Occultation event with (5144) Achates, event index number 1218
Regions able to see the event: SAmericaN,SAmericaS
Geocentric closest approach at 2025/08/10 08:12:43 UTC
J2000 position of star is 03:28:43.2 +27:55:19
Equinox of date position of star is 03:30:16.4 +28:00:32
Star is 86 degrees from the moon. Moon is 99% illuminated.
Stellar brightness G=15.6, apparent brightess of occulting body is G=15.0
Use an exposure time of 1.20 seconds with the standard RECON-QHY system.
SNR of 6.6 per integration for unocculted signal
Expected flux drop is 36% with SNR of 2.4 for the occulted depth (per occulted point)
Apparent velocity is 16.4 km/sec on the sky relative to the star, or, 15.1 arcsec/hr.
Position angle of asteroid motion is 60.5 degrees
The recommended exposure time corresponds to 19.6 km per image.
The 1-sigma error in the time of the event is 1.2 seconds.
The 1-sigma cross-track error in the shadow position is 20.7 km.
The sky-plane scale is 3904.2 km/arcsec.
Diameter estimates:
87.5 km assuming a 5% albedo, aximum of 5.3 sec for a central chord
35.7 km assuming a 30% albedo, maximum of 2.2 sec for a central chord
Cross-track diameter of 81.0 km used for deployment plan.
Star training set for 5144_Achates, (2025/08/10 08:13UT) Object RA Dec mag sep mel Aldebaran 04:37:23.6 +16:33:31 0.8 19.25 99 44Zet Per 03:55:44.9 +31:57:27 2.8 6.78 93 PPM 092402 03:21:53.7 +29:08:22 4.5 2.16 85 PPM 092568 03:32:33.9 +27:48:36 8.0 0.54 87 PPM 092519 03:29:11.3 +27:50:22 9.8 0.29 86 5144_Achates 03:30:16.4 +28:00:32 15.0 87 Positions are for equinox of date
Star training set for 5144_Achates, (2025/08/10 08:13UT) Object RA Dec mag sep mel Aldebaran 04:35:55.4 +16:30:29 0.8 19.25 99 44Zet Per 03:54:07.9 +31:53:01 2.8 6.78 93 PPM 092402 03:20:20.3 +29:02:54 4.5 2.16 85 PPM 092568 03:31:00.8 +27:43:27 8.0 0.54 87 PPM 092519 03:27:38.3 +27:45:06 9.8 0.29 86 5144_Achates 03:28:43.2 +27:55:19 15.0 86 Positions are for J2000