urn:nasa:pds:context:instrument:epps-fips.mess 1.0 1.15.0.0 Product_Context urn:nasa:pds:context:instrument:epps.mess 2021-03-23 1.0 extracted metadata from PDS3 catalog and modified to comply with PDS4 Information Model urn:nasa:pds:context:instrument_host:spacecraft.mess instrument_to_instrument_host 10.1007/s11214-007-9272-5 Andrews, G.B., T.H. Zurbuchen, B.H. Mauk, H. Malcom, L.A. Fisk, G. Gloeckler, G.C. Ho, J.S. Kelley, P.L. Koehn, T.W. LeFevere, S.S. Livi, R.A. Lundgren, and J.M. Raines, The Energetic Particle and Plasma Spectrometer instrument on the MESSENGER spacecraft, Space Science Reviews, 131, 523-556, 2007. EPPS Fast Imaging Plamsa Spectrometer Charged Particle Detector Energetic Particle Detector The Energetic Particle Spectrometer (EPS) is part of the MESSENGER Energetic Particle and Plasma Spectrometer (EPPS) system, which which also includes the Fast Imaging Plasma Spectrometer (FIPS). FIPS covers the energy/ charge range of < 50 eV/q to 20 keV/q. The desired throughput for FIPS charged particle and EPS event processing is 5 kHz. The FIPS instrument was constructed by the University of Michigan Space Physics Research Laboratory. The FIPS sensor is designed to measure the distributions and composition of magnetosphere ions, as well as to characterize the nature of the planetary magnetic field of Mercury. It will do this by measuring the mass per charge, the energy per charge, and incident angles for particles entering the sensor. The particle intensity is also calculated from the event rate information. FIPS generates a single 48-bit raw event packet format, which includes a 1-bit header that identifies the event as a proton event or a non-proton event; an 11-bit time-of-flight (TOF) value; as well as Wedge, Strip, and ZigZag values (each 12 bits in size). In addition, the FIPS system generates counter and housekeeping information that the EPPS software can access via the I2C bus interface. The FIPS consists of an electrostatic analyzer (ESA), located at the entrance to the sensor, a post-acceleration chamber between the output of the ESA and the carbon foil, and a time-of-flight telescope. The ESA at the entrance to the FIPS acts as a wide-angle lens for ions. It only allows ions with a specific energy/charge band to enter through its output plane. This band is stepped once per second by changing the deflection voltage of the ESA. A measurement cycle consists of 64 deflection voltage steps in nominal mode or 8 in burst mode. Associated with each step in a scan is a voltage setting, a threshold, a settling time, and a duration or time interval after which the next voltage step is performed. Ions exit the output plane of the ESA and are then accelerated in the post- acceleration chamber. This acceleration is done to boost low-energy ions to penetrate the carbon foil. The acceleration also helps to reduce energy straggling and angular scattering - effects that cause degradation in mass resolution and imaging. The carbon foil serves as the source for secondary electrons, which are scattered out by the penetration ions. After penetrating the foil, the particle resides within the TOF chamber where velocity and incoming angle are computed. Velocity is determined by the time difference between the generation of secondary electrons in the start foil and a stop surface, and angle is determined by spatially imaging the position of the generation of the start secondary electrons. From the velocity, energy per charge, and the post-acceleration potential, it is then possible to calculate the mass per charge. The measured species for the FIPS range from H to Fe. The FIPS instrument provides a single serial stream of event data to the EPPS system at rates of up to 50000 events per second. The EPPS software maintains a mass distribution spectrum for the FIPS instrument. This spectrum consists of a collection of 256 bins (each 24 bits wide) that count the number of events corresponding to mass- per-charge values. In addition, the software maintains a set of 5 element energy spectra. Each FIPS spectrum corresponds to a specified mass-per-charge range and consists of 64 24-bit bins. For events whose mass-per-charge values fall within one of the selected ranges, an energy value is computed and used to determine which bin within the corresponding spectrum to increment. The spectra are accumulated over an integral number of voltage scans, after which they are compressed and output in telemetry. FIPS also records 5 heavy-ion energy-summed images (called velocity distributions) for each of the same 5 mass-per-charge values plus one for protons. A commanded number of raw events will be recorded at each scan level. The EPPS instrument is described in full detail in Andrews, et al., 2007.