The scientific purpose of this proposal is three-fold: (1) Continue to quantify and correlate the Crab s X-ray and optical, temporal and spatial variations, developing a legacy database for high-spatial-resolution studies of this astrophysical archetype; (2) identify and explore phenomena responsible for the recently discovered fact that the Crab is not a standard candle in hard X-rays; and (3) establish X-ray and optical baselines, to aid in determining the location and physics of the Crab s gamma-ray flares. The program is part of a multiwavelength (X-ray and optical) monitoring campaign of the Crab pulsar and inner Nebula. It consists in a series of 4 ACS imaging observations in the F550M filter, to be performed quasi-simultaneously (within 10 days maximum) with Chandra/ACIS imaging observations. We ask to observe the target in early December 2013, as well as in January, April and August 2014. For each epoch, we have selected a time window (spanning 10 days) in which the target is visible. The HST visits (as well as the Chandra ones) should be scheduled within such windows. The same instrumental setup will be adopted for each visit. To fully cover the FOV of our Chandra observations (150"x150"), we will use the ACS/WFC with the WFC aperture. A box dithering pattern will be implemented to fill the inter-chip gap as well as to reject cosmic ray hits. Setting an exposure of 500 s for each position of the dithering pattern results in 2000 s exposure time per visit, which is well suited to achieve our goals and allows for an optimal use of the orbital visibility window. Default false false false false false SUPPORTED STAR NEUTRON STAR PULSAR J2000 J2000 ACS/WFC Imaging No No F550M ACS/WFC Imaging No No F550M ACS/WFC Imaging No No F550M ACS/WFC Imaging No No F550M POS-TARG DITHER 3.5 Dithering is aimed at filling the inter-chip gap as well as at rejecting CR hits LINE 0.5 false false 85.28 4 85.28 ACS-WFC-DITHER-BOX 1 false The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13510 :visit-id "01" :proposal-version -1 :trans-version "20130919" :date "21-Oct-2013 11:25:55.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13510 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13510 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2704 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3092 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13510 :visit-id "02" :proposal-version -1 :trans-version "20130919" :date "21-Oct-2013 11:36:22.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13510 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13510 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2704 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3092 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13510 :visit-id "03" :proposal-version -1 :trans-version "20130919" :date "21-Oct-2013 11:35:49.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13510 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13510 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2704 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3092 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13510 :visit-id "04" :proposal-version -1 :trans-version "20130919" :date "21-Oct-2013 11:35:25.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13510 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13510 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2704 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3092 :pcs-gap 0 ) true 1 0