Implement support for YYYY-DDD format epochs (#43)

Author: bradsease

oem/patterns.py

@@ -14,7 +14,7 @@
 FLOAT = f"(?:[+-]?\\d\\.\\d+(?:[eE][+-]\\d{{1,3}})){HS}|[+-]?\\d+\\.\\d+"
 """Floating-point number"""
 
-DATE = r"\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d+)?Z?"
+DATE = r"\d{4}-(?:\d{2}-\d{2}|\d{3})T\d{2}:\d{2}:\d{2}(?:\.\d+)?Z?"
 """Date and time"""
 
 KEY_VAL = f"([A-Z_]+){HS}={HS}(.+)"

oem/tools.py

@@ -27,15 +27,16 @@ def parse_datetime(epoch):
     Returns:
         parsed_epoch (DateTime):  Parsed epoch.
     """
+    ymd_fmt = "%Y-%m-%d" if epoch.count("-") == 2 else "%Y-%j"
     if "." in epoch:
         return dt.datetime.strptime(
             epoch.replace("Z", "")[:epoch.index(".")+7].strip(),
-            "%Y-%m-%dT%H:%M:%S.%f"
+            f"{ymd_fmt}T%H:%M:%S.%f"
         )
     else:
         return dt.datetime.strptime(
             epoch.replace("Z", "").strip(),
-            "%Y-%m-%dT%H:%M:%S"
+            f"{ymd_fmt}T%H:%M:%S"
         )
 
 
@@ -48,7 +49,7 @@ def parse_utc(epoch, metadata):
     Returns:
         parsed_epoch (Time): UTC epoch.
     """
-    return Time(epoch, format="isot", scale="utc")
+    return Time(parse_datetime(epoch), format="datetime", scale="utc")
 
 
 def parse_epoch(epoch, metadata):
@@ -65,14 +66,15 @@ def parse_epoch(epoch, metadata):
             this case, time calculations may be inaccurate.
     """
     time_system = metadata["TIME_SYSTEM"].lower()
+    dt_epoch = parse_datetime(epoch)
     if time_system in Time.SCALES:
-        parsed_epoch = Time(epoch, format="isot", scale=time_system)
+        parsed_epoch = Time(dt_epoch, format="datetime", scale=time_system)
     else:
         warnings.warn(
             f"Unsupported TIME_SYSTEM '{time_system}', falling back to "
             f"DateTime. Use caution with time calculations."
         )
-        parsed_epoch = parse_datetime(epoch)
+        parsed_epoch = dt_epoch
     return parsed_epoch
 
 

tests/samples/v2_0/valid/sample12.oem

@@ -0,0 +1,25 @@
+CCSDS_OEM_VERS = 2.0
+COMMENT Valid example of a single data block with YYYY-DDD dates
+CREATION_DATE = 1996-309T17:22:31
+ORIGINATOR = NASA/JPL
+
+META_START
+COMMENT This is a test comment
+COMMENT This is a test comment
+OBJECT_NAME         = MARS GLOBAL SURVEYOR
+OBJECT_ID           = 1996-062A
+CENTER_NAME         = MARS BARYCENTER
+REF_FRAME           = EME2000
+TIME_SYSTEM         = UTC
+START_TIME          = 1996-353T12:00:00.331
+STOP_TIME           = 1996-353T21:28:00.331
+INTERPOLATION       = HERMITE
+INTERPOLATION_DEGREE = 7
+META_STOP
+
+COMMENT This is a test comment
+COMMENT This is a test comment
+
+1996-353T12:00:00.331  2789.619 -280.045 -1746.755  4.73372 -2.49586 -1.04195
+1996-353T12:01:00.331  2783.419 -308.143 -1877.071  5.18604 -2.42124 -1.99608
+1996-353T12:02:00.331  2776.033 -336.859 -2008.682  5.63678 -2.33951 -1.94687