Retrieve calibration files for HARPS programatically

Dear Andrew,
The information that you should use the datalink service to get to the ancillary files is provided in the programmatic overview page: http://archive.eso.org/cms/eso-data/programmatic-access.html but I fully agree that that is not enough. I will publish a script for that.
Thanks for pointing this out. In the meantime...

Here I provide you preliminary snippets of the code necessary to do that, with explanations.
As said, it is the datalink service that allows you to find all kinds of files related to the input one.The datalink response for a HARPS calibrated spectrum contains, among others, the ancillary file you want to download (the tar ball).
As an example, try:

http://archive.eso.org/datalink/links?ID=ivo://eso.org/ID?ADP.2014-09-16T11:03:30.940

The ancillary files can be identified by the "semantics" field which must be set to "#auxiliary".
In python:
import eso_programmatic.py as eso

# The eso_programmatic.py
# is published here: http://archive.eso.org/programmatic/HOWTO/jupyter/authentication_and_authorisation/eso_programmatic.py

# Let's get the access_url of 3 HARPS products:
query = """SELECT top 3 access_url from ivoa.ObsCore where obs_collection='HARPS'"""
res = tap.search(query)
print(res)

                                      access_url                                     
                                        object                                       
-------------------------------------------------------------------------------------
http://archive.eso.org/datalink/links?ID=ivo://eso.org/ID?ADP.2014-09-16T11:03:30.940
http://archive.eso.org/datalink/links?ID=ivo://eso.org/ID?ADP.2014-09-16T11:03:30.947
http://archive.eso.org/datalink/links?ID=ivo://eso.org/ID?ADP.2014-09-16T11:03:30.973

# Let's loop through those 3, and for each of them loop through its #auxiliary entries (the tar ball is the only #auxiliary for an HARPS product anyway):
for rec in (res):
datalink = vo.dal.adhoc.DatalinkResults.from_result_url(rec['access_url'], session=session)
ancillaries = datalink.bysemantics('#auxiliary')
for anc in ancillaries: # for each ancillary, get its access_url, and use it to download the file
# other useful info available: print(anc['eso_category'], anc['eso_origfile'], anc['content_length'], anc['access_url'])
status_code, filepath = eso.downloadURL(anc['access_url'], session=session)
if status_code == 200:
print("File {0} downloaded as {1}".format(anc['eso_origfile'], filepath))

The result is:

File HARPS.2006-08-09T05:48:52.136_DRS_HARPS_3.5.tar downloaded as ./ADP.2014-09-16T11:08:02.037.tar
File HARPS.2006-01-30T08:42:04.135_DRS_HARPS_3.5.tar downloaded as ./ADP.2014-09-16T11:04:44.533.tar
File HARPS.2006-07-30T07:45:53.333_DRS_HARPS_3.5.tar downloaded as ./ADP.2014-09-16T11:04:48.567.tar

If you prefer to download the tar ball with its original name, then add "filename=anc['eso_origfile']" as in:
status_code, filepath = eso.downloadURL(anc['access_url'], filename=anc['eso_origfile'], session=session)
and you'll obtain:

File HARPS.2006-08-09T05:48:52.136_DRS_HARPS_3.5.tar downloaded as ./HARPS.2006-08-09T05:48:52.136_DRS_HARPS_3.5.tar
File HARPS.2006-01-30T08:42:04.135_DRS_HARPS_3.5.tar downloaded as ./HARPS.2006-01-30T08:42:04.135_DRS_HARPS_3.5.tar
File HARPS.2006-07-30T07:45:53.333_DRS_HARPS_3.5.tar downloaded as ./HARPS.2006-07-30T07:45:53.333_DRS_HARPS_3.5.tar

Thanks a lot for reporting the absence of examples on this!

Alberto Micol

ESO Archive Science Group