Occultation event with (20729) 99XS143, event index number 3693
Regions able to see the event: SAfrica
Geocentric closest approach at 2026/04/28 16:50:20 UTC
J2000 position of star is 10:53:29.7 -15:00:31
Equinox of date position of star is 10:54:48.0 -15:08:57
Star is 22 degrees from the moon. Moon is 91% illuminated.
Stellar brightness G=16.9, apparent brightess of occulting body is G=16.0
Use an exposure time of 1.70 seconds with the standard RECON-QHY system.
SNR of 3.1 per integration for unocculted signal
Expected flux drop is 30% with SNR of 0.9 for the occulted depth (per occulted point)
Apparent velocity is 9.4 km/sec on the sky relative to the star, or, 9.7 arcsec/hr.
Position angle of asteroid motion is 139.3 degrees
The recommended exposure time corresponds to 15.9 km per image.
The 1-sigma error in the time of the event is 4.2 seconds.
The 1-sigma cross-track error in the shadow position is 0.8 km.
The sky-plane scale is 3464.3 km/arcsec.
Diameter estimates:
48.3 km assuming a 5% albedo, maximum of 5.2 sec for a central chord
19.7 km assuming a 30% albedo, maximum of 2.1 sec for a central chord
Cross-track diameter of 51.0 km used for deployment plan.
Star training set for 20729_99XS143, (2026/04/28 16:50UT) Object RA Dec mag sep mel Regulus 10:09:46.3 +11:50:15 1.3 29.20 34 4Gam Crv 12:17:09.8 -17:41:17 2.6 19.90 14 PPM 223610 10:54:51.2 -15:35:12 6.3 0.44 22 PPM 223600 10:54:25.8 -14:56:10 9.7 0.23 22 20729_99XS143 10:54:48.0 -15:08:57 16.0 22 Positions are for equinox of date
Star training set for 20729_99XS143, (2026/04/28 16:50UT) Object RA Dec mag sep mel Regulus 10:08:21.9 +11:58:02 1.3 29.20 34 4Gam Crv 12:15:48.1 -17:32:30 2.6 19.90 14 PPM 223610 10:53:33.0 -15:26:46 6.3 0.44 22 PPM 223600 10:53:07.5 -14:47:44 9.7 0.23 22 20729_99XS143 10:53:29.7 -15:00:31 16.0 22 Positions are for J2000