Data Set Overview : The data set consists of uncalibrated observations, also known as EDRs.  For all the EDR products there is a detached PDS label file that describes the contents of one data file. Each label file will have the same base name as the data file it is describing, with the extension .LBL to denote a label file. The label file defines the start time and end of the observation, product creation time, and the structure of the binary (or ASCII) tables.  The EPS portion of the data archive will consist of four EDR data products, which correspond to the different types of science data packets generated by the instrument at high priority, medium priority, and low priority. The EPS instrument creates all of its different science data packets during one observation, but the packets are telemetered to the ground at different times based on priority. The different formats of these data packets do not lend themselves to standardization into one EDR file format. For example, the high priority science data packet contains the EPS high priority spectra, housekeeping information, and Pulse Hiehgt Analysis (PHA) data. Therefore, different EDR formats have been developed, each of which captures one specific data grouping spectra, housekeeping information, or PHA data. A given EDR data file will contain all the observations obtained on same earth day.  The FIPS portion of the data archive will consist of four EDR data products, which correspond to the three priorities of data produced by the FIPS instrument: high, medium, and low. As with the EPS the different priority modes result in the data being collected and downloaded in different packet formats. At high and medium priority, these packets contain multiple pieces of information, such as a spectral observation and housekeeping data. Therefore, different EDR formats have been developed, each of which captures one specific data grouping spectra, housekeeping information, or PHA data.  There will be an EDR data product containing the engineering and status information for the EPPS instrument the EPPS Status EDR. This data product will consist of an external PDS label file and its pointer to an ASCII table file. The data product is in ASCII to facilitate the browsing of instrument status parameters with commonly available text readers during mission operations.  In addition to the science data, associated instrument parameters are included.   Instrument Overview : The EPS sensor consists of a 60-mm diameter, tuna-can-like cylinder, in which a start foil and stop foil, wrapped around opposite curved sides of the cylinder, constitute the TOF chamber. The detectors are arranged so that each detector senses the events within a given range of incidence angles. Each of the 6 detector modules is composed of 4 pixels: large and small ion and large and small electron. 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.  See the EPPSINST.CAT file for more information and [ANDREWSETAL2007] for full details.   Calibration Overview : This data set is NOT calibrated; it only provides the uncalibrated sensor measurements.   Parameters : The principal parameters during normal science operations when observing with the EPPS are as follows:  * EPS Medium-Priority Integration Interval (N2): This parameter sets the integration interval for medium-priority data (commonly 30 s).  * EPS High-Priority Integration Interval (N1): This parameter sets the integration interval for high-priority data (commonly 300 s). N1 is an integer-multiple of N2.  * EPS Detector Selection: EPS possesses 24 detectors: 12 for ions and 12 for electrons. Half are large-pixel, and half are small-pixel. Only 12 detectors can be used simultaneously, so the operational detectors can be set by command.  * FIPS Mode Selection: This command allows selection of the mode of operation: normal, burst, and pick-up ion.  The EPPS also includes modes for testing the instrument and maintaince activities.   Data : The nine EDR data products are described as follows (the STANDARD_ DATA_PRODUCT_ID value is given in parentheses):  The High Priority EPS Spectra EDR (EPS_HI_SPECTRA) contains spectral data, hardware and software rate counters in binary table format. Data and counter values are taken from the High Priority Science Packet.  The High Priority Housekeeping EDR (EPS_HI_HOUSEKEEPING) is an ASCII table file that contains 33 fields of housekeeping data.  The Medium Priority EPS Spectra EDR (EPS_MED_SPECTRA) contains spectral data, hardware and software rate counters in binary table format. Data and counter values are taken from the Medium Priority Science Packet.  The EPS Pulse Height EDR (EPS_PULSE_HEIGHT) contains Pulse Height Analysis data in binary table format. The PHA data product is generated from the high, medium, or low priority science packet. The priority level will be identified within the PDS label.  The High Priority FIPS Spectra EDR (FIPS_HI_SPECTRA) contains spectral and velocity distribution, hardware and software rate counters in binary table format. Data and counter values are taken from the High Priority Science Packet.  The High Priority FIPS Housekeeping EDR (FIPS_HI_HOUSEKEEPING) is an ASCII table file that contains 33 fields of housekeeping data taken from the High Priority Science Packet.  The Medium Priority FIPS Spectra EDR (FIPS_MED_SPECTRA) contains proton velocity distribution, hardware and software rate counters in binary table format. Data and counter values are taken from the Medium Priority Science Packet.  The FIPS Pulse Height EDR (FIPS_PULSE_HEIGHT) contains FIPS Pulse Height Analysis data in binary table format. This data product is generated from either high, medium, or low priority FIPS packets. The priority level will be identified within the PDS label.  The EPPS Status EDR contains engineering and status information for the EPPS instrument. The data product is in ASCII to facilitate the browsing of instrument status parameters with commonly available text readers during mission operations.

Confidence Level Overview : The EPPS EDR data are the least processed data set released for the EPPS. Data presented here are an accurate representation of the EPPS data as received from the spacecraft, with minimal timing and no spatial processing.   Review : The EPPS EDR was reviewed internally by the EPPS team prior to release to the PDS. PDS also performed an external review of the EPPS EDR.   Data Coverage and Quality : Data reported are the minimally processed data received from the spacecraft during the seven mission phases: Launch, Earth_Cruise, Earth_Flyby, Venus_1_Cruise, Venus_1_Flyby, Venus_2_Cruise, Venus_2_Flyby, Mercury_1_Crusise, Mercury_1_Flyby. These mission phases are defined as:  Start time End time Phase Name Date (DOY) Date (DOY) ----------------- ---------------- ---------------- Launch 3 Aug 2004 (216) 12 Sep 2004 (256) Earth_Cruise 13 Sep 2004 (257) 18 Jul 2005 (199) Earth_Flyby 19 Jul 2005 (200) 16 Aug 2005 (228) Venus_1_Cruise 17 Aug 2005 (229) 9 Oct 2006 (282) Venus_1_Flyby 10 Oct 2006 (283) 7 Nov 2006 (311) Venus_2_Cruise 8 Nov 2006 (312) 22 May 2007 (142) Venus_2_Flyby 23 May 2007 (143) 20 Jun 2007 (171) Mercury_1_Cruise 21 Jun 2007 (172) 30 Dec 2007 (364) Mercury_1_Flyby 31 Dec 2007 (365) 28 Jan 2008 ( 28)  No EPPS data were collected during Venus_1_Flyby phases. The EPPS was on for brief periods during the other six mission phases. During these planned operational periods, the EPS sensor on the EPPS did not have high voltage enable, hence no Time-of-flight data and only spectra data were collected. The EPS was turned on for the Venus_2_Flyby and to be remained on throughout the remainder of the mission phases. EPPS data were collected during the Mercury_1_Flyby.  EPS High Ion Sector 1 and 5 have malfunction detectors and do not produce any data product.  The lowest energy channel (32 to 55 keV) on the High Ion Sector 3 and 5 have periodic high count that are due to flight software interaction with the instrument and should not be used. User of EPS data should consult with the instrument team at JHU/APL to verify the quality of specific data in certain time interval prior to publication.  During nominal cruise operations, the radial-flowing solar wind is in a blocked segment of the FIPS sensor field-of-view (FOV). Four times during the mission, the spacecraft was rotated such that the FIPS FOV can detect the nominal, radial-flowing solar wind. These periods lasted from 1 hr to roughly 12 hrs and are identified as: Start time End time Phase Name Date (DOY) Date (DOY) ----------------- ---------------- ---------------- Earth_Cruise 05 Apr 2005 (105) 05 Apr 2005 (105) Earth_Flyby 07 Aug 2005 (219) 07 Aug 2005 (219) Venus_1_Cruise 27 Feb 2006 (058) 27 Feb 2006 (058) Venus_2_Cruise 01 Mar 2006 (060) 01 Mar 2006 (060)  When FIPS is run in Magnetospheric Mapping mode (8s/scan), as it was during Mercury Flyby 1, the channels above channel 55 are not used in order speed up scanning. The rates in these channels are not updated properly by the flight software and should not be used.  In general, interpretation of FIPS measurements requires detailed understanding of the FIPS FOV at the time of each individual measurement. This FOV information is not incorporated into this data set in any way. Users of this data are thus urged to consult with the FIPS instrument team at University of Michigan for serious scientific studies.   Limitations : This data set is minimally processed data. The data are received from the spacecraft telemetry and ingested into the MESSENGER Science Operations Center (SOC).