P20130504 Occultation May 04, 2013

(last updated 2013 04 12)

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)

2013 May 04 08:21:32± 00:01:371 UT

Pluto Minimum Geocentric Separation 0.004± 0.0391 arcsec
Position Angle (Pluto relative to the star; measured north through east) +174.21 degrees
Geocentric Velocity 10.21 km/sec
Occultation Star UCAC2 magnitude 14.252

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
P20130504 Catalog 18 47 52.5286± 0.183 –19 41 24.7272± 0.173
P20130504 Measured3 18 47 52.5327± 0.014 –19 41 24.3859± 0.017
From 51 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

–0.1441± 0.041

+0.206± 0.031 See Notes 5, 6, and 7

3Measured position corresponds to RA offset of +0.0584'' and Dec. offset of +0.3413''.

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 8 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.

7Pluto position adjusted by an additional ~60mas (not included in these values) to correct for the offset observed at the 22 March 2013 appulse, as measured from Keck2, Lowell 42-inch, Lowell DCT, NOFS 61-inch, NOFS 1.3-m, and SARA-S.

 

Table 4: Site Information

Site
East Longitude
Latitude

Site Altitude8

(km)

Pluto Distance9

(km)

Velocity

(km/s)

Cerro Pachon
–70 40 12
–30 14 26
2.783
1003 S.
10.62
Cerro Tololo
–70 48 54
–30 09 54
2.2
994 S.
10.61
Flagstaff
–111 44 23
+35 11 02
2.3
5140 N.
10.47
La Silla
–70 43 48
–29 15 24
2.3
895 S.
10.62
Las Campanas
–70 42 00
–29 00 30
2.3
868 S.
10.61
Llano del Hato
–70 52 74
+8 47 18
3.6
3170 N.
10.67
McDonald Observatory
–104 01 21
+30 40 17
2.1
4935 N.
10.52
Santiago
–70 32 10
–33 23 45
0.9
1345 S.
10.60
Geocenter
----------
---------
center of Earth
103 N.
10.21

8Altitude of each observatory is measured in kilometers above sea level.

9"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 ±588 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: P20130504 Occultation Predictions for Individual Sites

Site
Pluto
Immersion (UT)10
Pluto
Mid-Time (UT)

Pluto
Emersion
(UT)10

Pluto Altitude
Solar
Altitude10
Cerro Pachon
08:20:56
08:22:28
08:24:00
-----------
-----------
Cerro Tololo
08:20:57
08:22:30
08:24:03
-----------
-----------
Flagstaff
-----------
08:26:41
-----------
-----------
-----------
La Silla
08:20:47
08:22:28
08:24:10
-----------
-----------
Las Campanas
08:20:45
08:22:28
08:24:11
-----------
-----------
Llano del Hato
-----------
08:21:58
-----------
-----------
-----------
McDonald Obs
-----------
08:26:09
-----------
-----------
-----------
Santiago
08:21:52
08:22:29
08:23:06
-----------
-----------
Geocenter
08:19:15
08:21:32
08:23:49
-----------
-----------

 

10The errors on all times are ±1:37 (1 minutes and 37 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) 2013-04-01 13:55

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