Editing Advanced Composition Explorer (section)

=== Solar Energetic Particle Ionic Charge Analyzer (SEPICA) ===
[[File:ACE-sepica sm.jpg|thumb|SEPICA]]
The Solar Energetic Particle Ionic Charge Analyzer (SEPICA) was the instrument on the Advanced Composition Explorer (ACE) that determined the ionic charge states of solar and interplanetary energetic particles in the energy range from ≈0.2 MeV nucl-1 to ≈5 MeV charge-1. The charge state of energetic ions contains key information to unravel source temperatures, acceleration, fractionation, and transport processes for these particle populations. SEPICA had the ability to resolve individual charge states with a substantially larger geometric factor than its predecessor ULEZEQ on [[ISEE-1]] and [[International Cometary Explorer|ISEE-3]], on which SEPICA was based. To achieve these two requirements at the same time, SEPICA was composed of one high-charge resolution sensor section and two low-charge resolution, but large geometric factor sections.<ref name=moebius98>{{cite journal |last=Moebius |first=E. |title=The Solar Energetic Particle Ionic Charge Analyzer (SEPICA) and the Data Processing Unit (S3DPU) for SWICS, SWIMS and SEPICA |journal=Space Science Reviews |date=July 1998 |volume=86 |pages=449–495 |doi=10.1023/A:1005084014850 |bibcode=1998SSRv...86..449M |s2cid=12879423 |display-authors=et al.}}</ref>

As of 2008, this instrument is no longer functioning due to failed gas valves.<ref name="ACE Home Page"/>