Using ObsΒΆ
Obs objects mostly share their functionality with
Ephem, but there are some unique features tailored to observational data.
For instance, this class allows you to query observations reported to the Minor Planet Center for a given target:
>>> from sbpy.data import Obs
>>> data = Obs.from_mpc('2019 AA', id_type='asteroid designation')
>>> data
<QTable masked=True length=33>
number desig discovery note1 ... DEC mag band observatory
... deg mag
int64 str7 str1 str1 ... float64 float64 str1 str3
------ ------- --------- ----- ... ------------------ ------- ---- -----------
-- 2019 AA -- -- ... 42.32416944444445 20.2 G F51
-- 2019 AA -- -- ... 42.32879722222223 20.3 G F51
-- 2019 AA -- -- ... 42.333225000000006 20.3 G F51
-- 2019 AA * -- ... 46.52321666666666 20.0 w F51
-- 2019 AA -- -- ... 46.52748611111111 20.0 w F51
-- 2019 AA -- -- ... 46.531755555555556 20.0 w F51
... ... ... ... ... ... ... ... ...
-- 2019 AA -- -- ... 46.706500000000005 20.2 V 033
-- 2019 AA -- -- ... 46.70652777777778 20.2 V 033
-- 2019 AA -- -- ... 49.73566111111111 20.1 i F52
-- 2019 AA -- -- ... 49.73788888888889 20.1 i F52
-- 2019 AA -- -- ... 49.74008611111111 20.1 i F52
-- 2019 AA -- -- ... 49.742266666666666 20.2 i F52
For a given Obs object, supplement
allows you to supplement the information content of this object by
adding ephemeris data for the target(s) and epochs provided. This
function makes use of the query functions that are part of
Ephem and allows you to pick a service from which you
would like to obtain the data.
>>> data.field_names
['number', 'desig', 'discovery', 'note1', 'note2', 'epoch', 'RA', 'DEC', 'mag', 'band', 'observatory']
>>> data_sup = data.supplement(id_field='desig')
>>> data_sup.field_names
['number', 'desig', 'discovery', 'note1', 'note2', 'epoch', 'RA_obs', 'DEC_obs', 'mag', 'band', 'observatory', 'targetname', 'H', 'G', 'solar_presence', 'flags', 'RA', 'DEC', 'RA_app', 'DEC_app', 'RA*cos(Dec)_rate', 'DEC_rate', 'AZ', 'EL', 'AZ_rate', 'EL_rate', 'sat_X', 'sat_Y', 'sat_PANG', 'siderealtime', 'airmass', 'magextinct', 'V', 'surfbright', 'illumination', 'illum_defect', 'sat_sep', 'sat_vis', 'ang_width', 'PDObsLon', 'PDObsLat', 'PDSunLon', 'PDSunLat', 'SubSol_ang', 'SubSol_dist', 'NPole_ang', 'NPole_dist', 'EclLon', 'EclLat', 'r', 'r_rate', 'delta', 'delta_rate', 'lighttime', 'vel_sun', 'vel_obs', 'elong', 'elongFlag', 'alpha', 'lunar_elong', 'lunar_illum', 'sat_alpha', 'sunTargetPA', 'velocityPA', 'OrbPlaneAng', 'constellation', 'TDB-UT', 'ObsEclLon', 'ObsEclLat', 'NPole_RA', 'NPole_DEC', 'GlxLon', 'GlxLat', 'solartime', 'earth_lighttime', 'RA_3sigma', 'DEC_3sigma', 'SMAA_3sigma', 'SMIA_3sigma', 'Theta_3sigma', 'Area_3sigma', 'RSS_3sigma', 'r_3sigma', 'r_rate_3sigma', 'SBand_3sigma', 'XBand_3sigma', 'DoppDelay_3sigma', 'true_anom', 'hour_angle', 'alpha_true', 'PABLon', 'PABLat']
>>> data_sup['r']
[1.87637455 1.87638696 1.87639935 1.8891401 1.88915504 1.88916999
1.88918492 1.88963885 1.88964435 1.88965078 1.8896515 1.88965233
1.88965306 1.88970198 1.88970271 1.88970353 1.88970426 1.88970508
1.88970581 1.88978031 1.88978103 1.88978186 1.8897826 1.88978341
1.88978415 1.88978497 1.88978569 1.88978653 1.88978725 1.90342431
1.903438 1.90345164 1.90346529] AU
supplement queries in this case ephemerides from the
JPL Horizons system (the default service to be used) and appends
the additional data as new columns to the Obs
object. Targetnames and epochs are taken from the underlying
Obs object and must hence be present there; keyword
arguments id_field and epoch_field control the fieldnames from
which these information are taken. In order to prevent duplicate
column names, the keyword argument modify_fieldnames defines
whether field names in the Obs object or in the new
Ephem data are to be modified.
Note that services using from_mpc and
from_miriade are not optimized for queries of
multiple epochs. Hence, using these service will result in long
loading times. from_horizons, however, is optimized
for this type of query.