Unsupported characters were found in Abstract and replaced with |*| Scientific Category is a required field. Science Keywords is a required field. Science Keywords: Select from 3 to 5 items. Please specify your scheduling constraints or 'No Constraints' on all Observation forms. Please specify your scheduling constraints or 'No Constraints' on all Observation forms. 0 Assigned ID: 2564 ----- Attempting Submission 1 (Thu Jan 08 17:26:25 GMT 2015) ----- HST Phase I Proposal 2564 (Spitzer-Radigan.apt) successfully submitted. ----- Attempting Submission 2 (Thu Jan 08 18:13:08 GMT 2015) ----- joint 0 ----- Attempting Submission 1 (Thu Jan 29 20:59:47 GMT 2015) ----- The T2 dwarf SIMP 1629+03 is a variable L/T transition dwarf, with a normal near-infrared spectrum. However, it is remarkable in that the wavelength dependence of its variability differs markedly from that of other L/T transition brown dwarfs. In particular, the absence of a water absorption feature in its variability spectrum indicates that a patchy, high-altitude haze, rather than a deeper cloud layer is responsible for the observed variations. We propose to obtain Spitzer+HST observations of SIMP1629+02 over two consecutive rotations periods in order to simultaneously map it's spectral variability across 1-5 um. The wide wavelength coverage will provide a suitable lever-arm for constraining the particle size distribution in the haze. A truly flat spectrum across this wavelength range would indicate large particle sizes in comparison to those inferred for red L-dwarf hazes, and would therefore provide direct evidence of grain growth with decreasing effective temperature and/or a grain-size dependence on surface gravity in brown dwarf atmospheres. ORIENTATION REQUIREMENTS: We require that the spectral traces of our targets do not overlap with those of other stars in the field. Orientation constraints were calculated as follows: PA=absolute position angle between target and background star d= distance between target and background star ORIENT = position angle of HST U3 axis A_WFC3 = angle of WFC3 "-x" axis wrt HST = -45 deg PA_WFC3 = PA - ORIENT - A_WFC3 = position angle between target and background star wrt WFC3 detector -x axis. dY = absolute distance between spectral traces, perpedicular to the direction of dispersion We have required that dy > 2 arcseconds, where dY=d * cos(PA_WFC3) for stars along the negative x-axis with d>18". For d< 18" constraints have been place in the -ve and +ve directions. In some cases an extra buffer of up to +/- 5 deg was added due to uncertainties in source and background star proper motions. TARGETS Our target is a brown dwarf (bright in the IR), and does not appear in optical images using the target confirmation tool. It also has significant proper motion, which has been provided. Default false false 14.5 false false false SUPPORTED STAR BROWN DWARF T This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J=15.3 WFC3/IR Spectroscopic No No G141 WFC3/IR Spectroscopic No No G141 1422565028543 The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. /Users/radigan/Documents/OP-cache/HST_Phase2_14051-v01.xml Continuous observation of 2MASS-J16291840+0335371 (Tic-Visit :proposal-id 14051 :visit-id "01" :proposal-version -1 :trans-version "20140605" :date "29-Jan-2015 15:57:05.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 4 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 697296 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14051 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14051 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2692 :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 3222 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14051 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2692 :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 3222 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14051 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2711 :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 3222 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14051 :visit-id "01" :orbit-number 4 :pcs-time 222 :si-vis-utilization 2666 :al-overhead-at-end 0 :internal-dur-at-end 438 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3222 :pcs-gap 0 ) true 4 0