Download STEREO tomography files¶

Goal¶

Fetch STEREO tomography files (.dat and preview .jpg) from the Aberystwyth archive to compare with COCONUT outputs.

Module¶

coconut_tools.download_tomo_file

What it downloads¶

Files of the form:

tomo_sta_cor2a_<YYYYMMDD>_<altitude>.dat
tomo_sta_cor2a_<YYYYMMDD>_<altitude>.jpg

From URLs shaped like:

https://solarphysics.aber.ac.uk/Archives/tomography/cor2a/<year>/distance_<altitude>/

API¶

def download_tomography_file(date: str, altitude: str, output_dir: str) -> None:
    """
    Download the .dat and .jpg tomography file for a given date and altitude.

    Args:
        date (str): The date in 'YYYYMMDD' format.
        altitude (str): The altitude string, e.g., '5-0', '4-4'.
        output_dir (str): The directory where to save the files.

    Returns:
        None
    """

Internals (simplified)¶

year = date[:4]
url = f"{BASE_URL}/{year}/distance_{altitude}/"
dat_filename = f"tomo_sta_cor2a_{date}_{altitude}.dat"
jpg_filename = f"tomo_sta_cor2a_{date}_{altitude}.jpg"

os.makedirs(output_dir, exist_ok=True)

for filename in [dat_filename, jpg_filename]:
    file_url = url + filename
    response = requests.get(file_url)
    if response.status_code == 200:
        with open(Path(output_dir) / filename, "wb") as f:
            f.write(response.content)
        logger.info(f"Downloaded: {filename}")
    else:
        raise FileNotFoundError

If the requested altitude is not available for that date, the code logs a list of available altitudes:

def list_available_altitudes(year: str) -> List[str]:
    """Return a list of available altitude strings for a given year."""
    ...

Best practices¶

Check availability first: the archive does not provide all altitudes for all dates. If a file is missing, use the logged list of available altitudes for that year and choose the closest one that matches your COCONUT radius of interest.
Keep a local cache: store downloads in a versioned folder (date/altitude in filename).
Compare apples to apples: use the same date (or closest in time) as your COCONUT snapshot.