C20130615 Occultation June 15, 2013

(last updated 2013 06 05)

Finder Charts

 

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 605 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
Charon Geocentric Mid-time (yyyy month dd hh:mm:ss)

2013 June 15 06:19:36 + 00:00:571 UT

Charon Minimum Geocentric Separation 0.291 + 0.0231 arcsec
Position Angle (Charon relative to the star; measured north through east) –7.16 degrees
Geocentric Velocity 22.66 km/sec
Occultation Star UCAC4 magnitude 14.862

1One standard deviation of random error.
2The UCAC bandpass (579-642nm) is between V and R.


Table 2: Reference Star Position
Reference star position:
(UCAC4, at epoch of event)
RA (h:m:s; J2000) Dec (d:m:s; J2000) Notes
C20130615 Catalog 18 44 37.9835 ± 0.0800 -19 46 43.442 ± 0.081
C20130615 Measured3 18 44 37.9397 ± 0.0029 -19 46 43.590 ± 0.005
From 5 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

–0.1361± 0.058

+0.240± 0.022 See Notes 5 and 6

3Measured position corresponds to RA offset of –0.6957'' and Dec. offset of –0.182''.

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 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)

Velocity

(km/s)

SVH
–74 56 45
40 57 41
0.22
1178 S.
23.01
Wallace
–71 29 06
42 36 36
0.11
1132 S.
23.00
Williams
–73 12 06
42 42 42
0.22
1105 S.
23.00
Geocenter
----------
---------
center of Earth
5125 S.
22.67

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 ±1931 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: C20130615 Occultation Predictions for Individual Sites

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

Charon
Emersion
(UT)9

Charon Altitude
Solar
Altitude9
SVH
-----------
06:18:58
-----------
-----------
-----------
Wallace
-----------
06:18:45
-----------
-----------
-----------
Williams
-----------
06:18:51
-----------
-----------
-----------
Geocenter
-----------
06:19:36
-----------
-----------
-----------

 

 


Last updated by Carlos Zuluaga (czuluaga@mit.edu) 2013-06-05 15:10

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