Where are Solar System objects located in TESS FFI data?
tess-ephem is a user-friendly package which enables users to compute the positions of Solar System objects -- asteroids, comets, and planets --
in the data archive of NASA's TESS Space Telescope.
python -m pip install tess-ephemtess-ephem allows you to search the entire archive of TESS FFI's for the presence of a known minor planet, and obtain the result as a Pandas DataFrame. The output pixel coordinates (column and row) follow the TESS convention, with (1,1) being the middle of the pixel in the lower left corner of the FFI. For example:
>>> from tess_ephem import ephem
>>> ephem("Sedna")
sector camera ccd column row tdb-ut pixels_per_hour ra dec vmag hmag sun_distance obs_distance phase_angle
time
2458438.5 5 1 4 1543.104021 1102.948351 69.182738 0.074363 57.11724 7.64961 20.803 1.49 84.947515 83.981039 0.1450
2458439.5 5 1 4 1544.978969 1103.000701 69.182758 0.075353 57.10692 7.64724 20.802 1.49 84.946739 83.978850 0.1423
2458440.5 5 1 4 1546.866007 1103.027415 69.182777 0.075362 57.09651 7.64500 20.801 1.49 84.945964 83.977315 0.1403
2458441.5 5 1 4 1548.750885 1103.040242 69.182797 0.075132 57.08610 7.64284 20.801 1.49 84.945188 83.976314 0.1394
2458442.5 5 1 4 1550.627199 1103.044020 69.182818 0.074800 57.07573 7.64074 20.801 1.49 84.944412 83.975782 0.1394
... ... ... ... ... ... ... ... ... ... ... ... ... ... ...
2460254.5 71 2 4 1984.578578 1003.555888 69.182570 0.072528 60.21660 8.36089 20.750 1.49 83.592715 82.661747 0.2395
2460255.5 71 2 4 1984.808484 1001.737047 69.182584 0.072889 60.20673 8.35803 20.749 1.49 83.591992 82.656583 0.2304
2460256.5 71 2 4 1985.037223 999.911091 69.182599 0.073002 60.19682 8.35517 20.747 1.49 83.591270 82.651896 0.2214
2460257.5 71 2 4 1985.258387 998.084718 69.182615 0.072664 60.18690 8.35235 20.745 1.49 83.590547 82.647726 0.2127
2460258.5 71 2 4 1985.460633 996.280013 69.182631 0.071257 60.17708 8.34965 20.744 1.49 83.589824 82.644125 0.2044
[75 rows x 14 columns]The time is in the UT scale. To convert this to the TDB timescale, the column tdb-ut (offset in seconds) should be used.
You can also obtain the ephemeris for one or more specific times
by passing the time parameter:
>>> ephem("Sedna", time="2018-11-21 17:35:00")
sector camera ccd column row tdb-ut pixels_per_hour ra dec vmag hmag sun_distance obs_distance phase_angle
time
2018-11-21 17:35:00.000 5 1 4 1553.858404 1103.035027 69.182854 0.074053 57.05786 7.63721 20.802 1.49 84.943069 83.975873 0.1419
>>> from astropy.time import Time
>>> ephem("Sedna", time=Time([2458441.5,2460258.5], format='jd'))
sector camera ccd column row tdb-ut pixels_per_hour ra dec vmag hmag sun_distance obs_distance phase_angle
time
2458441.5 5 1 4 1548.750885 1103.040242 69.182797 0.075132 57.08610 7.64284 20.801 1.49 84.945188 83.976314 0.1394
2460258.5 71 2 4 1985.460633 996.280013 69.182631 0.071257 60.17708 8.34965 20.744 1.49 83.589824 82.644125 0.2044Orbital elements can be obtained by passing the orbital_elements=True parameter. The function returns the average orbital elements of the target during the queried time. Perihelion distance is in AU and orbital inclination is in degrees.
>>> df_ephem, orbital_elements = ephem("Sedna", time="2018-11-21 17:35:00", orbital_elements=True)
>>> orbital_elements
{'perihelion_distance': 76.13300496827914, 'eccentricity': 0.8413468330602263, 'orbital_inclination': 11.929585189509927}You can alternatively obtain the ephemeris during a specific sector by passing
the sector parameter:
>>> ephem("Sedna", sector=70)
sector camera ccd column row tdb-ut pixels_per_hour ra dec vmag hmag sun_distance obs_distance phase_angle
time
2460208.5 70 4 2 1965.994639 1827.049672 69.182409 0.025550 60.53693 8.49483 20.815 1.49 83.625984 83.171959 0.6161
2460209.5 70 4 2 1966.304467 1826.442414 69.182402 0.029493 60.53386 8.49248 20.814 1.49 83.625260 83.156129 0.6112
2460210.5 70 4 2 1966.639579 1825.743198 69.182395 0.032766 60.53030 8.48989 20.813 1.49 83.624537 83.140186 0.6058
2460211.5 70 4 2 1966.995717 1824.975902 69.182389 0.035144 60.52638 8.48711 20.812 1.49 83.623813 83.124437 0.6001
2460212.5 70 4 2 1967.363962 1824.160062 69.182382 0.037045 60.52220 8.48421 20.811 1.49 83.623090 83.108950 0.5940
2460213.5 70 4 2 1967.743247 1823.299432 69.182377 0.038666 60.51778 8.48120 20.810 1.49 83.622366 83.093746 0.5878
2460214.5 70 4 2 1968.127856 1822.402268 69.182372 0.040092 60.51316 8.47812 20.809 1.49 83.621642 83.078838 0.5813
2460215.5 70 4 2 1968.516359 1821.470633 69.182367 0.041354 60.50835 8.47498 20.808 1.49 83.620919 83.064240 0.5747
2460216.5 70 4 2 1968.909479 1820.507912 69.182363 0.042441 60.50337 8.47178 20.806 1.49 83.620195 83.049971 0.5680
2460217.5 70 4 2 1969.301139 1819.520671 69.182359 0.043287 60.49825 8.46856 20.805 1.49 83.619472 83.036058 0.5611
2460218.5 70 4 2 1969.690629 1818.514364 69.182355 0.043699 60.49302 8.46533 20.804 1.49 83.618748 83.022538 0.5541
2460219.5 70 4 2 1970.070096 1817.504775 69.182353 0.043112 60.48776 8.46215 20.803 1.49 83.618025 83.009457 0.5471
2460220.5 70 4 2 1970.413447 1816.527398 69.182350 0.040265 60.48264 8.45920 20.802 1.49 83.617302 82.996750 0.5403
2460221.5 70 4 2 1970.685594 1815.593040 69.182349 0.039919 60.47768 8.45668 20.800 1.49 83.616578 82.983656 0.5337
2460222.5 70 4 2 1970.945096 1814.590453 69.182347 0.043872 60.47232 8.45415 20.799 1.49 83.615855 82.969867 0.5266
2460223.5 70 4 2 1971.226319 1813.505439 69.182347 0.046801 60.46652 8.45141 20.798 1.49 83.615131 82.956089 0.5192
2460224.5 70 4 2 1971.528584 1812.361144 69.182347 0.048934 60.46041 8.44849 20.796 1.49 83.614408 82.942565 0.5115
2460225.5 70 4 2 1971.840095 1811.172397 69.182347 0.050643 60.45406 8.44547 20.795 1.49 83.613685 82.929353 0.5035
2460226.5 70 4 2 1972.160145 1809.944650 69.182348 0.052095 60.44750 8.44236 20.794 1.49 83.612961 82.916471 0.4954
2460227.5 70 4 2 1972.484084 1808.682404 69.182350 0.053363 60.44075 8.43919 20.792 1.49 83.612238 82.903932 0.4871
2460228.5 70 4 2 1972.811565 1807.392809 69.182352 0.054473 60.43385 8.43597 20.791 1.49 83.611515 82.891750 0.4787
2460229.5 70 4 2 1973.139007 1806.076605 69.182354 0.055414 60.42680 8.43272 20.790 1.49 83.610791 82.879944 0.4701
2460230.5 70 4 2 1973.467494 1804.738876 69.182358 0.056123 60.41963 8.42944 20.788 1.49 83.610068 82.868542 0.4615
2460231.5 70 4 2 1973.791305 1803.387890 69.182361 0.056414 60.41238 8.42617 20.787 1.49 83.609345 82.857585 0.4528
2460232.5 70 4 2 1974.102222 1802.037747 69.182365 0.055711 60.40512 8.42297 20.785 1.49 83.608622 82.847125 0.4442When passing the sector parameter, the time_step is by default 1 day.
This can be changed as follows:
>>> ephem("Sedna", sector=70, time_step=0.1) sector camera ccd column row tdb-ut pixels_per_hour ra dec vmag hmag sun_distance obs_distance phase_angle time 2460207.6 70 4 2 1965.698467 1827.543203 69.182416 0.026894 60.539373 8.496977 20.815973 1.49 83.626635 83.185495 0.620233 2460207.7 70 4 2 1965.734658 1827.487317 69.182415 0.026487 60.539100 8.496720 20.816002 1.49 83.626563 83.184025 0.619771 2460207.8 70 4 2 1965.769986 1827.432018 69.182415 0.026102 60.538829 8.496468 20.816045 1.49 83.626491 83.182549 0.619312 2460207.9 70 4 2 1965.804410 1827.377187 69.182414 0.025764 60.538559 8.496221 20.816058 1.49 83.626418 83.181067 0.618856 2460208.0 70 4 2 1965.837889 1827.322705 69.182413 0.025498 60.538290 8.495980 20.816000 1.49 83.626346 83.179575 0.618400 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 2460233.0 70 4 2 1974.248380 1801.371667 69.182368 0.054524 60.401530 8.421430 20.785000 1.49 83.608260 82.842086 0.439900 2460233.1 70 4 2 1974.275695 1801.240320 69.182368 0.054170 60.400820 8.421134 20.784886 1.49 83.608188 82.841090 0.439050 2460233.2 70 4 2 1974.302128 1801.109815 69.182369 0.053786 60.400114 8.420844 20.784707 1.49 83.608115 82.840098 0.438204 2460233.3 70 4 2 1974.327659 1800.980176 69.182369 0.053386 60.399412 8.420560 20.784486 1.49 83.608043 82.839105 0.437364 2460233.4 70 4 2 1974.352268 1800.851430 69.182370 0.052985 60.398714 8.420282 20.784243 1.49 83.607971 82.838112 0.436529[259 rows x 14 columns]