diff --git a/config/runtime.exs b/config/runtime.exs
index 8eb460a3..a3aa50f1 100644
--- a/config/runtime.exs
+++ b/config/runtime.exs
@@ -310,13 +310,15 @@ if config_env() == :prod do
        # deploy clears it or new profiles need to fold into the means.
        # 02:30 UTC sits inside the quiet pre-NARR/HRRR ingestion gap.
        {"30 2 * * *", Microwaveprop.Workers.AdminTaskWorker, args: %{"task" => "climatology"}},
-       # Build the PSKR calibration corpus one hour at a time. HH:25
-       # is past the HRRR analysis publish window (~HH:50 of the
-       # previous hour, surfaces by HH:05) and past PSKR's 60s
-       # aggregator flush, so the previous-hour sample has the
-       # atmospheric and signal data it needs. Idempotent UPSERT, so
-       # missed fires are safe to backfill manually.
-       {"25 * * * *", Microwaveprop.Workers.PskrCalibrationWorker},
+       # Build the PSKR calibration corpus *early and often*: every
+       # 5 min, process the current hour + the prior hour. Each pass
+       # spreads the work across the hour as spots accumulate so we
+       # never bind a giant batch at the boundary, and the prior-
+       # hour pass guarantees the boundary is covered without
+       # waiting for the next fire. UPSERT is idempotent so the
+       # ~12 redundant passes per hour cost only the read+merge.
+       # Longer outages can be backfilled with `lookback_hours`.
+       {"*/5 * * * *", Microwaveprop.Workers.PskrCalibrationWorker},
        # Weekly recalibration analysis pass. The recalibrator
        # checks corpus density and bins each scoring feature ×
        # band when the corpus is large enough; otherwise records
diff --git a/lib/microwaveprop/workers/pskr_calibration_worker.ex b/lib/microwaveprop/workers/pskr_calibration_worker.ex
index 246c286e..40b5469d 100644
--- a/lib/microwaveprop/workers/pskr_calibration_worker.ex
+++ b/lib/microwaveprop/workers/pskr_calibration_worker.ex
@@ -1,29 +1,44 @@
 defmodule Microwaveprop.Workers.PskrCalibrationWorker do
   @moduledoc """
-  Hourly cron that builds `Pskr.CalibrationSample` rows by joining
+  Cron worker that builds `Pskr.CalibrationSample` rows by joining
   PSKR spot density with HRRR atmospheric state and SWPC space
-  weather at a given hour.
+  weather.
 
-  Default behaviour fires for the previous full hour — by HH:25 UTC
-  the HRRR cycle has analysis available and PSKR's hourly aggregator
-  has flushed its accumulator. Pass `"hour_utc"` in the args map to
-  rerun a specific hour:
+  ## Why frequent + rolling window
 
-      Microwaveprop.Workers.PskrCalibrationWorker.new(%{"hour_utc" => "2026-05-04T18:00:00Z"})
+  The naive design — one cron fire per hour, processing only the
+  previous hour — has two failure modes:
 
-  The sampler is idempotent (UPSERT on `(hour_utc, band, midpoint_lat,
-  midpoint_lon)`) so reruns are safe.
+  1. The whole hour's worth of cells is built in a single batch.
+     During peaks (50k+ spots/hour) one batch holds the DB pool
+     long enough to look like a backlog.
+  2. A pod restart between fires drops a full hour because the
+     next cron only catches the most-recent-prev hour.
 
-  Lives on the `:backfill_enqueue` queue rather than spawning a new
-  one — the workload is small (~1 query window, in-memory join,
-  bulk upsert) and cluster-wide single-slot is plenty for one fire
-  per hour.
+  Instead we fire every 5 minutes and process the **current hour
+  plus one prior hour** by default. Idempotent UPSERT on
+  `(hour_utc, band, midpoint_lat, midpoint_lon)` means each pass
+  merges new spots into existing rows; the work spreads across the
+  hour as spots arrive, and the boundary always has at least one
+  cron pass covering both sides without waiting for an hourly fire.
+
+  ## Manual reruns
+
+  - `hour_utc` (ISO 8601) — process exactly that one hour. Uniqueness
+    is keyed on args, so manual reruns slot in alongside cron fires.
+  - `lookback_hours` (integer) — override the default window size.
+    Useful after longer outages: `%{"lookback_hours" => 24}` will
+    sweep the last day.
   """
   use Oban.Worker,
     queue: :backfill_enqueue,
     max_attempts: 3,
     unique: [
-      period: 3600,
+      # Cron is every 5 min (300 s); 240 s window means the unique
+      # slot has expired by the time the next fire arrives. Manual
+      # reruns with explicit args use a different args fingerprint
+      # and bypass this check entirely.
+      period: 240,
       states: [:available, :scheduled, :executing, :retryable]
     ]
 
@@ -31,26 +46,37 @@ defmodule Microwaveprop.Workers.PskrCalibrationWorker do
 
   require Logger
 
+  # Default rolling window: current hour + 1 prior. Wide enough to
+  # cover a 5–10 min cron interval crossing an hour boundary; not
+  # so wide that every fire burns DB time on hours that are already
+  # complete. Use `lookback_hours` to widen for catch-up.
+  @default_lookback_hours 1
+
   @impl Oban.Worker
-  def perform(%Oban.Job{args: args}) do
-    hour = parse_hour(args)
-    Logger.info("PskrCalibrationWorker: building samples for #{hour}")
-    count = CalibrationSampler.build_for_hour(hour)
-    Logger.info("PskrCalibrationWorker: upserted #{count} samples for #{hour}")
+  def perform(%Oban.Job{args: %{"hour_utc" => iso}}) when is_binary(iso) do
+    {:ok, hour, _} = DateTime.from_iso8601(iso)
+    process_hour(hour)
     :ok
   end
 
-  defp parse_hour(%{"hour_utc" => iso}) when is_binary(iso) do
-    {:ok, dt, _} = DateTime.from_iso8601(iso)
-    dt
+  def perform(%Oban.Job{args: args}) do
+    lookback = lookback_hours(args)
+    now = truncate_to_hour(DateTime.utc_now())
+
+    Enum.each(0..lookback, fn offset ->
+      now |> DateTime.add(-offset * 3600, :second) |> process_hour()
+    end)
+
+    :ok
   end
 
-  defp parse_hour(_) do
-    # Default: the previous fully-completed hour.
-    DateTime.utc_now()
-    |> DateTime.add(-3600, :second)
-    |> Map.put(:minute, 0)
-    |> Map.put(:second, 0)
-    |> Map.put(:microsecond, {0, 0})
+  defp lookback_hours(%{"lookback_hours" => n}) when is_integer(n) and n >= 0, do: n
+  defp lookback_hours(_), do: @default_lookback_hours
+
+  defp process_hour(hour) do
+    count = CalibrationSampler.build_for_hour(hour)
+    if count > 0, do: Logger.info("PskrCalibrationWorker: upserted #{count} samples for #{hour}")
   end
+
+  defp truncate_to_hour(dt), do: %{dt | minute: 0, second: 0, microsecond: {0, 0}}
 end
diff --git a/test/microwaveprop/workers/pskr_calibration_worker_test.exs b/test/microwaveprop/workers/pskr_calibration_worker_test.exs
index b5bc6dc2..a8f8681e 100644
--- a/test/microwaveprop/workers/pskr_calibration_worker_test.exs
+++ b/test/microwaveprop/workers/pskr_calibration_worker_test.exs
@@ -7,56 +7,95 @@ defmodule Microwaveprop.Workers.PskrCalibrationWorkerTest do
   alias Microwaveprop.Repo
   alias Microwaveprop.Workers.PskrCalibrationWorker
 
-  defp insert_spot!(hour_utc) do
+  defp insert_spot!(hour_utc, opts \\ []) do
+    sender_grid = Keyword.get(opts, :sender_grid, "EM12KL")
+    midpoint_lat = Keyword.get(opts, :midpoint_lat, 33.0)
+    midpoint_lon = Keyword.get(opts, :midpoint_lon, -97.0)
+
     {:ok, _} =
       %SpotHourly{}
       |> SpotHourly.changeset(%{
         hour_utc: hour_utc,
         band: "10000",
-        sender_grid: "EM12KL",
+        sender_grid: sender_grid,
         receiver_grid: "DM43ST",
         spot_count: 1,
-        midpoint_lat: 33.0,
-        midpoint_lon: -97.0,
+        midpoint_lat: midpoint_lat,
+        midpoint_lon: midpoint_lon,
         distance_km: 200.0,
         modes: ["FT8"]
       })
       |> Repo.insert()
   end
 
-  test "perform/1 with explicit hour_utc samples that hour" do
-    hour = ~U[2026-05-04 18:00:00Z]
-    insert_spot!(hour)
+  defp truncate_to_hour(dt), do: %{dt | minute: 0, second: 0, microsecond: {0, 0}}
 
-    assert :ok =
-             perform_job(PskrCalibrationWorker, %{"hour_utc" => DateTime.to_iso8601(hour)})
+  describe "perform/1 with explicit hour_utc" do
+    test "samples just that hour" do
+      hour = ~U[2026-05-04 18:00:00Z]
+      insert_spot!(hour)
 
-    [sample] = Repo.all(CalibrationSample)
-    assert sample.hour_utc == hour
+      assert :ok =
+               perform_job(PskrCalibrationWorker, %{"hour_utc" => DateTime.to_iso8601(hour)})
+
+      [sample] = Repo.all(CalibrationSample)
+      assert sample.hour_utc == hour
+    end
+
+    test "succeeds when the hour has no spots" do
+      assert :ok =
+               perform_job(PskrCalibrationWorker, %{"hour_utc" => "2026-05-04T03:00:00Z"})
+
+      assert Repo.aggregate(CalibrationSample, :count) == 0
+    end
   end
 
-  test "perform/1 with no args defaults to the previous full hour" do
-    # Pick the hour just before "now" — the same logic the worker
-    # uses internally — so the spot we insert lines up with what the
-    # default arg path will pull.
-    target =
-      DateTime.utc_now()
-      |> DateTime.add(-3600, :second)
-      |> Map.put(:minute, 0)
-      |> Map.put(:second, 0)
-      |> Map.put(:microsecond, {0, 0})
+  describe "perform/1 default rolling window" do
+    test "samples both the current hour and the previous hour" do
+      # Frequent processing means a single fire must cover the hour
+      # boundary: spots in the just-ended hour and spots in the
+      # in-progress hour both get sample rows. Otherwise spots that
+      # arrive in the last few minutes of an hour wait up to a full
+      # cron interval before they're sampled.
+      now = truncate_to_hour(DateTime.utc_now())
+      previous = DateTime.add(now, -3600, :second)
 
-    insert_spot!(target)
-    assert :ok = perform_job(PskrCalibrationWorker, %{})
-    assert Repo.aggregate(CalibrationSample, :count) == 1
+      insert_spot!(now)
+      insert_spot!(previous, sender_grid: "EM10AA")
+
+      assert :ok = perform_job(PskrCalibrationWorker, %{})
+
+      hours = CalibrationSample |> Repo.all() |> Enum.map(& &1.hour_utc) |> Enum.sort()
+      assert hours == [previous, now]
+    end
+
+    test "is idempotent — re-running merges into the same rows" do
+      now = truncate_to_hour(DateTime.utc_now())
+      insert_spot!(now)
+
+      assert :ok = perform_job(PskrCalibrationWorker, %{})
+      first_count = Repo.aggregate(CalibrationSample, :count)
+
+      assert :ok = perform_job(PskrCalibrationWorker, %{})
+      assert Repo.aggregate(CalibrationSample, :count) == first_count
+    end
   end
 
-  test "perform/1 returns :ok even when no spots exist for the hour" do
-    assert :ok =
-             perform_job(PskrCalibrationWorker, %{
-               "hour_utc" => "2026-05-04T03:00:00Z"
-             })
+  describe "perform/1 with explicit lookback_hours" do
+    test "extends the rolling window to backfill recent gaps" do
+      # Operator sets lookback_hours=3 to recover from a short pod
+      # outage. The worker fires once and produces samples for the
+      # current hour plus the three before it.
+      now = truncate_to_hour(DateTime.utc_now())
 
-    assert Repo.aggregate(CalibrationSample, :count) == 0
+      Enum.each(0..3, fn offset ->
+        hour = DateTime.add(now, -offset * 3600, :second)
+        insert_spot!(hour, sender_grid: "EM1#{offset}AA")
+      end)
+
+      assert :ok = perform_job(PskrCalibrationWorker, %{"lookback_hours" => 3})
+
+      assert Repo.aggregate(CalibrationSample, :count) == 4
+    end
   end
 end