diff --git a/python/lsst/obs/lsst/script/rewrite_latiss_optics_file.py b/python/lsst/obs/lsst/script/rewrite_latiss_optics_file.py
new file mode 100644
index 000000000..b0c36cb1a
--- /dev/null
+++ b/python/lsst/obs/lsst/script/rewrite_latiss_optics_file.py
@@ -0,0 +1,82 @@
+# This file is part of obs_lsst.
+#
+# Developed for the LSST Data Management System.
+# This product includes software developed by the LSST Project
+# (https://www.lsst.org).
+# See the COPYRIGHT file at the top-level directory of this distribution
+# for details of code ownership.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+import os
+import re
+import dateutil.parser
+
+import numpy as np
+import astropy.units as u
+from astropy.table import Table, QTable
+
+import lsst.utils
+from lsst.meas.algorithms.simple_curve import DetectorCurve
+
+
+data_dir = lsst.utils.getPackageDir("obs_lsst_data")
+subaru_file = "subaru_m1_r_20200219.txt"
+valid_start = "1970-01-01T00:00:00"
+
+filename = os.path.join(data_dir, "latiss", "transmission_optics", subaru_file)
+
+subaru_data = Table.read(filename, format="ascii")
+
+wavelength = subaru_data["col1"]
+ref = np.mean(
+    np.array(subaru_data[["col2", "col3", "col4", "col5", "col6"]]).view("f8").reshape((len(subaru_data), 5)),
+    axis=1,
+)
+
+# Make sure it's sorted by wavelength.
+st = np.argsort(wavelength)
+
+optics_table = QTable(
+    {
+        "wavelength": np.array(wavelength[st], dtype=np.float64)*u.nanometer,
+        "efficiency": ref[st]*u.percent,
+    }
+)
+
+# Adjust the overall normalization to match AuxTel scans.
+optics_table["efficiency"] += 3.5*u.percent
+
+curve = DetectorCurve.fromTable(optics_table)
+
+valid_date = dateutil.parser.parse(valid_start)
+datestr = ''.join(re.split(r'[:-]', valid_date.isoformat()))
+
+outfile = os.path.join(data_dir, "latiss", "transmission_optics", datestr + ".ecsv")
+
+optics_table.meta.update(
+    {
+        "CALIBDATE": valid_start,
+        "INSTRUME": "LATISS",
+        "OBSTYPE": "transmission_optics",
+        "TYPE": "transmission_optics",
+        "CALIBCLS": "lsst.ip.isr.IntermediateOpticsTransmissionCurve",
+        "SOURCE": subaru_file,
+    }
+)
+
+optics_table.meta["CALIB_ID"] = (
+    f"calibDate={valid_start} filter=None"
+)
+
+curve.writeText(outfile)