DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set contains SREM omni-directional fluxes in MeV provided at
particular effective energies, converted from the equivalent SREM
Level 2 CDF products, which are provided in the EXTRAS directory.
Note that the CDF processing levels differ from the CODMAC definition
used within these PDS data sets. The SREM CDF Level 0 data are
equivalent to the PDS CODMAC Level 2 data while the SREM CDF Level 2
data are equivalent to the PDS CODMAC Level 5 data.
These data are useful for determining the energetic particle
environment experienced by the Standard Radiation Environment Monitor
onboard the Rosetta Orbiter.
Processing
==========
Differential fluxes have first been derived from the 'raw' Level 0 CDF
count rate data using a dedicated unfolding technique over pre-defined
energies. The unfolding technique is based on the regularized Singular
Value Decomposition (SVD) method described in [SANDBERGETAL2012], and
in the SREMDC_FINAL_REPORT_V1.0.PDF file found in the DOCUMENT directory.
The fluxes have then been rescaled according to cross-calibration
studies between fluxes before a rescaling step against selected reference
datasets. SEPEM Reference Dataset v2.0 (i.e. GOES/EPS fluxes cross-
calibrated with IMP-8/GME) has been selected as reference for proton
fluxes, while RBSP/MAGEIS spin averaged datasets were selected as a
reference for electron fluxes. As a result of this process, the highest
energy flux levels derived for the electron data were not reliable. Thus,
it was decided to reject entirely these products in the production of this
Level 5 data set. As such, only 10 energy channels are made available for
electron fluxes. These are #1-#10 in the table on page 48 of the
SREMDC_FINAL_REPORT_V1.0.PDF file, available in the DOCUMENT directory.
A quality value is also provided alongside the fluxes, giving
recommendations on their use, as described in the table below.
FPDO: Flux Proton Differential Omnidirectional
FEDO: Flux Electron Differential Omnidirectional
FQDO_Quality: Flux Q Differential Omnidirectional_Quality
where (Q=P,E)
Where:
---------------|-------------------------|------------------
FQDO_Quality | Comment | Recommendation
---------------|-------------------------|------------------
FQDO_Quality=0 | SREM count-rate data | Use FQDO
| determined by charged |
| particle fluxes Q. |
---------------|-------------------------|------------------
FQDO_Quality=1 | SREM count-rate data | Use FQDO with
| most likely determined | some caution
| by charged particle |
| fluxes Q. |
---------------|-------------------------|------------------
FQDO_Quality=2 | SREM count-rate | Do not use FQDO
| contaminated by |
| various sources. None |
| criterion is satisfied |
---------------|-------------------------|------------------
FQDO_Quality=3 | SREM count-rate | Do not use FQDO
| dominated by fluxes of |
| non-Q particles. |
---------------|-------------------------|------------------
FQDO_Quality=5 | SREM count-rate data | Do not use FQDO
| dominated by background |
| (cosmic, detector |
| electronics) |
---------------|-------------------------|------------------
(Table above is taken from SREMDC_Final_Report_V1.0.PDF,
available in the DOCUMENT directory)
Data
====
One data product is provided per day of measurement. Data products
are named according to the following convention:
SREM_L_YYYYMMDD.EXT
Where:
is the CODMAC processing level (2 for the count rate data and 5 for
the derived proton and electron flux data).
YYYMMDD is the date of the observation.
EXT is the file extension (TAB for the ASCII data table and LBL for
the detached PDS label file).
All data products are formatted as plain ASCII tables and have an
associated detached PDS label.
The CODMAC Level 5 data are given as protons and electrons energy
values and their associated quality values, with measurements
time tagged at the middle of the time interval (centered). The LBL
file contains metadata with information about the instrument,
mission, any important instrument parameters or measurement
parameters, start and stop time of the measurement, and the pointer
to the TAB object.
The data table is structured as follows:
- A first row with text headers defining each column in the subsequent
data table. For each column containing the proton and electron energy
measurements, the central energy value of the channel in MeV is used.
- A data table (called SREM_DATA_TABLE) with each row containing the
following columns:
Time: A time tag per measurement, at the center of the
observation.
Proton Energies: 13 proton energy values in MeV.
Proton Quality: An indication of the quality of the proton
measurements.
Electron Energies: 10 electron energy values in MeV.
Electron Quality: An indication of the quality of the electron
measurements.
IMPORTANT NOTES:
- As noted above, the time values provided mark the center time of
the observation.
- The PDS keyword MISSING_CONSTANT, which is provided in every LBL file,
indicates the value (-1.0E31) used in the data table if no measurement
data is available. Any zero values in the data tables are real
measurements.
- The quality values used are described above, and are also provided
directly within the DESCRIPTION field of each LBL file.
- As noted above, the electron data set was cross-calibrated with
RBSP/MAGEIS spin averaged data. It has been noted that as a result of
this process the highest energy flux levels derived were not reliable.
Thus, it was decided to reject entirely these products in the
production of the Level 2 CDF data. As such, only 10 energy channels
are made available, #1-#10 in the table on page 48 of the
SREMDC_FINAL_REPORT_V1.0.PDF file, available in the DOCUMENT directory.
Software
========
No software is provided with this data set. All products are provided as
plain ASCII tables and can be read using the standard freely available
NASAView and ReadPDS software packages.
Media/Format
============
The data set will be delivered and kept online.
|
CITATION_DESCRIPTION |
H. Evans, P. Nieminen,
I. Sandberg, I. Daglis, and M. Taylor,
ROSETTA-ORBITER X SREM 5 STEINS V1.0,
RO-X-SREM-5-AST1-V1.0,
ESA Planetary Science Archive and NASA
Planetary Data System, 2020.
|