PC20120909 Occultation September 09, 2012

(last updated 2012 09 08)

OBSERVER NOTES


 

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)