def _search_level1(self, archive_url, timerange):
 """
 Two-step HTTP search for Level 1 SP data.

 Level 1 scan directories are named after the scan *start* time, but
 each file within the directory carries its own per-exposure timestamp.
 The standard `Scraper` pattern matching requires identical timestamps
 in both the directory name and the filename, so only the very first
 exposure of each scan would be found. This method avoids that
 limitation by:

 1. Enumerating candidate scan directories via `Scraper.range()`.
 2. Fetching each directory listing and matching individual filenames
 against their own timestamps, then filtering by the requested time
 range.
 """
 dir_pattern = _L1_SP_DIR_PATTERN.replace('{archive}', archive_url)
 dir_scraper = Scraper(format=dir_pattern)
 directories = dir_scraper.range(timerange)
 filemeta = []
 for directory in directories:
 try:
 opn = urlopen(directory)
 try:
 soup = BeautifulSoup(opn, "html.parser")
 for link in soup.find_all("a"):
 href = link.get("href")
 if not href:
 continue
 filename = href.rstrip('/').split('/')[-1]
 meta = parse(_L1_SP_FILE_PARSE_PATTERN, filename)
 if meta is None:
 continue
 exdict = meta.named
 try:
 file_tr = get_timerange_from_exdict(exdict)
 except Exception:
 continue
 if file_tr.intersects(timerange):
 exdict['url'] = directory + filename
 filemeta.append(exdict)
 finally:
 opn.close()
 except HTTPError as http_err:
 if http_err.code == 404:
 continue
 raise
 except URLError:
 continue
 return filemeta