Four part program computes trajectory of space probe moving in solar system and subject to variety of forces

Joseph, A. E.

Khatib, A. R.

Strand, J. N.

Sturms, F. M., Jr.

Talbot, T. D.

Warner, M. R.

Witt, J.

English

NASA Technical Reports Server

October 1971	 Brief 71-10390 
NASA TECH BRIEF 
NASA Pasadena Office 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a &ubscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the. Tech Brief program may 
be directed to the Technology. Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Double Precision Trajectory Program(DPTRAJ 2.2C) 
The problem: 
To compute the precise trajectory of a space probe 
moving in the solar system and subject to a variety 
of forces. 
The solution: 
A generalized high precision trajectory program for 
mission use and research. 
How it's done: 
The differential equations of motion of the space 
probe are integrated by a second-sum numerical in-
tegration scheme relative to some central body 
(Cowell method). The equations are solved for the 
probe only, ignoring the negligible perturbations of 
the probe on the sun and planetary and lunar bodies. 
Hence, it is sufficient to obtain positions and 
velocities of the bodies in the form of planetary and 
lunar ephemerides in some convenient reference 
frame. The coordinates have been traditionally re-
ferred to the Cartesian system based on the Earth 
mean equator and equinox of 1950.0. To obtain 
information about the probe or any of the bodies in 
some other reference frame, an appropriate trans-
formation must be applied to the 1950.0 frame. 
Upon integration of the equations of motion, the 
following information is available: a probe ephemeris; 
planetary and lunar ephemerides; a list of events 
involving the probe (such as closest approach to a 
certain body, attainment of a given distance from 
some body, etc.); and a list of epochs. 
Due to its size, the program was written in four 
parts called links: ODIN, TRIC, PATH, and 
POST. Each link consists of a primary subroutine 
and a series of secondary subroutines. Transfer 
between secondary subroutines within each link 
is automatic. Transfer between links requires a
return to the main program. Each link accepts input 
from either external sources or other links, performs 
its portion of the problem, and outputs its results 
to the user or to subsequent links. 
ODIN sets up the arrays of nominal parameter 
values used by the program. TRIC performs any re-
quired coordinate transformations. Its major function 
is to convert the initial input conditions to Cartesian 
coordinates in the Earth mean equation and equinox 
of 1950.0 system for link PATH. An extensive set 
of transformations is available for this purpose. TRIC 
may also be used as a separate option, resulting in 
printed output of the transformed coordinates in a 
specified system. 
PATH numerically integrates the equations of 
motion. Inputs to PATH are the double-precision 
planetary ephemeris, the ODIN user inputs, and the 
probe injection conditions obtained either by 
TRIC or by user input. Outputs include the probe 
ephemeris file and a file containing end-of-step 
information. POST produces the printed output for 
the main program. Inputs to POST are the double-
precision planetary ephemeris, the PATH-generated 
probe ephemeris, and the ODIN user inputs. The 
output is a printed history of the probe trajectory, 
with the level of detail being specified by the user. 
A control program interprets the user's request 
and calls in the links in the proper order for execu-
tion. Options permit any combination of the four 
links, and each link may be executed more than once, 
if desired. 
The programmer's Reference Manual consists of 
seven volumes:	 - - - 
Volume I
	 - Design and implementation of models

Volume II - Link ODIN 
Volume III - Link TRIC 
Awak ICOIIIIIILICU t)CFIC.tI 
New
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19710000388 2020-03-17T02:30:30+00:00Z
Volume IV	 - Link PATH 
Volume V	 - Link POST 
Volume VI	 - User's guide 
Volume VII - Technical Memorandum 33-451
Notes: 
1. This program is written in FORTRAN V for use 
on the UNIVAC-I 108 Exec 8 Computer. 
2. Requests for further information may be directed 
to:
COSMIC 
112 Barrow Hall 
University of Georgia 
Athens, Georgia 30601 
Reference: B71-10390
Patent status: 
No patent action is contemplated by NASA. 
Source: A. R. Khatib, F. M. Sturms, Jr.,

A. E. Joseph, Dr. T. D. Talbot,

J. Strand, J. Witt, and M. R. Warner of

Caltech /J PL

under contract to

NASA Pasadena Office

(N PO- 1 1798)
.. 
Brief 71-10390	 Category 09 


Double precision trajectory program /DPTRAJ 2.2C/

Double precision trajectory program /DPTRAJ 2.2C/

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