1. Lockheed Martin Autonomous Systems, Littleton, CO, 80125.
2. Dept. of Computer Science, Univ. of New Mexico, Albuquerque, NM 87131 USA.
3. Dept. of Physics, Baldwin-Wallace College, Berea, OH, 44017, USA.
4. NASA, Kennedy Space Center, FL 32899 USA.
5. Dept. of Computer Science, Univ. of New Mexico, Albuquerque, NM 87131 USA; External faculty, Santa Fe Institute, Santa Fe, NM 87502.