SHORT FGS SCAN LENGTH MAY SIGNAL PROBLEMS SHORT FGS SCAN LENGTH MAY SIGNAL PROBLEMS 0 ----- Attempting Submission 1 (Wed Jun 28 18:16:11 GMT 2017) ----- Short FGS scan length will not be detrimental to the primary science goal of obtaining 40 Hz photometry of the target star. We propose to observe the July 17, 2017 stellar occultation by the Kuiper Belt object 2014 MU69, the close flyby target of the extended New Horizons mission. Our proposed program will constrain the possibility of rings or other debris near 2014 MU69 better than any other available probe of the system. This is a mission support proposal. Only HST can guarantee cloud-free observations of this event with a large aperture telescope. We plan to observe the 2014 MU69 July 17, 2017 stellar occultation star during 2 orbits 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 first 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. The second orbit will only include one exposure, 110 scans with scan length of 0.4 arcsec. This exposure (Exposure #3) will continue monitoring of target photometry. Solar System 0 SUPPORTED STAR K III-I J2000 J2000 G-band mag = 12.602 FGS POS No F583W 1498589872305 /home/josh/Dropbox/Proposals/HST 2017/phaseII/OP-cache/2017-DD-MU69-v01.xml The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 15003 :visit-id "01" :proposal-version -1 :trans-version "20170613" :date "27-Jun-2017 13:57:52.0" :trans-errors '(:WARNINGS 2 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "05" :si-bright-earth-limb-angle 15.5 :data-volume 0 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15003 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15003 :visit-id "01" :orbit-number 1 :pcs-time 333 :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 ) (Tic-Orbit :proposal-id 15003 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2962 :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 2 0