Occultation event with (11509) Thersilochos, event index number 1217
Regions able to see the event: Europe
Geocentric closest approach at 2025/08/10 00:54:01 UTC
J2000 position of star is 03:43:08.2 +16:13:43
Equinox of date position of star is 03:44:35.3 +16:18:31
Star is 91 degrees from the moon. Moon is 99% illuminated.
Stellar brightness G=16.0, apparent brightess of occulting body is G=15.5
Use an exposure time of 0.65 seconds with the standard RECON-QHY system.
SNR of 3.3 per integration for unocculted signal
Expected flux drop is 39% with SNR of 1.3 for the occulted depth (per occulted point)
Apparent velocity is 18.6 km/sec on the sky relative to the star, or, 19.2 arcsec/hr.
Position angle of asteroid motion is 95.8 degrees
The recommended exposure time corresponds to 12.1 km per image.
The 1-sigma error in the time of the event is 0.3 seconds.
The 1-sigma cross-track error in the shadow position is 28.5 km.
The sky-plane scale is 3491.0 km/arcsec.
Diameter estimates:
55.0 km assuming a 5% albedo, aximum of 3.0 sec for a central chord
22.4 km assuming a 30% albedo, maximum of 1.2 sec for a central chord
Cross-track diameter of 50.0 km used for deployment plan.
Star training set for 11509_Thersilochos, (2025/08/10 00:54UT) Object RA Dec mag sep mel Aldebaran 04:37:23.6 +16:33:31 0.8 12.66 103 Menkar 03:03:37.3 +04:11:19 2.5 15.75 78 PPM 119253 03:40:52.9 +16:37:05 6.2 0.94 90 PPM 119306 03:44:48.5 +16:29:59 8.1 0.20 91 11509_Thersilo 03:44:35.3 +16:18:31 15.5 91 Positions are for equinox of date
Star training set for 11509_Thersilochos, (2025/08/10 00:54UT) Object RA Dec mag sep mel Aldebaran 04:35:55.4 +16:30:29 0.8 12.66 103 Menkar 03:02:16.8 +04:05:21 2.5 15.75 78 PPM 119253 03:39:25.8 +16:32:11 6.2 0.94 90 PPM 119306 03:43:21.4 +16:25:12 8.1 0.20 91 11509_Thersilo 03:43:08.2 +16:13:43 15.5 91 Positions are for J2000