Occultation event with (17171) 99NB38, event index number 1394
Regions able to see the event: Europe
Geocentric closest approach at 2025/10/20 23:32:20 UTC
J2000 position of star is 03:05:37.4 +48:56:26
Equinox of date position of star is 03:07:25.6 +49:02:21
Star is 136 degrees from the moon. Moon is 0% illuminated.
Stellar brightness G=16.4, apparent brightess of occulting body is G=15.7
Use an exposure time of 0.95 seconds with the standard RECON-QHY system.
SNR of 3.1 per integration for unocculted signal
Expected flux drop is 34% with SNR of 1.1 for the occulted depth (per occulted point)
Apparent velocity is 14.5 km/sec on the sky relative to the star, or, 16.5 arcsec/hr.
Position angle of asteroid motion is 97.3 degrees
The recommended exposure time corresponds to 13.8 km per image.
The 1-sigma error in the time of the event is 0.2 seconds.
The 1-sigma cross-track error in the shadow position is 28.6 km.
The sky-plane scale is 3165.9 km/arcsec.
Diameter estimates:
46.1 km assuming a 5% albedo, aximum of 3.2 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, (2025/10/20 23:32UT) Object RA Dec mag sep mel Aldebaran 04:37:24.3 +16:33:32 0.8 37.27 131 Mirphak 03:26:10.7 +49:57:03 1.8 3.18 133 Iot Per 03:10:56.6 +49:42:35 4.0 0.88 135 PPM 045845 03:08:06.7 +49:21:05 8.2 0.33 136 PPM 045830 03:07:25.4 +48:58:29 9.3 0.06 136 17171_99NB38 03:07:25.6 +49:02:21 15.7 136 Positions are for equinox of date
Star training set for 17171_99NB38, (2025/10/20 23:32UT) Object RA Dec mag sep mel Aldebaran 04:35:55.4 +16:30:29 0.8 37.27 131 Mirphak 03:24:19.4 +49:51:40 1.8 3.18 133 Iot Per 03:09:07.3 +49:36:46 4.0 0.88 135 PPM 045845 03:06:18.1 +49:15:11 8.2 0.33 136 PPM 045830 03:05:37.3 +48:52:34 9.3 0.06 136 17171_99NB38 03:05:37.4 +48:56:26 15.7 136 Positions are for J2000