Remove WISE offset (#109)

* Times in the WISE IRSA Metadata table are mid-observation

There was a 4.4 second offset when downloading FOVs which should not exist.

* Optimize loading MPC Observations from text

* changelog

* black

CHANGELOG.md

@@ -17,10 +17,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   done at the Palomar Observatory.
 - Added sunshield rotation calculation for NEO Surveyor.
 
+### Fixed
 
-## [0.3.0] - 2024 - 8 - 28
+- Fixed a time offset in the FOV's downloaded from IRSA WISE/NEOWISE. They were offset
+  by 4.4 seconds.
 
 
+## [0.3.0] - 2024 - 8 - 28
+
 ### Added
 
 - Added an Omni-Directional Field of View.

src/kete/mpc.py

@@ -874,27 +874,26 @@ def from_lines(cls, lines, load_sc_pos=True):
         """
         Create a list of MPCObservations from a list of single 80 char lines.
         """
-        lines = lines.copy()
-
-        jds = []
-        for line in lines:
-            year, month, day = line[15:32].strip().split()
-            jds.append(Time.from_ymd(int(year), int(month), float(day)).jd)
-
         found = []
-        while len(lines) > 0:
-            line = cls._read_first_line(lines.pop(0))
-            line["jd"] = jds.pop(0)
-            if line["note2"] in "WwQqVvRrXx":
+        idx = 0
+        unsupported = set("WwQqVvRrXx")
+        while True:
+            if idx >= len(lines):
+                break
+            line = cls._read_first_line(lines[idx])
+            idx += 1
+            if line["note2"] in unsupported:
                 # unsupported or deprecated observation types
                 continue
-            if line["note2"] == "s" or line["note2"] == "t":
-                raise ValueError("Second line of spacecraft observation found alone")
-            if line["note2"] == "S" or line["note2"] == "T":
-                if len(lines) == 0:
-                    raise ValueError("Missing second line of spacecraft observation.")
-                pos_line = lines.pop(0)
-                jds.pop(0)
+            elif line["note2"] == "s" or line["note2"] == "t":
+                logger.warning("Second line of spacecraft observation found alone")
+                continue
+            elif line["note2"] == "S" or line["note2"] == "T":
+                if idx >= len(lines):
+                    logger.warning("Missing second line of spacecraft observation.")
+                    break
+                pos_line = lines[idx]
+                idx += 1
                 if load_sc_pos:
                     line["sun2sc"] = cls._read_second_line(pos_line, line["jd"])
             found.append(cls(**line))
@@ -903,6 +902,9 @@ def from_lines(cls, lines, load_sc_pos=True):
     @staticmethod
     def _read_first_line(line):
         mag_band = line[65:71].strip()
+
+        year, month, day = line[15:32].strip().split()
+        jd = Time.from_ymd(int(year), int(month), float(day)).jd
         if len(mag_band) > 0:
             mag_band = mag_band.split(maxsplit=1)[0]
         contents = dict(
@@ -915,6 +917,7 @@ def _read_first_line(line):
             mag_band=mag_band,
             obs_code=line[77:80],
             sun2sc=None,
+            jd=jd,
         )
         return contents
 

src/kete/wise.py

@@ -579,11 +579,7 @@ def fetch_WISE_fovs(phase):
         f"WHERE mjd >= {mjd_start} and mjd < {mjd_end}"
     )
 
-    # Adding 4.4 seconds for the offset due to W3/4 exposures taking 8.8 seconds
-    jd = [
-        Time.from_mjd(mjd, scaling="utc").jd + 5.092592592592592e-05
-        for mjd in list(res.mjd)
-    ]
+    jd = [Time.from_mjd(mjd, scaling="utc").jd for mjd in list(res.mjd)]
     res["jd"] = jd
 
     fovs = []