PH20110627 Occultation June 27, 2011

(last updated 2011 06 26)

Observer Notes

Across the globe pictured above, the three solid lines correspond to the northern limit, centerline, and southern limit of Pluto's (Black) and Hydra's (Red) shadow. The northern and southern limits correspond to a radius of 1400 km (50km for Hydra). 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.

Note that the plot with the black (Pluto) and red (Hydra) occultation tracks is drawn at the midtime of the Pluto event. The Hydra event occurs about 30 minutes later; the Earth has rotated a significant amount in that time, that's why the Pluto and Hydra tracks are not parallel.

Table 1: Prediction Details
Pluto Geocentric Mid-time (yyyy month dd hh:mm:ss)

2011 June 27 14:17:15± 00:00:161 UT
Pluto Minimum Geocentric Separation 0.211± 0.0161 arcsec
Hydra Geocentric Mid-time (yyyy month dd hh:mm:ss)

2011 June 27 14:50:23± 00:00:161 UT
Hydra Minimum Geocentric Separation 0.113± 0.0161 arcsec
Position Angle (Pluto relative to the star; measured north through east) -6.32 degrees
Geocentric Velocity 23.92 km/sec
Occultation Star UCAC2 magnitude 13.62
2-MASS Catalog IR Magnitudes 12.326 (J), 12.091 (H), 11.933 (K)
NOMAD Catalog BVR Magnitudes 13.6 (B), 13.5 (V), 13.7 (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
PH20110627 Catalog 18 25 29.0058± 0.1594 –18 48 47.4945± 0.151
PH20110627 Measured3 18 25 29.0124± 0.007 –18 48 47.6359± 0.011
From 70 USNO 61-inch Telescope frames. See note 4.
Table 3: Projected KBO Offsets from Reference Ephemeris at the Time of the Event
Body RA (arcsec) Dec (arcsec)  
Pluto

–0.1544± 0.0125

 +0.218± 0.012 See Notes 5 and 6

3Measured position corresponds to RA offset of +0.097'' and Dec. offset of –0.141''.

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. The Hydra offset from Pluto was provided by Dave Tholen based on analysis of HST data.

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)

Pluto Distance7

(km)

Hydra Distance7

(km)

Velocity

(km/s)
Beijing
+116 24 10
39 54 08
0.1
677 N.
2894 N.
24.22
Cairns, AUS
+145 46 28
–16 55 25
0.

4550 S.
2472 S.
24.34
Grove Creek Observatory (Sydney)
+149 21 59
–33 49 46
0.9

6432 S.
4355 S.
24.11
Hua Hin, Thailand
+99 57 06
12 35 33
0.
1602 S.
702 N.
24.22
IRTF
–155 28 29
19 49 46
4.18
2261 S.
358 S.
24.16
Leeward
–157 59 04
21 23 28
0.02
2031 S.
123 S.
24.14
Lulin Observatory & TAOS
+120 28 29
23 28 07
2.862
433 S.
1766 N.
24.32
Mt. Stromlo Observatory
+149 00 31
–35 19 09
0.77

6586 S.
4505 S.
24.30
Naha
+127 40 50
26 12 00
0.
207 S.
1960 N.
24.31
Nishi-Harima Astronomical Obs
+134 20 08
35 01 31
0.
403 N.
2545 N.
24.29
Sapporo
+141 21 00
43 05 00
0.
833 N.
2954 N.
24.26
Sendai uchukan
+130 20 33
31 49 26
0.25
201 N.
2358 N.
24.30
Tokyo
+139 33 00
35 40 00
0.
418 N.
2539 N.
24.29
Windward
–157 48 55
21 24 36
0.09
2035 S.
127 S.
24.14
Yunnan
+100 01 51
26 42 32
3.1
377 S.
1917 N.
24.25
Geocenter
----------
---------
center of Earth
4782 S.
2592 S.
23.92

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 ±363 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: PH20110627 Occultation Predictions for Individual Sites

Site
Pluto Immersion (UT)9
Pluto Mid-Time (UT)
PlutoEmersion (UT)9
Hydra Immersion (UT)9
Hydra
Mid-Time (UT)
Hydra Emersion (UT)9
Pluto Altitude
Solar Altitude9
Beijing
14:17:43
14:18:33
14:19:24
-----------
14:51:15
-----------
25
-----------
Cairns, AUS
-----------
14:17:19
-----------
-----------
14:49:50
-----------
88
-----------
Grove Creek Observatory (Sydney)
-----------
14:17:13
-----------
-----------
14:49:49
-----------
75
-----------
Hua Hin, Thailand
-----------
14:20:09
-----------
-----------
14:52:49
-----------
35
-----------
IRTF
-----------
14:13:32
-----------
-----------
14:46:24
-----------
23
15 (Hydra)
–13 (Hydra)
Leeward
-----------
14:13:39
-----------
-----------
14:46:30
-----------
23
16 (Hydra)
–14 (Hydra)
Lulin Observatory & TAOS
14:17:47
14:18:41
14:19:09
-----------
14:51:17
-----------
41
-----------
Mt. Stromlo Obs.
-----------
14:17:15
-----------
-----------
14:49:52
-----------
71
-----------
Naha
14:17:15
14:18:12
14:19:09
-----------
14:50:47
-----------
42
-----------
Nishi-Harima Astronomical Obs
14:16:43
14:17:38
14:18:34
-----------
14:50:16
-----------
35
-----------
Sapporo
14:16:22
14:17:08
14:17:54
-----------
14:49:49
-----------
28
-----------
Sendai uchukan
14:16:59
14:17:56
14:18:53
-----------
14:50:33
-----------
37
-----------
Tokyo
14:16:24
14:17:19
14:18:14
-----------
14:49:56
-----------
35
-----------
Windward
-----------
14:13:39
-----------
-----------
14:46:29
-----------
23
16 (Hydra)
–14 (Hydra)
Yunnan
14:18:52
14:19:48
14:20:44
-----------
14:52:30
-----------
26
-----------
Geocenter
-----------
14:17:15
-----------
-----------
14:50:23
-----------
-----------
-----------

9The errors on all times are ±0:15 (15 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) 2011-06-26 19:20

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

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