Occultation event with (11509) Thersilochos, event index number 4223
Regions able to see the event: Europe
Geocentric closest approach at 2026/09/12 02:01:45 UTC
J2000 position of star is 06:05:48.8 +10:18:25
Equinox of date position of star is 06:07:17.4 +10:18:10
Star is 89 degrees from the moon. Moon is 1% illuminated.
Stellar brightness G=13.4, apparent brightess of occulting body is G=15.9
Use an exposure time of 0.15 seconds with the standard RECON-QHY system.
SNR of 9.9 per integration for unocculted signal
Expected flux drop is 91% with SNR of 9.0 for the occulted depth (per occulted point)
Apparent velocity is 20.2 km/sec on the sky relative to the star, or, 19.0 arcsec/hr.
Position angle of asteroid motion is 116.8 degrees
The recommended exposure time corresponds to 3.0 km per image.
The 1-sigma error in the time of the event is 0.9 seconds.
The 1-sigma cross-track error in the shadow position is 23.2 km.
The sky-plane scale is 3833.8 km/arcsec.
Diameter estimates:
55.0 km assuming a 5% albedo, maximum of 2.7 sec for a central chord
22.4 km assuming a 30% albedo, maximum of 1.1 sec for a central chord
Cross-track diameter of 50.0 km used for deployment plan.
Star training set for 11509_Thersilochos, (2026/09/12 02:02UT) Object RA Dec mag sep mel Betelgeuse 05:56:37.1 +07:24:35 0.4 3.91 92 Alhena 06:39:15.2 +16:22:27 1.9 9.86 82 PPM 121823 06:04:54.3 +11:40:41 6.0 1.49 90 PPM 121854 06:06:08.8 +10:30:23 7.9 0.35 89 PPM 121882 06:06:56.6 +10:29:53 9.0 0.21 89 11509_Thersilo 06:07:17.4 +10:18:10 15.9 89 Positions are for equinox of date
Star training set for 11509_Thersilochos, (2026/09/12 02:02UT) Object RA Dec mag sep mel Betelgeuse 05:55:10.3 +07:24:26 0.4 3.91 92 Alhena 06:37:42.8 +16:23:56 1.9 9.86 82 PPM 121823 06:03:24.8 +11:40:51 6.0 1.49 90 PPM 121854 06:04:40.1 +10:30:35 7.9 0.35 89 PPM 121882 06:05:27.9 +10:30:07 9.0 0.21 89 11509_Thersilo 06:05:48.8 +10:18:25 15.9 89 Positions are for J2000