PC20110522 Occultation May 22, 2011

(last updated 2011 05 12)

Observer Notes

 

Across the globe pictured above and to the left, the dark solid line correspond to the southern limit of Pluto's shadow. The southern limits of Pluto correspond to a radius of 1208 km.

Across the globe pictured above and to the right, the six solid lines correspond to the northern limit, centerline, and southern limit of Pluto's and Charon's 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 1-sigma error in 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)

2011 May 22 06:22:06± 00:00:281 UT

Pluto Minimum Geocentric Separation 0.289± 0.0211 arcsec
Charon Geocentric Mid-time (yyyy month dd hh:mm:ss)

2011 May 22 06:09:24± 00:00:281 UT

Charon Minimum Geocentric Separation 0.102± 0.0211arcsec
Position Angle (Pluto relative to the star; measured north through east) -3.04 degrees
Geocentric Velocity 18.20 km/sec
Occultation Star UCAC2 magnitude 15.32

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
PC20110522 Catalog 18 29 03.0745± 0.1537 –18 44 19.832± 0.170
PC20110522 Measured3 18 29 03.0900± 0.0110 –18 44 19.891± 0.013
from 17 USNO 61-inch frames
Table 3: Projected KBO Offsets from Reference Ephemeris at the Time of the Event
Body RA (arcsec) Dec (arcsec)  
Pluto

–0.1376± 0.0201

+0.094± 0.017 See Notes 5 and 6

3Measured position corresponds to RA offset of +0.2289 and Dec. offset of –0.059''.

All "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.

Data 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.

The measured RA and DEC take into account a nearby companion resolved using Magellan data. The calculated offset of the companion star from the occultation star is RA=0.51" DEC=–0.95" with a magnitude difference of 3.5 magnitudes (fainter).

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 du Pont 2.5m, 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)

Distance7

(km)

Velocity

(km/s)

Arne Henden's Obs
–71 33 48
43 41 15
0.60
1003 S. (Pluto)
18.4
Belfast, ME
–69 03 21
44 20 26
0.0
970 S. (Pluto)
18.4
Biddeford, ME
–70 36 09
43 27 16
0.0
1015 S. (Pluto)
18.4
Brasilia, Brazil
–47 54 41
–15 53 29
1.072
5850 S. (Charon)
18.4
Clay Center
–71 08 14
42 18 27
0.1
1075 S. (Pluto)
18.4
Gloucester, MA
–70 41 46
42 39 03
0.0
1056 S. (Pluto)
18.4
Doug Rich Obs.
–68 50 09
44 44 39
0.0
950 S. (Pluto)
18.4
Littleton, MA
–71 28 29
42 30 24
0.0
1065 S. (Pluto)
18.4
Lion's Head, ON
–81 15 28
44 59 17
0.0
968 S. (Pluto)
18.4
Magdalena Ridge Obs.
–107 11 05
33 58 36
2.22
1923 S. (Pluto)
18.4
Maria Mitchell Obs.
–70 06 42
41 16 42
0.0
1130 S. (Pluto)
18.5
McDonald Obs (Mt. Locke)
–104 01 21
30 40 17
2.08
2108 S. (Pluto)
18.4
Middlebury College
–73 10 01
44 00 45
0.
989 S. (Pluto)
18.4
Mt. Megantic
–71 09 00
45 28 01
1.0
914 S. (Pluto)
18.4
SVH Observatory
–74 56 45
40 57 41
0.22
1154 S. (Pluto)
18.5
USNO
–111 44 24
35 11 00
2.31
1924 S. (Pluto)
18.3
Vassar
–73 52 47
41 37 48
0.15
1115 S. (Pluto)
18.5
Wallace
–71 29 06
42 36 36
0.11
1059 S. (Pluto)
18.5
Weston, VT
–72 47 28
43 17 29
1.4
1025 S. (Pluto)
18.5
Williams
–73 12 06
42 42 42
0.22
1056 S. (Pluto)
18.5
WIRO
–105 58 34
41 05 49
2.94
1438 S. (Pluto)
18.3
Yerkes Observatory
–88 33 22

42 34 13

0.0
1143 S. (Pluto)
18.4
Geocenter
----------
---------
center of Earth
6653 S. (Pluto)
2334 S. (Charon)
18.2

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 ±481 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: PC20110522 Occultation Predictions for Individual Sites

Site
Pluto Immersion (UT)9
UT Mid-Time
Pluto Altitude
Solar Altitude9

PlutoEmersion (UT)9

Arne Henden's Obs
06:21:53
06:22:46
26
-----------
06:23:39
Belfast, ME
06:21:39
06:22:34
26
-----------
06:23:29
Biddeford, ME
06:21:49
06:22:42
26
-----------
06:23:34
Clay Center
06:21:57
06:22:45
28
-----------
06:23:34
Gloucester, MA
06:21:53
06:22:43
27
-----------
06:23:33
Doug Rich Obs.
06:21:37
06:22:33
26
-----------
06:23:29
Lion's Head, ON
06:22:29
06:23:24
23
-----------
06:24:18
Littleton, MA
06:21:57
06:22:47
28
-----------
06:23:36
Magdalena Ridge Obs.
-----------
06:25:29
21
-----------
-----------
McDonald Obs (Mt. Locke)
-----------
06:25:26
25
-----------
-----------
Maria Mitchell Obs.
06:21:57
06:22:42
28
-----------
06:23:27
Middlebury College
06:21:58
06:22:52
25
-----------
06:23:46
Mt. Megantic
06:21:44
06:22:42
25
-----------
06:23:39
SVH Observatory
06:22:21
06:23:04
28
-----------
06:23:47
USNO
-----------
06:25:40
17
-----------
-----------
Vassar
06:22:12
06:22:58
28
-----------
06:23:44
Wallace
06:21:57
06:22:46
28
-----------
06:23:36
Weston, VT
06:22:00
06:22:51
26
-----------
06:23:43
Williams
06:22:04
06:22:54
27
-----------
06:23:44
WIRO
-----------
06:25:03
16
-----------
-----------
Yerkes Observatory
06:23:13
06:23:57
22
-----------
06:24:41
Geocenter
-----------
06:22:06
-----------
-----------
-----------

9The errors on all times are ±0:28 (0 minutes and 28 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) 2011-05-12 09:00

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