PC20120909 Occultation September 09, 2012

(last updated 2012 09 08)

Across the globe pictured above, the three solid lines correspond to the northern limit, centerline, and southern limit of Pluto's shadow. The northern and southern limits correspond to a radius of 1400 km. The upper and lower dashed lines indicate 3-sigma errors on Pluto's prediction. The shaded area represents where the sun is more than 12 degrees below the horizon.

Table 1: Prediction Details
Pluto Geocentric Mid-time (yyyy month dd hh:mm:ss)	2012 September 09 02:58:02± 00:02:19¹ UT
Charon Geocentric Mid-time (yyyy month dd hh:mm:ss)	2012 September 09 03:37:21± 00:02:19¹ UT
Pluto Minimum Geocentric Separation	0.044± 0.035¹ arcsec
Charon Minimum Geocentric Separation	0.207± 0.035¹ arcsec
Position Angle (Pluto relative to the star; measured north through east)	–40.52 degrees
Geocentric Velocity	5.52 km/sec
Occultation Star USNO-B R magnitude	15.2²

¹One standard deviation of random error.
²The UCAC bandpass (579-642nm) is between V and R.

Table 2: Reference Star Position
Reference star position: (UCAC2, at epoch of event)	RA (h:m:s; J2000)	Dec (d:m:s; J2000)	Notes
PC20120909 Catalog	18 28 47.3947± 0.183	–19 36 35.430± 0.492
PC20120909 Measured³	18 28 47.3766± 0.028	–19 36 36.774± 0.037	From 339 Lowell 42-inch and SARA-S Telescope frames. See note 4; See Note 6
Table 3: Projected KBO Offsets from Reference Ephemeris at the Time of the Event
Body	RA (arcsec)	Dec (arcsec)
Pluto	–0.1648± 0.0103	+0.199± 0.010	From 339 Lowell 42-inch and SARA-S Telescope frames. See note 4; See Notes 5 and 6
³Measured position corresponds to RA offset of –0.2555'' and Dec. offset of –1.3439''. 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: PLU017; Earth center source file: DE405). 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 Lowell 42-inch and SARA-S telescopes taken when both Pluto and PC20120909 were both in the same image.

Table 4: Site Information

Site	East Longitude	Latitude	Site Altitude⁶ (km)	Pluto Distance⁷ (km)	Charon Distance⁷ (km)	Velocity (km/s)
Apache Point Observatory	–105 49 13	32 46 49	2.788	2392 N.	7280 N.	5.82
Cerro Pachon	–70 40 12	–30 14 26	2.783	4733 S.	267 N.	5.66
CTIO	–70 48 54	–30 09 54	2.215	4720 S.	280 N.	5.69
Denton, Tx	–97 07 59	33 12 53	0.0	1888 N.	6747 N.	5.79
Florida Inst. of Tech	–80 37 25	28 03 44	0.0	472 N.	5286 N.	5.74
Las Campanas	–70 42 00	–29 00 30	2.282	4658 S.	330 N.	5.66
Lowell Obs (Perkins)	–111 39 54	35 12 12	2.219	2866 N.	7796 N.	5.81
Magdalena Ridge Obs.	–107 11 05	33 58 36	2.22	2541 N.	7442 N.	5.81
McDonald Obs.	–104 01 21	30 40 17	2.076	2156 N.	7025 N.	5.81
Mt. Graham (VATT)	–109 53 31	32 42 04	3.191	2630 N.	7537 N.	5.82
New Smyrna Beach, FL	–81 07 33	28 54 55	0.0	570 N.	5388 N.	5.74
Santiago, Chile	–70 32 10	–33 23 45	0.903	4918 S.	116 N.	5.66
Starlight Observatory	–77 22 31	39 13 30	0.0	1114 N.	6000 N.	5.70
SVH Observatory	–74 56 45	40 57 41	0.0	1105 N.	6009 N.	5.69
Tzec Maun Observatory	–105 31 42	35 54 11	0.0	2381 N.	7268 N.	5.81
Univ. of Virgin Islands	–64 58 21	18 20 36	0.0	1361 S.	3461 N.	5.67
WAO	–71 29 06	42 36 36	0.107	1041 N.	5965 N.	5.67
Geocenter	----------	---------	center of Earth	997 S.	4673 N.	5.57

⁶Altitude of each observatory is measured in kilometers above sea level.

⁷"Distance" refers to the closest approach distance of the "Site" to the center of Pluto's shadow in the shadow plane. The errors on all closest approach distances are ±814 km (one standard deviation). "S." means the site is south of the center of Pluto's shadow. "N." means the site is north of the center of Pluto's shadow.

Table 5: PC20120909 Occultation Predictions for Individual Sites

Site	Pluto Immersion (UT)⁹	Pluto Mid-Time (UT)	Pluto Emersion (UT)⁹	Charon Immersion (UT)⁹	Charon Mid-Time (UT)	Charon Emersion (UT)⁹	Pluto Altitude	Solar Altitude⁹
Apache Point Observatory	-----------	02:47:01	-----------	-----------	03:25:00	-----------	-----------	–19
Cerro Pachon	-----------	02:51:58	-----------	03:29:58	03:31:34	03:33:10	41 (Charon)	-----------
CTIO	-----------	02:51:58	-----------	03:29:59	03:31:34	03:33:08	41 (Charon)	-----------
Denton, Tx	-----------	02:45:17	-----------	-----------	03:23:29	-----------	-----------	-----------
Florida Inst. of Tech	02:38:56	02:42:45	02:46:35	-----------	03:21:28	-----------	33	-----------
Las Campanas	-----------	02:51:38	-----------	03:29:43	03:31:13	03:32:42	40 (Charon)	-----------
Lowell Obs (Perkins)	-----------	02:47:56	-----------	-----------	03:25:48	-----------	-----------	–14
Magdalena Ridge Obs.	-----------	02:47:10	-----------	-----------	03:25:07	-----------	-----------	–17
McDonald Obs.	-----------	02:46:53	-----------	-----------	03:24:53	-----------	-----------	–21
Mt. Graham (VATT)	-----------	02:47:51	-----------	-----------	03:25:44	-----------	-----------	–16
New Smyrna Beach, FL	02:39:04	02:42:46	02:46:29	-----------	03:21:28	-----------	33	-----------
Santiago, Chile	-----------	02:52:51	-----------	03:30:44	03:32:29	03:34:14	40 (Charon)	-----------
Starlight Obs	02:39:14	02:41:43	02:44:12	-----------	03:20:31	-----------	23	-----------
SVH Observatory	02:38:51	02:41:22	02:43:53	-----------	03:20:15	-----------	21	-----------
Tzec Maun Obs	-----------	02:46:57	-----------	-----------	03:24:56	-----------	-----------	–19
Univ. of Virgin Islands	02:40:24	02:41:21	02:42:19	-----------	03:20:43	-----------	31	-----------
WAO	02:38:12	02:40:57	02:43:42	-----------	03:19:55	-----------	18	-----------
Geocenter	-----------	02:58:02	-----------	-----------	03:37:21	-----------	-----------	-----------

⁹The errors on all times are ±2:19 (2 minutes and 19 seconds; one standard deviation). The solar altitude is given for locations where it is relevant (solar altitude greater than -18°). No entry in the immersion and emersion columns indicates that the occultation is not predicted to be visible at that site.

Last updated by Carlos Zuluaga (czuluaga@mit.edu) 2012-09-08 11:40

Please direct all inquiries to PAL (planetary-astronomy@mit.edu)

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