LOW ENERGY PARTICLES IN THE GLOBAL HELIOSPHERE 2001–2004: 1 TO 90 AU L. J. LANZEROTTI Bell Laboratories, Lucent Technologies, Murray Hill, NJ 07974, U.S.A. (E-mail: ljl@lucent.com) S. M. KRIMIGIS, R. B. DECKER, S. E. HAWKINS, III, R. E. GOLD and E. C. ROELOF The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723–6099, U.S.A. T. P. ARMSTRONG Fundamental Technologies LLP, Lawrence, KS, U.S.A. Abstract. Charged particle instrumentation that will be flying on six spacecraft in the heliosphere between 1 and 90 AU during 2001–2004 will provide a global view of the interplanetary medium that has not heretofore been available. Comparative analyses of the data that will be obtained will provide new understanding of the global evolution of heliospheric features such as traveling shock waves, coronal mass ejections, solar activity-produced particle injections, and anomalous cosmic rays. 1. Introduction The interval 2001–2004 provides an unprecedented opportunity for studies of low energy interplanetary particles on six different spacecraft in the global heliosphere. The locations of these spacecraft in heliographic coordinates during these years are shown in Figure 1. The ACE and IMP8 spacecraft at 1 AU and Cassini between about 4 and 10 AU en route to Saturn will provide in-ecliptic data. The Voyager 1 and 2 spacecraft will be between about 80–90 and 63–73 AU, respectively, and at heliolatitudes ∼33 ◦ N and ∼25 ◦ S, respectively. The Ulysses mission will be in its orbit across the solar poles, covering the South Pole (December/2000), the North Pole (November/2001), and then on an outbound trajectory to the ecliptic plane at 5 AU (September/2004). Each spacecraft carries low energy particle instrumen- tation of various designs, but all instruments basically perform measurements of low energy electrons (∼50 to ∼2000 keV) and ion species (H through Fe; ∼0.5 to 20 MeV nucl -1 ). Details of the instrumentation on IMP8 (Sarris et al., 1976), ACE (Gold et al., 1998), Ulysses (Lanzerotti et al., 1992), Cassini (Krimigis et al., 2000), and Voyager 1/2 (Krimigis et al., 1977) can be found in the references. In what follows, data from several of the 2001–2004 spacecraft are presented for selected time intervals from the launch of the Voyagers in 1977 to the present. Examination of the past data can provide some perspectives, but not predictions, as Space Science Reviews 97: 243–248, 2001. © 2001 Kluwer Academic Publishers. Printed in the Netherlands.