PDS3_DATA_SET_ID =
"MESS-E/V/H/SW-EPPS-3-EPS-CDR-V1.0"
DATA_SET_NAME =
"MESSENGER E/V/H/SW EPPS CALIBRATED EPS CDR V1.0"
DATA_SET_COLLECTION_MEMBER_FLG = "N"
DATA_OBJECT_TYPE = TABLE
START_TIME = 2004-229T19:54:21
STOP_TIME = 2015-120T15:08:25
DATA_SET_RELEASE_DATE = 2016-05-06
ARCHIVE_STATUS = "ARCHIVED"
PRODUCER_FULL_NAME = "GEORGE HO"
DETAILED_CATALOG_FLAG = "N"
CITATION_DESC = "{George C. Ho}, MESSENGER E/V/H/SW
EPPS CALIBRATED EPS V1.0, MESS-E/V/H/SW-EPPS-3-EPS-CDR-V1.0,
NASA Planetary Data System, 2009."
DATA_SET_TERSE_DESC = "The MESSENGER EPPS calibrated
observations consist of energetic particle and plasma data
collected by the EPPS instrument during fly-by and orbital
operations of Mercury. Also included are cruise observations for
calibration purposes."
ABSTRACT_DESC = "
Abstract
========
This data set consists of the MESSENGER Energetic Particle and
Plasma Spectrometer (EPPS) calibrated observations, also known
as CDRs. The system encompasses 2 instrument subsystems - the
Energetic Particle Spectrometer (EPS) and the Fast Imaging Plasma
Spectrometer (FIPS). This data set contains EPS instrument data.
EPS covers the energy range of 25 to ❯ 500 keV for electrons, and
10 keV/nucleon to ~3 MeV total energy for ions. There are seven
CDR data products for EPS"
DATA_SET_DESC = "
Data Set Overview
=================
The data set consists of calibrated observations, also known as
CDRs.
For all the CDR 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 ASCII tables. Each data product is identified
within the PDS label by a STANDARD_DATA_PRODUCT_ID value, shown in
parentheses in the table below.
The EPS portion of the data archive currently consists of seven CDR
data products. The different CDR formats represent different Energy
Resolution Spectra with different sampling rates. There is also
a Pulse Height/Event Record file and one representing SCAN mode data.
A given CDR data file will contain all the observations obtained on
same earth day. The following table shows the different EPS data
products. Following is a description of each of the current EPS CDRs.
A more complete description of each may be found in the EPPS CDR SIS
document, located in the DOCUMENT directory of the document volume.
Current EPS Data Products:
EPS Pulse Height (EPS_PULSE_HEIGHT)
Contains Pulse Height Analysis data in ASCII table format. The
lack of priority groups after the FSW6 load on 8/18/2008 means the
weight and group columns of the data are not meaningful after that
time.
EPS High Resolution Spectra (EPS_HIRES_SPECTRA)
High resolution (energy channels) ion and electron energy
spectra. Replaces EPS_HI_SPECTRA after FSW6 (loaded on 8/18/2008).
EPS Low Resolution Spectra (EPS_LORES_SPECTRA)
Low resolution (energy channel) ion and electron energy spectra
and rate counters. Replaces EPS_MED_SPECTRA after FSW6 (loaded on
8/18/2008).
EPS Summary Spectra (EPS_SUMMARY_SPECTRA)
Contains a subset of rate counters and low resolution energy
spectra. CDR available only after FSW6 (8/18/2008).
EPS Scan (EPS_SCAN_RATES)
Contains the integrated hardware counters over four energy
thresholds. Each threshold setting and integration lasts 1/4
second. Rates are reported in both raw and 'delta' form, see
SIS document for details. CDR available only after FSW6
(8/18/2008).
EPS High Priority EPS Spectra (EPS_HI_SPECTRA)
This product contains high energy resolution spectra similar to
the EPS_HIRES_SPECTRA product, but with the configuration from
before the new FSW6 load on 8/18/2008.
EPS Medium Priority EPS Spectra (EPS_MED_SPECTRA)
This product contains lower energy resolution spectra similar to
the EPS_LORES_SPECTRA product, but with the configuration from
before the new FSW6 load on 8/18/2008.
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.
Calibration Overview
====================
This data set is calibrated. Spectral rates have been converted from
raw counts to counts/sec and, where possible, to fluxes. Pulse height
measurements are reported in calibrated keVs. See the calibration
implementation document for details.
Parameters
==========
The accumulation times for spectral rate collection are programmable
as described in the SIS document and in the EDR Dataset Catalog. For
the CDRs, accumulation time is reported in the table directly so
initial raw counts can be recovered from counts/sec by a simple
multiplication. Calibration parameters are described in the
Calibration Implementation document.
Data
====
The EPS CDR data set products are described as follows (the STANDARD_
DATA_PRODUCT_ID value is given in parentheses). All data is in ASCII
table format.
The High Priority EPS Spectra (EPS_HI_SPECTRA_CDR) contains
spectral data, hardware and software count rates and flux.
[BEFORE FSW6, 8/18/2008]
The Medium Priority EPS Spectra (EPS_MED_SPECTRA_CDR) contains
spectral data, hardware and software count rates and flux.
[BEFORE FSW6, 8/18/2008]
The EPS High Resolution Spectra (EPS_HIRES_SPECTRA_CDR) contains
high resolution (in energy) ion and electron energy spectra as count
rates and flux. [AFTER FSW6, 8/18/2008]
The EPS Low Resolution Spectra (EPS_LORES_SPECTRA_CDR) contains
Low resolution (in energy) ion and electron energy spectra
as count rates and flux and rate counters as count rates.
[AFTER FSW6, 8/18/2008]
The EPS Summary Spectra (EPS_SUMMARY_SPECTRA_CDR) contains the same
quantities as the LORES data but sampled at the longer accumulation
times of the HIRES data. [AFTER FSW6,8/18/2008]
The EPS Scan (EPS_SCAN_SPECTRA_CDR) contains the integrated hardware
counters over four energy thresholds. Each threshold setting and
integration lasts 1/4 second reported as rates and differential
inferred fluxes. [AFTER FSW6, 8/18/2008]
The EPS Pulse Height CDR (EPS_PULSE_HEIGHT_CDR) contains
Pulse Height Analysis data."
CONFIDENCE_LEVEL_NOTE = "
Confidence Level Overview
=========================
The EPPS CDR data are the processed data set released for the
EPPS. Data presented here are an accurate representation of the EPPS
data as received from the spacecraft and have been processed from
instrument unit to physical unit.
Review
======
The EPPS CDR was reviewed internally by the EPPS team prior to
release to the PDS. PDS also performed an external review of the
EPPS CDR.
Data Coverage and Quality
=========================
Data reported are the processed data received from the
spacecraft during the following mission phases: Launch, Earth Cruise,
Earth Flyby, Venus 1 Cruise, Venus 1 Flyby, Venus 2 Cruise,
Venus 2 Flyby, Mercury 1 Cruise, Mercury 1 Flyby, Mercury 2 Cruise,
Mercury 2 Flyby, Mercury 3 Cruise, Mercury 3 Flyby, Mercury 4 Cruise,
Mercury Orbit, Mercury Orbit Year 2, Mercury Orbit Year 3, Mercury
Orbit Year 4, and Mercury Orbit Year 5.
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 (028)
Mercury 2 Cruise 29 Jan 2008 (029) 21 Sep 2008 (265)
Mercury 2 Flyby 22 Sep 2008 (266) 20 Oct 2008 (294)
Mercury 3 Cruise 21 Oct 2008 (295) 15 Sep 2009 (258)
Mercury 3 Flyby 16 Sep 2009 (259) 14 Oct 2009 (287)
Mercury 4 Cruise 15 Oct 2009 (288) 3 Mar 2011 (062)
Mercury Orbit 4 Mar 2011 (063) 17 Mar 2012 (077)
Mercury Orbit Year 2 18 Mar 2012 (078) 17 Mar 2013 (076)
Mercury Orbit Year 3 18 Mar 2013 (077) 17 Mar 2014 (076)
Mercury Orbit Year 4 18 Mar 2014 (077) 17 Mar 2015 (076)
Mercury Orbit Year 5 18 Mar 2015 (077) 30 Apr 2015 (120)
No EPPS data were collected during Venus 1 Flyby phases. The EPPS
was on for brief periods during the other six mission phases prior to
Venus 2 Cruise.
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 all Mercury Flybys.
The nominal thresholds are set at 35 keV for both ion and electron
detectors. Energy channels that are below the energy threshold are
not calibrated.
The EPS rate data have not been corrected for priority scheme in the
instrument processor. During high count rate periods, the rate
channels in different look directions are not a true representation of
particle direction. Users are advised to contact the instrument team
to obtain anisotropy information from EPS.
The instrument background counts have not been subtracted in the rate
data. Users should do proper background subtraction before using the
data. During orbital phase, EPS routinely switches between large and
small pixel on both the ion and electron detector. Users should check
the pixel size flag in the data to know which pixel the detectors are
using. The background rate correction should be done for proper pixel
size. But the user should always consult with the instrument team at
JHU/APL to verify the quality of specific data prior to publication.
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 orbital phase, a certain sector in the EPS field-of-view has a
direct view of the sunlit side of the planet. During these periods, the
single event data (Fast, Scanned, etc) may be susceptible to photon
contamination. The science event data (all rate and spectra data) have
additional on-board software processing that should eliminate this
photon contamination. But the user should always consult with the
instrument team at JHU/APL to verify the quality of specific data prior
to publication.
During spacecraft noon-midnight orbits, EPS instrument temperature can
rise to levels that affect the low energy channels. We have noticed
during some of these orbits, the temperature induced noise renders
those energy channels below 100 keV to be useless. In addition, the
higher than normal temperature also induced a data 'drop-out' where the
count in all rate drops by a factor during one integration period and
remains so for a few minutes to hours. The EPS team is currently
investigating the cause of this 'drop-out'. Users should always
consult the instrument team at JHU/APL to verify the quality of
specific data prior to publication.
During orbital phase, EPS routinely switches between large and small
pixel on both the ion and electron detector. User should check the
pixel size flag in the data to know which pixel the detectors are
using.
On 18 Aug 2008 (231), a new Flight Software (FSW) was uploaded to EPPS.
This new FSW (v6) enhances the energy resolution for EPS and adds a
high-resolution proton distribution data packet on FIPS. Description of
these new data products are included in the FMT file. In addition, the
new FSW v6 fixed the data spikes in the EPS data (as mentioned in the
previous paragraph).
On 18 Aug 2009 (230), another new FSW was uploaded to EPPS. This new
FSW (v7) only affects the FIPS data.
In the nominal flight configuration, the FIPS sensor on the EPPS
field-of-view will not measure the solar wind. Periodically, the
spacecraft was rotated such that the FIPS field-of-view can detect
the nominal radial flowing solar wind. These periods typically lasted
less than 3 hours 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 02 Aug 2005 (214) 02 Aug 2005 (214)
07 Aug 2005 (219) 07 Aug 2005 (219)
Venus 1 Cruise 27 Feb 2006 (058) 27 Feb 2006 (058)
06 Sep 2006 (249) 10 Sep 2006 (253)
Venus 1 Flyby No Data
Venus 2 Cruise 01 Mar 2006 (060) 01 Mar 2006 (060)
A dark count signature was discovered in the FIPS PHA data.
These counts appear in a time-of-flight -- E/q histogram of PHA
data as straight tracks in E/q, centered at about 8 different
time-of-flights. These dark counts significantly complicate the
analysis of FIPS PHA data, though not significantly for low mass
ions (H+, He+ and He2+). All data since launch is affected.
This situation is being heavily investigated by the FIPS team.
A small bug was found in FSW v7 which causes only the high order 4 bits
of the wedge, strip and zigzag values are transmitted in
the data. This has the effect of reducing the position
resolution for heavy ions in the FSW v7 data. A software patch
which eliminates this bug was uploaded to the spacecraft at 19:15Z on
16 Dec 2009 (350).
There are gaps in the EPS scan spectra (EPS_SCAN_SPECTRA) products
inclusively spanning 2014-078 through 2014-083 and 2014-246 through
2014-254 due to lack of corresponding EDR source data.
There are data gaps in the EPS scan spectra (EPS_SCAN_SPECTRA) products
inclusively spanning 2014-334 to 2014-350 (production halted to reduce
data volume during a low speed downlink during a solar conjunction),
2014-352 to 2015-022 (production halted for a high voltage check), and
2015-092 to end of mission on 2015-120 (production halted to reduce
solid state recorder load during a solar conjunction).
As always, users of the EPPS data should consult with the instrument
team at JHU/APL to verify the quality of specific data prior to
publication.
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).
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