Refactor astroquery.heasarc to use VO protocols

CHANGES.rst

@@ -7,6 +7,10 @@ New Tools and Services
 
 Service fixes and enhancements
 ------------------------------
+heasarc
+^^^^^^^
+
+- Refactor heasarc to use the VO backend. [#2997]
 
 astrometry_net
 ^^^^^^^^^^^^^^

astroquery/heasarc/__init__.py

@@ -5,10 +5,6 @@
 
 The High Energy Astrophysics Science Archive Research Center (HEASARC)
 is the primary archive for NASA's (and other space agencies') missions.
-
-The initial version of this was coded in a sprint at the
-"Python in astronomy" workshop in April 2015 by Jean-Christophe Leyder,
-Abigail Stevens, Antonio Martin-Carrillo and Christoph Deil.
 """
 from astropy import config as _config
 
@@ -27,6 +23,20 @@ class Conf(_config.ConfigNamespace):
         30,
         'Time limit for connecting to HEASARC server.')
 
+    VO_URL = _config.ConfigItem(
+        'https://heasarc.gsfc.nasa.gov/xamin/vo',
+        'Base Url for VO services')
+
+    TAR_URL = _config.ConfigItem(
+        'https://heasarc.gsfc.nasa.gov/xamin/TarServlet',
+        'URL for the xamin tar servlet'
+    )
+
+    S3_BUCKET = _config.ConfigItem(
+        'nasa-heasarc',
+        'The name of the AWS S3 bucket that contain the HEASARC data'
+    )
+
 
 conf = Conf()