 The northern
limit, centerline, and southern limit of Pluto's shadow are shown by the
three lines across the globe pictured above. The shaded area represents
where the sun is more than 12 degrees below the horizon. |
P445.3 Prediction (as of: 2007 04 04) |
| Geocentric Mid-time (yyyy month dd hh:mm:ss) | 2007 March 18 10:56:41± 00:01:25 UT |
| Minimum Geocentric Separation | 0.264± 0.025 arcsec |
| Position Angle (Pluto relative to the star; measured north through east) | –15.99 degrees |
| Geocentric Velocity | 7.1 km/sec |
| Prediction Version | P445.3-AST-1.9 |
| Star position: (at epoch of event) |
RA (h:m:s; J2000) | Dec (d:m:s; J2000) | UCAC Mag1 |
| P445.3 (Reference; UCAC2) | 17 55 05.6921 | –16 28 34.4573 | 15.3 |
| P445.3 (Measured) | 17 55 05.6941 | –16 28 34.3425 | |
| 1The
UCAC bandpass (579-642nm) is between V and R. |
|||
| Offsets
from Reference Position/Ephemeris2 |
|||
| Body | RA (arcsec) | Dec (arcsec) | Notes |
P445.3 |
+0.029± 0.017 | +0.115± 0.015 | From 33 strip scans |
| Pluto | –0.047± 0.019 | +0.084± 0.020 | From 34 strip scans |
| 2All
"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. |
|||
Discussion
On March 18th, 2007, Pluto occulted P445.3 (= 2UCAC 25823784; as originally published in McDonald & Elliot 2000a, 2000b; Table). The above map and the following prediction results are from the analysis of 34 strip scans obtained at the Lowell Observatory Astrograph by Rosemary Pike and Amanda Bosh during 2005-2007 (the strip scans from earlier years did not contain Pluto-Charon images). Four strips taken the day after the occultation were used for the current prediction. Results from 13 frames taken on 2007 March 14 UT by Steve Levine with the 1.55-m Kaj Strand Astrometric Reflector have been analyzed and agree with the astrograph results.
Proper motion of the star has been applied up to the time of the occultation (according to the UCAC2 catalog, dRA: –10.8 ± 8.0 mas/yr, dDec: –21.4 ± 7.9 mas/yr). The offsets between the measured RA and Dec of P445.3 and its UCAC2 values at the time of the event are also given in the table.
Pluto and Charon are unresolved on the strip scans, so a point-spread function (PSF) model is fit to the blended image, with Charon's position and light ratio set as fixed parameters. The resulting Pluto positions are then compared with the light-time corrected, geocentric JPL Horizons ephemeris (System DE413 - Pluto source file; PLU013; Earth center source file; DE405), and the measured offsets from the ephemeris are calculated. The offsets are folded at Charon's period about Pluto and fit with a Fourier series of three terms (mean, sine, and cosine coefficients). The resulting Fourier model is then used to calculate the model offset in the position of Pluto (and its error) from its ephemeris at the time of the occultation. These are the RA and Dec offets listed for Pluto in the above table.
Prediction Notes
Archive of all P445.3 occultation predictions based on alternate sources of data, including past predictions
Site Information*
Site |
East Longitude |
Latitude |
Altitude3 (km) |
Distance4 (km) |
Velocity (km/s) |
Flagstaff |
–111 44 23 |
35 11 02 |
2.31 |
776 S. |
6.78 |
Fremont Peak |
–121 29 55 |
36 45 37 |
0.84 |
697 S. |
6.83 |
JPL Table Mountain |
–117 40 54 |
34 22 54 |
2.29 |
823 S. |
6.80 |
Lick Obs. |
–121 38 12 |
37 20 36 |
1.29 |
665 S. |
6.83 |
Magdalena Ridge Obs. |
–107 11 05 |
33 58 36 |
3.18 |
866 S. |
6.76 |
Mt. Graham |
–109 53 31 |
32 42 04 |
3.191 |
932 S. |
6.78 |
Mt. Hopkins |
–110 53 04 |
31 41 19 |
2.61 |
993 S. |
6.77 |
Palomar |
–116 51 54 |
33 21 24 |
1.71 |
885 S. |
6.80 |
Geocentric |
---------- |
--------- |
center of Earth |
6276 S. |
7.09 |
3Altitude of each observatory is measured in kilometers above sea level.
4"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 ±571 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.
Predicted Occultation and Orbit Crossing Times for Individual Sites*
Site |
Hydra Imm Orbit Crossing
Time (UT)5 |
Nix Imm Orbit Crossing Time
(UT)5 |
Charon Imm Orbit Crossing
(UT)5 |
Pluto Immersion (UT)5 |
Mid-Time (UT)5 |
Pluto Emersion (UT)5 |
Charon Em Orbit Crossing (UT)5 |
Nix Em Orbit Crossing Time
(UT)5 |
Hydra Em Orbit Crossing
Time (UT)5 |
Flagstaff |
09:08:33 |
09:31:16 |
10:20:19 |
10:49:31 |
10:51:46 (24°) |
10:54:01 |
11:24:20 |
12:10:02 |
12:45:23 |
Fremont Peak |
09:08:05 |
09:29:25 |
10:19:16 |
10:48:07 |
10:50:30 (18°) |
10:52:53 |
11:22:49 |
12:08:20 |
12:44:49 |
JPL Table Mountain |
09:07:52 |
09:33:32 |
10:19:22 |
10:48:32 |
10:50:41 (21°) |
10:52:49 |
11:23:08 |
12:08:44 |
12:44:43 |
Lick Obs. |
09:08:12 |
09:30:23 |
10:19:22 |
10:48:09 |
10:50:35 (17°) |
10:53:01 |
11:22:53 |
12:08:23 |
12:44:29 |
Magdalena Ridge Obs. |
09:08:47 |
09:31:20 |
10:20:50 |
10:50:21 |
10:52:24 (28°) |
10:54:27 |
11:25:06 |
12:10:51 |
12:45:35 |
Mt. Graham |
09:08:15 |
09:32:01 |
10:20:12 |
10:49:52 |
10:51:44 (25°) |
10:53:35 |
11:24:25 |
12:10:08 |
12:44:41 |
Mt. Hopkins |
09:07:57 |
09:31:06 |
10:19:53 |
10:49:45 |
10:51:25 (28°) |
10:53:04 |
11:24:05 |
12:10:03 |
12:43:22 |
Palomar |
09:07:43 |
09:32:25 |
10:19:16 |
10:48:40 |
10:50:39 (23°) |
10:52:38 |
11:23:09 |
12:08:46 |
12:42:35 |
Geocentric |
09:16:15 |
09:31:07 |
10:27:14 |
---------- |
10:56:41 |
---------- |
11:26:18 |
12:09:49 |
12:37:04 |
5The errors on all times are ±1:25 (1 minute and 25 seconds; one standard deviation). In parenthesis is the elevation of the body above the celestial horizon in degrees.
* Based on the analysis of the astrometric data, not on the analysis of the occultation light curves.
Results of Previous Occultations
Results of the 2006 Pluto occultation are described and compared with results of the 1988 and 2002 occultation in a preprint, Changes in Pluto's Atmosphere: 1988-2006
Please direct all inquiries to Planetary Astronomy Lab (planetary-astronomy@mit.edu)
Last updated by Carlos A Zuluaga (czuluaga@mit.edu) 2007-04-04 9:40
