1. INTRODUCTION
This chapter describes the top-level structure of the planned
Naval Observatory Solar System Ephemeris program, called
Newcomb.
1
Newcomb is intended to be the successor of, and
loosely derives its structural inheritance more or less from,
PEP, the Planetary Ephemeris Program at the Smithsonian As-
trophysical Observatory.
2
Computer program design and lan-
guage capabilities have advanced far beyond the anticipations
of three and a half decades ago when PEP and the JPL DE pro-
grams were originally developed. (DE and PEP are the only
existing high-precision solar system ephemeris programs.)
Program technology that is several generations out of date,
combined with the practical inability to add further significant
capabilities or modifications to PEP, has been deemed suffi-
cient cause for development of a new ephemeris program. Ad-
ditional motivations are that it is to the USNO's great advan-
tage to have a comprehensive ephemeris capability in-house,
and that Newcomb will provide a check against PEP and the
JPL DE programs.
2. ASTRONOMICAL CONTEXT
3. PROGRAM DESIGN AND LANGUAGE CONSIDERATIONS
Chief among the advantages of writing a new program is the
opportunity to make use of modern programming and design
technologies, including object-oriented design (OOD) and
object-oriented programming (OOP), as well as graphical user
interfaces (GUIs) and the highly productive "components"
programming associated with rapid application development
(RAD) environments. Newcomb is written entirely in C++,
and development and testing are done entirely within the best
RAD environment currently available.
3
We take full advan-
tage of standard OOP/OOD concepts and techniques, includ-
ing data encapsulation, template classes, polymorphism, and,
where necessary, multiple inheritance.
The benefits of a completely object-oriented approach are
many, including faster prototyping and development, fewer
and more easily locatable coding errors, vastly simpler and
more intuitive design, more sophisticated functionality, easily
extensible architecture, and (most importantly) drastically
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M
ARC
A. M
URISON
Astronomical Applications Department
U.S. Naval Observatory, Washington, DC
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3
http://www.borland.com/bcppbuilder/
2
See
http://cfa-www.harvard.edu/~reasen/ssd.html
for information about PEP.
1
See
http://aa.usno.navy.mil/Newcomb/
for the official Newcomb web site.
Figure 1 -- Reference frame hierarchy.
Stellar Reference
Frame
Solar System
Reference Frame
Earth Reference
Frame
Extragalactic
Reference Frame
Quasars
(VLBI, optical)
Local Reference
Frame
Space
Astrometry
Ground
Astrometry
Planetary
Positions
Natural Satellite
Positions
Dynamical
Models
Earth Rotation
VLBI
GPS
GPS
HIPPARCOS
FAME
Where am I?
What time is it?
NPOI
- Spacecraft navigation
- Tests of GR
- Celestial mechanics
- Asteroid masses
- Stellar occultations
- Geophysics
Figure 2 -- Major dependencies.
Planetary
Ephemerides
Solar System
Reference
Frame
Star Positions
Geodynamics
Asteroid
Motions
Planetary
Motions
Gravity Model
General
Relativity
Time
Military
Astronomy
Observations
Application
Theory
Observation
