# # Program information file # PROGRAM_ID 2021B022 PROGRAM_TITLE Stellar occultation by Echeclus of an exceptionally bright star PROGRAM_INV1 Amanda Sickafoose PROGRAM_INV2 Carlos Zuluaga PROGRAM_INV3 Amanda Bosh PROGRAM_INV4 Michael Person PROGRAM_INV5 Stephen Levine PROGRAM_SCICAT solar system PROGRAM_ABSTRACT_BEG The capabilities of MORIS+SpeX, combined with Hawaii's unique geographic location, have proven successful for observing stellar occultations by small bodies in the outer Solar System. High-quality, high-time-resolution, multiple-wavelength datasets have been obtained for occultations by two centaurs: Chiron and Chariklo. In 2021B, we propose for 4 hours to observe a predicted stellar occultation of a very bright star by the active centaur [60558] 174P/Echeclus. Successful observations will [i] constrain the object/nucleus size and [ii] detect and characterize any tenuous atmosphere or surrounding rings/material. The midtime for the predicted occultation is 06 January 08:36 UT. We request 4 hours, centered on 08:30 UT, to observe the event. We observe at high cadence for +/-20 min centered on the predicted midtime. Long-exposure, calibration frames will be taken before and after, when the star and object are well separated. MORIS will be run with no filter at the fastest cadence that allows for a light-curve signal-to-noise of at least a few tens: for this target, the resulting integration time will be approximately 0.01 sec. SpeX GuideDog will be employed to obtain simultaneous K-band images at either 0.5- or 0.25-s integrations. Visible data are used to constrain object size, as well as the extent and structure of surrounding material. Multi-color data provide an additional level of characterization, through providing insight into [i] particle sizes in surrounding material and [ii] nucleus shape. PROGRAM_ABSTRACT_END