct. Also, the "Doppler Factor",
k, mentioned in the Hipparcos documentation and other papers, is now applied in computing the
space-motion vector. The change in the units of proper motion and parallax is also implemented

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