This Phase 2 implementation follow closely the Phase 1 proposal. The main difficulty for this proposal is accurate scheduling. Exposure C250 needs to be executed within 1 minute of 20 possible times during Cycle 13. In order to improve schedulability, five visits were created with the same exposures, but in different order, so that exposure C250 is located in various parts after the start of the orbit. Only one of these five visits needs to be executed. More information is given in the comments of Target 1. ----- Submission 1 (Wed May 12 20:46:28 GMT 2004) ----- Assigned ID: 314 ----- Submission 1 (Fri Jan 23 05:33:36 GMT 2004) ----- Phase I Proposal 314 (ganymedeb) successfully submitted. ----- Submission 2 (Fri Jan 23 23:54:04 GMT 2004) ----- Phase I Proposal 314 (ganymedeb) successfully submitted. Jupiter's Upper Stratospheric Hazes Probed with Ganymede I propose to observe a disappearance of Ganymede behind the dark limb of Jupiter with five filters of the ACS/HRC camera. Two exposures in each filter can be taken during such an event. The images will provide the spectral variation of the altitude of the apparent limb of Jupiter. The altitude of the apparent limb is dependent on the presence of hazes in Jupiter's stratosphere. Hazes of vertical optical depths below 0.001 could be detected with these observations, providing an extremely sensitive probe of high hazes. The observations probe altitudes levels near the 1-mb pressure level, for which we have very limited data. The creation of aerosols, their growth, and their transport by winds is currently a mostly theoretical study. It would significantly benefit from constraints derived from the proposed observations. ACS/HRC is the only instrument capable of the required spatial resolution in the ultraviolet. Furthermore, a favorable geometry of Ganymede's orbit occurs only once every six years. This proposal achieves unique results with a minimum of HST time.
I propose to image the disappearance or reappearance of Ganymede behind Jupiter's dark limb from 16 minutes before the midpoint (when half of Ganymede is covered by Jupiter) to 16 minutes past the midpoint. The ACS/HRC camera is used with five filters, F250W, F330W, F435W, F658N, and F892N. Exposure times are 3 seconds for filter F435W, 20 seconds for F250W, and 10 seconds otherwise. HRC will record more than a quarter of Jupiter's disk together with Ganymede. The filters are cycled four times. One cycle of five exposures (each filter once) takes 8 minutes including all overheads. Additionally, the same part of Jupiter is imaged once with ACS/HRC and filters F220W (at least 200 seconds exposure time), F550M (3 s), and three wavelength settings of FR656N (10 s each). F220W probes the highest altitudes in Jupiter's atmosphere, closest to the levels probed by Ganymede. F550M fills in between F435W and F658N. FR656N probes the ammonia absorption at 647 nm. For each filter, the first or last Ganymede exposure will show the whole disk of Ganymede unaffected by Jupiter's atmosphere, while the last or first exposure records the background level. The two intermediate exposures record the location of Jupiter's limb for all filters except F250W with only one exposure due to the limited duration of the event. The exposures on Ganymede in filters F330W, F658N, and F892N are expected to reach signals of about 30,000 electrons per pixel, corresponding to signal-to-noise ratios of almost 200. Filters F435W and F250W will give signals of 80,000 and 8,000electrons per pixel, respectively. The Jupiter exposures with F220W, F550M, and FR656N are expected to reach signals of 8,000, 90,000, and 30,000 electrons/pixel, respectively. HST will be tracking Jupiter. This will cause a smear of up to one HRC-pixel of Ganymede due to its orbital motion (except two pixels for F250W). This does not significantly affect the observations. The observations need to be scheduled around an occultation disappearance or reappearance of Ganymede behind Jupiter's dark limb, so that the 32-minute time interval centered on the mid-event (half of Ganymede behind Jupiter) can be used for imaging. SOLAR SYSTEM 12 false 0.0 false false false false false SUPPORTED SOLAR SYSTEM Southern part of Jupiter including Ganymede. Position Angle needs to be 157 after April 2005. Radius needs to be adjusted with the month due to the changing apparent size of Jupiter, in Dec 2004-Jan 2005: 12, in Feb 2005: 13, in Mar-May 2005: 14, in Jun-Jul 2005: 13. These positions work with the requested orientations. Other orientations are possible, but require slightly modified positioning. Exposure C250 needs to be executed within a minute of the middle of a occultation disappearance or reappearance of Ganymede at Jupiter's dark limb. In order to improve schedulability, five visits were created with the 24 exposures in a different order, so that the Visit 01 has C250 very late, while Visit 05 has it very early. Only one of the five visit needs to be executed. Preferred months are close to Jupiter's opposition in ealy April 2005 due to the larger apparent diameter of Jupiter. For example, in early March and early May 2005, Jupiter is 20 percent larger than in late December 2004 or ealy July 2005, which increases the accuracy of measurements by about the same amount. However, the primary goals of the program are not dependent on a 20 percent increase in apparent diameter. PLANET OFFSET PLANET STD=JUPITER TYPE=POS_ANGLE,RAD=13.0,ANG=252.0,REF=NORTH ACS/HRC Imaging No No F250W ACS/HRC Imaging No No F330W ACS/HRC Imaging No No F435W ACS/HRC Imaging No No F658N ACS/HRC Imaging No No F892N ACS/HRC Imaging No No F220W ACS/HRC Imaging No No F550M Must include an occultation disappearance or reappearance of Ganymede at Jupiter's dark limb centered on exposure C250. 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(Tic-Visit :proposal-id 10192 :visit-id "03" :proposal-version -1 :trans-version "20040225" :date "11-May-2004 11:38:45.0" :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 441632 :tdrss-contact-duration 0 ) (Tic-Obset :proposal-id 10192 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 10192 :visit-id "03" :orbit-number 1 :pcs-time 365 :si-vis-utilization 2677 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3056 :pcs-gap 0 ) true -1 -1 Must include an occultation disappearance or reappearance of Ganymede at Jupiter's dark limb centered on exposure C250. (Tic-Visit :proposal-id 10192 :visit-id "04" :proposal-version -1 :trans-version "20040225" :date "11-May-2004 12:18:08.0" :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 441632 :tdrss-contact-duration 0 ) (Tic-Obset :proposal-id 10192 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 10192 :visit-id "04" :orbit-number 1 :pcs-time 365 :si-vis-utilization 2636 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3056 :pcs-gap 0 ) true -1 -1 Must include an occultation disappearance or reappearance of Ganymede at Jupiter's dark limb centered on exposure C250. (Tic-Visit :proposal-id 10192 :visit-id "05" :proposal-version -1 :trans-version "20040225" :date "11-May-2004 11:38:02.0" :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 441632 :tdrss-contact-duration 0 ) (Tic-Obset :proposal-id 10192 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 10192 :visit-id "05" :orbit-number 1 :pcs-time 365 :si-vis-utilization 2644 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3056 :pcs-gap 0 ) true -1 -1