diff --git a/iris/__init__.py b/iris/__init__.py
index ef0c456..85a91bf 100644
--- a/iris/__init__.py
+++ b/iris/__init__.py
@@ -1,3 +1,5 @@
 """
 Python package for analyzing observations from the Interface Region Imaging Spectrograph
-"""
\ No newline at end of file
+"""
+
+from . import planning
diff --git a/iris/planning.py b/iris/planning.py
new file mode 100644
index 0000000..fea6e0b
--- /dev/null
+++ b/iris/planning.py
@@ -0,0 +1,23 @@
+import astropy.units as u
+import astropy.time
+
+__all__ = [
+    "num_repeats",
+]
+
+
+def num_repeats(
+    time_start: str | astropy.time.Time,
+    time_stop: str | astropy.time.Time,
+    time_raster: u.Quantity,
+    time_slew: u.Quantity = 10 * u.min,
+):
+    if not isinstance(time_start, astropy.time.Time):
+        time_start = astropy.time.Time(time_start)
+    if not isinstance(time_stop, astropy.time.Time):
+        time_stop = astropy.time.Time(time_stop)
+
+    result = (time_stop - time_start - time_slew) / time_raster
+    result = result.to(u.dimensionless_unscaled)
+
+    return result