P20140727; July 27, 2014

³Measured position corresponds to RA offset of –0.0083'' and Dec. offset of +0.125" for the brighter sta. For the fainter star, the offsets are an RA offset of –0.2473'' and Dec. offset of +0.0306"

⁴All "offsets" are defined in the ("corrected" – "reference") or ("observed" – "calculated") sense. The offsets should be added to reference positions to get the measured positions, which we use to calculate the prediction.

⁴Data analyzed using UCAC2 reference network. A weighted average of the data from the two telescopes was used to calculate the RA and DEC. The errors given are 1 standard deviation.

⁵The reference positions for Pluto and Charon are those given by JPL Horizon's ephemeris (Pluto source file: PLU043; Earth center source file: DE431). Our residual model is based on the assumption that the same offsets in RA and Dec apply to both Pluto and Charon.

⁶Data from the USNO 61-inch, Lowell 42-inch telescope, SARA-South 24-inch telescope, and Lowell Astrograph telescopes over the span of 5 years were reduced with respect to stars in the UCAC2 catalog. A model was developed to fit the residuals obtained from our measured positions compared to that of the object's JPL ephemeris. All residuals obtained from the different telescopes were consistent with the model. The model includes the first-order effects of errors in the orbital elements of Pluto: (i) constant offsets in RA and Dec, (ii) linear (in time) offsets in RA and Dec, (iii) sinusoidal terms with the Earth's orbital period, and (iv) sinusoidal terms with the Pluto-Charon mutual orbit. The model was propagated to obtain the predicted position and error of the Pluto at the time of the occultation. The errors listed for the Pluto are the RMS of the models fitted.

Table 1: Prediction Details
Bright Star Occultation (Blue tracks)
Pluto Geocentric Mid-time (yyyy month dd hh:mm:ss)	2014 July 27 07:17:36± 00:00:42¹ UT
Pluto Minimum Geocentric Separation	0.307± 0.042¹ arcsec
Position Angle (Pluto relative to the star; measured north through east)	169.42 degrees
Geocentric Velocity	21.82 km/sec
Occultation Star UCAC2 magnitude	15.98²
Measured Magnitude (USNO frames)	15.86

Faint Star Occultation (Black tracks)
Pluto Geocentric Mid-time (yyyy month dd hh:mm:ss)	2014 July 27 07:22:14± 00:00:42¹ UT
Pluto Minimum Geocentric Separation	0.198± 0.042¹ arcsec
Position Angle (Pluto relative to the star; measured north through east)	169.42 degrees
Geocentric Velocity	21.82 km/sec
Delta magnitude from brighter star	~0.5 magnitudes fainter

Table 2: Reference Star Position
Reference star position: (USNOB, at epoch of event)	RA (h:m:s; J2000)	Dec (d:m:s; J2000)	Notes
P20140727 Catalog	18 49 10.1816± 0.2205	–20 23 18.633± 0.213
P20140727 Measured³	18 49 10.1810± 0.0132	–20 23 18.508± 0.014	USNO 61-inch Telescope frames. See note 4.
P20140727 fainter Measured³	18 49 10.1640± 0.0132	–20 23 18.664± 0.014	USNO 61-inch Telescope frames. See note 4.
Table 3: Projected KBO Offsets from Reference Ephemeris at the Time of the Event
Body	RA (arcsec)	Dec (arcsec)
Pluto	+0.0202± 0.0381	+0.030± 0.039	See Notes 5 and 6
³Measured position corresponds to RA offset of –0.0083'' and Dec. offset of +0.125" for the brighter sta. For the fainter star, the offsets are an RA offset of –0.2473'' and Dec. offset of +0.0306" ⁴All "offsets" are defined in the ("corrected" – "reference") or ("observed" – "calculated") sense. The offsets should be added to reference positions to get the measured positions, which we use to calculate the prediction. ⁴Data analyzed using UCAC2 reference network. A weighted average of the data from the two telescopes was used to calculate the RA and DEC. The errors given are 1 standard deviation. ⁵The reference positions for Pluto and Charon are those given by JPL Horizon's ephemeris (Pluto source file: PLU043; Earth center source file: DE431). Our residual model is based on the assumption that the same offsets in RA and Dec apply to both Pluto and Charon. ⁶Data from the USNO 61-inch, Lowell 42-inch telescope, SARA-South 24-inch telescope, and Lowell Astrograph telescopes over the span of 5 years were reduced with respect to stars in the UCAC2 catalog. A model was developed to fit the residuals obtained from our measured positions compared to that of the object's JPL ephemeris. All residuals obtained from the different telescopes were consistent with the model. The model includes the first-order effects of errors in the orbital elements of Pluto: (i) constant offsets in RA and Dec, (ii) linear (in time) offsets in RA and Dec, (iii) sinusoidal terms with the Earth's orbital period, and (iv) sinusoidal terms with the Pluto-Charon mutual orbit. The model was propagated to obtain the predicted position and error of the Pluto at the time of the occultation. The errors listed for the Pluto are the RMS of the models fitted.

Site	East Longitude	Latitude	Site Altitude⁶ (km)	Pluto Distance^{7 (BRIGHT STAR)} (km)	Pluto Distance⁷ ^{(FAINT STAR)} (km)	Velocity (km/s)
Cerro Calan	–70 32 48	–33 23 48	0.860	3908 N.	1337 N.	21.96
Kwajalein	167 29 11	09 10 55	0.0	10092 N.	7586 N.	22.09
LCGTO - CTIO	–70 48 54	–30 09 54	2.215	4201 N.	1629 N.	21.82
LCGTO - Haleakala	–156 15 24	20 42 24	3.054	11457 N.	8921 N.	22.23
Las Campanas	–70 42 00	–29 00 30	2.282	4301 N.	1728 N.	21.97
LCGTO - McDonald Obs	–104 01 21	30 40 17	2.076	11271 N.	8707 N.	22.14
Mt. John	170 27 50	–43 59 22	1.041	4581 N.	2067 N.	22.03
Geocenter	----------	---------	center of Earth	7078 N.	4548 N.	21.82

Site	Pluto Immersion (UT)⁹	Pluto Mid-Time (UT)	Pluto Emersion (UT)⁹	Pluto Immersion (UT)⁹	Pluto Mid-Time (UT)	Pluto Emersion (UT)⁹	Pluto Altitude	Solar Altitude⁹
Cerro Calan	-----------	07:14:29	-----------	07:18:45	07:19:04	07:19:22	35	-----------
Kwajalein	-----------	07:21:22	-----------	-----------	07:25:57	-----------	25	–3
LCGTO - CTIO	-----------	07:14:19	-----------	-----------	07:18:54	-----------	35	-----------
LCGTO - Haleakala	-----------	07:18:53	-----------	-----------	07:23:26	-----------	42	-----------
Las Campanas	-----------	07:14:16	-----------	-----------	07:18:50	-----------	35	-----------
LCGTO - McDonald Obs	-----------	07:15:06	-----------	-----------	07:19:40	-----------	32	-----------
Mt. John	-----------	07:20:56	-----------	-----------	07:25:32	-----------	38	–20
Geocenter	-----------	07:17:36	-----------	-----------	07:22:14	-----------	-----------	-----------

P20140727 Occultation July 27, 2014