Processing for a lo/l1b/goodtimes product

imap_processing/cdf/config/imap_lo_l1b_variable_attrs.yaml

@@ -171,3 +171,135 @@ count_per_bin:
   LABLAXIS: Sample Count
   DEPEND_0: epoch
   DEPEND_1: spin_angle
+
+pivot:
+  CATDESC: Pivot angle derived from housekeeping data
+  FIELDNAM: Pivot Angle
+  FORMAT: F8.3
+  FILLVAL: -1.0000000E+31
+  VALIDMIN: 0.0
+  VALIDMAX: 180.0
+  VAR_TYPE: support_data
+  UNITS: deg
+  LABLAXIS: Pivot Angle
+
+pivot_de:
+  CATDESC: Pivot angle derived from direct event data
+  FIELDNAM: Pivot Angle (DE)
+  FORMAT: F8.3
+  FILLVAL: -1.0000000E+31
+  VALIDMIN: 0.0
+  VALIDMAX: 180.0
+  VAR_TYPE: support_data
+  UNITS: deg
+  LABLAXIS: Pivot Angle DE
+
+gt_start_met:
+  <<: *default
+  CATDESC: Good time interval start in Mission Elapsed Time
+  FIELDNAM: Good Time Start MET
+  FORMAT: F19.3
+  FILLVAL: -1.0000000E+31
+  VALIDMAX: 1.0000000E+31
+  VAR_TYPE: support_data
+  UNITS: s
+  LABLAXIS: GT Start
+
+gt_end_met:
+  <<: *default
+  CATDESC: Good time interval end in Mission Elapsed Time
+  FIELDNAM: Good Time End MET
+  FORMAT: F19.3
+  FILLVAL: -1.0000000E+31
+  VALIDMAX: 1.0000000E+31
+  VAR_TYPE: support_data
+  UNITS: s
+  LABLAXIS: GT End
+
+h_background_rates:
+  CATDESC: Hydrogen background rates per ESA level
+  FIELDNAM: H Background Rates
+  FORMAT: F12.6
+  FILLVAL: -1.0000000E+31
+  VALIDMIN: 0.0
+  VALIDMAX: 1.0000000E+31
+  VAR_TYPE: data
+  UNITS: counts/s
+  LABLAXIS: H BG Rate
+
+h_background_variance:
+  CATDESC: Hydrogen background rate variance per ESA level
+  FIELDNAM: H Background Variance
+  FORMAT: F12.6
+  FILLVAL: -1.0000000E+31
+  VALIDMIN: 0.0
+  VALIDMAX: 1.0000000E+31
+  VAR_TYPE: data
+  UNITS: (counts/s)^2
+  LABLAXIS: H BG Variance
+
+h_synthetic_floor:
+  CATDESC: Hydrogen synthetic background floor
+  FIELDNAM: H Synthetic Floor
+  FORMAT: F12.6
+  FILLVAL: -1.0000000E+31
+  VALIDMIN: 0.0
+  VALIDMAX: 1.0000000E+31
+  VAR_TYPE: support_data
+  UNITS: counts/s
+  LABLAXIS: H Synthetic Floor
+
+h_proxy_floor:
+  CATDESC: Hydrogen proxy background floor
+  FIELDNAM: H Proxy Floor
+  FORMAT: F12.6
+  FILLVAL: -1.0000000E+31
+  VALIDMIN: 0.0
+  VALIDMAX: 1.0000000E+31
+  VAR_TYPE: support_data
+  UNITS: counts/s
+  LABLAXIS: H Proxy Floor
+
+o_background_rates:
+  CATDESC: Oxygen background rates per ESA level
+  FIELDNAM: O Background Rates
+  FORMAT: F12.6
+  FILLVAL: -1.0000000E+31
+  VALIDMIN: 0.0
+  VALIDMAX: 1.0000000E+31
+  VAR_TYPE: data
+  UNITS: counts/s
+  LABLAXIS: O BG Rate
+
+o_background_variance:
+  CATDESC: Oxygen background rate variance per ESA level
+  FIELDNAM: O Background Variance
+  FORMAT: F12.6
+  FILLVAL: -1.0000000E+31
+  VALIDMIN: 0.0
+  VALIDMAX: 1.0000000E+31
+  VAR_TYPE: data
+  UNITS: (counts/s)^2
+  LABLAXIS: O BG Variance
+
+o_synthetic_floor:
+  CATDESC: Oxygen synthetic background floor
+  FIELDNAM: O Synthetic Floor
+  FORMAT: F12.6
+  FILLVAL: -1.0000000E+31
+  VALIDMIN: 0.0
+  VALIDMAX: 1.0000000E+31
+  VAR_TYPE: support_data
+  UNITS: counts/s
+  LABLAXIS: O Synthetic Floor
+
+o_proxy_floor:
+  CATDESC: Oxygen proxy background floor
+  FIELDNAM: O Proxy Floor
+  FORMAT: F12.6
+  FILLVAL: -1.0000000E+31
+  VALIDMIN: 0.0
+  VALIDMAX: 1.0000000E+31
+  VAR_TYPE: support_data
+  UNITS: counts/s
+  LABLAXIS: O Proxy Floor

imap_processing/lo/constants.py

@@ -0,0 +1,59 @@
+"""Contains constants variables to support IMAP-Lo processing."""
+
+# ------- Constants for L1B processing -------
+
+# Ion species tracked. "H" is mandatory; any others for which we have histrates
+# may be added here.
+ELEMS = ("H", "O")
+
+# Hours into the day (UTC) for HK data to calculate median for pivot angle estimation.
+PIVOT_HK_HOUR_RANGE: tuple[int, int] = (3, 15)
+
+# Per-day overrides for the anti-RAM background rate. Keyed by (year, day-of-year)
+BG_RATE_ANTI_RAM_OVERRIDES: dict[tuple[int, int], float] = {
+    (2026, 62): 0.0014,
+    (2026, 64): 0.0,
+    (2026, 65): 0.0,
+    (2026, 91): 0.03,
+}
+
+# One histogram accumulation cycle duration [s]
+HISTOGRAM_CYCLE_EPOCHS: int = 420
+
+N_CYCLE_SUM: int = 1  # Granularity of goodtime boundaries
+N_CYCLE_AVE: int = 7  # Cycles to average over when estimating background rates
+N_ESA_LEVELS: int = 7  # Total number of ESA levels
+RAM_ESA_LEVELS: tuple[int, ...] = (
+    6,
+    7,
+)  # ESA levels for RAM estimation (1-indexed)
+
+# Histogram angular bins (0-indexed) corresponding to the RAM and anti-RAM look
+# directions
+RAM_HISTOGRAM_BINS: tuple[slice, ...] = (slice(0, 20), slice(50, 60))
+ANTI_RAM_HISTOGRAM_BINS: tuple[slice, ...] = (slice(20, 50),)
+
+# Nominal background rates [counts/s] for each species
+BG_RATES = {"H": 0.0014925, "O": 0.000136635}
+# When no exposure is available, scale the nominal rate down as a conservative estimate.
+BG_RATE_FALLBACK_SCALE: dict[str, float] = {"H": 1.0, "O": 0.3}
+# Minimum non-zero background rate floor = nominal / divisor
+BG_RATE_FLOOR_DIVISOR: dict[str, float] = {"H": 50.0, "O": 150.0}
+
+# Maximum acceptable background count rates [counts/s]. There are separate thresholds
+# for RAM vs. anti-RAM, and for pivot near 90 deg vs. others.
+THRESHOLD_BG_RATE_RAM_90: float = 0.014
+THRESHOLD_BG_RATE_ANTI_RAM_90: float = 0.007
+THRESHOLD_BG_RATE_RAM_NON_90: float = 0.0175
+THRESHOLD_BG_RATE_ANTI_RAM_NON_90: float = 0.00875
+
+# Maximum time gap [s] between consecutive histogram epochs before treating them as
+# separate intervals.
+DELAY_MAX: int = 100
+# Pivot angles within this range [degrees] are treated as "near 90".
+PIVOT_90_RANGE: tuple[float, float] = 88.0, 92.0
+# Fraction of each cycle duration that contributes actual exposure.
+EXPOSURE_FACTOR: float = 0.5
+# Padding [s] added to begin/end of each goodtime interval to ensure complete
+# cycles are covered at interval edges.
+GOODTIME_PADDING: float = 2.0