Occultation event with (1872) Helenos, event index number 4253
Regions able to see the event: SAmericaN
Geocentric closest approach at 2026/09/17 07:27:52 UTC
J2000 position of star is 05:05:17.6 +09:55:51
Equinox of date position of star is 05:06:45.8 +09:57:56
Star is 160 degrees from the moon. Moon is 36% illuminated.
Stellar brightness G=16.7, apparent brightess of occulting body is G=16.5
Use an exposure time of 1.25 seconds with the standard RECON-QHY system.
SNR of 3.1 per integration for unocculted signal
Expected flux drop is 46% with SNR of 1.4 for the occulted depth (per occulted point)
Apparent velocity is 10.9 km/sec on the sky relative to the star, or, 10.4 arcsec/hr.
Position angle of asteroid motion is 129.7 degrees
The recommended exposure time corresponds to 13.6 km per image.
The 1-sigma error in the time of the event is 2.1 seconds.
The 1-sigma cross-track error in the shadow position is 27.4 km.
The sky-plane scale is 3784.8 km/arcsec.
Diameter estimates:
42.1 km assuming a 5% albedo, maximum of 3.9 sec for a central chord
17.2 km assuming a 30% albedo, maximum of 1.6 sec for a central chord
Cross-track diameter of 34.0 km used for deployment plan.
Star training set for 1872_Helenos, (2026/09/17 07:28UT) Object RA Dec mag sep mel Aldebaran 04:37:27.4 +16:33:39 0.8 9.71 169 Bellatrix 05:26:33.9 +06:22:18 1.6 6.08 154 16 Ori 05:10:47.9 +09:51:42 5.4 1.00 159 PPM 120540 05:04:44.5 +10:03:58 8.5 0.51 160 PPM 120565 05:06:18.1 +10:17:52 9.7 0.35 160 PPM 148403 05:06:00.6 +09:52:55 10.9 0.20 160 1872_Helenos 05:06:45.8 +09:57:56 16.5 160 Positions are for equinox of date
Star training set for 1872_Helenos, (2026/09/17 07:28UT) Object RA Dec mag sep mel Aldebaran 04:35:55.4 +16:30:29 0.8 9.71 169 Bellatrix 05:25:07.8 +06:20:58 1.6 6.08 154 16 Ori 05:09:19.7 +09:49:46 5.4 1.00 159 PPM 120540 05:03:16.3 +10:01:49 8.5 0.51 160 PPM 120565 05:04:49.7 +10:15:46 9.7 0.35 160 PPM 148403 05:04:32.4 +09:50:49 10.9 0.20 160 1872_Helenos 05:05:17.6 +09:55:51 16.5 160 Positions are for J2000