PC20121002 Occultation October 02, 2012

(last updated 2012 09 19)

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. 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 October 02 02:32:48± 00:01:391 UT
Charon Geocentric Mid-time (yyyy month dd hh:mm:ss)

2012 October 02 03:09:15± 00:01:391 UT
Pluto Minimum Geocentric Separation 0.067± 0.0391 arcsec
Charon Minimum Geocentric Separation 0.075± 0.0391 arcsec
Position Angle (Pluto relative to the star; measured north through east) –156.773 degrees
Geocentric Velocity 7.89 km/sec
Occultation Star USNO-B R magnitude 15.72

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
PC20121002 Catalog 18 28 56.2393± 0.085 -19 41 25.9100± 0.135
PC20121002 Measured3 18 28 56.2510± 0.0275 -19 41 24.8059± 0.032
From 65 Lowell 42-inch 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

–0.0931± 0.014

 +0.170± 0.024 From 65 Lowell 42-inch Telescope frames. See note 4; See Notes 5 and 6

3Measured position corresponds to RA offset of +0.1655'' and Dec. offset of +1.104''.

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 telescopes taken when both Pluto and PC20121002 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)
Cerro Pachon (SOAR)
–70 44 13
–30 14 26
2.701
1524 N.
1428 N.
7.65
CTIO
–70 48 54
–30 09 54
2.215
1533 N.
1438 N.
7.65
Las Campanas
–70 42 00
–29 00 30
2.282
1659 N.
1561 N.
7.65
La Silla
–70 43 48
–29 15 24
2.347
1632 N.
1535 N.
7.65
Magdalena Ridge Obs.
–107 11 05
33 58 36
2.22
7023 N.
7342 N.
7.55
Mt. Graham (VATT)
–109 53 31
32 42 04
3.191
6893 N.
7239 N.
7.52
Santiago, Chile
–70 32 10
–33 23 45
0.903
1175 N.
1083 N.
7.66
Geocenter
----------
---------
center of Earth
1592 N.
1767 N.
7.89

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 ±915 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: PC20121002 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
Cerro Pachon (SOAR)
-----------
02:44:15
-----------
-----------
03:21:39
-----------
-----------
-----------
CTIO
-----------
02:44:15
-----------
-----------
03:21:39
-----------
-----------
-----------
Las Campanas
-----------
02:44:17
-----------
-----------
03:21:41
-----------
-----------
-----------
La Silla
-----------
02:44:16
-----------
-----------
03:21:41
-----------
-----------
-----------
Mt. Graham (VATT)
-----------
02:32:25
-----------
-----------
03:10:56
-----------
-----------
-----------
Magdalena Ridge Obs.
-----------
02:32:47
-----------
-----------
03:11:15
-----------
-----------
-----------
Santiago, Chile
02:42:33
02:44:12
02:45:51
-----------
03:21:32
-----------
-----------
-----------
Geocenter
-----------
02:32:48
-----------
-----------
03:09:15
-----------
-----------
-----------

9The errors on all times are ±1:39 (1 minutes and 39 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) 2012-09-19 13:25

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

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