Midcourse Maneuver Operations Program /MMOP/ computes the required velocity change to correct a spacecraft trajectory. The program establishes the existence of maneuvers which satisfy spacecraft constraints, explores alternate trajectories in the event that some out-of-tolerance condition forces a change in plans, and codes the maneuvers into commands

Gordon, H. J.

Hamburg, R. L.

Mitchell, R. T.

Pass, D.

Royer, D. R.

English

NASA Technical Reports Server

April 1969
	 Brief 69-10105 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information Springfield, Virginia 22151. 
Midcourse Maneuver Operations Program 
The problem: 
To develop a method which is capable of establish-
ing the existence of maneuvers which satisfy space-
craft and associated constraints, and which possess the 
capability to explore alternate trajectories in the event 
that some out-of-tolerance condition forces a change in 
plans, and to code the maneuvers into commands 
acceptable to the spacecraft. 
The solution: 
The Midcourse Maneuver Operations Program 
(MMOP) was specifically designed to compute the 
required velocity change to correct a spacecraft trajec-
tory. Various general classes of constraints are ex-
amined, and the required velocity change is adjusted, 
if necessary, to avoid violation of constraints. Other-
wise the program evaluates consequences of the con-
straint violation and computes a maneuver which 
represents a least violation. 
How it's done: 
The MMOP serves two primary purposes. It per-
forms calculations which enable the operations per-
sonnel to select the most advantageous maneuver 
after the orbit achieved by the spacecraft is known. 
If the mission proceeds according to plan, the selec-
tion of the maneuver will be straightforward; other-
wise, an appreciable quantity of trajectory and per-
formance information must be rapidly analyzed under 
operational pressure to ensure that the capabilities 
of the spacecraft are used intelligently. The space-
craft can still gather significant scientific information 
even if it follows a trajectory different from nominal. 
Operations personnel must make appropriate guidance 
decisions as long as there is any chance of obtaining 
useful scientific or engineering information. The pro-
gram also codes the commands that will make the
spacecraft perform the desired maneuver. The mid-
course maneuver requires three 26-bit stored quanti-
tative commands, which are transmitted to the space-
craft and stored until receipt of the real-time direct 
command that initiates the sequence. 
In computing the maneuver, various practical con-
straints imposed by the limitations of the spacecraft 
have to be considered. Accordingly, the program con-
sists of two subprograms: (1) a set of drivers for the 
trajectory program, and (2) decision routines which 
are used to compute and code the desired maneuvers. 
In computing and executing the midcourse maneu-
ver, the spacecraft is first tracked from launch 
and a definitive orbit determination is made. The mid-
course velocity impulse required to modify the trajec-
tory of the spacecraft so that it flies by the target 
planet in an acceptable way and at a favorable time is 
then computed. The velocity impulse vector is con-
verted to the appropriate coordinates: pitch turn angle, 
roll turn angle, and magnitude of impulse.These values 
are then converted to the binary coded-form acceptable 
to the spacecraft. The three stored commands are 
transmitted, properly coded, to the appropriate deep 
space instrumentation facility where they are verified; 
and the direct command, EXECUTE MIDCOURSE 
MANEUVER, is transmitted. The spacecraft executes 
the pitch and roll turns, the midcourse motor is ignited, 
and, after completing the maneuver, the spacecraft 
returns to -the cruise mode, orienting itself through 
Sun and Canopus sensors. 
The inputs to the operations program can be -con-
veniently divided into three classifications: (1) the 
basic inputs from the tracking program are the best 
estimates of the six injection coordinates and the 
injection time; (2) the prelaunch input generally con-
sists of items which can be considered constants of 
(continued overleaf( 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19690000105 2020-03-16T17:56:01+00:00Z
the spacecraft system and thus not subject to variation 
during either nominal or unexpected operating con-
diti&ns; (3) items in the post-launch input are items 
which are subject to change during the mission and 
control commands for the program. The input from 
the tracking program and the post launch input will be 
read in during operations. The prelaunch input will 
be the nominal values unless changes have been made. 
The capability to enter all inputs will be provided for 
nonoperational use of the program, which is expected 
to be extensive before each flight. 
There are three operational options which will gen-
erally be used before selecting the midcourse. All 
three operational options require access to the pre-
launch input, and the inputs from the tracking pro-
gram. The first option is the Midcourse Maneuver 
Program which is the only option that has the capa-
bility of computing a maneuver. 
Notes: 
1. The program is written partly in FORTRAN II 
language and partly in FAP language for use on 
the IBM 7094 II machine.
2. The program is of use to anyone working on a 
space project to perform near-planet measure-
ments, where it may be necessary to correct 
the initial trajectory of the spacecraft with a mid-
course maneuver in order to ensure success of the 
mission. 
3. Inquiries regarding this innovation may be di-
rected to:
COSMIC 
Computer Center 
University of Georgia 
Athens, Georgia 30601 
Reference: B69-10105 
Patent status: 
No patent action is contemplated by NASA. 
Source: Robert T. Mitchell, Harold J. Gordon, 
R. L. Hamburg, D. Pass, 
and Donald R. Royer 
Jet Propulsion Laboratory 
(N P0-10735) 
Brief 69-10105	 Category 06


Midcourse maneuver operations program

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