Release Notes

Quality, calibration, and other issues that may affect certain time periods of the data are documented in the data anomalies & quality notes. Before using data, please check current release notes (below) and the quality notes for the period of interest.

2024-09-16 Release 20

This release extends the dataset through 2024-06-16. This includes Encounter 18 and outbound orbit 18, all of orbit 19, and some of the inbound leg of orbit 20. Pitch angle tags are provided through 2024-04-29. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-19 data if needed for comparison.

  1. No changes have been made to the processing of IS☉IS data.
  2. The IS☉IS event list has been updated through 2024-04-09 (outbound orbit 19).

2024-03-08 Release 19

This release extends the dataset through 2023-12-14. This includes Encounter 17, the outbound leg of orbit 17, and some of the inbound leg of orbit 18. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-18 data if needed for comparison.

  1. No changes have been made to the IS☉IS event list.
  2. No changes have been made to the processing of IS☉IS data.

2023-10-30 Release 18

This release extends the dataset through 2023-08-03. This includes Encounter 16 and most of the outbound leg of orbit 16. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-17 data if needed for comparison.

  1. The IS☉IS event list has been updated through the beginning of orbit 16.
  2. No changes have been made to the processing of IS☉IS data.

2023-08-28 Release 17

This release extends the dataset through 2023-06-04. This includes the rest of orbit 15, including Encounter 15, and part of the inbound leg of orbit 16. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-16 data if needed for comparison.

  1. EPI-Lo and EPI-Hi data have new variables with quality flags; these variables and their interpretation are described in the PSP/IS☉IS Data User Guide.
  2. EPI-Lo data have been updated with improved geometric factors for the "particle" SSD; this affects the calibration of the TOF-only (T) flux.

2023-05-12 Release 16

This release extends the dataset through 2023-02-09. This includes the rest of orbit 14, including Encounter 14, and part of the inbound leg of orbit 15. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-15 data if needed for comparison.

  1. Relative to release 15, pitch angle tags for the period 2022-09-22 through 2022-11-14 were added; they are included for the entire release (through 2023-02-09).
  2. To avoid an instrument overcurrent condition, EPI-Lo raised thresholds during periods of high rates. This happened on 2022-12-11 from 8:20:40 through 8:45:40. Data in look directions 40 - 59 are not science quality during this period and fluxes have been replaced with fill.

No other changes have been made to processing of the IS☉IS data. There are no updates to the IS☉IS event list.

2023-02-20 Release 15

This release extends the dataset through 2022-11-14. This includes the rest of orbit 13, including Encounter 13, and part of the inbound leg of orbit 14. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-14 data if needed for comparison.

No changes have been made to processing of the IS☉IS data.

2022-11-14 Release 14

This release extends the dataset through 2022-08-15. This includes the rest of orbit 12, including Encounter 12, and part of the inbound leg of orbit 13. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-13 data if needed for comparison.

  1. EPI-Lo livetime calculations have been updated to better account for quadrant-specific deadtime effects. This will have little effect on fluxes averaged over all apertures; however, quadrant 1 (look directions 20-39) fluxes and count rates may be increased with a smaller decrease in all other quadrants. This effect is most pronounced for high-rate periods and may reach a 50% effect in quadrant 1.
  2. EPI-Lo underwent two tests characterizing instrument performance leading up to and during the first portion of encounter 12. During these tests, the data is quadrant 1 are not entirely of science quality. The fluxes have been replaced with fill values and count rates should not be used. Tests were run 2022-05-24T16:13:09 through 2022-05-29T16:13:09 and 2022-05-30T11:50:08 through 2022-06-04T11:50:08. Future work may recover some quadrant 1 science data from this period.

No changes have been made to processing of the EPI-Hi data.

2022-08-01 Release 13

This release extends the dataset through 2022-04-29. This includes the rest of orbit 11, including Encounter 11, and part of the inbound leg of orbit 12. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-12 data if needed for comparison.

  1. Pitch angles are included for all times where FIELDS data are available, including times omitted in release 12.
  2. EPI-Lo calibrations have been updated for apertures with thick entrance foils (L23, L30-L33, L40). The energy binning for these look directions is substantially different from others, particularly at lower energies, and care should be used when combining data from multiple look directions.

2022-04-25 Release 12

This release extends the dataset through 2022-01-23. This includes the rest of orbit 10, including Encounter 10, and part of the inbound leg of orbit 11. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-11 data if needed for comparison.

The following changes and caveats apply to both EPI-Hi and EPI-Lo data, or to IS☉IS suite products:

  1. H_CountRate_ChanT-related variables have been removed from the psp_isois_l2-summary files, as these time-of-flight only rates contain substantial background. They have been replaced with H_CountRate_ChanP-derived varaibles, containing protrons with a triple coincidence (TOFxE) requirement. These contain all look directions and a similar energy range to the previous ChanT variables. As a reminder, these summary files are intended to support high-level surveys for periods of interest and should not be used for science analysis.
  2. Pitch angles are not available after 2021-12-31.

The following changes and caveats apply only to EPI-Hi:

  1. Calibrations for high rate operational modes have been updated. HET calibrations H and He for dynamic threshold mode 1 have been updated; initial LET calibrations are included for H and He in dynamic threshold mode 1.
  2. HET calibrations for H and He in dynamic threshold mode 0 (the normal mode for the lowest count rates) have been updated to account for the non-flat response of the instrument.
  3. Processing of the data at EPI-Hi dynamic threshold changes has been updated to ensure proper timing of the transition.

No changes have been made to processing of the EPI-Lo data.

2022-02-07 Release 11

This release extends the dataset through 2021-11-04. This includes the rest of orbit 9, including Encounter 9, and part of the inbound leg of orbit 10, including Venus flyby 5. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-10 data if needed for comparison.

No changes have been made to the processing of the EPI-Hi data; caveats remain the same. The following updates have been made to EPI-Lo data.

  1. Updated EPI-Lo energy channel assignments and efficiencies for all species and energies before 14 June 2021, reflecting the imprecise on-board energy normalization that was in use at that time. The resulting energies are much more strongly dependent on look direction.
  2. Minor updates to the calculation of EPI-Lo livetimes, resulting in flux increases of order 1% in some circumstances.
  3. Corrected EPI-Lo energy assignments for electron channels after 14 June 2021 (release 10 erroneously used development tables which were not uploaded).

2021-10-26 Release 10

This release extends the dataset through 2021-07-24. This includes all of orbit 8, including Encounter 8, and part of the inbound leg of orbit 9. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-9 data if needed for comparison.

No changes have been made to the processing of the data; caveats remain the same.

  1. EPI-Lo species identification tables were updated on 2021-06-14. Ion composition (IC) files after this day will have records populated in the N and Ne count rate variables added in release 9.

2021-09-20 Release 9

This release contains data quality enhancements only and ends on 2021-03-27. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-8 data if needed for comparison.

  1. EPI-Hi processing and calibrations have been improved for high rate periods, the most notable of which to date is the large event of 2020-11-30 through 2020-12-02.
    • Count rates and fluxes are corrected to account for the fraction of particle detections which are not fully processed by the flight software. This is described in more detail in the data user guide.
    • Calibrations for high rate operational modes have been updated. HET calibrations for dynamic threshold mode 1 are those used by Cohen et al. (2021, doi:10.1051/0004-6361/202140967). HET modes 2 and 3, and all high rate modes of LET1 and LET2, do not have mature calibrations at this time, so fluxes are not reported for the high rate modes.
  2. Minor adjustments to EPI-Lo telemetry processing may result in slightly higher (of order one percent) count rates and fluxes during active times.
  3. EPI-Lo ion composition (IC) files have new count rate variables for N and Ne, in anticipation of refined tracks for these species. These variables contain no records until the refined tracks are implemented on-orbit.
  4. Due to ongoing dust effects, several more look directions are excluded from the look-averaged TOF-only products in the summary file. The complete list is now 21, 24-29, 31, 34, 35, and 39.

2021-06-28 Release 8

This release extends the dataset through 2021-03-27. This includes Encounter 7 and the rest of orbit 7. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-7 data if needed for comparison.

  1. The large event of 2020-11-30 through 2020-12-02 was the first event of the mission where EPI-Hi switched into operational modes for handling high rates. These modes have not been fully calibrated: count rate and flux data for this period should not be used without consulting the EPI-Hi team.

2021-04-05 Release 7

This release extends the dataset through 2021-01-04. This includes Encounter 6 and the rest of orbit 6. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-6 data if needed for comparison.

  1. EPI-Hi LET electron count rate variables are now included. These match the naming scheme for the HET electron variables, e.g. A_Electrons_Rate is the count rate for electrons in LET1-A.
  2. Most quantities that are included as a count rate are now also reported as counts per integration, for those interested in performing their own statistical analysis. These variables have descriptions with simply "counts", units of "counts", and variable names with "Counts" or no specific notation. Examples are A_H for EPI-Hi A-side protons or H_Counts_ChanP for EPI-Lo triple-coincidence protons. Count rate variables have "Rate" or "CountRate" in the name, "count rate" in the description, and units of "counts/s". Examples A_H_Rate; H_CountRate_ChanP. Count rates are properly corrected for instrument livetime; counts are not.
  3. EPI-Lo calibrations were updated based on observations from the large event of 29 November 2020. This is not the final calibration that will result from that event, but it is significant enough of an improvement that we are releasing it now.
    • Updated efficiencies were calculated for H, He, O, and Fe. These incorporate contributions from grid transmission fraction, scattering, and MCP detection efficiency. Updates primarily affect the ion composition triple coincidence channels P and C. The ion composition TOF-only channel T was corrected based on the updated channel P values.
    • Updated instrument geometric factors were calculated, including large-scale instrument geometry, not finer corrections such as grid transmission. Flat fielding corrections were calculated from a period of high isotropy (November 30, 2020 19:00 to December 1, 2020 02:00)
  4. Due to a dust impact on 2020-12-30 between 02:00 and 07:00Z (while EPI-Lo was off), look direction 35 of the EPI-Lo TOF-only products (channel T) is highly susceptible to UV photon contamination after this time. Release 7 removed calibrated fluxes for this look direction after this time. This look direction was excluded from look-averaged TOF-only products starting in release 3.
  5. The large event of 2020-11-30 through 2020-12-02 was the first event of the mission where EPI-Hi switched into operational modes for handling high rates. These modes have not been fully calibrated: count rate and flux data for this period should not be used without consulting the EPI-Hi team.

2020-11-16 Release 6

This release extends the dataset through 2020-08-13. This includes Encounter 5 and the rest of orbit 5. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-5 data if needed for comparison.

  1. Data may include brief periods of counts generated internally to the instrument for calibration purposes. These will be filtered in a future release and are noted in the Data Anomalies & Quality list.
  2. Pitch angles for the periods 2019 Jan through Aug and 2020 Jan through Feb were added for this release.

2020-09-24 Release 5

This release includes data through 2020-04-29, with no additional dates since release 4. This includes Encounter 4 and the rest of orbit 4. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-4 data if needed for comparison.

  1. Release 4 was made using the EPI-Lo calibration data from release 2; release 5 uses the latest calibration data. This results in small (a few percent) changes in energy channels and fluxes throughout the mission, similar to release 3.
  2. Release 4 also included fluxes for look direction 31 of the time-of-flight products after the dust impact on 2019-04-03; these fluxes are largely from UV photon contamination and should not be used. They are properly filtered from release 5.
  3. EPI-Hi data are the same as release 4, but the files are reproduced in release 5 to avoid confusion.
  4. Suitewide summary data are largely the same as release 4, but may have small changes in energy channels in the variables related to EPI-Lo.

2020-08-04 Release 4

This release extends the dataset through 2020-04-29. This includes Encounter 4 and the rest of orbit 4. Files included cover the entire mission; thus this release supersedes all previous releases. Contact the SOC for access to release 1-3 data if needed for comparison.

  1. The EPI-Hi instrument was off for operational reasons from 2019-10-07 through 2020-02-12.
  2. Due to a dust impact on 2019-04-03 around 16:45Z, look direction 31 of the EPI-Lo TOF-only products (channel T) is highly susceptible to UV photon contamination after this time (see doi:10.3847/1538-4365/ab643d). Release 3 removed calibrated fluxes for this look direction after this time. In release 4, L31 is also excluded from count rate products that are summed over look direction. This includes H_CountRate_ChanT_SP in psp_isois_l2-summary and related quicklook plots. This exclusion is for all time, so that rates before and after the dust impact can be compared. Look directions 34 and 35, although they retain intact foils, can also be heavily contaminated by UV and are excluded from summed count rate products as well.
  3. During the EPI-Lo high voltage ramp-up immediately after turn-on (approximately 15 minutes), count rates and fluxes are not accurate measurements of the incident population. These periods have been filtered out from the flux and count rate variables.
  4. All pitch angle variables now have a corresponding "spiral angle" variable, containing the angle the particle flow direction makes with the outward nominal Parker Spiral. "Nominal" is defined as 400km/s solar wind speed with corotation breakdown at 10Rs. For EPI-Lo, these variables are named like SA_ChanX; for EPI-Hi, names are similar to LET1_A_SA and LET1_A_R1_SECT_SA (for non-sectored and sectored rates, respectively.)
  5. Many small metadata updates have been made for greater clarity; variable names remain the same.
    • EPI-Hi energy unit labeling is consistent (MeV/nuc for ions heavier than protons; MeV for all else) and all energy labels have consistent formatting.

2020-04-14 Release 3

This release extends the dataset through 2020-01-06. This includes the end of Orbit 3 and beginning of Orbit 4, including Venus Flyby 2, but with no new encounter data. Files included cover the entire mission; thus it supersedes previous releases. Contact the SOC for access to release 1 and 2 data if needed for comparison.

  1. Much of the CDF metadata has been updated to provide better descriptions and make data easier to find. In particular, pitch angle and related pointing data are tagged as data rather than support_data to make them more visible in many tools. Variable names have not been changed.
  2. Updated calibration tables for EPI-Lo have been applied. This results in small (a few percent) changes in energy channels and fluxes throughout the mission.

2020-01-27 Release 2

This release extends the dataset through 2019-10-10 (after third encounter). Files included cover the entire mission; thus it supersedes release 1. Contact the SOC for access to release 1 data if needed for comparison.

  1. Pitch angles for 2019 use updated FIELDS calibrations. The 2018 pitch angles have not changed from release 1, as FIELDS calibrations from 2018 required no updating.
  2. The summary product (psp_isois_l2-summary) includes a new variable, A_Heavy_Rate_TS. This is a total heavy-ion count rate from the EPI-Hi LET1A telescope.

2019-11-15 Release 1

Proper analysis of this first release of the data requires knowledge of several caveats and possible instrumental effects.

  1. Pitch angles are using preliminary calibrations from the FIELDS magnetic field instrument. This may result in errors in pitch angle determination up to about 1.5 degrees.
  2. EPI-Hi and EPI-Lo data use different units for energies and thus for fluxes. EPI-Hi data are reported MeV for protons and electrons, and MeV/nuc for heavy ions. EPI-Lo uses keV for all species except for time-of-flight only data, which uses keV/nuc. These differences are important when combiningdata across the two sensors.
  3. Ions heavier than helium and electrons are likely to have substantial background, including from other species, and are thus provided as count rates only until commissioning of these species can be completed for inclusion in a future release.
  4. EPI-Hi data below approximately 2MeV may be subject to instrumental effects that are currently being quantified. At these energies, the incident energy may be under reported by as much as 10% and the flux may be underreported by as much as 30%.
  5. EPI-Hi hourly (3600) data is compiled on the hour according to the spacecraft clock. The first integration after turn-on may be substantially shorter than an hour depending on when turn-on occurred. This may result in poor counting statistics from a short integration and unrealistic spectra for this first integration. The same effect is present, but less apparent, for the first integration of shorter periods.
  6. Spacecraft position is provided for every timebase in a file. Position is in HCI (variable names starting with HCI_R, HCI_Lat, HCI_Lon for each timebase) and HGC (names starting with HGC_R, HGC_Lat, HGC_Lon). Particle flow direction for each look direction is provided as unit vectors in HCI and RTN, as well as pitch angle, also on every timebase; variable names start with HCI, RTN, and PA.