NAV file sourcing

src/prx/rinex_nav/evaluate.py

@@ -524,7 +524,8 @@ def compute_ephemeris_and_clock_offset_reference_times(group):
     )
     df = df.reset_index(drop=True)
     df = compute_gal_inav_fnav_indicators(df)
-    df["frequency_slot"] = df.FreqNum.where(df.sv.str[0] == "R", 1).astype(int)
+    if "R" in df.constellation.unique():
+        df["frequency_slot"] = df.FreqNum.where(df.sv.str[0] == "R", 1).astype(int)
     df.attrs["ionospheric_corr_GPS"] = nav_ds.ionospheric_corr_GPS
     return df
 

src/prx/rinex_nav/nav_file_discovery.py

@@ -1,13 +1,13 @@
 import argparse
 import os
 import re
-from ftplib import FTP
 from pathlib import Path
 import georinex
 import urllib.request
+import urllib.error
 import pandas as pd
 import prx.util
-import requests
+import ftplib
 
 from prx import converters, util
 from prx.converters import anything_to_rinex_3
@@ -16,27 +16,72 @@
 
 log = util.get_logger(__name__)
 
+IGS_FTP_SERVER = {
+    "gssc.esa.int": "/gnss/data/daily/",
+    "igs.ign.fr": "/pub/igs/data/",
+}
+
 
 def is_rinex_3_mixed_mgex_broadcast_ephemerides_file(file: Path):
     pattern = r"^[A-Za-z0-9]{9}_[A-Za-z]_\d{11}_[A-Za-z0-9]{3}_[A-Za-z]N\.rnx.*"
     return bool(re.match(pattern, file.name))
 
 
+def check_online_availability_ftp(day: pd.Timestamp) -> bool:
+    """
+    Check availability of NAV file on FTP server without downloading it.
+    """
+    file = f"BRDC00IGS_R_{day.year}{day.day_of_year:03}0000_01D_MN.rnx.gz"
+    for server, remote_folder in IGS_FTP_SERVER.items():
+        remote_folder_for_day = remote_folder + f"{day.year}/{day.day_of_year:03}"
+        ftp = ftplib.FTP(server)
+        ftp.login()
+        ftp.cwd(remote_folder_for_day)
+        try:
+            ftp.size(file)
+            return True
+        except ftplib.error_perm:
+            log.warning(f"{file} not available on {server}")
+            return False
+
+
+def check_online_availability_http(day: pd.Timestamp) -> bool:
+    """
+    Check if a remote file exists/accessible without downloading it.
+    """
+    availability = False
+    file = f"BRDC00IGS_R_{day.year}{day.day_of_year:03}0000_01D_MN.rnx.gz"
+    remote_directory = (
+        f"https://igs.bkg.bund.de/root_ftp/IGS/BRDC/{day.year}/{day.day_of_year:03}/"
+    )
+    url = remote_directory + file
+    # Try HEAD first
+    try:
+        req = urllib.request.Request(url, method="HEAD")
+        _ = urllib.request.urlopen(req)
+        return True
+    except urllib.error.HTTPError:
+        availability = False
+
+    # Fallback: request only the first byte so we avoid full download
+    try:
+        req = urllib.request.Request(url, headers={"Range": "bytes=0-0"})
+        _ = urllib.request.urlopen(req)
+        return True
+    except urllib.error.HTTPError:
+        availability = False
+
+    return availability
+
+
 def try_downloading_ephemerides_http(day: pd.Timestamp, local_destination_folder: Path):
     # IGS BKG Rinex 3.04 mixed file paths follow this pattern:
-    # https://igs.bkg.bund.de/root_ftp/IGS/BRDC/2023/002/BRDC00<code that changes over time>_R_20230020000_01D_MN.rnx.gz
-    file_regex = f"BRDC00(?:IGS|WRD)_R_{day.year}{day.day_of_year:03}0000_01D_MN.rnx.gz"
+    # https://igs.bkg.bund.de/root_ftp/IGS/BRDC/2023/002/BRDC00IGS_R_20230020000_01D_MN.rnx.gz
+    file = f"BRDC00IGS_R_{day.year}{day.day_of_year:03}0000_01D_MN.rnx.gz"
     remote_directory = (
         f"https://igs.bkg.bund.de/root_ftp/IGS/BRDC/{day.year}/{day.day_of_year:03}/"
     )
     try:
-        # List available files whose names fit the pattern
-        directory_listing = requests.get(remote_directory, timeout=30).text
-        matches = list(set(re.findall(file_regex, directory_listing)))
-        if len(matches) == 0:
-            log.warning(f"Could not find broadcast ephemerides file for {day}")
-            return None
-        file = sorted(matches, key=lambda x: int("IGS" in x), reverse=True)[0]
         local_compressed_file = local_destination_folder / file
         url = remote_directory + file
         urllib.request.urlretrieve(url, local_compressed_file)
@@ -50,51 +95,29 @@ def try_downloading_ephemerides_http(day: pd.Timestamp, local_destination_folder
         return None
 
 
-def list_ftp_directory(server: str, folder: str):
-    ftp = FTP(server)
-    ftp.login()
-    ftp.cwd(folder)
-    dir_list = []
-    ftp.dir(dir_list.append)
-    return [c.split()[-1].strip() for c in dir_list]
-
-
-def try_downloading_ephemerides_ftp(day: pd.Timestamp, folder: Path):
-    server = "igs.ign.fr"
-    remote_folder = f"/pub/igs/data/{day.year}/{day.day_of_year:03}"
-    candidates = list_ftp_directory(server, remote_folder)
-    candidates = [
-        c
-        for c in candidates
-        if f"_R_{day.year}{day.day_of_year:03}0000_01D_MN.rnx.gz" in c
-    ]
-    if len(candidates) == 0:
-        log.warning(f"Could not find broadcast ephemerides file for {day}")
-        return None
-    candidates = sorted(
-        candidates,
-        key=lambda x: int("BRDC00" in x) + int("IGS" in x),
-        reverse=True,
-    )  #
-    file = candidates[0]
-    ftp_file = f"ftp://{server}/{remote_folder}/{file}"
-    local_compressed_file = folder / file
-    urllib.request.urlretrieve(ftp_file, local_compressed_file)
+def try_downloading_ephemerides_ftp(day: pd.Timestamp, local_destination_folder: Path):
+    file = f"BRDC00IGS_R_{day.year}{day.day_of_year:03}0000_01D_MN.rnx.gz"
+    local_compressed_file = local_destination_folder / file
+    for server, remote_folder in IGS_FTP_SERVER.items():
+        remote_folder_for_day = remote_folder + f"{day.year}/{day.day_of_year:03}"
+        ftp_file = f"ftp://{server}/{remote_folder_for_day}/{file}"
+        urllib.request.urlretrieve(ftp_file, local_compressed_file)
+        if not local_compressed_file.exists():
+            log.warning(f"Could not download {ftp_file}")
+            continue
+        local_file = converters.compressed_to_uncompressed(local_compressed_file)
+        os.remove(local_compressed_file)
+        log.info(f"Downloaded broadcast ephemerides file {ftp_file}")
+        prx.util.try_repair_with_gfzrnx(local_file)
     if not local_compressed_file.exists():
-        log.warning(f"Could not download {ftp_file}")
         return None
-    local_file = converters.compressed_to_uncompressed(local_compressed_file)
-    os.remove(local_compressed_file)
-    log.info(f"Downloaded broadcast ephemerides file {ftp_file}")
-    prx.util.try_repair_with_gfzrnx(local_file)
     return local_file
 
 
 def try_downloading_ephemerides(mid_day: pd.Timestamp, folder: Path):
-    # Try downloading from HTTP server first, files on FTP server sometimes do not have all constellations
-    local_file = try_downloading_ephemerides_http(mid_day, folder)
+    local_file = try_downloading_ephemerides_ftp(mid_day, folder)
     if not local_file:
-        local_file = try_downloading_ephemerides_ftp(mid_day, folder)
+        local_file = try_downloading_ephemerides_http(mid_day, folder)
     if not local_file:
         log.warning(f"Could not download broadcast ephemerides for {mid_day}")
     return local_file

src/prx/rinex_nav/test/test_nav_file_discovery.py

@@ -56,6 +56,22 @@ def test_download_remote_ephemeris_files(set_up_test):
     assert isinstance(aux_files, dict)
 
 
+def test_nav_file_ftp_availability_after_2016():
+    dates = [pd.Timestamp(y, 1, 1) for y in range(2016, pd.Timestamp.now().year)]
+    for date in dates:
+        assert aux.check_online_availability_ftp(date), (
+            f"NAV file for day {date} not available"
+        )
+
+
+def test_nav_file_http_availability_after_2022():
+    dates = [pd.Timestamp(y, 1, 1) for y in range(2022, pd.Timestamp.now().year)]
+    for date in dates:
+        assert aux.check_online_availability_http(date), (
+            f"NAV file for day {date} not available"
+        )
+
+
 def test_command_line_call(set_up_test):
     test_file = set_up_test["test_obs_file"]
     aux_file_script_path = (