ssdatalab/tess-ephem

Where are Solar System objects located in TESS data?

tess-ephem's Issues

Automatically detect & exclude periods with extreme motion rates

This is a follow-up of #2.

Because tess-ephem downloads and interpolates ephemeris from JPL Horizons with a pre-determined resolution (currently 12 hours), it will not yield accurate results for extremely fast-moving objects.

The good news:

1. We can automatically detect periods affected by extreme motion from the ephemeris data.
2. It would likely be fine to automatically exclude those periods from the ephemeris analysis, because TESS cannot usefully observe objects moving at many degrees per day.

Hence, I propose we address this issue by automatically excluding episodes of extreme motion from the TESS visibility assessment. The maximum rate of motion supported could be documented in the documentation, and a warning message could be issued when such extreme motion is encountered for an object.

Comets sometimes result in a "ambiguous target name" error

When using tess_ephem to check on a comet, sometimes a ValueError is raised due to an ambiguous target name. For example:

tt = ephem("C/1995 O1", verbose=True)

Results in:

ValueError Traceback (most recent call last)
in
----> 1 tt = ephem("C/1995 O1", verbose=True)

/opt/anaconda3/lib/python3.8/site-packages/tess_ephem/ephem.py in ephem(target, time, verbose, id_type, interpolation_step)
175 start = time[0] - 7
176 stop = time[-1] + 7
--> 177 te = TessEphem(
178 target, start=start, stop=stop, step=interpolation_step, id_type=id_type
179 )

/opt/anaconda3/lib/python3.8/site-packages/tess_ephem/ephem.py in init(self, target, start, stop, step, location, id_type)
41 """
42 log.info(f"Started querying JPL/Horizons for for ephemeris (id='{target}')")
---> 43 eph = _get_horizons_ephem(
44 id=target,
45 id_type=id_type,

/opt/anaconda3/lib/python3.8/site-packages/tess_ephem/ephem.py in _get_horizons_ephem(id, start, stop, step, id_type, location, quantities)
127 )
128 t = Horizons(id=id, id_type=id_type, location=location, epochs=epochs)
--> 129 result = t.ephemerides(quantities=quantities)
130 log.debug(f"Received {len(result)} ephemeris results")
131 return result

/opt/anaconda3/lib/python3.8/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)

/opt/anaconda3/lib/python3.8/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

/opt/anaconda3/lib/python3.8/site-packages/astroquery/jplhorizons/core.py in _parse_result(self, response, verbose)
1294 return None
1295 else:
-> 1296 data = self._parse_horizons(response.text)
1297
1298 return data

/opt/anaconda3/lib/python3.8/site-packages/astroquery/jplhorizons/core.py in _parse_horizons(self, src)
1153 end_idx = i
1154 break
-> 1155 raise ValueError(('Ambiguous target name; provide '
1156 'unique id:\n%s' %
1157 '\n'.join(src[idx + 2:end_idx])))

ValueError: Ambiguous target name; provide unique id:
Record # Epoch-yr >MATCH DESIG< Primary Desig Name
-------- -------- ------------- ------------- -------------------------
90002087 1996 C/1995 O1 C/1995 O1 Hale-Bopp
90002088 2008 C/1995 O1 C/1995 O1 Hale-Bopp

Option to *not* perform DVA correction

I see tess-locator now uses the tess-point approximate DVA correction. I'm concerned the ~0.1 pixel error in the approximation is already large compared to our centroiding precision. I would like to request the option to not perform the DVA correction when calling ephem. This will allow for some comparisons with other DVA correction methods.

`interpolation_step="7D"` raises a ValueError

@jessie-dotson pointed me to the following failure for "2004 QX2", which occurs when interpolation_step="7D" but not when interpolation_step="12H".

>>> from tess_ephem import ephem
>>> ephem("2004 QX2", interpolation_step="7D")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/gb/dev/tess-ephem/src/tess_ephem/ephem.py", line 180, in ephem
    return te.predict(time=time, verbose=verbose)
  File "/Users/gb/dev/tess-ephem/src/tess_ephem/ephem.py", line 100, in predict
    crd = SkyCoord(sky.ra, sky.dec, unit="deg")
  File "/Users/gb/Library/Caches/pypoetry/virtualenvs/tess-ephem-_eKBvW1X-py3.8/lib/python3.8/site-packages/astropy/coordinates/sky_coordinate.py", line 315, in __init__
    skycoord_kwargs, components, info = _parse_coordinate_data(
  File "/Users/gb/Library/Caches/pypoetry/virtualenvs/tess-ephem-_eKBvW1X-py3.8/lib/python3.8/site-packages/astropy/coordinates/sky_coordinate_parsers.py", line 301, in _parse_coordinate_data
    _components[frame_attr_name] = attr_class(arg, unit=unit)
  File "/Users/gb/Library/Caches/pypoetry/virtualenvs/tess-ephem-_eKBvW1X-py3.8/lib/python3.8/site-packages/astropy/coordinates/angles.py", line 536, in __new__
    self._validate_angles()
  File "/Users/gb/Library/Caches/pypoetry/virtualenvs/tess-ephem-_eKBvW1X-py3.8/lib/python3.8/site-packages/astropy/coordinates/angles.py", line 557, in _validate_angles
    raise ValueError('Latitude angle(s) must be within -90 deg <= angle <= 90 deg, '
ValueError: Latitude angle(s) must be within -90 deg <= angle <= 90 deg, got [ 2.57963712e+01  2.59729000e+01  2.61491591e+01  2.63251927e+01
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  1.62692314e+01  1.64604919e+01  1.66533856e+01  1.68481400e+01
  1.70448962e+01  1.72434476e+01  1.74435011e+01  1.76447633e+01
  1.78469409e+01  1.80497409e+01  1.82528700e+01  1.84561426e+01
  1.86598019e+01  1.88641986e+01  1.90696837e+01  1.92766081e+01
  1.94853232e+01  1.96961800e+01  1.99093958e+01  2.01246512e+01
  2.03414929e+01  2.05594670e+01  2.07781203e+01  2.09969990e+01
  2.12156500e+01  2.14337748e+01  2.16516945e+01  2.18698849e+01
  2.20888223e+01  2.23089829e+01  2.25308434e+01  2.27548800e+01
  2.29813875e+01  2.32099338e+01  2.34399046e+01  2.36706858e+01
  2.39016632e+01  2.41322226e+01  2.43617500e+01  2.45897987e+01
  2.48165892e+01  2.50425094e+01  2.52679468e+01  2.54932892e+01
  2.57189244e+01  2.59452400e+01  2.61724254e+01  2.63998779e+01
  2.66267961e+01  2.68523783e+01  2.70758227e+01  2.72963272e+01
  2.75130900e+01  2.77254309e+01  2.79331569e+01  2.81361966e+01
  2.83344786e+01  2.85279311e+01  2.87164823e+01  2.89000600e+01
  2.90783484e+01  2.92500560e+01  2.94136464e+01  2.95675820e+01
  2.97103241e+01  2.98403334e+01  2.99560700e+01  3.00559884e+01
  3.01385220e+01  3.02021001e+01  3.02451526e+01  3.02661094e+01
  3.02633995e+01  3.02354500e+01  3.01800315e+01  3.00922955e+01
  2.99667398e+01  2.97978664e+01  2.95801879e+01  2.93082372e+01
  2.89765800e+01  2.85790547e+01  2.81063863e+01  2.75483930e+01
  2.68947005e+01  2.61346915e+01  2.52574644e+01  2.42518100e+01
  2.31171103e+01  2.18963991e+01  2.06442765e+01  1.94158857e+01
  1.82665423e+01  1.72513635e+01  1.64250400e+01  1.58266643e+01
  1.54345202e+01  1.52119865e+01  1.51226988e+01  1.51304297e+01
  1.51989760e+01  1.52920900e+01  1.53811544e+01  1.54682793e+01
  1.55632828e+01  1.56760095e+01  1.58163456e+01  1.59942528e+01
  1.62198200e+01  1.65005910e+01  1.68332254e+01  1.72113505e+01
  1.76281238e+01  1.80761313e+01  1.85473308e+01  1.90330500e+01
  1.95386033e+01  2.01275568e+01  2.08791845e+01  2.18754198e+01
  2.32037011e+01  2.49610172e+01  2.72586700e+01  3.02267270e+01
  3.40158149e+01  3.87912231e+01  4.47100920e+01  5.18693126e+01
  6.02196925e+01  6.94768300e+01  7.91100857e+01  8.84771241e+01
  9.70402895e+01  1.04505716e+02  1.10816309e+02  1.16063376e+02] deg
>>> ephem("2004 QX2", interpolation_step="12H")
Empty DataFrame
Columns: [sector, camera, ccd, column, row]
Index: []

`tess-ephem` does not cache the JPL query behind an `ephem` result

At the moment I am running
tess_ephem.ephem('Chirotenmondai', tpf.astropy_time)

But, if I rerun the same cell, I have to wait, and it seems liketess-ephem isn't caching the JPL query. I think it;s supposed to cache, but I'm not sure!

Incorrect (col, row) returned for asteroid 4077 in sector 2

Asteroid 4077 in sector 2 was reported by @christinahedges to display a strange kink in its (col, row) trajectory, which is almost certainly incorrect because its (ra, dec) trajectory on the sky is a straight line. It looks like the WCS transform can yield incorrect (col, row) values after an object has moved off the ccd.

I'm in the process of debugging this and adding a unit test.

Example bug: