DM-48023: Offset script shall enable and then disable M1M3 slew flag.

doc/news/DM-48023.feature.1.rst

@@ -0,0 +1 @@
+Updated ``MTCS`` to implement ``ready_to_offset``, which uses the ``m1m3_booster_valve`` context manager to enable/disable slew flag before/after offseting.

doc/news/DM-48023.feature.rst

@@ -0,0 +1,4 @@
+Updated ``BaseTCS`` to introduce a mechanism to execute code to prepare the telescope for offsetting.
+
+This consist of having an async context manager that is used when calling the offset command.
+By default this context manager does nothing.

python/lsst/ts/observatory/control/base_tcs.py

@@ -22,6 +22,7 @@
 
 import abc
 import asyncio
+import contextlib
 import enum
 import logging
 import typing
@@ -1367,7 +1368,8 @@ async def _offset(
         """
         self.flush_offset_events()
 
-        await offset_cmd
+        async with self.ready_to_offset():
+            await offset_cmd
 
         try:
             await self.offset_done()
@@ -1379,6 +1381,14 @@ async def _offset(
         await asyncio.sleep(self.tel_settle_time)
         self.log.debug("Done")
 
+    @contextlib.asynccontextmanager
+    async def ready_to_offset(self) -> typing.AsyncIterator[None]:
+        """A context manager to handle preparing the telescope for offset.
+
+        By default it does nothing.
+        """
+        yield
+
     async def ready_to_take_data(self) -> None:
         """Wait for the telescope control system to be ready to take data."""
         if (

python/lsst/ts/observatory/control/maintel/mtcs.py

@@ -2721,6 +2721,16 @@ async def m1m3_booster_valve(self) -> typing.AsyncIterator[None]:
             await self.wait_m1m3_settle()
             await self.close_m1m3_booster_valve()
 
+    @contextlib.asynccontextmanager
+    async def ready_to_offset(self) -> typing.AsyncIterator[None]:
+        """Make sure telescope is ready to perform an offset.
+
+        Overrides the parent class to implement setting/unsetting
+        the slew flag on m1m3.
+        """
+        async with self.m1m3_booster_valve():
+            yield
+
     async def wait_m1m3_settle(self) -> None:
         """Wait until m1m3 has settle."""
         # For now this method will only sleep for m1m3_settle_time.

tests/maintel/test_mtcs.py

@@ -558,6 +558,13 @@ async def test_offset_radec(self) -> None:
             type=1, off1=ra_offset, off2=dec_offset, num=0
         )
 
+        self.mtcs.rem.mtm1m3.cmd_setSlewFlag.set_start.assert_awaited_with(
+            timeout=self.mtcs.fast_timeout,
+        )
+        self.mtcs.rem.mtm1m3.cmd_clearSlewFlag.set_start.assert_awaited_with(
+            timeout=self.mtcs.fast_timeout,
+        )
+
     async def test_offset_azel(self) -> None:
         az_offset, el_offset = 10.0, -10.0
 
@@ -567,6 +574,12 @@ async def test_offset_azel(self) -> None:
         self.mtcs.rem.mtptg.cmd_offsetAzEl.set_start.assert_called_with(
             az=az_offset, el=el_offset, num=1
         )
+        self.mtcs.rem.mtm1m3.cmd_setSlewFlag.set_start.assert_awaited_with(
+            timeout=self.mtcs.fast_timeout,
+        )
+        self.mtcs.rem.mtm1m3.cmd_clearSlewFlag.set_start.assert_awaited_with(
+            timeout=self.mtcs.fast_timeout,
+        )
 
     async def test_offset_azel_with_defaults(self) -> None:
         az_offset, el_offset = 10.0, -10.0
@@ -701,6 +714,13 @@ async def test_offset_xy(self) -> None:
             az=az, el=el, num=1
         )
 
+        self.mtcs.rem.mtm1m3.cmd_setSlewFlag.set_start.assert_awaited_with(
+            timeout=self.mtcs.fast_timeout,
+        )
+        self.mtcs.rem.mtm1m3.cmd_clearSlewFlag.set_start.assert_awaited_with(
+            timeout=self.mtcs.fast_timeout,
+        )
+
     async def test_offset_xy_with_defaults(self) -> None:
         x_offset, y_offset = 10.0, -10.0