diff --git a/imap_processing/ultra/l1b/de.py b/imap_processing/ultra/l1b/de.py
index 219100a15..d9b4466cc 100644
--- a/imap_processing/ultra/l1b/de.py
+++ b/imap_processing/ultra/l1b/de.py
@@ -133,6 +133,8 @@ def calculate_de(
     e_bin_l1a = np.full(len(de_dataset["epoch"]), FILLVAL_UINT8, dtype=np.uint8)
     species_bin = np.full(len(de_dataset["epoch"]), FILLVAL_UINT8, dtype=np.uint8)
     t2 = np.full(len(de_dataset["epoch"]), FILLVAL_FLOAT32, dtype=np.float32)
+    event_times = np.full(len(de_dataset["epoch"]), FILLVAL_FLOAT32, dtype=np.float64)
+    spin_starts = np.full(len(de_dataset["epoch"]), FILLVAL_FLOAT32, dtype=np.float64)
     shape = (len(de_dataset["epoch"]), 3)
     sc_velocity = np.full(shape, FILLVAL_FLOAT32, dtype=np.float32)
     sc_dps_velocity = np.full(shape, FILLVAL_FLOAT32, dtype=np.float32)
@@ -162,11 +164,11 @@ def calculate_de(
     start_type[valid_indices] = de_dataset["start_type"].data[valid_indices]
     spin_ds = get_spin_info(aux_dataset, de_dataset["shcoarse"].data)
 
-    (event_times, spin_starts) = get_event_times(
+    (event_times[valid_mask], spin_starts[valid_mask]) = get_event_times(
         aux_dataset,
-        de_dataset["shcoarse"].data,
-        de_dataset["phase_angle"].data,
-        spin_ds,
+        de_dataset["shcoarse"].data[valid_mask],
+        de_dataset["phase_angle"].data[valid_mask],
+        spin_ds.isel(epoch=valid_mask),
     )
 
     de_dict["spin"] = spin_ds.spin_number.data
@@ -323,15 +325,21 @@ def calculate_de(
     # Annotated Events.
     ultra_frame = getattr(SpiceFrame, f"IMAP_ULTRA_{sensor}")
 
-    valid_events = np.ones(event_times.shape, bool)
-
+    # Account for counts=0 (event times have FILL value)
+    valid_events = (event_times != FILLVAL_FLOAT32).copy()
     if repoint_id is not None:
-        in_pointing = calculate_events_in_pointing(repoint_id, et_to_met(event_times))
-        events_to_flag = ~in_pointing
+        # Check all valid event times to see which are in the pointing
+        in_pointing = calculate_events_in_pointing(
+            repoint_id, et_to_met(event_times[valid_events])
+        )
+        # Initialize an array of all events as False
+        events_to_flag = np.zeros(len(quality_flags), dtype=bool)
+        # Identify valid events that are outside the pointing
+        events_to_flag[valid_events] = ~in_pointing
         # Update quality flags for valid events that are not in the pointing
         quality_flags[events_to_flag] |= ImapDEOutliersUltraFlags.DURINGREPOINT.value
         # Update valid_events to only include times within a pointing
-        valid_events &= in_pointing
+        valid_events[valid_events] &= in_pointing
 
     (
         sc_velocity[valid_events],
@@ -419,10 +427,8 @@ def calculate_events_in_pointing(
         combined with the valid_events mask.
     """
     pointing_start_met, pointing_end_met = get_pointing_times_from_id(repoint_id)
-
     # Check which events are within the pointing
     in_pointing = (event_times >= pointing_start_met) & (
         event_times <= pointing_end_met
     )
-
     return in_pointing