Many observations now indicate that the progenitors of today's massive galaxies are very compact at high redshift and that they must have experienced significant growth in size over the past 11 Gyr. Remarkably, the rate of growth appears to increase toward z~2, posing a challenge for physical mechanisms proposed to account for this assembly. Environmental trends can discriminate between growth mechanisms that are sensitive to local density (galaxy mergers) and those that are not (secular processes). While the size evolution of field galaxies is probed adequately in exisiting HST field surveys, these do not sample the densest environments. We propose WFC3 imaging and grism spectroscopy of the z~2 evolved galaxy cluster JKCS041, detected as a strong overdensity of red galaxies that present a tight red sequence. This is among the most distant clusters known and is seen at an epoch when the growth of massive galaxies appears quite rapid. Uniquely among the few known clusters at z > 1.5, JKCS041 exhibits an intracluster medium unambiguously detected in extended X-ray emission by Chandra. The goals of this proposal are (1) to confirm the cluster membership of red galaxies, (2) to measure the structral properties of these members in order to establish whether growth is accelerated in cluster environments at z~2, and if so, whether this is likely due to enhanced merging, (3) to determine the stellar ages, masses, and star-formation activity of cluster galaxies seen at a lookback time of 10 Gyr to constrain the effect of environment in quenching star formation in the early universe. Our program requires both deep imaging with adequate sub-pixel sampling and observations using both the G102 and G141 grisms at several orientations to facilitate deblending. Most of the imaging is conducted in visit 1, with 4/3 orbits in F160W and 2/3 orbits in F105W. A 4-point dither pattern is used in each, identical to the CANDELS survey. The remaining 14 orbits are split over Visits 2-4. The first 2 orbits of Visit 2 contain a direct F105W image followed by 4 G102 grism exposures that are dithered in a 4-point pattern. The pattern is slightly wider than that used for the imaging in order to dither over defects (IR blobs, etc.). This is acceptable given that variations in the sub-pixel sampling pattern over the array are not crucial for spectroscopy. Orbits 3-4 of Visit 2 are the same as Orbits 1-2 using F160W+G141. Visits 3 and 4 each contain 5 orbits. The structure is identical to Visit 2 with one additional orbit of two grism exposures inserted. For visit 3 and 4 the extra orbit is devoted to G141 and G102, respectively. The additional two grism exposures are positioned at the integer,integer and half-integer,half-integer points of the dither pattern (i.e. a two-point pattern). Original Phase 2 submission: Visits 1 and 2 are unrestricted in orientation, and the need for varying orientations is implemented using ORIENT FROM constraints. These require visit 3 to excute with an ORIENT of 25-80 deg relative to visit 2, and visit 4 to execute 25-80 deg relative to visit 3. ***Post planning windows: All visits have now been restricted to a narrow ORIENT range, just wide enough to allow for observations throughout the provided plan windows. This allowed us to arrange the pointing centers at each ORIENT to maximize the number of spectra. UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE 12 false 0.0 0.0 false false false false SUPPORTED CLUSTER OF GALAXIES HIGH REDSHIFT CLUSTER J2000 J2000 J = 20-23 CLUSTER OF GALAXIES HIGH REDSHIFT CLUSTER J2000 J2000 J = 20-23 CLUSTER OF GALAXIES HIGH REDSHIFT CLUSTER J2000 J2000 J = 20-23 CLUSTER OF GALAXIES HIGH REDSHIFT CLUSTER J2000 J2000 J = 20-23 WFC3/IR Imaging No No F160W WFC3/IR Spectroscopic No No G102 WFC3/IR Spectroscopic No No G141 The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12927 :visit-id "01" :proposal-version -1 :trans-version "20120802" :date "31-Aug-2012 11:37:40.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 1410112 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12927 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12927 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2675 :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 3015 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12927 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2705 :al-overhead-at-end 0 :internal-dur-at-end 443 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3015 :pcs-gap 0 ) false 2 0 The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. 1351406071000 347.84106000208817 (Tic-Visit :proposal-id 12927 :visit-id "02" :proposal-version -1 :trans-version "20120802" :date "31-Aug-2012 11:46:58.0" :trans-errors '(:WARNINGS 1 :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 2419808 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12927 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12927 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2693 :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 3015 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12927 :visit-id "02" :orbit-number 2 :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 3015 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12927 :visit-id "02" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2739 :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 3015 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12927 :visit-id "02" :orbit-number 4 :pcs-time 222 :si-vis-utilization 2711 :al-overhead-at-end 0 :internal-dur-at-end 481 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3015 :pcs-gap 0 ) false 4 1 The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. 1352198856000 13.543871349434909 (Tic-Visit :proposal-id 12927 :visit-id "03" :proposal-version -1 :trans-version "20120802" :date "31-Aug-2012 11:37:46.0" :trans-errors '(:WARNINGS 1 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 2942064 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12927 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12927 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2693 :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 3015 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12927 :visit-id "03" :orbit-number 2 :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 3015 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12927 :visit-id "03" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2739 :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 3015 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12927 :visit-id "03" :orbit-number 4 :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 3015 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12927 :visit-id "03" :orbit-number 5 :pcs-time 222 :si-vis-utilization 2710 :al-overhead-at-end 0 :internal-dur-at-end 519 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3015 :pcs-gap 0 ) false 5 1 The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. 1358672179000 60.0 (Tic-Visit :proposal-id 12927 :visit-id "04" :proposal-version -1 :trans-version "20120802" :date "31-Aug-2012 11:37:50.0" :trans-errors '(:WARNINGS 1 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 2942064 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12927 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12927 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2693 :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 3015 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12927 :visit-id "04" :orbit-number 2 :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 3015 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12927 :visit-id "04" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2710 :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 3015 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12927 :visit-id "04" :orbit-number 4 :pcs-time 222 :si-vis-utilization 2739 :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 3015 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12927 :visit-id "04" :orbit-number 5 :pcs-time 222 :si-vis-utilization 2711 :al-overhead-at-end 0 :internal-dur-at-end 481 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3015 :pcs-gap 0 ) false 5 1