PC20110623 Occultation June 23, 2011

(last updated 2011 06 21)

Observer Notes

 

Across the globe pictured above, the six solid lines correspond to the northern limit, centerline, and southern limit of Pluto's (Black) and Charon's (Red) shadow. The northern and southern limits of Pluto correspond to a radius of 1400 km (605km for Charon). 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)

2011 June 23 11:25:07± 00:00:231 UT

Pluto Minimum Geocentric Separation 0.113± 0.0181 arcsec
Charon Geocentric Mid-time (yyyy month dd hh:mm:ss)

2011 June 23 11:14:31± 00:00:231 UT

Charon Minimum Geocentric Separation 0.173± 0.0171arcsec
Position Angle (Pluto relative to the star; measured north through east) -6.13 degrees
Geocentric Velocity 23.85 km/sec
Occultation Star UCAC2 magnitude 14.432
2-MASS Catalog IR Magnitudes 10.957 (J), 10.054 (H), 9.743 (K)
NOMAD Catalog BVR Magnitudes 15.7 (B), 14.4 (V), 13.6 (R)

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
PC20110623 Catalog 18 25 55.4890± 0.1650 –18 48 07.047± 0.063
PC20110623 Measured3 18 25 55.4731± 0.0073 –18 48 06.990± 0.011
From 75 USNO 61-inchTelescope frames. See note 4.
Table 3: Projected KBO Offsets from Reference Ephemeris at the Time of the Event
Body RA (arcsec) Dec (arcsec)  
Pluto

–0.109± 0.024

+0.198± 0.014 See Notes 5 and 6

3Measured position corresponds to RA offset of -0.2387'' and Dec. offset of +0.056''.

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, SMARTS, du Pont, USNO 61-inch, and Lowell Astrograph telescopes over the span of 6 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 4: Site Information

Site
East Longitude
Latitude

Site Altitude6

(km)

Pluto Distance7

(km)

Charon Distance7

(km)

Velocity

(km/s)

Breit Ideas Observatory
–121 42 10
37 06 47
0.28

1850 N.

605 N.
24.06
Cairns, AUS
+145 46 28
–16 55 25
0.

2499 S.

3934 S.
24.14
CSUSB
–117 19 19
34 10 54
0.

1510 N.

274 N.
24.04
Grove Creek Observatory
+149 21 59
–33 49 46
0.9

4272 S.

5690 S.
24.11
IRTF
–155 28 29
19 49 46
4.18

1243 N.

52 S.

24.23
Leeward
–157 59 04
21 23 28
0.02

1414 N.

113 N.
24.24
Mt. Stromlo Observatory
+149 00 31
–35 19 09
0.77

4433 S.

5851 S.
24.11
Table Mountain
–117 40 54
34 22 54
2.29

1537 N.

301 N.
24.05
Sonoma, CA
–122 27 28
38 17 31
0.

1954 N.

706 N.
24.06
USNO-FS
–111 44 24
35 11 00
2.31

1430 N.

199 N.
24.01
Windward
–157 48 55
21 24 36
0.09

1414 N.

113 N.
24.24
Geocenter
----------
---------
center of Earth

2561 S.

3907 S.
23.86

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 ±408 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: PC20110623 Occultation Predictions for Individual Sites

Site
Charon
Immersion (UT)9
Charon
Mid-Time (UT)

Charon
Emersion
(UT)9

Pluto
Immersion (UT)9
Pluto
Mid-Time (UT)

Pluto
Emersion
(UT)9

Pluto Altitude
Solar
Altitude9
Breit Ideas Observatory
11:11:52
11:11:53
11:11:54
-----------
11:22:19
-----------
21
–14
Cairns, AUS
-----------
11:17:49
-----------
-----------
11:28:17
-----------
44
-----------
CSUSB
11:11:14
11:11:37
11:11:59
-----------
11:22:03
-----------
20
–14
Grove Creek Observatory
-----------
11:17:22
-----------
-----------
11:27:50
-----------
48
-----------
IRTF
11:13:17
11:13:42
11:14:07
11:23:38
11:24:05
11:24:32
50
-----------
Leeward
11:13:28
11:13:53
11:14:17
-----------
11:24:15
-----------
49
-----------
Mt. Stromlo Obs.
-----------
11:17:21
-----------
-----------
11:27:49
-----------
48
-----------
Table Mountain
11:11:16
11:11:38
11:12:00
-----------
11:22:05
-----------
20
–14
Sonoma, CA
-----------
11:11:57
-----------
-----------
11:22:23
-----------
20
–14
USNO-FS
11:11:01
11:11:25
11:11:48
-----------
11:21:52
-----------
16
–10
Windward
11:13:27
11:13:52
11:14:16
-----------
11:24:15
-----------
49
-----------
Geocenter
-----------
11:14:31
-----------
-----------
11:25:07
-----------
-----------
-----------

9The errors on all times are ±0:20 (20 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) 2011-06-21 20:50

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