0 Assigned ID: 13 ----- Attempting Submission 1 (Wed Jun 27 18:13:50 GMT 2018) ----- HST Phase I Proposal 13 (2018-DD-MU69.apt) successfully submitted. Receipt: # 13-1 SHORT FGS SCAN LENGTH MAY SIGNAL PROBLEMS 0 ----- Attempting Submission 1 (Tue Jul 03 15:03:18 GMT 2018) ----- Short scan length will not affect science goals, which are based only on photometry of the target star. Probing the Hill Sphere of 2014 MU69 We propose to observe the August 4, 2018 stellar occultation by the Kuiper Belt object 2014 MU69, the close flyby target of the extended New Horizons mission. HST is the best guaranteed probe of the debris environment near 2014 MU69. The 0.025 second time resolution of the FGS instrument using the F583W filter in TRANS mode will provide sufficient capability to search for rings and other spatially large debris signatures. We propose to execute this program only if HST is in position to probe much closer to 2014 MU69 than observed by our previous program 15003. We plan to observe the 2014 MU69 August 4, 2018 stellar occultation star during 1 orbit using the FGS instrument in TRANS mode with the F583W filter. The start time optimizes the phasing of the observation with the central time of the occultation, ensuring that enough time is available for initial target acquisition and instrument configuration. The orbit will include two exposures: 1) 5 scans with scan length of 2 arcsec, and 2) 89 scans with scan length of 0.4 arcsec. Exposure #1 will be used as a check for stellar binarity. Exposure #2 begins the primary measurement of target photometry. Solar System 0 false AVAILABLE STAR UNDESIGNATED J2000 J2000 G-band mag = 13.36 FGS TRANS No F583W /private/var/folders/56/c_jk44c970v8fj73rtx427cm0006v6/T/OPVisit9134969830617651687.xml The scheduling data was generated by CASM 26.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 15598 :visit-id "01" :proposal-version -1 :trans-version "20180409" :date "09-Jul-2018 15:13:17.0" :trans-errors '(:WARNINGS 1 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "05" :si-bright-earth-limb-angle 15.5 :data-volume 0 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15598 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15598 :visit-id "01" :orbit-number 1 :pcs-time 241 :si-vis-utilization 2871 :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 3217 :pcs-gap 0 ) true 1 0