Occultation event with (17171) 99NB38, event index number 1690
Regions able to see the event: Europe
Geocentric closest approach at 2025/12/17 05:40:55 UTC
J2000 position of star is 02:28:44.7 +46:03:59
Equinox of date position of star is 02:30:26.4 +46:10:52
Star is 155 degrees from the moon. Moon is 7% illuminated.
Stellar brightness G=15.0, apparent brightess of occulting body is G=15.7
Use an exposure time of 0.65 seconds with the standard RECON-QHY system.
SNR of 7.9 per integration for unocculted signal
Expected flux drop is 66% with SNR of 5.2 for the occulted depth (per occulted point)
Apparent velocity is 14.7 km/sec on the sky relative to the star, or, 16.5 arcsec/hr.
Position angle of asteroid motion is 32.0 degrees
The recommended exposure time corresponds to 9.6 km per image.
The 1-sigma error in the time of the event is 1.9 seconds.
The 1-sigma cross-track error in the shadow position is 5.3 km.
The sky-plane scale is 3215.1 km/arcsec.
Diameter estimates:
46.1 km assuming a 5% albedo, aximum of 3.1 sec for a central chord
18.8 km assuming a 30% albedo, maximum of 1.3 sec for a central chord
Cross-track diameter of 40.9 km used for deployment plan.
Star training set for 17171_99NB38, (2025/12/17 05:41UT) Object RA Dec mag sep mel Aldebaran 04:37:24.8 +16:33:34 0.8 39.64 162 57Gam1And 02:05:30.3 +42:27:11 2.3 5.81 155 PPM 044985 02:20:51.6 +46:35:26 6.2 1.70 154 PPM 045139 02:31:28.1 +46:08:45 6.7 0.18 155 17171_99NB38 02:30:26.4 +46:10:52 15.7 155 Positions are for equinox of date
Star training set for 17171_99NB38, (2025/12/17 05:41UT) Object RA Dec mag sep mel Aldebaran 04:35:55.4 +16:30:29 0.8 39.64 162 57Gam1And 02:03:54.1 +42:19:46 2.3 5.81 155 PPM 044985 02:19:10.8 +46:28:20 6.2 1.70 154 PPM 045139 02:29:46.2 +46:01:53 6.7 0.18 155 17171_99NB38 02:28:44.7 +46:03:59 15.7 155 Positions are for J2000