Occultation event with (20729) 99XS143, event index number 3529
Regions able to see the event: Australia
Geocentric closest approach at 2026/03/28 17:38:59 UTC
J2000 position of star is 11:04:07.4 -16:35:15
Equinox of date position of star is 11:05:25.6 -16:43:46
Star is 44 degrees from the moon. Moon is 81% illuminated.
Stellar brightness G=16.4, apparent brightess of occulting body is G=15.6
Use an exposure time of 0.95 seconds with the standard RECON-QHY system.
SNR of 3.0 per integration for unocculted signal
Expected flux drop is 33% with SNR of 1.0 for the occulted depth (per occulted point)
Apparent velocity is 17.1 km/sec on the sky relative to the star, or, 18.7 arcsec/hr.
Position angle of asteroid motion is 111.6 degrees
The recommended exposure time corresponds to 16.2 km per image.
The 1-sigma error in the time of the event is 2.0 seconds.
The 1-sigma cross-track error in the shadow position is 18.8 km.
The sky-plane scale is 3292.5 km/arcsec.
Diameter estimates:
48.3 km assuming a 5% albedo, maximum of 2.8 sec for a central chord
19.7 km assuming a 30% albedo, maximum of 1.2 sec for a central chord
Cross-track diameter of 51.0 km used for deployment plan.
Star training set for 20729_99XS143, (2026/03/28 17:39UT) Object RA Dec mag sep mel Regulus 10:09:46.0 +11:50:17 1.3 31.71 14 4Gam Crv 12:17:09.6 -17:41:15 2.6 17.15 57 PPM 223760 11:00:48.8 -16:29:41 5.3 1.13 43 PPM 223839 11:03:38.5 -16:54:00 8.5 0.46 44 PPM 223863 11:04:35.8 -16:55:33 9.5 0.28 44 20729_99XS143 11:05:25.6 -16:43:46 15.6 44 Positions are for equinox of date
Star training set for 20729_99XS143, (2026/03/28 17:39UT) Object RA Dec mag sep mel Regulus 10:08:21.9 +11:58:02 1.3 31.71 14 4Gam Crv 12:15:48.1 -17:32:30 2.6 17.15 57 PPM 223760 10:59:30.8 -16:21:13 5.3 1.13 43 PPM 223839 11:02:20.4 -16:45:30 8.5 0.46 44 PPM 223863 11:03:17.7 -16:47:02 9.5 0.28 44 20729_99XS143 11:04:07.4 -16:35:15 15.6 44 Positions are for J2000