Release Notes for Level 2 SIS processing C.M.S. Cohen Time periods to use with some caution (updated: July 3, 2025): -----START----- -----STOP------ Year Mnth/Day DOY HR Mnth/Day DOY HR Note (see below for more details) ---------------------------------------------------------------------------------- 1997 11/07 311 16 11/11 315 16 thresholds raised on some stack detectors 1998 04/21 111 15 04/25 115 16 thresholds raised on all stack detectors 1998 08/25 237 16 08/27 237 17 thresholds raised on some stack detectors 2000 07/14 196 11 07/15 197 19 livetime < 10% 2000 07/14 196 16 07/18 200 19 thresholds raised on all stack detectors 2000 11/09 314 00 11/13 318 17 livetime < 10% 2001 04/03 093 06 04/03 093 07 livetime < 10% 2001 09/24 267 20 09/26 269 12 livetime < 10% 2001 10/02 275 06 10/02 275 08 livetime < 10% 2001 11/05 309 01 11/06 310 12 livetime < 10% 2001 11/23 327 06 11/24 328 15 livetime < 10% 2002 04/21 111 07 04/22 112 07 livetime < 10% 2003 10/28 301 13 10/30 303 21 livetime < 10% 2003 11/02 306 20 11/03 307 22 livetime < 10% 2003 12/04 338 06 12/04 338 08 livetime < 10% 2005 01/17 017 15 01/18 018 11 livetime < 10% 2005 01/20 020 06 01/20 020 16 livetime < 10% 2005 05/15 135 00 05/15 135 05 livetime < 10% 2005 09/10 253 09 09/12 255 22 livetime < 10% 2005 10/13 286 16 10/13 286 17 livetime < 10% 2005 11/02 306 16 11/02 306 18 livetime < 10% 2005 11/09 313 16 11/09 313 17 livetime < 10% 2006 12/07 341 15 12/08 342 06 livetime < 10% 2012 01/23 023 09 01/27 027 21 livetime < 10% 2024 01/04 004 00 01/11 011 00 livetime < 10% (times are approximate) 2024 10/09 283 00 10/11 285 00 livetime < 10% (times are approximate) 2024 10/20 294 00 11/15 320 00 livetime < 10% (times are approximate) 2024 11/19 324 00 12/31 366 24 livetime < 10% (times are approximate) 2025 01/01 001 00 03/12 071 00 livetime < 10-20% (times are approximate) 2025 03/31 090 12 04/02 092 00 livetime < 10-20% (times are approximate) 2025 06/01 152 00 06/02 153 00 livetime < 10-20% (times are approximate) November 13, 2025 cmsc As we continue to adjust the routine analysis of the SIS data, accounting for noisy and off strips, we have found that intensities from the two SIS telescopes differ by about 25-30% since approximately December 2024. We have yet to determine the source of this discrepancy, but it appears not to be element or energy dependent. The level 2 SIS data are an average of the two telescopes (for all elements except He), so we suggest users consider the systematic uncertainty in the level 2 intensities to be ~15% since late 2024. July 3, 2025 cmsc We continue to monitor the matrix strips affected by high temperatures. Ground processing has been updated to ignore the noisiest of the strips and data for rotations 2606 and beyond have been reprocessed. There remain time periods where the livetime was extremely low (see table above) and the data are very uncertain during these times. We are still investigating further possible corrections to the intensity calculations (particularly reduced geometry factor due to noisy and off strips). Currently we assess that the intensities are accurate to ~20% for rotations 2606 and beyond. For rotations 2607 and 2608, unfortunately the data are still problematic and require more analysis to recover useful data. While we continue this effort these rotations have fill data for all the intensities and time integrations. December 19, 2024 cmsc SIS continues to age and is affected by increasing temperatures (particularly in the winter months) which cause increased noise on the matrix strips. Additional low livetime periods have been added to the table above. Routine processing for the intensities has been altered to correct for this up to (and including) rotation 2606. The team is investigating the cause of the increased noise in the remaining rotations to make better corrections. These rotations will be released once those corrections are detemined and included in the processing. It should be noted that the effect of the low livetime/noisy strips is not possible to correct in either the browse or the real time (RTSW at SWPC) data, so related artifacts in those data will remain. Of course, those data should not be used for science in any case. January 11, 2024 cmsc As SIS ages, more matrix strips are susceptible to being noisy. The team is currently investigating a time period where there is an unusually large number of strips that are occasionally noisy. The effect on the data appears to be minimal, with primarily ranges 6 and 7 of carbon and nitrogen being affected at the ~20% level. This period (Jan 6, 2024 to present) has been added to the list above. September 27, 2017 cmsc In reviewing the level 2 data for rotation 2511 (August 26 - September 22), a discrepancy was noticed between the two SIS telescopes in the rotation-averaged intensities for ranges 6 and 7. The disagreements is ~10-30% for most elements C-Fe. The SIS team is investigating possible causes. In the meantime users are advised to consider the reported range 6 and 7 intensities during the SEP events of Sept 5-17 to be uncertain by ~20% (regardless of small statistical uncertainty indicated by the number of counts reported in the level 2 data). January 27, 2016 cmsc The number of matrix strips with raised thresholds is limited to 20 for each telescope. The number of strips requiring increased thresholds now exceeds this value for both telescopes and necessitates an increase in the overall M1 matrix detector threshold. The current values are set at 1.9 and 2.6 MeV for the A and B telescopes, respectively. The small M1 pulse heights for deep range He fall below these thresholds, resulting in significantly reduced efficiency for ranges 5, 6 and 7. From DOY 348 (12/14) 2015 onwards these ranges for He will be set to fill data. Ranges 0-4 for He and all ranges for C-Ni are unaffected. Version 2.4 July 9, 2014 cmsc The SIS level 2 data were reprocessed from the start of mission to present to include a better calculation of the time-dependent geometry factor and a data cut to eliminate chance-coincidence events resulting from disabled strips. This update has changed the hourly level 2 intensities by typically less than 10% (or by less than 1 sigma, based on the statistical uncertainties). An exception is DOYs 341-343 of 2006 during which the heavy ion intensities for ranges > 2 are reduced by ~15%. February 24, 2012 cmsc During time periods of extremely low livetime, the SIS on-board processing gives priority to analyzing and telemetering higher-energy, Z>=6 ions. During such times the efficiency corrections for He and low-energy heavy ions are substantial and the raw counts can be quite low. Users are cautioned that high-time resolution (e.g., 256 sec) intensities during such time periods may be very uncertain and are encouraged to use a lower-time resolution (e.g., 1 hour) products when the raw counts for the species of interest are low (raw counts are available through the level 2 data). Below is a listing of time periods during which the SIS livetime was below 10% of nominal. Users should be aware that the effect on He intensities can last longer than the effect on heavier ions and so should be cautious using 256-sec He data a few hours before and after the time periods listed below. START STOP Year DOY HR DOY HR 2000 196 11 197 19 2000 314 0 318 17 2001 93 6 93 7 2001 267 20 269 12 2001 275 6 275 8 2001 309 1 310 12 2001 327 6 328 15 2002 111 7 112 7 2002 143 10 143 10 2003 301 13 303 21 2003 306 20 307 22 2003 338 6 338 8 2004 208 22 208 22 2005 17 15 18 11 2005 20 6 20 16 2005 135 0 135 5 2005 253 9 255 22 2005 286 16 286 17 2005 306 16 306 18 2005 313 16 313 17 2005 349 16 349 16 2006 341 15 342 6 2012 23 9 27 21 Version 2.3 October 25, 2010 cmsc 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. The difference in the particle counts with the new and old cuts for an integrated quiet time period of 4/19/09 through 11/20/09 for the level 2 range 7 elements is given in the following table: Z old cnts new cnts new/old ----------------------------------------------------- 6.00000 4228 4077 0.964286 7.00000 1114 1074 0.964093 8.00000 5451 5410 0.992478 10.0000 869 857 0.986191 11.0000 239 157 0.656904 12.0000 1627 1415 0.869699 13.0000 283 215 0.759717 14.0000 1251 1184 0.946443 16.0000 210 171 0.814286 18.0000 159 91 0.572327 20.0000 391 189 0.483376 26.0000 1270 1250 0.984252 28.0000 64 63 0.984375 The effect on periods integrated over an SEP event are still being evaluated but are estimated to be below 5% for all level 2 elements. Please note that the new cuts affect Range 7 intensities only (no changes have been made to the other ranges). All the data from mission start to date were reprocessed with the new Range 7 cut. Version 2.2 March 22, 2010 cmsc 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. Version 2.1 June 6, 2008 cmsc The largest change to the level 2 analysis is the addition of more elements. We have added intensities for Na, Al, Ar, Ca, and Ni. It should be noted that for Na (and potentially Al) the intensities during large SEP events maybe more uncertain due to spill over from the neighboring abundant elements. Although we have not corrected the Na intensities on a case by case basis (which would have to be done by hand), the uncertainty in the absolute intensities should be <20% during high rate periods. It was determined that the detection efficiency for small pulse heights in one of the matrix detectors of the B telescope has fallen significantly since 2005. This primarily affects long range He. We have reprocess the data from 4 January 2005 onwards (Bartels rotations 2340 and beyond) to make use of only data from telescope A for calculating the He intensities. This effect is not a concern for the heavier elements so that processing has remained unchanged. A few minor changes in the analysis code have been made. One deals with the handling of noisy strips. These strips are ignored when a better alternative exists for the analysis. Unfortunately, the code was not set up to handle a list of noisy strips that was not in strip number order or to account for reactivated off strips. The code has been updated to correctly handle these situations. A second item is that the code has been updated to automatically calculate the revise geometry factor based on the current listing of off strips. Version 2.0 April 18, 2007 cmsc Major upgrade (including a new major program) of the level 2 processing has been done. The previous level 2 program (level2_flux.pro) is no longer being used. The required program and subroutines are given below. The largest change in the processing will be evident in the range 0 intensities. This is primarily due to a new analysis check which removes events that penetrated deeper in the instrument but were incorrectly tagged as range 0 events due to incomplete collection of the deeper range pulse heights. The upgraded analysis will result in lower range 0 intensities in general. Another large change is evident in the range 7 He intensities. This is due to a reanalysis of the trigger levels required for deep range He. The upgraded analysis will result in higher range 7 He intensities in some time periods (particularly quiet times). A listing of the current analysis checks and cuts is given below. For reasons of brevity the descriptions are terse, but feel free to contact Christina Cohen (cohen@srl.caltech.edu) for a more complete description/ explanation. We remind users that effects due to low livetime conditions are still present in the data. When particle intensities are very high (generally when the >10 MeV Proton rate exceeds ~2000 (cm^2-sr-sec)^-1) large corrections for low instrument livetime and pileup are somewhat uncertain. This may result in the reported absolute intensities to be low (by an amount that is undetermined at the moment, but probably less than a factor of 10). Since all the Z >= 6 intensity calculations involve the same livetime, the relative intensities of the heavy ions should be reasonably accurate even during these high rate periods. Users of daily and Bartel rotation averaged files should be aware of the limitations of calculating uncertainties based on the square root of the reported number of particles (i.e., counts). For averages that include time periods of very low livetime, the average intensities may be dominated by counts accumulated during the those low livetime portions. Since the counts are typically low during these periods, the uncertainty of the corresponding intensity is high. This should be taken into account when calculating uncertainties for the full time-average period, but will not be if the user calculates uncertainties based on sqrt(counts). We encourage users to examine the intensities and counts for a higher time resolution product during such instances to correctly assess the uncertainties. Current analysis checks/cuts (new items are indicated by *): - removes stim events - corrects geometry factor for 15 off strips (through 2002 1/21) - includes a patch for noisy strips (ignores strips considered to be noisy - time dependent) - removes out of geometry events - requires He events to be in buffers <= 60 - requires HIZ events to be in buffers > 60 - corrects for priority system and livetime -*corrects range based on low pha energies before stopping detector (ranges 3-7, not for He) -*cuts based on time to peak -*uses better gains and offsets for matrix energy calculations -*adds neighboring matrix strips together -*uses better matrix thickness maps -*cuts based on consistency between ground and high voltage sides of detectors -*better cuts based on Z consistency -*He R7 uses T4 for dE in one of the Z calculations rather than T1 -*cut based on coincidence with He for range 0 HIZ events -*cut based on consistency between energy deposited in stack and matrix detectors -*cut requiring range 0 HIZ events to have a minimum energy deposited in M2 -*cut requiring trajectory to land inside both matrix detectors - buffer rate spike filter applied - changes range 0 He data by factor of 1.6 and zeros out range 1 He data prior to 1998 1/28 22:40 due to thresholds - livetime includes correction for timing window Processing prior to ASC processing: Primary Program: make_level2.pro Language: IDL Required Subroutines: read_calcfile, read_calcfile_HHe, fluxcalc, various standard ACEware routines Run on files: *.HIZ and *.HHe, created by make_calcfiles* which runs read_datafile_se1_pro these files are stored in 10 day increments on /home/idunn1/cohen/ Program: level2_flux.pro Language: IDL Required Subroutines: pha_livetime.pro, various ACEware routines Version 1.6 November 17, 2005 cmsc Code has been added to the level 2 processing to ignore signals from known noisy strips on the matrix detectors. This should improve the trajectory calculations and subsequently the elemental resolution leading to more accurate intensities. The effect was most noticable for Bartel rotations 2349 and 2350. These have been reprocessed. Version 1.5 January 22, 2002 cmsc Data from several big events (most notably the July 14, 2000 and November 9, 2000 events) have been added to the level 2 dataset. During the highest-rate portions of these events (see below), large corrections are necessary for pileup and instrument livetime which are somewhat uncertain. The resulting reported absolute intensities near the peaks of these events are probably low and for the singles rates (such as the >10 MeV Proton rate) can be uncertain by as much as a factor of 10. It is expected that the heavy ion (Z >= 6) intensities will be uncertain by a smaller factor but the precise amount is unknown at this time. Since all Z >= 6 intensity calculations involve the same livetime, the relative intensities during these events should be reasonably accurate. In general, these livetime issues are a concern when the >10 MeV Proton rate exceeds ~2000 (cm^2-sr-sec)^-1. High-rate, suspect periods: 2000 7/14 12:00 - 7/14 16:00 (when thresholds were changed) 2000 11/9 00:00 - 11/10 00:00 2001 11/5 16:00 - 11/6 08:00 2001 11/23 12:00 - 11/24 16:00 Users are further cautioned that during the November 9, 2000 event there was a noisy strip on SIS that drove the livetime down precipitously. This resulted in a substantially reduced number of good events being telemetered. Users will see the effects of this most strongly in the scant Fe counts during the peak of this event. Version 1.5 January 1, 2001 cmsc A new formula for the event livetime was determined that is more accurate than the simple instrument reported livetime during time periods when the livetime is very low. This correction results in more accurate intensities of all heavy ions during several big events. Bartel rotations during which these events occurred were reprocessed: 2283 2275 2257 2256 2254 2253 2249 2243 Version 1.3 October 12, 1999 cmsc It was determined that long range He often may not trigger the T1 detector causing the event to be thrown out by the current z consistency cuts. This caused range 7 He fluxes to be artificially low. One of the two consistency cuts for He was eliminated and resulted in an approximate increase in the range 7 flux by a factor of 2. It has also been observed that in time periods during which the detector thresholds were changed (during 3 large solar events) the low Z, high range fluxes are artifically low. This is probably due to failure of events to trigger the T1 detector and and being thrown out by one of the consistency checks. No correction has been made and the user is cautioned about low fluxes in the high ranges for low Z elements appearing during the following time periods: 97/11/07 16:00 - 97/11/11 16:30 98/04/21 15:10 - 98/04/25 16:05 98/08/25 16:40 - 98/08/27 16:55 Quiet time selection is being made by the ACE Science Center. Examination of the quiet time data indicates there the low range He data are not entirely quiet. Since tightening the quiet time criterion may eliminate quiet time heavy ion data, we have chosen not to change the criterion but suggest that users be aware that quiet time low range He may still contain some solar activity. Version 1.2 September 10, 1999 cmsc Better z consistency cuts were determined. This will increase the flux levels at the high ranges (6 and 7) by about ~10% for CNO, by about ~5% for Ne, Mg and less than 1% for Si-Fe. Currently we suggest a 5% systematic error be added to all the flux uncertainties. In comparing the range 7 data with range 2 data from CRIS we have found an ~10% discrepancy. We will continue our efforts to determine the cause of the discrepancy and correct it, but currently take it as a measure of how accurately we know the absolute flux levels. Headers on the files were changed to tabulate the new Z consistency cuts (which are now a function of Z, range and which Z estimates are being compared - there are 2 comparisons being made). See program for a complete listing of the zcut boundaries. ** All data were reprocessed as of September 10, 1999 ** Version 1.1 August 13, 1999 cmsc Better nominal geometry factors were obtained. The following are now used: GF for He: GF for C-Fe: Range 0 = 42.8 Range 0 = 42.8 Range 1 = 42.8 Range 1 = 42.8 Range 2 = 41.2 Range 2 = 41.4 Range 3 = 41.2 Range 3 = 41.2 Range 4 = 39.0 Range 4 = 39.0 Range 5 = 37.6 Range 5 = 37.6 Range 6 = 32.2 Range 6 = 32.2 Range 7 = 24.6 Range 7 = 24.6 Note: the entry on Jun 29, 1999 regarding actual geometry factors used still applies, i.e., these nominal geometry factors listed above are reduced to account for disabled matrix strips when fluxes are calculated. Instead of providing errors in the flux for each range we are now providing the raw number of counts in each range. ** All data were reprocessed as of August 13, 1999 ** August 5, 1999 cmsc On Jan 28, 1998 at 22:40 UT the matrix thresholds on SIS were lowered. This resulted in a change in the SIS efficiency in measuring He fluxes which predominantly affects the range 0 and 1 data. In order to make the He data prior to the threshold change available and useful to the community we have made the following modifications to the data. For data prior to Jan 28, 1998 22:40 UT -- He range 1 is not given, the data in the files is fill data. He range 0 has been increased by a factor of 1.6 which corresponds to our best estimate of the efficiency reduction related to the higher matrix thresholds The quiet time flag is calculated using the average of the He range 0 and 2 fluxes (rather than the average of the He range 0, 1, and 2 fluxes) For data after Jan 28, 1998 22:40 UT -- He fluxes for all ranges are given. The quiet time flag is based on the average of the He range 0, 1, and 2 fluxes. On Feb 10, 1998 at 18:26 UT the H and He timers were altered which affects the amount of H and He livetime. When examining the He data at maximum resolution (256 seconds), the difference in livetime results in a factor of 2.4 increase in the minimum detectable He fluxes (i.e., the single count level) for all ranges. When averaged over a longer time interval (1 hour or greater) it becomes clear that the actual measured flux value is unchanged by the timer command. ** He data for the affected rotations (2241-2246) were reprocessed as of August 6, 1999 ** Version 1.0 June 29, 1999 cmsc A filter to search for and eliminate spikes in the rate data (used to convert to flux) was added to the pha_livetime.pro subroutine. The algorithm for identifying spike is to compare each point to its 2 non-zero neighbors (one on each side) and if the point is greater (less) than a factor of 50 higher (lower) than both neighboring points the point is labeled as a spike. The corresponding flux data for the entire 256 second period is zeroed out (regardless of Z). A filter to identify spikes in the calculated flux due to HIZ Z events tagged with a buffer ID corresponding to He or H was added to the level2_flux.pro program. The bad data were identified by requiring all events with Z > 5 to have buffer ids < 60. The geometry factors were altered to reflect the fact that at launch 2 strips (of 64) were off on detector M1B. After 1997 Dec 8 (day 342) 17:42 UT, 4 additional strips on M1B were turned off. The nominal geometry factors assumed identical telescopes (i.e., gf(tel A) = gf(tel B)). The correction made was to multiply the nominal geometry factor of telescope B by a factor of 62/64 from launch to day 342 17:42 UT and by a factor of 58/64 for times after day 342 17:42 UT. ** All data were reprocessed as of August 3, 1999 ** Version 0.1 Original program outputs 256-second data for a given Z range (corresponding to one element) for all 8 instrument ranges. 1 file is created for each element. Data are in flux units. Uncertainties are fractional uncertainties and based on statistical uncertainties only (i.e., 1/sqrt(N)). Currently range 8 flux and uncertainties are set to 0. Nominal geometry factors and energy intervals are used: GF for He: GF for C-Fe: Range 0 = 41.4 Range 0 = 38.4 Range 1 = 41.4 Range 1 = 38.4 Range 2 = 41.4 Range 2 = 37.5 Range 3 = 40.3 Range 3 = 36.7 Range 4 = 38.4 Range 4 = 34.4 Range 5 = 37.0 Range 5 = 33.1 Range 6 = 31.8 Range 6 = 27.2 Range 7 = 24.5 Range 7 = 19.4 (See program for nominal energy intervals) Very loose z consistency cuts are made to the data. Z1/Z0 and Z2/Z0 are required to be 1.0 +- 0.03, where Z0 is Z calculated using dE = sum of all previous detectors, E' = stopping detector, Z1 is Z calculated using dE = M1 detector, E' = sum of all following detectors, and Z2 is Z calculated using dE = next to last detector, E' = stopping detector.