P598.2 Occultation August 25, 2008

(last updated 2008 07 28)

The shaded area represents where the sun is more than 12 degrees below the horizon. Across the globe pictured above, the three lines correspond to the northern limit, centerline, and southern limit of Pluto's shadow. The northern and southern limits correspond to a radius of 1208 km (the 50% normalized stellar-flux level) for Pluto.

 

Geocentric Mid-time (yyyy month dd hh:mm:ss) 2008 August 25 04:38:16± 00:00:50 UT
Minimum Geocentric Separation 0.0099± 0.0190 arcsec
Position Angle (Pluto relative to the star; measured north through east) 148.83 degrees
Geocentric Velocity 8.38 km/sec
Prediction Version P598.2-AST-2.0

 

Reference star position:
(USNO-B1.0, at epoch of event)
RA (h:m:s; J2000) Dec (d:m:s; J2000) R Mag1
P598.2 Catalog2 17 53 27.1133 –17 15 27.340 16.1
P598.2 Measured 17 53 27.0962 –17 15 27.450  

1From USNO-B Catalog.

2USNO-B, at epoch 1970.3.

Offsets from Reference Position/Ephemeris3
Body RA (arcsec) Dec (arcsec) Notes

P598.2

–0.2550± 0.0057 –0.110± 0.005 From 144 Strips
Pluto4

–0.0013± 0.0184

+0.071± 0.018 See note 5

3All "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.

4The reference position for Pluto is that given by JPL Horizon's ephemeris (Pluto source file: PLU013; Earth center source file: DE405).

5315 strip scans and 89 USNO-61inch Telescope frames were used to develop a model to fit the residuals obtained from our measured positions compared to that of the object's JPL ephemeris.. 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.

Discussion

Site Information

Site
East Longitude
Latitude

Altitude6

(km)

Distance7

(km)

Velocity

(km/s)

Flagstaff
–111 44 23
35 11 02
2.31
3469 N.
8.66
Las Campanas
–70 42 00
–29 00 30
2.28
4203 S.
8.48
Lick Obs.
–121 38 12
37 20 36
1.29
4103 N.
8.68
Magdalena Ridge Obs.
–107 11 05
33 58 36
2.21
3151 N.
8.65
Mauna Kea (IRTF)
–155 28 29
19 49 46
4.18
4497 N.
8.76
Mt. Hopkins
–110 53 04
31 41 19
2.61
3172 N.
8.67
Geocentric
----------
---------
center of Earth
227 S.
8.38

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 ±428 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.

P598.2 Appulse Predictions for Individual Sites

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

Pluto Emersion (UT)9

Solar Elevation 10
Flagstaff
-----------
04:30:08 (33°)
-----------
–28°
Las Campanas
-----------
04:31:53 (34°)
-----------
–71°
Lick Obs.
-----------
04:31:25 (34°)
-----------
–21°
Magdalena Ridge Obs.
-----------
04:29:35 (33°)
-----------
–31°
Mauna Kea (IRTF)
-----------
04:38:11 (48°)
-----------
Mt. Hopkins
-----------
04:30:09 (36°)
-----------
–31°
Geocentric
04:35:31
04:38:16
04:41:00
 

9The errors on all times are ±0:50 (50 seconds; one standard deviation). In parenthesis is the elevation of the body above the celestial horizon in degrees.

10At the closest approch time for that location.


Last updated by Carlos A Zuluaga (czuluaga@mit.edu) 2008-07-28 3:00

Please direct all inquiries to Planetary Astronomy Lab (planetary-astronomy@mit.edu)