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Astronomical Applications Department, U.S. Naval Observatory - Newcomb Manual (Page 4)

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Astronomical Applications Department, U.S. Naval Observatory - Newcomb Manual
1.
use GUI application frameworks
package (such as ZAF from Zinc) to en-
sure platform portability
E.
reduction of observations
1.
2.
F.
individual class design and testing
II.
Science Issues and Projects to Consider
A.
asteroids
1.
masses from orbital interactions
2.
provide ephemerides (services to the
community)
3.
cumulative effects on planetary
motions
i.
Asteroids are the largest source of
"noise" in the orbits of Mars, Earth-
Moon system.
B.
lunar motion
1.
chaotic dynamics
i.
predictions from numerical
models
ii.
comparisons with LLR data
2.
radiation pressure
[ref]
3.
resonant interaction between tidal
and GR terms
4.
lunar librations
C.
Nordtvedt
parameter (anomalous gravi-
tational field energy effects -- i.e., a differ-
ence between gravitational and inertial mass
proportional to the gravitational binding en-
ergy of a body)
D.
GR precession
1.
lunar orbit
2.
Earth's spin
E.
bounds on time variation of the gravita-
tional constant
F.
millisecond pulsars
1.
derive Earth orbit
G.
bounds on dark matter in the solar
system?
H.
planetary satellites?
1.
centroiding vs. satellite-derived cen-
ter of mass
I.
other science?
III.
Documentation
A.
code
1.
source documentation model (see
TM96-01)
2.
interface ("user's manual")
B.
algorithms
C.
physics
1.
GR and partial derivatives
D.
parameter estimation and error and corre-
lation analysis
E.
numerical integration design
F.
reduction of observations
1.3. Top Level Structure.
The top level process structure of Newcomb is
shown in Figure 1. Basic operation is as follows.
The observations module is responsible for reading
input astrometric observations and "massaging" them
as necessary. Massaging operations are listed in
Chapter 2. The observations will be of various types
(cf. Figure 30), taken at various observing locations
(cf. Figure 2), including spacecraft.
The integration module is responsible for nu-
merically integrating a sophisticated dynamical
model of the solar system -- including general rela-
tivistic terms, a detailed Earth-Moon system, plane-
tary spin vectors including precession and nutation,
and an unlimited number of asteroids -- to produce
an ephemeris.
The model ephemeris is then compared with the
observations in the O-C section of the parameter
adjustment module to produce a set of residuals. The
parameter estimator uses the partial derivatives of the
model equations with respect to the model parame-
ters (including initial conditions) to solve in a least
squares sense for the most probable set of model pa-
rameter values that minimizes the O-C residuals.
The adjusted model parameters are then fed back into
both the ephemeris generator and the observation
transformation methods. The data are rereduced as
necessary, and a new ephemeris is generated. These
are again combined to produce a new set of residuals.
This process is iterated until the residuals satisfy pre-
determined success criteria.
Chapter 1: Top-Level Structure
D:\Newcomb\Documentation\NewcombManual.lwp
4 of 19
10:42pm April 23, 1997

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