What is id of Earth?

[gandalfsaxe]

I'm trying to get some coordinates for Earth with Sun as location on Horizons, as here:

However id=399 is not Earth, but Persephone (1895 BP). I also tried:

• [399]
• earth
• Earth
• Earth (Geocenter)
• Earth (Geocenter) 399
• earth

Is looked closely at the documentation page JPL Horizons Queries, but no luck.

What is the id of Earth?

[bsipocz]

cc @mommermi

[mommermi]

399 is correct, but then you also have to use id_type='id' when initializing your Horizons object. If you only use id=399, it will return asteroid 399, as id_type is by default set to smallbody, querying the asteroid and comet database.

[bsipocz]

If it's not yet in the docs, would it be possible to include?

[mommermi]

I think it's written up in the final paragraph here. @GandalfSaxe if you think it should be explained in a different way or more thoroughly, please let me know.

[gandalfsaxe]

Ah ok I see. I was probably just tired when looking at the documentation. Perhaps a single example with a planet would be beneficial, but as you said, it was already there 🙂

I am having some trouble with my query though:

from astroquery.jplhorizons import Horizons

obj = Horizons(id='399',
               location='@sun',
               epochs={'start':'2010-01-01',
                       'stop':'2010-03-01',
                       'step':'1d'},
               id_type='majorbody')

results in KeyError: 'Obsrv-lon' error when I try to extract ephemerides:

[MNRK01]

I'm having a similar KeyError: 'Obsrv-lon' error when trying to query JPL Horizons for the Moon when observed from an earth location.

e.g.

from astroquery.jplhorizons import Horizons
obj = Horizons(id='301', id_type='id', location={'lon': 0.0000, 'lat': 51.0000, 'elevation':0., 'body':'399'}, epochs=2451545.0)
obj.ephemerides()

gives me the following output:

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-174-765a66533942> in <module>()
----> 1 obj.ephemerides()

C:\Anaconda3\lib\site-packages\astroquery\utils\class_or_instance.py in f(*args, **kwds)
     23         def f(*args, **kwds):
     24             if obj is not None:
---> 25                 return self.fn(obj, *args, **kwds)
     26             else:
     27                 return self.fn(cls, *args, **kwds)

C:\Anaconda3\lib\site-packages\astroquery\utils\process_asyncs.py in newmethod(self, *args, **kwargs)
     27             if kwargs.get('get_query_payload') or kwargs.get('field_help'):
     28                 return response
---> 29             result = self._parse_result(response, verbose=verbose)
     30             self.table = result
     31             return result

C:\Anaconda3\lib\site-packages\astroquery\jplhorizons\core.py in _parse_result(self, response, verbose)
   1221             return None
   1222         else:
-> 1223             data = self._parse_horizons(response.text)
   1224
   1225         return data

C:\Anaconda3\lib\site-packages\astroquery\jplhorizons\core.py in _parse_horizons(self, src)
   1184         rename = []
   1185         for col in data.columns:
-> 1186             data[col].unit = column_defs[col][1]
   1187             if data[col].name != column_defs[col][0]:
   1188                 rename.append(data[col].name)

KeyError: 'Obsrv-lon'

Copying and pasting the obj.uri string into a browser works well though.

I have tried using other id_types:

obj = Horizons(id='Moon', id_type='majorbody', location={'lon': 0.0000, 'lat': 51.0000, 'elevation':0., 'body':'399'}, epochs=2451545.0)
obj.ephemerides()

which gives me an ambiguous target name error but shows that the ID for the Moon is correct above:

ValueError: Ambiguous target name; provide unique id:
  ID#      Name                               Designation  IAU/aliases/other
  -------  ---------------------------------- -----------  -------------------
        3  Earth-Moon Barycenter                           EMB
      301  Moon                                            Luna

Also, using the same query style for other bodies like the Sun (10), Mars (499), Jupiter (599), etc. does not produce any errors. e.g.

obj = Horizons(id='499', id_type='id', location={'lon': 0.0000, 'lat': 51.0000, 'elevation':0., 'body':'399'}, epochs=2451545.0)
obj.ephemerides()

<Table masked=True length=1>
targetname       datetime_str       datetime_jd ... alpha_true  PABLon   PABLat
   ---               ---                 d      ...    deg       deg      deg
  str10             str24             float64   ...  float64   float64  float64
---------- ------------------------ ----------- ... ---------- -------- -------
Mars (499) 2000-Jan-01 12:00:00.000   2451545.0 ...     31.459 343.7026 -1.2928

I'm using the Anaconda distribution on Windows 10. My version of astroquery is 0.3.9.dev582 from pypi.org.

Thank you.

[mommermi]

This looks like a bug. I will look into this! Thanks!

[mommermi]

This has been addressed in #1268

[gandalfsaxe]

Nice!

[bsipocz]

@GandalfSaxe - you should be able to update now with pip install --pre --upgrade astroquery to have this fixed locally.