sensitive to such activity to take preventative action. The RTSW system gathers solar wind and energetic particle data at high time resolution from four ACE instruments (MAG, SWEPAM, EPAM, and SIS), packs the data into a low-rate bit stream, and broadcasts the data continuously. NASA sends real-time data to NOAA each day when downloading science data. With a combination of dedicated ground stations (CRL in Japan and RAL in Great Britain), and time on existing ground tracking networks (NASA DSN and the USAF's AFSCN), the RTSW system can receive data 24 hours per day throughout the year. The raw data are immediately sent from the ground station to the Space Weather Prediction Center in Boulder, Colorado, processed, and then delivered to its Space Weather Operations Center where they are used in daily operations; the data are also delivered to the CRL Regional Warning Center at Hiraiso Station, Japan, to the USAF 55th Space Weather Squadron, and placed on the World Wide Web. The data are downloaded, processed and dispersed within 5 minutes from the time they leave ACE. The RTSW system also uses the low-energy energetic particles to warn of approaching interplanetary shocks, and to help monitor the flux of high-energy particles that can produce radiation damage in satellite systems. Solar Energetic Particle Ionic Charge Analyzer (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 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. As of 2008, this instrument is no longer functioning due to failed gas valves. Solar Isotope Spectrometer (SIS) The Solar Isotope Spectrometer (SIS) provides high-resolution measurements of the isotopic composition of energetic nuclei from He to Zn (Z = 2 to 30) over the energy range from ~10 to ~100 MeV/nucleon. During large solar events, SIS measures the isotopic abundances of solar energetic particles to