This file chronicles data processing changes/improvements to the ACE level 2
data accessible from the ACE Science Center. Routine updates of new data
are NOT reported here. This file only records changes in data processing
which result in changed data, i.e. new versions of the data.

February, 2021 SWEPAM Level 2 data from 2013 to the present have been reprocessed to account
for changes in CEM detector gains over time. While for many years gain
changes were observed in only 2 of the detectors, in recent years additional
detectors have begun to show gain changes. This reprocessing accounts for
changes in these additional detectors with time, and significantly improves
the density values calculated from SWEPAM data.
Spacecraft pointing continues to have a significant effect on SWEPAM moments
quality, but this new data set extends the range of pointing angles at
which valid moments can be calculated.

March, 2017 For SWICS, An issue has been corrected in which, for proton speeds lower than
300 km/s, the calculation of proton densities was sometimes off by an
aspect-angle dependent scaling factor.
Please see the Release notes for more details:
http://www.srl.caltech.edu/ACE/ASC/DATA/level2/ssprotons/swics_protons_release_notes.txt

Aug 08, 2016 Complete reprocess of SWEPAM/SWICS merged solar wind data set,
from beginning of mission, using SWICS Level 2
Version 1.1 Proton Data, now available as an independent data set from
http://www.srl.caltech.edu/ACE/ASC/level2/lvl2DATA_SWICS_PROTONS.html

Jul 13, 2016 New release of SWICS Solar Wind proton data, completely reprocessed,
from 1998-2015. This is therefore a new version (v1.1) and has some
corrections and bug fixes applied that were sufficient to warrant a
re-processing of the data set.
Please see the Release notes for more details:
http://www.srl.caltech.edu/ACE/ASC/DATA/level2/ssprotons/swics_protons_release_notes.txt

Feb 2016 New release of SWICS 2.0 Level 2 data from Jan 1 2015
onwards. Fixes a problem where some data were incorrect by a few %.

Sept 30, 2015 Release of EPAM 12-second fluxes. Same data items as in the 5-minute
and hourly EPAM data.

June 2015 New release of SWICS 1.1 Level 2 data.
SWICS 1.1 Version 4.09 contains a few incremental improvements
that optimize the ion identification model and reveal more
counts of low-density species. The process for removing
accidental coincidence events has been improved, leading to a
small increase in identification of rare ions such as Fe6+,
Fe7+, and C4+. In addition, the forward model for ion
identification now uses all charge states of all 11 elements,
making the ion count assignment as accurate as possible.
Statistical improvements were also made in the model so that
ion thermal speeds are calculated with a higher degree of
accuracy, particularly in the slow wind.
Please see the Release notes for more details:
http://www.srl.caltech.edu/ACE/ASC/DATA/level2/ssv4/swics_lv2_v4_release_notes.txt

May 2015 Release of SWICS Solar Wind Proton Data at 12-minute time-resolution.
Please see the Release notes for more details:
http://www.srl.caltech.edu/ACE/ASC/DATA/level2/ssprotons/swics_protons_release_notes.txt

April 2015 The 5-minute and hourly EPAM spin-averaged flux data sets provided by the ASC
have been reprocessed, using updated energy-bands and geometry factors.
Statistical uncertainties are now handled in a consistent manner for both the
hourly and the 5-minute averages. All fluxes are now calculated by the ASC
from rates data provided directly by the EPAM team.

March 2015 A major new release of the SWICS Level 2 data, using completely redesigned analysis
methods.
Please see the Release notes for more details:
http://www.srl.caltech.edu/ACE/ASC/DATA/level2/ssv4/swics_lv2_v4_release_notes.txt
and
http://www.srl.caltech.edu/ACE/ASC/DATA/level2/ss2/swics_lv2_V2_release_notes.txt

July 22, 2014 The SIS team has released a new version of the SIS Level 2
data. The new analysis includes a better calculation of the
time-dependent geometry factor and a data cut to eliminate
chance-coincidence events resulting from disabled strips. <a
href="/ACE/ASC/DATA/level2/sis/sis_release_notes">Release
Notes</a> for details.

Jun 17, 2014: MAG data from 2013/151 onwards have been re-released with new calibrations.
Less than 0.2nT changes...see the release notes for details:
http://www.srl.caltech.edu/ACE/ASC/DATA/level2/mag/mag_release_notes

Jun 13, 2013: Re-release of SWICS Level2 2hr for the whole mission. Corrected bug
that caused rates to be too low.
Please see the Release notes for more details:
http://www.srl.caltech.edu/ACE/ASC/DATA/level2/ssv3/swics_lv2_v3_release_notes.txt

Jan 23, 2013: The CRIS Level 2 data product has been re-evaluated following changes made to
the data cuts and the calculation of the geometry factors and SOFT hodoscope
efficiencies. Bugs in the positioning and thicknesses of the silicon detector
stacks and the calculation of the depth of incident particles have been
corrected.
Please review the Release notes:
http://www.srl.caltech.edu/ACE/ASC/DATA/level2/cris/cris_release_notes

Apr 30, 2012: Re-release of SWICS Level2 2hr and daily averages for the
whole mission. Corrected issue which caused Fe-containing data products to differ
substantially between 2h and 1d resolution, evident mainly in long (~30
day) averages. Fe/O ratio changed by up to 50% in portions of both 2h
and 1d datasets (unchanged in other portions).
Please see the Release notes for more details:
http://www.srl.caltech.edu/ACE/ASC/DATA/level2/ssv3/swics_lv2_v3_release_notes.txt

Nov 10, 2010: Re-release of the SIS Level 2 data for the whole mission.
We identified and eliminated contamination from penetrating
particles evident in the range 7 intensities. The effect is
most evident when examining long time integrations of quiet
time periods.
Please see the Release notes for more details:
http://www.srl.caltech.edu/ACE/ASC/DATA/level2/sis/sis_release_notes

Apr 2, 2010: Re-release of the CRIS Level 2 data for the whole mission.
The CRIS Team has re-evaluated the production of CRIS Level 2 data,
implementing several changes that were incorporated in the analysis
presented in George et al., ApJ 698, 1666 (2009). These include
revisions to the hodoscope grammage, interaction probabilities, and
data cuts and geometry factors for events stopping deep in the
instrument. In addition, a bug in the maps of the SOFT hodoscope has
been repaired, slightly changing the calculation of trajectories, and
the parsing of the data telemetry stream has been made more robust,
which results in the recovery of a small number (~0.1%) of additional
events. The overall effect of these changes is typically to reduce the
absolute intensities by a small amount, by up to a few percent. Together
these changes have some effect on the width and centers of the CRIS
energy bins; PLEASE USE THE NEW ENERGY VALUES (available at
http://www.srl.caltech.edu/ACE/ASC/DATA/level2/cris/cris_energy_bands.txt)
WITH THESE NEW DATA!
Also, please review the Release notes:
http://www.srl.caltech.edu/ACE/ASC/DATA/level2/cris/cris_release_notes

Mar 31, 2010: Re-release of the SIS Level 2 data for the whole mission.
We added a small correction for spallation within the
instrument to the calculated intensities. These corrections
are greatest for deep range and heavier ions; they range from
0.9993 for range 0 He to 0.9227 for range 7 Ni (note: these
are division factors; i.e., the intensities are divided by
these numbers). All the data from mission start to date were
reprocessed to incorporate these corrections.
Release notes are accessable from the SIS Level
2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/sis_l2desc.html.

Mar 3, 2010: Unintended CRIS Data Change

The CRIS Team has re-evaluated the production of CRIS Level 2 data,
implementing several changes that were incorporated in the analysis
presented in George et al., ApJ 698, 1666 (2009). These include
revisions to the hodoscope grammage, interaction probabilities, and
data cuts and geometry factors for events stopping deep in the
instrument. In addition, a bug in the maps of the SOFT hodoscope has
been repaired, slightly changing the calculation of trajectories, and
the parsing of the data telemetry stream has been made more robust,
which results in the recovery of a small number (~0.1%) of additional
events. The overall effect of these changes is typically to reduce the
absolute intensities by a small amount, by up to a few percent. At
present we are evaluating the effects of these changes on our energy
bins (which are expected to be at the few percent level), and once
this is completed in a few weeks we will release the new data.

Unfortunately, test files using this new analysis were inadvertently
placed on the CRIS level 2 site on Feb 24, 2010, 2:40pm PST, replacing
the older files there; also data from Bartels Rotations 2407 and 2408
were generated using the new analysis. CRIS DATA FILES DOWNLOADED
BETWEEN FEB 24 and MAR 3 2010, OR ANYTHING FROM BR 2407 DOWNLOADED
PRIOR TO MAR 3, SHOULD NOT BE USED WITHOUT THE APPROPRIATE CHANGES TO
THE ENERGY BINS, WHICH WE ARE STILL WORKING ON. For the time being, we
are restoring the old files to the site until we have finished
evaluating the new ones.

We thank the users who called this issue to our attention, and we
apologize for any inconvenience this may have caused.

Sep 30, 2009: Re-release of the SWICS Level 2 data for the whole mission.
Data have been reprocessed to remove/greatly-reduce a 6-month
periodicity in the elemental abundances.
Releae notes are available at
http://www.srl.caltech.edu/ACE/ASC/level2/ssv3_l2desc.html

Aug 21, 2008: Release of new version of ULEIS Level 2 data for whole mission,
generated with udf_lister program including all efficiency updates.
List of instrument saturations updated; several additional periods added.

Jun 23, 2008: Re-release of the SIS Level 2 data for the whole mission.
Addition of intensities for Na, Al, Ar, Ca, and Ni, plus a few
other minor changes in teh analysis code.
Release notes are accessable from the SIS Level
2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/sis_l2desc.html.

Jan 24, 2008: Re-release of the SWEPAM Level 2 data for Bartels rotations
2366 - 2372 (12/07/2006 thru 06/13/2007).
Data have been reprocessed to incorporate updated instrument
calibrations which account for changing CEM gains over time.
Changes were based on weekly on-board calibrations.

Apr 28, 2007: First release of MAG Level 2 data at 1-second resolution.
The MAG team will release data in stages, working backwards
in time from the present to the beginning of the mission.

Apr 26, 2007: Re-release of the SIS Level 2 data for the whole mission.
Release notes are accessable from the SIS Level
2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/sis_l2desc.html.

Apr 4, 2007: Re-release of the SWEPAM Level 2 data for Bartels rotations
2342 - 2361 (02/27/2005 thru 08/20/2006). Data have been reprocessed
to incorporate updated instrument calibrations. Based on increased
time at CEM voltage Level 2, the instrument geometric factors have
been better defined, particularly for the off-axis CEMs. We also
better account for changing CEM gains over time, based on weekly
on-board calibrations.

Jan 19, 2007: The EPAM team identified a timing drift in the EPAM data. This timing
drift was ~ 1 minute/year. The team has identified the source of this
drift and fixed the problem. The entire entire EPAM hourly-averaged
dataset has been regenerated. The 5-minute averages have not yet been
regenerated.

Feb 14, 2006: Re-release of the SWEPAM Level 2 data for Bartels rotations
2342 - 2348 (02/27/2005 thru 09/03/2005). Incorporates the new geometric
factors for operation at CEM voltage level 2.

Oct 1, 2005: an entirely new version of the SWICS-SWIMS level 2 data has been
released. Release notes are accessable from the SWICS/SWIMS Level
2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/ssv2_l2desc.html.

Mar 31, 2005: Re-release of the SWEPAM Level 2 data for Bartels rotations
2331 - 2335, and rotation 2324.
This change was required to update the instrument calibrations.
See the SWEPAM Release Notes for details. Release notes
are accessable from the SWEPAM Level 2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/swepam_l2desc.html.

Mar 28, 2005: New version of MAG level 2 data for 2003-087 onwards.
An incorrect calibration had been applied, affecting
only periods with |B| < 4 nt. Error was < 1 nT, in the
direction of the spacecraft spin-axis.
See the MAG Release Notes for details. Release notes
are accessable from the MAG Level 2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/mag_l2desc.html.

Dec 31, 2003: noise on EPAM P1, P2, P3, P4, P5, P6 channels from 2003-302
onwards - the data for these channels is replaced with fill-data.

Nov 30, 2003: New release of ULEIS level 2 data, from start of mission
to date. Updated instrument calibration efficiency.

May 28, 2003: New version of SWEPAM data for entire mission. Updated
instrument calibrations. Included velocities even at
times when all other moments are unreliable. Reprocessed data
during most solar particle events to account for the high
background levels.
See the SWEPAM Release Notes for details. Release notes
are accessable from the SWEPAM Level 2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/swepam_l2desc.html.

Dec 13, 2002: New version of SWEPAM level 2 data for Bartels rotations 2295
and 2297. This change adds some data points during several high
background intervals.
See the SWEPAM Release Notes for details. Release notes
are accessable from the SWEPAM Level 2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/swepam_l2desc.html.

Nov 26, 2002: New version of SWEPAM level 2 data for Bartels rotation 2295.
This change adds some data points during the high background
interval on days 267-270 (Sept 24-27, 2001).
See the SWEPAM Release Notes for details. Release notes
are accessable from the SWEPAM Level 2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/swepam_l2desc.html.

Aug 19, 2002: New version of CRIS level 2 data, from the CRIS team.
See the CRIS Release Notes for details. Release notes
are accessable from the CRIS Level 2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/cris_l2desc.html.

Jun 11, 2002: Release of new version of SWEPAM level 2 data for Bartels rotations
2279-2295. New data incorporate the results of the weekly on-board
instrument calibrations.
See the SWEPAM Release Notes for details. Release notes
are accessable from the SWEPAM Level 2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/swepam_l2desc.html.

Apr 18, 2002: Improved handling of data gaps in SWEPAM 64-second averages,

Mar 29, 2002: New version of CRIS level 2 data, from the CRIS team.
See the CRIS Release Notes for details. Release notes
are accessable from the CRIS Level 2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/cris_l2desc.html.

Feb 25, 2002: Improved handling of fill-data in EPAM daily and Bartels averages.

Nov 20, 2001: Improved accuracy of spacecraft position vector in GSM coordinate
system (included in MAG and SWEPAM level 2 data).

Nov 20, 2001: Release of new version of EPAM level 2 data - improved LEMS30 ion
data.
See the EPAM Release Notes for details. Release notes
are accessable from the EPAM Level 2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/epam_l2desc.html.

Oct 30, 2001: Release of new version of SEPICA level 2 data - more species and
more energy ranges.
See the SEPICA Release Notes for details. Release notes
are accessable from the SEPICA Level 2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/sepica_l2desc.html.

Jun 19, 2001: MAG data processing improved:
1. Improved filling of time-periods where no data exists from
the MAG instrument.
2. Fixed bug where first record of a day was skipped when there
were more than one maneuvers in the header of the MAG ascii data
file.
3. Modified code so that the MAG ascii data file for the day
before the beginning of a bartels rotations is scanned for
records that might fit into the rotation time-range.

Feb 6, 2001: SIS: require at least 25.5 days coverage for a valid Bartels average,
to ensure that the average includes all solar events during the
period.

Feb 3, 2001: New version of CRIS level 2 data, from the CRIS team.
See the CRIS Release Notes for details. Release notes
are accessable from the CRIS Level 2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/cris_l2desc.html.

Oct 25, 2000: Added release notes for EPAM data - these notes apply to
EPAM data for July 14 - 16, 2000.: Release notes
are accessable from the EPAM Level 2 data documentation
web page:
http://www.srl.caltech.edu/ACE/ASC/level2/epam_l2desc.html.

Oct 3, 2000: SWEPAM level 2 data reprocessed to correct some problems
with filling of data gaps and mapping record numbers to
time/date.

Sep 22, 2000: Documentation of EPAM level 2 composition data (from the
CA60 telescope) was incorrect in some places, including
headers of downloaded data. Energy ranges and intensities
were quoted in units of MeV. The correct units are MeV/nucleon.

Sep 19, 2000: New version of SWEPAM level 2 data, from the SWEPAM team.
See the SWEPAM Release Notes for details. Release notes
are accessable from the SWEPAM Level 2 data documentation
web page:
http://www.srl.caltech.edu/ACE/ASC/level2/swepam_l2desc.html.

Sep 18, 2000: Minor change to CRIS Bartels Rotation averages data processing:
livetime for a valid Bartels rotation average was lowered from
30% to 3%. This means that 3 Bartels averages that previously
contained fill-data now contain valid data.

June 2000 : New version of CRIS level 2 data, from the CRIS team.
See the CRIS Release Notes for details. Release notes
are accessable from the CRIS Level 2 data documentation web page:
http://www.srl.caltech.edu/ACE/ASC/level2/cris_l2desc.html.