Occultation event with (17171) 99NB38, event index number 1657
Regions able to see the event: SAfrica
Geocentric closest approach at 2025/12/08 19:02:28 UTC
J2000 position of star is 02:32:11.2 +46:49:58
Equinox of date position of star is 02:33:53.9 +46:56:46
Star is 78 degrees from the moon. Moon is 80% illuminated.
Stellar brightness G=16.6, apparent brightess of occulting body is G=15.7
Use an exposure time of 1.20 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 15.8 km/sec on the sky relative to the star, or, 18.0 arcsec/hr.
Position angle of asteroid motion is 43.0 degrees
The recommended exposure time corresponds to 19.0 km per image.
The 1-sigma error in the time of the event is 1.7 seconds.
The 1-sigma cross-track error in the shadow position is 10.9 km.
The sky-plane scale is 3169.0 km/arcsec.
Diameter estimates:
46.1 km assuming a 5% albedo, aximum of 2.9 sec for a central chord
18.8 km assuming a 30% albedo, maximum of 1.2 sec for a central chord
Cross-track diameter of 40.9 km used for deployment plan.
Star training set for 17171_99NB38, (2025/12/08 19:02UT) Object RA Dec mag sep mel Aldebaran 04:37:24.7 +16:33:33 0.8 39.66 60 57Gam1And 02:05:30.2 +42:27:10 2.3 6.75 85 PPM 045001 02:22:23.2 +47:25:42 6.0 2.01 80 PPM 045170 02:33:36.8 +46:41:55 7.2 0.25 78 17171_99NB38 02:33:53.9 +46:56:46 15.7 78 Positions are for equinox of date
Star training set for 17171_99NB38, (2025/12/08 19:02UT) Object RA Dec mag sep mel Aldebaran 04:35:55.4 +16:30:29 0.8 39.66 60 57Gam1And 02:03:54.1 +42:19:46 2.3 6.75 85 PPM 045001 02:20:41.7 +47:18:38 6.0 2.01 80 PPM 045170 02:31:54.4 +46:35:07 7.2 0.25 78 17171_99NB38 02:32:11.2 +46:49:58 15.7 78 Positions are for J2000