                                Program IPTO              
                                                           
                    Interplanetary Trajectory Optimization 

IPTO is a program for IBM PC (tm) compatible computers which determines the  
"patched conic" interplanetary trajectory between any two planets of our solar
system. A patched-conic trajectory ignores the gravitational effect of both
the launch and arrivals planets on the trajectory. The solution is based on
solving Lambert's problem relative to the Sun (heliocentric). Patched-conic
trajectories are suitable for preliminary mission design.

Program IPTO can solve for the following types of optimized space missions:

    - minimized launch energy
    - minimized arrival energy
    - minimized launch + arrival energy

The program is "data-driven" by a user-defined namelist of information which
specifies such things as the departure and arrival planets, the number of
heliocentric revolutions of the transfer trajectory, an initial guess for the 
launch and arrival calendar dates, and the type of optimization.

The software will begin by asking you to input the name of the namelist data 
file to use with the following prompt:

    Please input the name of the IPTO data file
    (be sure to include the filename extension)

Be sure to include the complete file name and its extension.

The following is a typical IPTO namelist data file. It is a minimized arrival
energy trajectory from Earth to Venus. 

     &INPUTS
      IP         = 3, 2
      LDATE      = 8, 12, 1970, 0, 0, 0
      ADATE      = 12, 20, 1970, 0, 0, 0
      NREV       = 0
      IOPT       = 2
    &END

Please note that the namelist data file MUST begin with &INPUTS and end with 
&END. Also, a value for all data items must be present.

The contents of a typical IPTO namelist data file are as follows:

    IP(1) = launch planet
    
    IP(2) = arrival planet

where 0 is the Sun, 1 is Mercury, 2 is Venus, 3 is Earth and so forth.

An initial guess for the launch and arrival calendar dates are contained in
the following two data items:

    LDATE = launch calendar date and Universal Time
    
    ADATE = arrival calendar date and Universal Time
    
The format of the launch date is 

    month, day, year, UT hours, UT minutes, UT seconds

Be sure to include all four digits of the calendar year and separate the data
items with commas.

The number of revolutions around the Sun during the transfer is set with the
NREV data item. For transfer trajectories less than one revolution around the
Sun, NREV = 0.

The type of trajectory optimization performed by IPTO is determined by the
value of the IOPT indicator in the namelist file. The possible values are

    IOPT = 1 - minimized launch energy
    IOPT = 2 - minimized arrival energy
    IOPT = 3 - minimized launch + arrival energy
    IOPT = 4 - no optimization

The following is the output generated by the IPTO software when using the 
IPTO2.DAT namelist data file for input:

                       Program IPTO                                             
          Interplanetary Trajectory Optimization                                
                                                                                
INITIAL GUESS                                                                   
                                                                                
Launch Julian Date        2440810.50000000                                      
Arrival Julian Date       2440940.50000000                                      
                                                                                
Launch Calendar Date      Aug 12 1970      0 h  0 m  0 s  UT                    
                                                                                
Arrival Calendar Date     Dec 20 1970      0 h  0 m  0 s  UT                    
                                                                                
                                                                                
FINAL SOLUTION - No optimization                                                
                                                                                
Launch Julian Date        2440810.50000000                                      
Arrival Julian Date       2440940.50000000                                      
                                                                                
Launch Calendar Date      Aug 12 1970      0 h  0 m  0 s  UT                    
                                                                                
Arrival Calendar Date     Dec 20 1970      0 h  0 m  0 s  UT                    
                                                                                
                                                                                
LAUNCH HYPERBOLA                                                                
                                                                                
(Earth equator and equinox of B1950)                                            
                                                                                
                                                                                
Launch V-infinity vector (kilometers/second)                                    
   -1.55438209372189        -2.75809898980665        0.961070693126354          
                                                                                
Launch V-infinity magnitude (kilometers/second)                                 
    3.30860553829587                                                            
                                                                                
Launch energy (kilometers/second)**2                                            
    10.9468706080421                                                            
                                                                                
Right ascension of launch asymptote (degrees)                                   
    240.595692773777                                                            
                                                                                
Declination of launch asymptote (degrees)                                       
    16.8864590450346                                                            
                                                                                
                                                                                
ARRIVAL HYPERBOLA                                                               
                                                                                
(Earth equator and equinox of B1950)                                            
                                                                                
                                                                                
Arrival V-infinity vector (kilometers/second)                                   
   -1.48636725887297        -1.21422658305550        -5.18092280101137          
                                                                                
Arrival V-infinity magnitude (kilometers/second)                                
    5.52499727540998                                                            
                                                                                
Arrival energy (kilometers/second)**2                                           
    30.5255948932877                                                            
                                                                                
Right ascension of arrival asymptote (degrees)                                  
    219.245690733344                                                            
                                                                                
Declination of arrival asymptote (degrees)                                      
   -69.6727864746084                                                            
                                                                                
Total energy (kilometers/second)**2                                             
    41.4724655013298                                                            
                                                                                
                                                                                
 ORBITAL ELEMENTS OF THE DEPARTURE PLANET AT LAUNCH                             
                                                                                
    Classical Orbital Elements                                                  
    Sun         centered, Earth ecliptic and equinox of B1950                   
 Semi-major Axis    149597927.000000     km                                     
 Eccentricity      0.167214619722866E-01                                        
 Inclination       0.269465191964520E-02 deg                                    
 Node Angle        0.000000000000000     deg                                    
 Arg of Periapsis   102.147164617850     deg                                    
 True Anomaly      -143.550488170394     deg                                    
                                                                                
    Position & Velocity Elements                                                
    Sun         centered, Earth ecliptic and equinox of B1950                   
 X Distance         113707359.486719     km                                     
 Y Distance        -100258245.192306     km                                     
 Z Distance         4166.78799405887     km                                     
 X Velocity         19.2140564009450     km/s                                   
 Y Velocity         22.2389896862596     km/s                                   
 Z Velocity        -.112966047817444E-02 km/s                                   
                                                                                
                                                                                
 ORBITAL ELEMENTS OF THE DESTINATION PLANET AT ARRIVAL                          
                                                                                
    Classical Orbital Elements                                                  
    Sun         centered, Earth ecliptic and equinox of B1950                   
 Semi-major Axis    108208880.000000     km                                     
 Eccentricity      0.678685644113323E-02                                        
 Inclination        3.39394836732197     deg                                    
 Node Angle         76.1714085783211     deg                                    
 Arg of Periapsis   54.6982998113260     deg                                    
 True Anomaly      -19.6416685936321     deg                                    
                                                                                
    Position & Velocity Elements                                                
    Sun         centered, Earth ecliptic and equinox of B1950                   
 X Distance        -38824540.3328578     km                                     
 Y Distance         100195407.175215     km                                     
 Z Distance         3656015.53178787     km                                     
 X Velocity        -32.7758282494981     km/s                                   
 Y Velocity        -12.8482048891351     km/s                                   
 Z Velocity         1.70530638042067     km/s                                   
                                                                                
                                                                                
 ORBITAL ELEMENTS OF THE TRANSFER TRAJECTORY AT LAUNCH                          
                                                                                
    Classical Orbital Elements                                                  
    Sun         centered, Earth ecliptic and equinox of B1950                   
 Semi-major Axis    128665229.490587     km                                     
 Eccentricity      0.178219955982045                                            
 Inclination        4.22910787662533     deg                                    
 Node Angle        -41.4246207647019     deg                                    
 Arg of Periapsis   179.615569505409     deg                                    
 True Anomaly      -179.594214133983     deg                                    
                                                                                
    Position & Velocity Elements                                                
    Sun         centered, Earth ecliptic and equinox of B1950                   
 X Distance         113707359.486719     km                                     
 Y Distance        -100258245.192306     km                                     
 Z Distance         4166.78799406054     km                                     
 X Velocity         17.6596743072231     km/s                                   
 Y Velocity         20.0909997383263     km/s                                   
 Z Velocity         1.97798784445580     km/s                                   
                                                                                
                                                                                
 ORBITAL ELEMENTS OF THE TRANSFER TRAJECTORY AT ARRIVAL                         
                                                                                
    Classical Orbital Elements                                                  
    Sun         centered, Earth ecliptic and equinox of B1950                   
 Semi-major Axis    128665229.490587     km                                     
 Eccentricity      0.178219955982044                                            
 Inclination        4.22910787662533     deg                                    
 Node Angle        -41.4246207647019     deg                                    
 Arg of Periapsis   179.615569505409     deg                                    
 True Anomaly      -27.0740552018060     deg                                    
                                                                                
    Position & Velocity Elements                                                
    Sun         centered, Earth ecliptic and equinox of B1950                   
 X Distance        -38824540.3328578     km                                     
 Y Distance         100195407.175214     km                                     
 Z Distance         3656015.53178780     km                                     
 X Velocity        -34.2621955083710     km/s                                   
 Y Velocity        -16.0235730131421     km/s                                   
 Z Velocity        -2.56474567336955     km/s                                   
                                                                                
 Transfer angle (degrees)     152.520158932177                                  

*****************************************************************************

Program Notes

(1) B1950 is the Besselian calendar year 1950.

(2) The V-infinity vector and right ascension are inertial coordinates.

(3) C3 is the specific (per unit mass) orbital energy.

(4) IPTO is freeware from Science Software.

(5) Please address all questions, comments, etc. to CompuServe 74561,606 or
    the Internet 74561.606@compuserve.com.

(6) Program IPTO was created with Lahey FORTRAN and the Multimission (MASL) 
    library from JPL. Thanks to Dave Skinner, Don Yeomans, and others.

(7) Last updated December 6, 1995.
