The dwarf planet Haumea has a fascinating history, including the formation of two large satellites by an ancient mantle-shattering collision. Haumea also has an exciting future with many observable mutual events between Haumea and the smaller inner moon Namaka predicted for the next several years. The Haumea-Namaka mutual events will provide a wealth of information that is otherwise unattainable: the size, shape, and spin pole of Haumea; the size, albedo, and density of Namaka; and precise orbital constraints. The orbital orientation is not as favorable for the outer, larger satellite Hi'iaka, but the last two possible mutual events between Hi'iaka and Namaka occur in 2009 and will not occur again for decades. We propose a short (5-orbit) WFPC2 resolved photometry program to observe the first of these events, which will occur with an estimated ~75% probability. Even catching a partial event will measure the density of Hi'iaka to within ~15% and provide unique insight in the formation and evolution of this exciting system.

Observations of a satellite-satellite mutual event of the dwarf planet Haumea. The goal is to obtain precise photometry of a (resolved) faint satellite to a moving object. The observations are designed to maximize overall signal-to-noise (by maximizing total exposure time), while taking multiple observations to produce a high-cadence light curve. All 5 orbits must be taken as close as possible to (04-FEB-2009 21:20:00). Five consecutive orbits must be taken, with the first exposure occurring between 04-FEB-2009:16:20:00 and 04-FEB-2009:18:20:00. SOLAR SYSTEM 0 false 0.0 0.0 false false false false false SUPPORTED SOLAR SYSTEM At the time of the observations, the approximate RA and Dec are 13:43:09.10 +18:53:40.3 ASTEROID (136108) Dwarf Planet Haumea and its Two Satellites TYPE=ASTEROID,A=43.1359862,E=0.1949506,I=28.22440,O=122.10320,W=239.18665,M=202.66919,EQUINOX=J2000,EPOCH=30-NOV-2008:00:00:00 EARTH WFPC2 Imaging No F606W Using ephemeris for target 11971-01-HAUMEA ephemeris data for target 11971-01-HAUMEA does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 07.182 to 10.001. ephemeris interval: 08.366 to 11.001 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. Observation of the Haumea Satellite-Satellite Mutual Event. The 5 consecutive orbits should be centered as closely as possible to 04-FEB-2009:21:20:00, the best estimate of the event time. The observations are designed to maximize overall signal-to-noise (by maximizing total exposure time), while taking multiple observations to produce a high-cadence light curve. To decrease overhead and maintain photometric stability, we chose not to dither the observations, though the satellites will move between observations and orbits (overall motion of ~1 pixel). Observations should consist of the maximum number of 100-second exposures possible over the course of 5 orbits. 1233768656000 279.1114501704292 (Tic-Visit :proposal-id 11971 :visit-id "01" :proposal-version -1 :trans-version "20080807" :date "23-Jan-2009 08:39:51.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "26" :si-bright-earth-limb-angle 20.0 :data-volume 3047488 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11971 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11971 :visit-id "01" :orbit-number 1 :pcs-time 355 :si-vis-utilization 2709 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3132 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11971 :visit-id "01" :orbit-number 2 :pcs-time 355 :si-vis-utilization 2709 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3132 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11971 :visit-id "01" :orbit-number 3 :pcs-time 355 :si-vis-utilization 2709 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3132 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11971 :visit-id "01" :orbit-number 4 :pcs-time 355 :si-vis-utilization 2709 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3132 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11971 :visit-id "01" :orbit-number 5 :pcs-time 355 :si-vis-utilization 2349 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3132 :pcs-gap 0 ) true 5 0