Occultation event with (11509) Thersilochos, event index number 4075
Regions able to see the event: SAmericaN,SAmericaS
Geocentric closest approach at 2026/08/22 09:00:51 UTC
J2000 position of star is 05:54:16.6 +11:22:34
Equinox of date position of star is 05:55:45.7 +11:22:46
Star is 163 degrees from the moon. Moon is 71% illuminated.
Stellar brightness G=15.6, apparent brightess of occulting body is G=15.9
Use an exposure time of 0.45 seconds with the standard RECON-QHY system.
SNR of 3.8 per integration for unocculted signal
Expected flux drop is 58% with SNR of 2.2 for the occulted depth (per occulted point)
Apparent velocity is 27.7 km/sec on the sky relative to the star, or, 24.7 arcsec/hr.
Position angle of asteroid motion is 106.1 degrees
The recommended exposure time corresponds to 12.5 km per image.
The 1-sigma error in the time of the event is 0.5 seconds.
The 1-sigma cross-track error in the shadow position is 26.4 km.
The sky-plane scale is 4031.3 km/arcsec.
Diameter estimates:
55.0 km assuming a 5% albedo, maximum of 2.0 sec for a central chord
22.4 km assuming a 30% albedo, maximum of 0.8 sec for a central chord
Cross-track diameter of 50.0 km used for deployment plan.
Star training set for 11509_Thersilochos, (2026/08/22 09:01UT) Object RA Dec mag sep mel Betelgeuse 05:56:36.9 +07:24:35 0.4 3.98 159 Bellatrix 05:26:33.7 +06:22:18 1.6 8.78 158 PPM 121631 05:58:18.8 +11:31:20 5.9 0.64 163 PPM 121572 05:56:05.9 +11:29:18 8.4 0.14 163 11509_Thersilo 05:55:45.7 +11:22:46 15.9 162 Positions are for equinox of date
Star training set for 11509_Thersilochos, (2026/08/22 09:01UT) Object RA Dec mag sep mel Betelgeuse 05:55:10.3 +07:24:26 0.4 3.98 159 Bellatrix 05:25:07.8 +06:20:58 1.6 8.78 158 PPM 121631 05:56:49.6 +11:31:14 5.9 0.64 163 PPM 121572 05:54:36.8 +11:29:07 8.4 0.14 163 11509_Thersilo 05:54:16.6 +11:22:34 15.9 163 Positions are for J2000