Time Data Sequential Processor /TDSP/ computer program provides preflight predictions for lunar trajectories from injection to impact, and for planetary escape trajectories for up to 100 hours from launch. One of the major options TDSP performs is the determination of tracking station view periods

Joseph, A. E.

Pavlovitch, T.

Roth, R. Y.

Sturms, F. M., Jr.

English

NASA Technical Reports Server

December Cl970	 Brief 70-10720 
NASA TECH BRIEF 
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Time Data Sequential Processor (TDSP) 
second mode of input is punched cards containing a 
set or sets of injection conditions for each launch azi-
muth, time data, and other required data. The third 
mode of input is a polynomial input option where the 
program 'accepts a set or sets of injection conditions 
and time data in the form of polynomials. 
Given the injection conditions, TDSP can generate 
a chronologically ordered set of events, consisting of 
(a) solutions of the classical two-body problem, to ob-
tain position and velocity as a function of time, and 
(b) variables which are functions of position and ve-
locity. A variety of output formats corresponding to 
the specific option requested are available. It is also 
possible to save, on magnetic tape, the time-sequential 
history of the spacecraft ephemeris, events which 
have occurred, related tracking station data from up 
to a maximum of 10 stations, and additional TDSP 
computed quantities which are of interest in mission 
planning and predicting. This magnetic save tape is 
then used' for data plotting. The tape is requested by 
input option and is written in the binary mode in a 
fixed format. Provision has been made to control the 
volume of data by varying the step size and then 
writing a record every nth step. 
TDSP uses the JPL ephemeris system tapes to 
determine lunar position and velocity when these 
quantities are required. Reading the ephemeris tape 
results in extracting Cartesian coordinates of the 
Moon referenced to the mean equator and equinox of 
1950. These coordinates are then rotated to the mean 
equator and equinox of date. 
TDSP provides two input means for externally 
controlling the volume of printed output: variable 
trajectory termination time, and print only at re-
quested time points. The former is convenient 
when, for example, tracking ships are requested and 
data are only desired for a short period of time. 
AOL	 (continued overleaf) 
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. 
The problem: 
A program was needed to study near-Earth conic 
trajectories and to provide approximate preflight 
predictions for tracking stations. 
The solution: 
The Time Data Sequential Processor (TDSP) com-
puter program was developed to provide preflight pre-
dictions for lunar trajectories from injection to impact, 
and for planetary escape trajectories for up to 100 
hours from launch. 
How it's done: 
When the hardware configuration of the launch 
vehicle is such that engine burn duration is from 
launch to injection, then the case is referred to as 
direct ascent. No attempt is made to simulate the 
powered flight portion of a direct ascent case; TDSP 
commences from the injection epoch. 
An alternate launch method boosts the vehicle into 
an Earth parking orbit and, after a short coast time, 
initiates a second burn which injects the vehicle 
on a predetermined flight path. When this is the case, 
TDSP simulates the parking orbit and second burn 
phases in addition to the free fall phase. No attempt 
is made to simulate the powered flight portion from 
launch to parking orbit injection; TDSP commences 
from the parking orbit injection epoch. 
When the target i's the Moon, an encounter phase 
of the flight is initiated as the probe enters the Moon's 
gravitational field. The lunar encounter portion of the 
trajectory is approximated by a rectilinear hyperbola 
as determined by conditions near the Moon's sphere 
of influence. 
Three modes of input are available for data input 
to the program. The first of these is a magnetic tape, 
written by the conic programs SPARC for planetary 
targets or STACT when the target is the Moon. The
https://ntrs.nasa.gov/search.jsp?R=19700000689 2020-03-17T01:07:15+00:00Z
Tracking stations of the Deep Space Instrumenta-
tion Facility (DSIF) may be simulated using a topo-
centric spherical coordinate system, the positions of 
the 10 DSIF stations being defined by nominal values 
in TDSP. Certain quantities computed relative to the 
stations are oriented toward the hardware configura-
tion of the DSIF stations. 
One of the major options TDSP performs is the 
determination of tracking station view periods. The 
times of spacecraft rise, extreme elevation, and set 
with respect to the stations, and the orientation of 
the spacecraft relative to the station at these times, 
are computed and printed. Included in the view period 
capability is the ability to predict the entering and 
exiting of the Earth's shadow by the probe. View 
periods for a maximum of 10 stations are available. 
Another major option is the capability to generate 
geocentric and station fine prints.
Notes: 
1. This program is written in FORTRAN IV and 
MAP for use on the IBM-7094 computer. 
2. Inquiries concerning this innovation should be 
directed to: 
COSMIC 
Barrow Hall 
University of Georgia 
Athens, Georgia 30601 
Patent status: 
No patent action is contemplated by NASA. 
Source: F. M. Sturms, T. Pavlovitch, A. E. Joseph, 
and R. Y. Roth of 
Jet Propulsion Laboratory 
under contract to 
NASA Pasadena Office 
(NPO-1 1327)
. 
. 
Brief 70-10720
	
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Time Data Sequential Processor /TDSP/

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