From 452127227486b1cb2d87e945f9f3c582c7a29845 Mon Sep 17 00:00:00 2001
From: Anne Archibald <peridot.faceted@gmail.com>
Date: Sat, 10 Feb 2024 17:16:07 +0000
Subject: [PATCH 1/7] Use cached_property and types

---
 src/pint/observatory/__init__.py | 122 +++++++++++++++++++------------
 src/pint/observatory/topo_obs.py |  78 ++++++++++----------
 2 files changed, 116 insertions(+), 84 deletions(-)

diff --git a/src/pint/observatory/__init__.py b/src/pint/observatory/__init__.py
index 895d46411..2935613fe 100644
--- a/src/pint/observatory/__init__.py
+++ b/src/pint/observatory/__init__.py
@@ -21,14 +21,17 @@
 necessary.
 """
 
-from copy import deepcopy
 import os
 import textwrap
 from collections import defaultdict
+from collections.abc import Callable
+from copy import deepcopy
 from io import StringIO
 from pathlib import Path
+from typing import Optional, Union
 
 import astropy.coordinates
+import astropy.time
 import astropy.units as u
 import numpy as np
 from astropy.coordinates import EarthLocation
@@ -97,7 +100,7 @@ def _load_gps_clock():
         )
 
 
-def _load_bipm_clock(bipm_version):
+def _load_bipm_clock(bipm_version: str):
     bipm_version = bipm_version.lower()
     if bipm_version not in _bipm_clock_versions:
         try:
@@ -136,34 +139,40 @@ class Observatory:
     position.
     """
 
+    fullname: str
+    aliases: list[str]
+    include_gps: bool
+    include_bipm: bool
+    bipm_version: str
+
     # This is a dict containing all defined Observatory instances,
     # keyed on standard observatory name.
-    _registry = {}
+    _registry: dict[str, "Observatory"] = {}
 
     # This is a dict mapping any defined aliases to the corresponding
     # standard name.
-    _alias_map = {}
+    _alias_map: dict[str, str] = {}
 
     def __init__(
         self,
-        name,
-        fullname=None,
-        aliases=None,
-        include_gps=True,
-        include_bipm=True,
-        bipm_version=bipm_default,
-        overwrite=False,
+        name: str,
+        fullname: Optional[str] = None,
+        aliases: Optional[list[str]] = None,
+        include_gps: bool = True,
+        include_bipm: bool = True,
+        bipm_version: str = bipm_default,
+        overwrite: bool = False,
     ):
-        self._name = name.lower()
-        self._aliases = (
+        self._name: str = name.lower()
+        self._aliases: list[str] = (
             list(set(map(str.lower, aliases))) if aliases is not None else []
         )
         if aliases is not None:
             Observatory._add_aliases(self, aliases)
-        self.fullname = fullname if fullname is not None else name
-        self.include_gps = include_gps
-        self.include_bipm = include_bipm
-        self.bipm_version = bipm_version
+        self.fullname: str = fullname if fullname is not None else name
+        self.include_gps: bool = include_gps
+        self.include_bipm: bool = include_bipm
+        self.bipm_version: str = bipm_version
 
         if name.lower() in Observatory._registry:
             if not overwrite:
@@ -175,16 +184,18 @@ def __init__(
         Observatory._register(self, name)
 
     @classmethod
-    def _register(cls, obs, name):
-        """Add an observatory to the registry using the specified name
-        (which will be converted to lower case).  If an existing observatory
+    def _register(cls, obs: "Observatory", name: str):
+        """Add an observatory to the registry using the specified name (which will be converted to lower case).
+
+        If an existing observatory
         of the same name exists, it will be replaced with the new one.
         The Observatory instance's name attribute will be updated for
-        consistency."""
+        consistency.
+        """
         cls._registry[name.lower()] = obs
 
     @classmethod
-    def _add_aliases(cls, obs, aliases):
+    def _add_aliases(cls, obs: "Observatory", aliases: list[str]):
         """Add aliases for the specified Observatory.  Aliases
         should be given as a list.  If any of the new aliases are already in
         use, they will be replaced.  Aliases are not checked against the
@@ -196,14 +207,17 @@ def _add_aliases(cls, obs, aliases):
             cls._alias_map[a.lower()] = obs.name
 
     @staticmethod
-    def gps_correction(t, limits="warn"):
+    def gps_correction(t: astropy.time.Time, limits: str = "warn"):
         """Compute the GPS clock corrections for times t."""
         log.info("Applying GPS to UTC clock correction (~few nanoseconds)")
         _load_gps_clock()
+        assert _gps_clock is not None
         return _gps_clock.evaluate(t, limits=limits)
 
     @staticmethod
-    def bipm_correction(t, bipm_version=bipm_default, limits="warn"):
+    def bipm_correction(
+        t: astropy.time.Time, bipm_version: str = bipm_default, limits: str = "warn"
+    ):
         """Compute the GPS clock corrections for times t."""
         log.info(f"Applying TT(TAI) to TT({bipm_version}) clock correction (~27 us)")
         tt2tai = 32.184 * 1e6 * u.us
@@ -214,7 +228,7 @@ def bipm_correction(t, bipm_version=bipm_default, limits="warn"):
         )
 
     @classmethod
-    def clear_registry(cls):
+    def clear_registry(cls) -> None:
         """Clear registry for ground-based observatories."""
         cls._registry = {}
         cls._alias_map = {}
@@ -229,7 +243,7 @@ def names(cls):
         return cls._registry.keys()
 
     @classmethod
-    def names_and_aliases(cls):
+    def names_and_aliases(cls) -> dict[str, list[str]]:
         """List all observatories and their aliases"""
         import pint.observatory.topo_obs  # noqa
         import pint.observatory.special_locations  # noqa
@@ -241,15 +255,15 @@ def names_and_aliases(cls):
     # setter methods that update the registries appropriately.
 
     @property
-    def name(self):
+    def name(self) -> str:
         return self._name
 
     @property
-    def aliases(self):
+    def aliases(self) -> list[str]:
         return self._aliases
 
     @classmethod
-    def get(cls, name):
+    def get(cls, name: str) -> "Observatory":
         """Returns the Observatory instance for the specified name/alias.
 
         If the name has not been defined, an error will be raised.  Aside
@@ -303,9 +317,12 @@ def get(cls, name):
     # Any which raise NotImplementedError below must be implemented in
     # derived classes.
 
-    def earth_location_itrf(self, time=None):
-        """Returns observatory geocentric position as an astropy
-        EarthLocation object.  For observatories where this is not
+    def earth_location_itrf(
+        self, time: Optional[astropy.time.Time] = None
+    ) -> Union[None, np.ndarray]:
+        """Returns observatory geocentric position as an astropy EarthLocation object.
+
+        For observatories where this is not
         relevant, None can be returned.
 
         The location is in the International Terrestrial Reference Frame (ITRF).
@@ -319,8 +336,9 @@ def earth_location_itrf(self, time=None):
         """
         return None
 
-    def get_gcrs(self, t, ephem=None):
-        """Return position vector of observatory in GCRS
+    def get_gcrs(self, t: astropy.time.Time, ephem=None):
+        """Return position vector of observatory in GCRS.
+
         t is an astropy.Time or array of astropy.Time objects
         ephem is a link to an ephemeris file. Needed for SSB observatory
         Returns a 3-vector of Quantities representing the position
@@ -329,14 +347,17 @@ def get_gcrs(self, t, ephem=None):
         raise NotImplementedError
 
     @property
-    def timescale(self):
-        """Returns the timescale that TOAs from this observatory will be in,
-        once any clock corrections have been applied.  This should be a
+    def timescale(self) -> str:
+        """Returns the timescale that TOAs from this observatory will be in, once any clock corrections have been applied.
+
+        This should be a
         string suitable to be passed directly to the scale argument of
         astropy.time.Time()."""
         raise NotImplementedError
 
-    def clock_corrections(self, t, limits="warn"):
+    def clock_corrections(
+        self, t: astropy.time.Time, limits: str = "warn"
+    ) -> u.Quantity:
         """Compute clock corrections for a Time array.
 
         Given an array-valued Time, return the clock corrections
@@ -356,7 +377,7 @@ def clock_corrections(self, t, limits="warn"):
 
         return corr
 
-    def last_clock_correction_mjd(self):
+    def last_clock_correction_mjd(self) -> float:
         """Return the MJD of the last available clock correction.
 
         Returns ``np.inf`` if no clock corrections are relevant.
@@ -365,6 +386,7 @@ def last_clock_correction_mjd(self):
 
         if self.include_gps:
             _load_gps_clock()
+            assert _gps_clock is not None
             t = min(t, _gps_clock.last_correction_mjd())
         if self.include_bipm:
             _load_bipm_clock(self.bipm_version)
@@ -374,7 +396,13 @@ def last_clock_correction_mjd(self):
             )
         return t
 
-    def get_TDBs(self, t, method="default", ephem=None, options=None):
+    def get_TDBs(
+        self,
+        t: astropy.time.Time,
+        method: Union[str, Callable] = "default",
+        ephem: Optional[str] = None,
+        options: Optional[dict] = None,
+    ):
         """This is a high level function for converting TOAs to TDB time scale.
 
         Different method can be applied to obtain the result. Current supported
@@ -409,13 +437,13 @@ def get_TDBs(self, t, method="default", ephem=None, options=None):
             t = Time([t])
         if t.scale == "tdb":
             return t
-        # Check the method. This pattern is from numpy minimize
-        meth = "_custom" if callable(method) else method.lower()
         if options is None:
             options = {}
-        if meth == "_custom":
+        if callable(method):
             options = dict(options)
             return method(t, **options)
+        else:
+            meth = method.lower()
         if meth == "default":
             return self._get_TDB_default(t, ephem)
         elif meth == "ephemeris":
@@ -428,17 +456,17 @@ def get_TDBs(self, t, method="default", ephem=None, options=None):
         else:
             raise ValueError(f"Unknown method '{method}'.")
 
-    def _get_TDB_default(self, t, ephem):
+    def _get_TDB_default(self, t: astropy.time.Time, ephem):
         return t.tdb
 
-    def _get_TDB_ephem(self, t, ephem):
+    def _get_TDB_ephem(self, t: astropy.time.Time, ephem):
         """Read the ephem TDB-TT column.
 
         This column is provided by DE4XXt version of ephemeris.
         """
         raise NotImplementedError
 
-    def posvel(self, t, ephem, group=None):
+    def posvel(self, t: astropy.time.Time, ephem, group=None):
         """Return observatory position and velocity for the given times.
 
         Position is relative to solar system barycenter; times are
@@ -451,7 +479,7 @@ def posvel(self, t, ephem, group=None):
 
 
 def get_observatory(
-    name, include_gps=None, include_bipm=None, bipm_version=bipm_default
+    name: str, include_gps=None, include_bipm=None, bipm_version: str = bipm_default
 ):
     """Convenience function to get observatory object with options.
 
diff --git a/src/pint/observatory/topo_obs.py b/src/pint/observatory/topo_obs.py
index 1d7fe8868..33fc8b0e2 100644
--- a/src/pint/observatory/topo_obs.py
+++ b/src/pint/observatory/topo_obs.py
@@ -17,12 +17,15 @@
 --------
 :mod:`pint.observatory.special_locations`
 """
+import copy
 import json
 import os
+from functools import cached_property
 from pathlib import Path
-import copy
+from typing import Optional
 
 import astropy.constants as c
+import astropy.time
 import astropy.units as u
 import numpy as np
 from astropy.coordinates import EarthLocation
@@ -36,9 +39,9 @@
     NoClockCorrections,
     Observatory,
     bipm_default,
+    earth_location_distance,
     find_clock_file,
     get_observatory,
-    earth_location_distance,
 )
 from pint.pulsar_mjd import Time
 from pint.solar_system_ephemerides import get_tdb_tt_ephem_geocenter, objPosVel_wrt_SSB
@@ -149,36 +152,36 @@ class TopoObs(Observatory):
 
     def __init__(
         self,
-        name,
+        name: str,
         *,
-        fullname=None,
-        tempo_code=None,
-        itoa_code=None,
-        aliases=None,
+        fullname: Optional[str] = None,
+        tempo_code: Optional[str] = None,
+        itoa_code: Optional[str] = None,
+        aliases: Optional[list[str]] = None,
         location=None,
         itrf_xyz=None,
-        lat=None,
-        lon=None,
+        lat: Optional[float] = None,
+        lon: Optional[float] = None,
         height=None,
-        clock_file="",
-        clock_fmt="tempo",
+        clock_file: str = "",
+        clock_fmt: str = "tempo",
         clock_dir=None,
-        include_gps=True,
-        include_bipm=True,
-        bipm_version=bipm_default,
+        include_gps: bool = True,
+        include_bipm: bool = True,
+        bipm_version: str = bipm_default,
         origin=None,
-        overwrite=False,
-        bogus_last_correction=False,
+        overwrite: bool = False,
+        bogus_last_correction: bool = False,
     ):
         input_values = [lat is not None, lon is not None, height is not None]
-        if sum(input_values) > 0 and sum(input_values) < 3:
+        if any(input_values) and not all(input_values):
             raise ValueError("All of lat, lon, height are required for observatory")
         input_values = [
             location is not None,
             itrf_xyz is not None,
             (lat is not None and lon is not None and height is not None),
         ]
-        if sum(input_values) == 0:
+        if not any(input_values):
             raise ValueError(
                 f"EarthLocation, ITRF coordinates, or lat/lon/height are required for observatory '{name}'"
             )
@@ -209,11 +212,12 @@ def __init__(
 
         # Save clock file info, the data will be read only if clock
         # corrections for this site are requested.
-        self.clock_files = [clock_file] if isinstance(clock_file, str) else clock_file
-        self.clock_files = [c for c in self.clock_files if c != ""]
-        self.clock_fmt = clock_fmt
+        clock_files: list[str] = (
+            [clock_file] if isinstance(clock_file, str) else clock_file
+        )
+        self.clock_files: list[str] = [c for c in clock_files if c != ""]
+        self.clock_fmt: str = clock_fmt
         self.clock_dir = clock_dir
-        self._clock = None  # The ClockFile objects, will be read on demand
 
         # If using TEMPO time.dat we need to know the 1-char tempo-style
         # observatory code.
@@ -315,10 +319,9 @@ def separation(self, other, method="cartesian"):
     def earth_location_itrf(self, time=None):
         return self.location
 
-    def _load_clock_corrections(self):
-        if self._clock is not None:
-            return
-        self._clock = []
+    @cached_property
+    def _clock(self) -> list:
+        clock = []
         for cf in self.clock_files:
             if cf == "":
                 continue
@@ -326,7 +329,7 @@ def _load_clock_corrections(self):
             if isinstance(cf, dict):
                 kwargs.update(cf)
                 cf = kwargs.pop("name")
-            self._clock.append(
+            clock.append(
                 find_clock_file(
                     cf,
                     format=self.clock_fmt,
@@ -334,8 +337,11 @@ def _load_clock_corrections(self):
                     **kwargs,
                 )
             )
+        return clock
 
-    def clock_corrections(self, t, limits="warn"):
+    def clock_corrections(
+        self, t: astropy.time.Time, limits: str = "warn"
+    ) -> u.Quantity:
         """Compute the total clock corrections,
 
         Parameters
@@ -344,17 +350,16 @@ def clock_corrections(self, t, limits="warn"):
             The time when the clock correcions are applied.
         """
 
-        corr = super().clock_corrections(t, limits=limits)
-        # Read clock file if necessary
-        self._load_clock_corrections()
+        corr: u.Quantity = super().clock_corrections(t, limits=limits)
         if self._clock:
             log.info(
                 f"Applying observatory clock corrections for observatory='{self.name}'."
             )
             for clock in self._clock:
                 corr += clock.evaluate(t, limits=limits)
-
         elif self.clock_files:
+            # clock_files is not empty, but no clock corrections found
+            # FIXME: what if only some were found?
             msg = f"No clock corrections found for observatory {self.name} taken from file {self.clock_files}"
             if limits == "warn":
                 log.warning(msg)
@@ -365,19 +370,18 @@ def clock_corrections(self, t, limits="warn"):
             log.info(f"Observatory {self.name} requires no clock corrections.")
         return corr
 
-    def last_clock_correction_mjd(self):
+    def last_clock_correction_mjd(self) -> float:
         """Return the MJD of the last clock correction.
 
         Combines constraints based on Earth orientation parameters and on the
         available clock corrections specific to the telescope.
         """
         t = super().last_clock_correction_mjd()
-        self._load_clock_corrections()
         for clock in self._clock:
             t = min(t, clock.last_correction_mjd())
         return t
 
-    def _get_TDB_ephem(self, t, ephem):
+    def _get_TDB_ephem(self, t: astropy.time.Time, ephem):
         """Read the ephem TDB-TT column.
 
         This column is provided by DE4XXt version of ephemeris. This function is only
@@ -406,7 +410,7 @@ def _get_TDB_ephem(self, t, ephem):
             location=self.earth_location_itrf(),
         )
 
-    def get_gcrs(self, t, ephem=None):
+    def get_gcrs(self, t: astropy.time.Time, ephem=None):
         """Return position vector of TopoObs in GCRS
 
         Parameters
@@ -423,7 +427,7 @@ def get_gcrs(self, t, ephem=None):
         )
         return obs_geocenter_pv.pos
 
-    def posvel(self, t, ephem, group=None):
+    def posvel(self, t: astropy.time.Time, ephem, group=None):
         if t.isscalar:
             t = Time([t])
         earth_pv = objPosVel_wrt_SSB("earth", t, ephem)

From 32b28241ca048f9b3f53dd2707d439d064d78240 Mon Sep 17 00:00:00 2001
From: Anne Archibald <peridot.faceted@gmail.com>
Date: Sat, 10 Feb 2024 17:31:57 +0000
Subject: [PATCH 2/7] Fix python 3.8-incompatible syntax

---
 src/pint/observatory/__init__.py | 18 ++++++++--------
 src/pint/observatory/topo_obs.py | 35 +++++++++++++++++++++++++++-----
 2 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/src/pint/observatory/__init__.py b/src/pint/observatory/__init__.py
index 2935613fe..65f4bcf5e 100644
--- a/src/pint/observatory/__init__.py
+++ b/src/pint/observatory/__init__.py
@@ -28,7 +28,7 @@
 from copy import deepcopy
 from io import StringIO
 from pathlib import Path
-from typing import Optional, Union
+from typing import Optional, Union, List, Dict
 
 import astropy.coordinates
 import astropy.time
@@ -140,31 +140,31 @@ class Observatory:
     """
 
     fullname: str
-    aliases: list[str]
+    aliases: List[str]
     include_gps: bool
     include_bipm: bool
     bipm_version: str
 
     # This is a dict containing all defined Observatory instances,
     # keyed on standard observatory name.
-    _registry: dict[str, "Observatory"] = {}
+    _registry: Dict[str, "Observatory"] = {}
 
     # This is a dict mapping any defined aliases to the corresponding
     # standard name.
-    _alias_map: dict[str, str] = {}
+    _alias_map: Dict[str, str] = {}
 
     def __init__(
         self,
         name: str,
         fullname: Optional[str] = None,
-        aliases: Optional[list[str]] = None,
+        aliases: Optional[List[str]] = None,
         include_gps: bool = True,
         include_bipm: bool = True,
         bipm_version: str = bipm_default,
         overwrite: bool = False,
     ):
         self._name: str = name.lower()
-        self._aliases: list[str] = (
+        self._aliases: List[str] = (
             list(set(map(str.lower, aliases))) if aliases is not None else []
         )
         if aliases is not None:
@@ -195,7 +195,7 @@ def _register(cls, obs: "Observatory", name: str):
         cls._registry[name.lower()] = obs
 
     @classmethod
-    def _add_aliases(cls, obs: "Observatory", aliases: list[str]):
+    def _add_aliases(cls, obs: "Observatory", aliases: List[str]):
         """Add aliases for the specified Observatory.  Aliases
         should be given as a list.  If any of the new aliases are already in
         use, they will be replaced.  Aliases are not checked against the
@@ -243,7 +243,7 @@ def names(cls):
         return cls._registry.keys()
 
     @classmethod
-    def names_and_aliases(cls) -> dict[str, list[str]]:
+    def names_and_aliases(cls) -> Dict[str, List[str]]:
         """List all observatories and their aliases"""
         import pint.observatory.topo_obs  # noqa
         import pint.observatory.special_locations  # noqa
@@ -259,7 +259,7 @@ def name(self) -> str:
         return self._name
 
     @property
-    def aliases(self) -> list[str]:
+    def aliases(self) -> List[str]:
         return self._aliases
 
     @classmethod
diff --git a/src/pint/observatory/topo_obs.py b/src/pint/observatory/topo_obs.py
index 33fc8b0e2..4afc341e9 100644
--- a/src/pint/observatory/topo_obs.py
+++ b/src/pint/observatory/topo_obs.py
@@ -22,7 +22,7 @@
 import os
 from functools import cached_property
 from pathlib import Path
-from typing import Optional
+from typing import Optional, Union, List
 
 import astropy.constants as c
 import astropy.time
@@ -150,6 +150,31 @@ class TopoObs(Observatory):
 
     """
 
+    tempo_code: Optional[str]
+    """One-character TEMPO code."""
+    itoa_code: Optional[str]
+    """Two-character ITOA code."""
+    location: EarthLocation
+    """Location of the observatory."""
+    clock_files: List[str]
+    """List of files to read for clock corrections.  If empty, no clock corrections are applied."""
+    clock_fmt: str
+    """Format of the clock files.
+    
+    See :class:`pint.observatory.clock_file.ClockFile` for allowed values.
+    """
+    bogus_last_correction: bool
+    """Clock correction files include a bogus last correction.
+    
+    This is common with TEMPO/TEMPO2 clock files since neither program does
+    a good job with times past the end ot the table. It makes detecting values
+    past the end of real calibration difficult if it's not marked as bogus.
+    """
+    clock_dir: Optional[Union[str, Path]]
+    """Where to look for the clock files."""
+    origin: Optional[str]
+    """Documentation of the origin/author/date for the information."""
+
     def __init__(
         self,
         name: str,
@@ -157,7 +182,7 @@ def __init__(
         fullname: Optional[str] = None,
         tempo_code: Optional[str] = None,
         itoa_code: Optional[str] = None,
-        aliases: Optional[list[str]] = None,
+        aliases: Optional[List[str]] = None,
         location=None,
         itrf_xyz=None,
         lat: Optional[float] = None,
@@ -169,7 +194,7 @@ def __init__(
         include_gps: bool = True,
         include_bipm: bool = True,
         bipm_version: str = bipm_default,
-        origin=None,
+        origin: Optional[str] = None,
         overwrite: bool = False,
         bogus_last_correction: bool = False,
     ):
@@ -212,10 +237,10 @@ def __init__(
 
         # Save clock file info, the data will be read only if clock
         # corrections for this site are requested.
-        clock_files: list[str] = (
+        clock_files: List[str] = (
             [clock_file] if isinstance(clock_file, str) else clock_file
         )
-        self.clock_files: list[str] = [c for c in clock_files if c != ""]
+        self.clock_files: List[str] = [c for c in clock_files if c != ""]
         self.clock_fmt: str = clock_fmt
         self.clock_dir = clock_dir
 

From 10a7248aa4dd78bc4c4a7c9dc4bac6ca9847ee8f Mon Sep 17 00:00:00 2001
From: Anne Archibald <peridot.faceted@gmail.com>
Date: Sat, 10 Feb 2024 17:46:17 +0000
Subject: [PATCH 3/7] Fill out typing more

---
 src/pint/observatory/__init__.py | 27 +++++++++++++--------------
 src/pint/observatory/topo_obs.py | 32 +++++++++++++++-----------------
 2 files changed, 28 insertions(+), 31 deletions(-)

diff --git a/src/pint/observatory/__init__.py b/src/pint/observatory/__init__.py
index 65f4bcf5e..8803b655b 100644
--- a/src/pint/observatory/__init__.py
+++ b/src/pint/observatory/__init__.py
@@ -39,7 +39,7 @@
 
 from pint.config import runtimefile
 from pint.pulsar_mjd import Time
-from pint.utils import interesting_lines
+from pint.utils import interesting_lines, PosVel
 
 # Include any files that define observatories here.  This will start
 # with the standard distribution files, then will read any system- or
@@ -90,7 +90,7 @@ class ClockCorrectionOutOfRange(ClockCorrectionError):
 _bipm_clock_versions = {}
 
 
-def _load_gps_clock():
+def _load_gps_clock() -> None:
     global _gps_clock
     if _gps_clock is None:
         log.info("Loading global GPS clock file")
@@ -100,7 +100,7 @@ def _load_gps_clock():
         )
 
 
-def _load_bipm_clock(bipm_version: str):
+def _load_bipm_clock(bipm_version: str) -> None:
     bipm_version = bipm_version.lower()
     if bipm_version not in _bipm_clock_versions:
         try:
@@ -140,7 +140,6 @@ class Observatory:
     """
 
     fullname: str
-    aliases: List[str]
     include_gps: bool
     include_bipm: bool
     bipm_version: str
@@ -184,7 +183,7 @@ def __init__(
         Observatory._register(self, name)
 
     @classmethod
-    def _register(cls, obs: "Observatory", name: str):
+    def _register(cls, obs: "Observatory", name: str) -> None:
         """Add an observatory to the registry using the specified name (which will be converted to lower case).
 
         If an existing observatory
@@ -195,7 +194,7 @@ def _register(cls, obs: "Observatory", name: str):
         cls._registry[name.lower()] = obs
 
     @classmethod
-    def _add_aliases(cls, obs: "Observatory", aliases: List[str]):
+    def _add_aliases(cls, obs: "Observatory", aliases: List[str]) -> None:
         """Add aliases for the specified Observatory.  Aliases
         should be given as a list.  If any of the new aliases are already in
         use, they will be replaced.  Aliases are not checked against the
@@ -207,7 +206,7 @@ def _add_aliases(cls, obs: "Observatory", aliases: List[str]):
             cls._alias_map[a.lower()] = obs.name
 
     @staticmethod
-    def gps_correction(t: astropy.time.Time, limits: str = "warn"):
+    def gps_correction(t: astropy.time.Time, limits: str = "warn") -> u.Quantity:
         """Compute the GPS clock corrections for times t."""
         log.info("Applying GPS to UTC clock correction (~few nanoseconds)")
         _load_gps_clock()
@@ -217,7 +216,7 @@ def gps_correction(t: astropy.time.Time, limits: str = "warn"):
     @staticmethod
     def bipm_correction(
         t: astropy.time.Time, bipm_version: str = bipm_default, limits: str = "warn"
-    ):
+    ) -> u.Quantity:
         """Compute the GPS clock corrections for times t."""
         log.info(f"Applying TT(TAI) to TT({bipm_version}) clock correction (~27 us)")
         tt2tai = 32.184 * 1e6 * u.us
@@ -466,7 +465,7 @@ def _get_TDB_ephem(self, t: astropy.time.Time, ephem):
         """
         raise NotImplementedError
 
-    def posvel(self, t: astropy.time.Time, ephem, group=None):
+    def posvel(self, t: astropy.time.Time, ephem, group=None) -> PosVel:
         """Return observatory position and velocity for the given times.
 
         Position is relative to solar system barycenter; times are
@@ -519,14 +518,14 @@ def get_observatory(
     return Observatory.get(name)
 
 
-def earth_location_distance(loc1, loc2):
+def earth_location_distance(loc1: EarthLocation, loc2: EarthLocation) -> u.Quantity:
     """Compute the distance between two EarthLocations."""
     return (
         sum((u.Quantity(loc1.to_geocentric()) - u.Quantity(loc2.to_geocentric())) ** 2)
     ) ** 0.5
 
 
-def compare_t2_observatories_dat(t2dir=None):
+def compare_t2_observatories_dat(t2dir: Optional[str] = None) -> Dict[str, List[Dict]]:
     """Read a tempo2 observatories.dat file and compare with PINT
 
     Produces a report including lines that can be added to PINT's
@@ -617,7 +616,7 @@ def compare_t2_observatories_dat(t2dir=None):
     return report
 
 
-def compare_tempo_obsys_dat(tempodir=None):
+def compare_tempo_obsys_dat(tempodir: Optional[str] = None) -> Dict[str, List[Dict]]:
     """Read a tempo obsys.dat file and compare with PINT.
 
     Produces a report including lines that can be added to PINT's
@@ -657,8 +656,8 @@ def compare_tempo_obsys_dat(tempodir=None):
                 y = float(line_io.read(15))
                 z = float(line_io.read(15))
                 line_io.read(2)
-                icoord = line_io.read(1).strip()
-                icoord = int(icoord) if icoord else 0
+                icoord_str = line_io.read(1).strip()
+                icoord = int(icoord_str) if icoord_str else 0
                 line_io.read(2)
                 obsnam = line_io.read(20).strip().lower()
                 tempo_code = line_io.read(1)
diff --git a/src/pint/observatory/topo_obs.py b/src/pint/observatory/topo_obs.py
index 4afc341e9..0b810aa12 100644
--- a/src/pint/observatory/topo_obs.py
+++ b/src/pint/observatory/topo_obs.py
@@ -45,7 +45,7 @@
 )
 from pint.pulsar_mjd import Time
 from pint.solar_system_ephemerides import get_tdb_tt_ephem_geocenter, objPosVel_wrt_SSB
-from pint.utils import has_astropy_unit, open_or_use
+from pint.utils import has_astropy_unit, open_or_use, PosVel
 
 # environment variables that can override clock location and observatory location
 pint_obs_env_var = "PINT_OBS_OVERRIDE"
@@ -277,7 +277,7 @@ def __init__(
             overwrite=overwrite,
         )
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         aliases = [f"'{x}'" for x in self.aliases]
         origin = (
             f"{self.fullname}\n{self.origin}"
@@ -309,7 +309,7 @@ def get_json(self):
         """Return as a JSON string"""
         return json.dumps(self.get_dict())
 
-    def separation(self, other, method="cartesian"):
+    def separation(self, other: "TopoObs", method: str = "cartesian"):
         """Return separation between two TopoObs objects
 
         Parameters
@@ -341,7 +341,7 @@ def separation(self, other, method="cartesian"):
             )
             return (c.R_earth * dsigma).to(u.m, equivalencies=u.dimensionless_angles())
 
-    def earth_location_itrf(self, time=None):
+    def earth_location_itrf(self, time=None) -> EarthLocation:
         return self.location
 
     @cached_property
@@ -364,9 +364,7 @@ def _clock(self) -> list:
             )
         return clock
 
-    def clock_corrections(
-        self, t: astropy.time.Time, limits: str = "warn"
-    ) -> u.Quantity:
+    def clock_corrections(self, t: Time, limits: str = "warn") -> u.Quantity:
         """Compute the total clock corrections,
 
         Parameters
@@ -406,7 +404,7 @@ def last_clock_correction_mjd(self) -> float:
             t = min(t, clock.last_correction_mjd())
         return t
 
-    def _get_TDB_ephem(self, t: astropy.time.Time, ephem):
+    def _get_TDB_ephem(self, t: Time, ephem) -> Time:
         """Read the ephem TDB-TT column.
 
         This column is provided by DE4XXt version of ephemeris. This function is only
@@ -418,8 +416,8 @@ def _get_TDB_ephem(self, t: astropy.time.Time, ephem):
         # Topocenter to Geocenter
         # Since earth velocity is not going to change a lot in 3ms. The
         # differences between TT and TDB can be ignored.
-        earth_pv = objPosVel_wrt_SSB("earth", t.tdb, ephem)
-        obs_geocenter_pv = gcrs_posvel_from_itrf(
+        earth_pv: PosVel = objPosVel_wrt_SSB("earth", t.tdb, ephem)
+        obs_geocenter_pv: PosVel = gcrs_posvel_from_itrf(
             self.earth_location_itrf(), t, obsname=self.name
         )
         # NOTE
@@ -447,22 +445,22 @@ def get_gcrs(self, t: astropy.time.Time, ephem=None):
         np.array
             a 3-vector of Quantities representing the position in GCRS coordinates.
         """
-        obs_geocenter_pv = gcrs_posvel_from_itrf(
+        obs_geocenter_pv: PosVel = gcrs_posvel_from_itrf(
             self.earth_location_itrf(), t, obsname=self.name
         )
         return obs_geocenter_pv.pos
 
-    def posvel(self, t: astropy.time.Time, ephem, group=None):
+    def posvel(self, t: astropy.time.Time, ephem, group=None) -> PosVel:
         if t.isscalar:
             t = Time([t])
-        earth_pv = objPosVel_wrt_SSB("earth", t, ephem)
-        obs_geocenter_pv = gcrs_posvel_from_itrf(
+        earth_pv: PosVel = objPosVel_wrt_SSB("earth", t, ephem)
+        obs_geocenter_pv: PosVel = gcrs_posvel_from_itrf(
             self.earth_location_itrf(), t, obsname=self.name
         )
         return obs_geocenter_pv + earth_pv
 
 
-def export_all_clock_files(directory):
+def export_all_clock_files(directory: Union[str, Path]) -> None:
     """Export all clock files PINT is using.
 
     This will export all the clock files PINT is using - every clock file used
@@ -494,7 +492,7 @@ def export_all_clock_files(directory):
                     clock.export(directory / Path(clock.filename).name)
 
 
-def load_observatories(filename=observatories_json, overwrite=False):
+def load_observatories(filename=observatories_json, overwrite: bool = False) -> None:
     """Load observatory definitions from JSON and create :class:`pint.observatory.topo_obs.TopoObs` objects, registering them
 
     Set `overwrite` to ``True`` if you want to re-read a file with updated definitions.
@@ -528,7 +526,7 @@ def load_observatories(filename=observatories_json, overwrite=False):
         TopoObs(name=obsname, **obsdict)
 
 
-def load_observatories_from_usual_locations(clear=False):
+def load_observatories_from_usual_locations(clear: bool = False) -> None:
     """Load observatories from the default JSON file as well as ``$PINT_OBS_OVERRIDE``, optionally clearing the registry
 
     Running with ``clear=True`` will return PINT to the state it is on import.

From f39772687f24604cfdee26dd1eb95b28f8502586 Mon Sep 17 00:00:00 2001
From: Anne Archibald <peridot.faceted@gmail.com>
Date: Sat, 10 Feb 2024 18:16:46 +0000
Subject: [PATCH 4/7] Improve attribute documentation

---
 src/pint/observatory/__init__.py | 13 +++++++++++++
 src/pint/observatory/topo_obs.py |  4 ++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/pint/observatory/__init__.py b/src/pint/observatory/__init__.py
index 8803b655b..8a5663b7d 100644
--- a/src/pint/observatory/__init__.py
+++ b/src/pint/observatory/__init__.py
@@ -140,9 +140,13 @@ class Observatory:
     """
 
     fullname: str
+    """Full human-readable name of the observatory."""
     include_gps: bool
+    """Whether to include GPS clock corrections."""
     include_bipm: bool
+    """Whether to include BIPM clock corrections."""
     bipm_version: str
+    """Version of the BIPM clock file to use."""
 
     # This is a dict containing all defined Observatory instances,
     # keyed on standard observatory name.
@@ -255,10 +259,19 @@ def names_and_aliases(cls) -> Dict[str, List[str]]:
 
     @property
     def name(self) -> str:
+        """Short name of the observatory.
+
+        This is the name used in TOA files and in the observatory registry.
+        """
         return self._name
 
     @property
     def aliases(self) -> List[str]:
+        """List of aliases for the observatory.
+
+        These are short names also used to specify this observatory.
+        Includes ITOA and TEMPO codes, and any other common names.
+        """
         return self._aliases
 
     @classmethod
diff --git a/src/pint/observatory/topo_obs.py b/src/pint/observatory/topo_obs.py
index 0b810aa12..4a247e701 100644
--- a/src/pint/observatory/topo_obs.py
+++ b/src/pint/observatory/topo_obs.py
@@ -306,11 +306,11 @@ def get_dict(self):
         return {self.name: output}
 
     def get_json(self):
-        """Return as a JSON string"""
+        """Return as a JSON string."""
         return json.dumps(self.get_dict())
 
     def separation(self, other: "TopoObs", method: str = "cartesian"):
-        """Return separation between two TopoObs objects
+        """Return separation between two TopoObs objects.
 
         Parameters
         ----------

From 6da627a1ecae2e2a82410da87dd647a66b91e34e Mon Sep 17 00:00:00 2001
From: Anne Archibald <peridot.faceted@gmail.com>
Date: Wed, 21 Feb 2024 18:50:07 +0000
Subject: [PATCH 5/7] Additional type annotations

---
 src/pint/observatory/__init__.py | 33 +++++++++++++++++---------------
 src/pint/observatory/topo_obs.py | 18 ++++++++---------
 2 files changed, 27 insertions(+), 24 deletions(-)

diff --git a/src/pint/observatory/__init__.py b/src/pint/observatory/__init__.py
index 8a5663b7d..ad889ded1 100644
--- a/src/pint/observatory/__init__.py
+++ b/src/pint/observatory/__init__.py
@@ -28,7 +28,7 @@
 from copy import deepcopy
 from io import StringIO
 from pathlib import Path
-from typing import Optional, Union, List, Dict
+from typing import Optional, Union, List, Dict, Literal
 
 import astropy.coordinates
 import astropy.time
@@ -348,7 +348,7 @@ def earth_location_itrf(
         """
         return None
 
-    def get_gcrs(self, t: astropy.time.Time, ephem=None):
+    def get_gcrs(self, t: astropy.time.Time, ephem: Optional[str] = None):
         """Return position vector of observatory in GCRS.
 
         t is an astropy.Time or array of astropy.Time objects
@@ -468,17 +468,17 @@ def get_TDBs(
         else:
             raise ValueError(f"Unknown method '{method}'.")
 
-    def _get_TDB_default(self, t: astropy.time.Time, ephem):
+    def _get_TDB_default(self, t: astropy.time.Time, ephem: Optional[str]):
         return t.tdb
 
-    def _get_TDB_ephem(self, t: astropy.time.Time, ephem):
+    def _get_TDB_ephem(self, t: astropy.time.Time, ephem: Optional[str]):
         """Read the ephem TDB-TT column.
 
         This column is provided by DE4XXt version of ephemeris.
         """
         raise NotImplementedError
 
-    def posvel(self, t: astropy.time.Time, ephem, group=None) -> PosVel:
+    def posvel(self, t: astropy.time.Time, ephem: Optional[str], group=None) -> PosVel:
         """Return observatory position and velocity for the given times.
 
         Position is relative to solar system barycenter; times are
@@ -491,7 +491,10 @@ def posvel(self, t: astropy.time.Time, ephem, group=None) -> PosVel:
 
 
 def get_observatory(
-    name: str, include_gps=None, include_bipm=None, bipm_version: str = bipm_default
+    name: str,
+    include_gps: Optional[bool] = None,
+    include_bipm: Optional[bool] = None,
+    bipm_version: str = bipm_default,
 ):
     """Convenience function to get observatory object with options.
 
@@ -753,7 +756,7 @@ def convert_angle(x):
     return report
 
 
-def list_last_correction_mjds():
+def list_last_correction_mjds() -> None:
     """Print out a list of the last MJD each clock correction is good for.
 
     Each observatory lists the clock files it uses and their last dates,
@@ -784,7 +787,7 @@ def list_last_correction_mjds():
                 print(f"    {c.friendly_name:<20} MISSING")
 
 
-def update_clock_files(bipm_versions=None):
+def update_clock_files(bipm_versions: Optional[list[str]] = None) -> None:
     """Obtain an up-to-date version of all clock files.
 
     This up-to-date version will be stored in the Astropy cache;
@@ -826,13 +829,13 @@ def update_clock_files(bipm_versions=None):
 
 # Both topo_obs and special_locations need this
 def find_clock_file(
-    name,
-    format,
-    bogus_last_correction=False,
-    url_base=None,
-    clock_dir=None,
-    valid_beyond_ends=False,
-):
+    name: str,
+    format: Literal["tempo", "tempo2"],
+    bogus_last_correction: bool = False,
+    url_base: Optional[str] = None,
+    clock_dir: Union[str, Path, None] = None,
+    valid_beyond_ends: bool = False,
+) -> "ClockFile":
     """Locate and return a ClockFile in one of several places.
 
     PINT looks for clock files in three places, in order:
diff --git a/src/pint/observatory/topo_obs.py b/src/pint/observatory/topo_obs.py
index 4a247e701..53ad6362e 100644
--- a/src/pint/observatory/topo_obs.py
+++ b/src/pint/observatory/topo_obs.py
@@ -22,7 +22,7 @@
 import os
 from functools import cached_property
 from pathlib import Path
-from typing import Optional, Union, List
+from typing import Optional, Union, List, Any
 
 import astropy.constants as c
 import astropy.time
@@ -183,14 +183,14 @@ def __init__(
         tempo_code: Optional[str] = None,
         itoa_code: Optional[str] = None,
         aliases: Optional[List[str]] = None,
-        location=None,
+        location: Optional[EarthLocation] = None,
         itrf_xyz=None,
         lat: Optional[float] = None,
         lon: Optional[float] = None,
         height=None,
         clock_file: str = "",
         clock_fmt: str = "tempo",
-        clock_dir=None,
+        clock_dir: Union[str, Path, None] = None,
         include_gps: bool = True,
         include_bipm: bool = True,
         bipm_version: str = bipm_default,
@@ -287,10 +287,10 @@ def __repr__(self) -> str:
         return f"TopoObs('{self.name}' ({','.join(aliases)}) at [{self.location.x}, {self.location.y} {self.location.z}]:\n{origin})"
 
     @property
-    def timescale(self):
+    def timescale(self) -> str:
         return "utc"
 
-    def get_dict(self):
+    def get_dict(self) -> dict[str, dict[str, Any]]:
         """Return as a dict with limited/changed info"""
         # start with the default __dict__
         # copy some attributes to rename them and remove those that aren't needed for initialization
@@ -305,11 +305,11 @@ def get_dict(self):
         output["itrf_xyz"] = [x.to_value(u.m) for x in self.location.geocentric]
         return {self.name: output}
 
-    def get_json(self):
+    def get_json(self) -> str:
         """Return as a JSON string."""
         return json.dumps(self.get_dict())
 
-    def separation(self, other: "TopoObs", method: str = "cartesian"):
+    def separation(self, other: "TopoObs", method: str = "cartesian") -> u.Quantity:
         """Return separation between two TopoObs objects.
 
         Parameters
@@ -433,7 +433,7 @@ def _get_TDB_ephem(self, t: Time, ephem) -> Time:
             location=self.earth_location_itrf(),
         )
 
-    def get_gcrs(self, t: astropy.time.Time, ephem=None):
+    def get_gcrs(self, t: astropy.time.Time, ephem: Optional[str] = None):
         """Return position vector of TopoObs in GCRS
 
         Parameters
@@ -450,7 +450,7 @@ def get_gcrs(self, t: astropy.time.Time, ephem=None):
         )
         return obs_geocenter_pv.pos
 
-    def posvel(self, t: astropy.time.Time, ephem, group=None) -> PosVel:
+    def posvel(self, t: astropy.time.Time, ephem: Optional[str], group=None) -> PosVel:
         if t.isscalar:
             t = Time([t])
         earth_pv: PosVel = objPosVel_wrt_SSB("earth", t, ephem)

From 23f5d6d6025d6af721328d7e751474f5f745a839 Mon Sep 17 00:00:00 2001
From: Anne Archibald <peridot.faceted@gmail.com>
Date: Wed, 21 Feb 2024 18:54:43 +0000
Subject: [PATCH 6/7] Fix list->List

---
 src/pint/observatory/__init__.py | 2 +-
 src/pint/observatory/topo_obs.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/pint/observatory/__init__.py b/src/pint/observatory/__init__.py
index ad889ded1..bccb40d53 100644
--- a/src/pint/observatory/__init__.py
+++ b/src/pint/observatory/__init__.py
@@ -787,7 +787,7 @@ def list_last_correction_mjds() -> None:
                 print(f"    {c.friendly_name:<20} MISSING")
 
 
-def update_clock_files(bipm_versions: Optional[list[str]] = None) -> None:
+def update_clock_files(bipm_versions: Optional[List[str]] = None) -> None:
     """Obtain an up-to-date version of all clock files.
 
     This up-to-date version will be stored in the Astropy cache;
diff --git a/src/pint/observatory/topo_obs.py b/src/pint/observatory/topo_obs.py
index 53ad6362e..8cbe1ddc0 100644
--- a/src/pint/observatory/topo_obs.py
+++ b/src/pint/observatory/topo_obs.py
@@ -404,7 +404,7 @@ def last_clock_correction_mjd(self) -> float:
             t = min(t, clock.last_correction_mjd())
         return t
 
-    def _get_TDB_ephem(self, t: Time, ephem) -> Time:
+    def _get_TDB_ephem(self, t: Time, ephem: Optional[str]) -> Time:
         """Read the ephem TDB-TT column.
 
         This column is provided by DE4XXt version of ephemeris. This function is only

From 6fda954b49bcf79c9d25c3ffa59ea9dc2b6baf37 Mon Sep 17 00:00:00 2001
From: Anne Archibald <peridot.faceted@gmail.com>
Date: Wed, 21 Feb 2024 18:58:17 +0000
Subject: [PATCH 7/7] dict -> Dict

---
 src/pint/observatory/topo_obs.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/pint/observatory/topo_obs.py b/src/pint/observatory/topo_obs.py
index 8cbe1ddc0..3e47d9b5b 100644
--- a/src/pint/observatory/topo_obs.py
+++ b/src/pint/observatory/topo_obs.py
@@ -22,7 +22,7 @@
 import os
 from functools import cached_property
 from pathlib import Path
-from typing import Optional, Union, List, Any
+from typing import Optional, Union, List, Any, Dict
 
 import astropy.constants as c
 import astropy.time
@@ -290,7 +290,7 @@ def __repr__(self) -> str:
     def timescale(self) -> str:
         return "utc"
 
-    def get_dict(self) -> dict[str, dict[str, Any]]:
+    def get_dict(self) -> Dict[str, Dict[str, Any]]:
         """Return as a dict with limited/changed info"""
         # start with the default __dict__
         # copy some attributes to rename them and remove those that aren't needed for initialization