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.

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.