CCC-0024 CARSTEP.

1. NAME OR DESIGNATION OF PROGRAM:  CARSTEP.

3. DESCRIPTION OF PROGRAM OR FUNCTION

The CARSTEP code determines the flux of particles from the Van Allen zones that strike a space vehicle which is executing a mission in that volume of space. Using  latitude, longitude, altitude of perigee, inclination and eccentricity of orbits, and mission time as input, the following data is given: latitude, longitude, and altitude of the vehicle at points along the trajectory, the flux of particles at these points,  and time integrated flux for the total mission.

4. METHOD OF SOLUTION

The position of the vehicles as a function of time is determined by a two-body analysis. The program is divided into three parts: lunar transfer trajectories, lunar return trajectories, and geocentric orbits.
The environment portion of CARSTEP uses a coordinate system (B,L) for mapping the distribution of geomagnetically trapped particles which has been developed by C.E. McIlwain.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The earth is considered a perfect sphere and atmospheric drag is neglected. One energy spectrum for particles is valid throughout the volume of space.

6. TYPICAL RUNNING TIME:  Estimated running time of sample problem: 5 minutes.

NEA-DB executed the test case included in this package  on an IBM 3090 computer in 2 seconds of CPU time.

7. UNUSUAL FEATURES OF THE PROGRAM:

8. RELATED AND AUXILIARY PROGRAMS

This code was developed by combining a two-body trajectory program with NASA Goddard's environment routine.

10. REFERENCES:

- M. R. Morrison  and A. E. Tate :
  Determination of Particle Fluxes Impinging on a Spacescraft
  NSL 63-63R-1 (September 1963)

11. MACHINE REQUIREMENTS

The code was designed for an IBM 7090 or 7094 computer. A 32,768 core memory and three tape units are required.

The test case ran on IBM 3090 in 224K bytes of main storage.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED

The code was designed for, and is operable on the IBM FORTRAN II Monitor System.  The only tape assignments necessary are for input, output and the system. It may easily be made compatible with other FORTRAN compilers.

(1) An IBM version of the code has been generated by converting the source from FORTRAN-II to FORTRAN-IV and compiling it under MVS/XA using the FORTRAN VS2 compiler with option LEVEL-66. (2) For implementation on VAX machines, a FORTRAN-77 version was produced and run on a VAX-11/780 under VMS V4.6.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHORS

          Northrop Space Laboratory
          Hawthorne, California

          Aerospace Medical Research Laboratory
          Wright-Patterson Air Force Base, Ohio

File name	File description	Records
CCC0024_01.001	Information file	65
CCC0024_01.002	JCL to compile, link and execute a sample	80
CCC0024_01.003	CARSTEP source (Fortran-77, level-66)	876
CCC0024_01.004	Sample problem input (unit 5)	276
CCC0024_01.005	Sample problem print (unit 6)	1026