! $Id: 5220,v 30.1 1994/07/27 16:00:08 pepsa Exp $ coverpage: title_1: THE AURORA AND AIRGLOW OF URANUS sci_cat: SOLAR SYSTEM sci_subcat: GIANT PLANETS proposal_for: GTO/WF2 pi_title: DR. pi_fname: JOHN pi_lname: TRAUGER pi_inst: 2370 pi_country: USA pi_phone: 818-354-9594 keywords_1: JUPITER hours_pri: 1.48 num_pri: 1 wf_pc: Y time_crit: Y pi_position: PROJECT SCIENTIST off_fname: JOHN off_mi: T. off_lname: TRAUGER off_title: DR. off_inst: JET PROPULSION LABORATORY off_addr_1: 4800 OAK GROVE DRIVE off_addr_2: MAIL STOP 179-225 off_city: PASADENA off_state: CA off_zip: 91109 off_country: USA off_phone: 818-354-9594 ! end of coverpage abstract: line_1: WFPC2 observations of Uranus in the FUV will show the spatial line_2: distribution of the H Ly a and H2 Lyman and Werner band emissions line_3: with 20-80 pixels across the disk (depending on read-out and line_4: limiting sensitivity). The Uranus aurora are known to be variable, line_5: but present in the sunlit hemisphere, and spatial variations in line_6: the airglow emission appear in the Voyager UVS data. We will line_7: have a good sensitivity to discrete auroral regions, or ovals, line_8: and best measure the airglow emissions near the limb where they line_9: are enhanced in both optical depth and brightness. We will also line_10: study the extended H cloud (and in cycle 5 the possible OH cloud) line_11: coming from Uranus and its ring/satellite system. This proposal line_12: is the first phase of a WFPC2 GTO program on Uranus. ! ! end of abstract general_form_proposers: lname: TRAUGER fname: JOHN title: DR. mi: T. inst: 2370 country: USA esa: N ! lname: CLARKE fname: JOHN title: PROF. mi: T. inst: 2660 country: USA esa: N ! lname: BURROWS fname: CHRIS inst: STSCI country: USA ! lname: CRISP fname: DAVID inst: JPL country: USA ! lname: HOESSEL fname: JOHN inst: UNIV. OF WISCONSIN country: USA ! lname: GALLAGHER fname: JAY inst: UNIV. OF WISCONSIN country: USA ! lname: GRIFFITHS fname: RICHARD inst: JOHNS HOPKINS UNIV country: USA ! lname: HESTER fname: JEFF inst: ARIZONA STATE UNIV. country: USA ! lname: HOLTZMAN fname: JOHN inst: LOWELL OBSERVATORY country: USA ! lname: MOULD fname: JEREMY inst: CALTECH country: USA ! lname: WESTPHAL fname: JAMES inst: CALTECH country: USA ! ! end of general_form_proposers block general_form_text: ! question: 3 section: 1 line_1: Uranus is roughly as bright as Saturn in its FUV emissions, and has line_2: a much higher reflectivity over 1500-2100 A. Auroral/airglow images line_3: with the WFC will give 40 pixels across the 3.8 arcsec disk, and the line_4: 2x2 readout may be used for good sensitivity above the read noise. line_5: We will use F160W with and without F130LP to separate the optically line_6: thick H Lya from the optically thin H2 band emissions. Images with line_7: F160W and F165LP will measure the reflected solar component for line_8: subtraction from the images, and may show haze absorption. Short line_9: F673N images will register the limb position. The FUV images line_10: should reveal for the first time the spatial distribution of the line_11: UV emissions to identify their auroral and airglow components. line_12: The altitude resolution will be limited, but we may still find line_13: azimuthal variations in the limb airglow brightness arising from line_14: possible strong conjugate plasma flows across the terminator line_15: resulting from Uranus' particular magnetic field geometry. The line_16: images will also be co-added to image the extended H atmosphere in line_17: Ly a resonant scattering, and we can search for different scale line_18: heights in different directions revealing different exobase line_19: temperatures. Voyager data suggested UV auroral hot spots on line_20: Uranus that would be presently observable from Earth for ~30% of line_21: the time. Recent IR observations of H3+ emissions from Uranus may line_22: show evidence for auroral related structure, in which case we would line_23: time the HST observations optimized to view the aurora. ! question: 4 section: 1 line_1: The far-UV emissions of Uranus's aurora and airglow can only be line_2: recorded from a space-based platform due to atmospheric absorption. line_3: The UV emissions are important because they are directly excited by line_4: the precipitating energetic articles. IUE has observed temporal line_5: variations in the disk-integrated H Ly a emissions for which the line_6: emitting region area has not been identified. It is therefore line_7: important to image these emissions with HST to resolve the auroral line_8: component, which would be spatially confined. The near-IR H3+ line_9: emissions from Uranus detected with ground-based telescopes should line_10: have an auroral component but these emissions can also be thermally line_11: excited by non-auroral processes, and are thus not sufficient to line_12: resolve the morphology of the primary auroral processes. In line_13: addition, 2x2 WF images would have at least a factor of two better line_14: spatial resolution than the ground-based H3+ images. The extended line_15: hydrogen corona particular to Uranus can only be detected in the UV. ! question: 5 section: 1 line_1: The Voyager UV data show indication of auroral hot spots on Uranus' line_2: dayside that would be visible from Earth at present for only about line_3: 30% of the time. There may of course be additional auroral emission line_4: regions which were not active during the Voyager encounter. The line_5: large uncertainty in the rotation period does not allow prediction line_6: of the visibility of the auroral region from the Earth extended from line_7: the Voyager data in 1986. Recent IR observations of H3+ emissions line_8: from Uranus may show evidence for auroral related structure, and we line_9: will use any information derived from these H3+ observations to line_10: optimize the time of the HST observations to view the aurora. line_11: We will also try to coordinate simultaneous ground-based imaging of line_12: the H3+ emissions and the WFPC2 images of the aurora. line_13: This will be important to determine the relation between the line_14: different emission processes in Uranus' ionosphere. ! question: 6 section: 1 line_1: Scheduling during dark time is required. We are imaging FUV line_2: emissions from H (Lyman alpha) and H2 (Lyman and Werner bands), line_3: some very weak emissions, and therefore require minimum line_4: contamination from geocoronal Ly a and oxygen airglow emissions line_5: in order to obtain the best possible S/N. line_6: The exposures cannot be interrupted because of Uranus's fast line_7: rotation (~17.24 hours) and known temporal variability in the line_8: emissions, and the exposures series have been planned accordingly. ! ! question: 8 section: 1 line_1: NONE ! question: 9 section: 1 line_1: No images of Uranus in the UV have been obtained with HST or any line_2: other instrument. We estimate that WFPC2 with the Na metal line_3: filter will have 4-5 times higher efficiency and a much larger line_4: dynamic range than would be possible with the FOC. ! question: 10 section: 1 line_1: Unix workstations are available with IDL and the WFPC2 system line_2: SPICA software packages. ! question: 13 section: 1 line_1: Uranus and Neptune form a class of giant planet substantially line_2: smaller than Jupiter and Saturn, with much colder lower atmospheres line_3: (changing the composition), and with bizarrely tilted and offset line_4: magnetic fields. Uranus is roughly as bright as Saturn in the FUV line_5: despite being twice as far from the Sun and can be imaged with line_6: WFPC2. In addition to bright and highly variable FUV airglow and line_7: auroral emissions, Uranus has an extensive hydrogen corona resulting line_8: from the planet's low gravity and hot (~800K) upper atmospheric line_9: temperature. IUE has observed strong and highly variable H Ly a line_10: emissions from Uranus, and it is now known from Voyager and IUE data line_11: that these emissions are composed of resonant scattering components line_12: combined with poorly understood airglow and auroral emissions. line_13: The difficulty in understanding the observed variations with time is line_14: due in part to the lack of spatial resolution combined with a large line_15: uncertainty in the planetary (magnetic) rotation period of 17.24 +/- line_16: 0.01 hours derived in 1986 from Voyager data. We will therefore line_17: attempt to resolve the spatial distribution of the H Ly a and the H2 line_18: auroral and airglow emissions and help understand the nature of line_19: the observed changes with time with WFPC2 images in cycle 4. line_20: In cycle 5, with repeated FUV observations we will study the line_21: temporal variations and may refine Uranus' rotational period. We line_22: may also image (in the NUV) Uranus' extended OH cloud sputtered line_23: from the icy ring particles and/or satellites. ! !end of general form text general_form_address: lname: TRAUGER fname: JOHN mi: T. title: DR. category: PI inst: 2370 addr_1: MS 179-225 addr_2: 4800 Oak Grove Drive city: Pasadena state: CA zip: 91109 country: USA phone: 818-354-9594 ! lname: CLARKE fname: JOHN mi: T. title: DR. inst: 2660 phone: 313-747-3540 ! lname: BALLESTER fname: GILDA mi: E. title: DR. inst: 2660 phone: 313-747-3670 ! ! end of general_form_address records ! No fixed target records found solar_system_targets: targnum: 1 name_1: URANUS-AUR1 descr_1: PLANET URANUS lev1_1: STD = URANUS wind_1: OLG OF URANUS BETWEEN 330 60 comment_1: URANUS AURORA/AIRGLOW FUV IMAGES WITH comment_2: WFC AND WITH 2 FILTER COMBINATIONS TO comment_3: BE MADE IN SEQUENTIAL ORBITS. comment_4: THE F160BW EXPOSURES SHOULD SCHEDULED comment_5: ACCORDING TO THE LATEST POSSIBLE comment_6: INFORMATION ON H3+ IR OBSERVATIONS TO comment_7: HAVE BEST CHANCE TO OBSERVE THE AURORA. comment_8: OLG WINDOWS CAN BE EXPANDED SOMEWHAT comment_9: IF NEEDED FOR SCHEDULING. comment_10: SCHEDULE DURING DARK TIME. fluxnum_1: 1 fluxval_1: V = -0.6 +/- 0.5 fluxnum_2: 2 fluxval_2: F-LINE(1400)=1+/-3E-14,W-LINE(1400)=420 fluxnum_3: 3 fluxval_3: F-CONT(1800) = 2 +/- 5 E-13 fluxnum_4: 4 fluxval_4: SIZE = 3.9 +/- 1 fluxnum_5: 5 fluxval_5: F-CONT(5500) = 2.1 +/- 1 E-12 fluxnum_6: 6 fluxval_6: SIZE = 1.1 ! ! end of solar system targets ! No generic target records found exposure_logsheet: linenum: 1.100 targname: URANUS-AUR1 config: WFPC2 opmode: IMAGE aperture: WF4-FIX sp_element: F673N num_exp: 1 time_per_exp: 12.0 S s_to_n: 120 fluxnum_1: 5 fluxnum_2: 6 priority: 1 param_1: ATD-GAIN = 15 param_2: CR-SPLIT=NO req_1: CYCLE 4; req_2: GROUP 1.1 - 1.5 NO GAP; req_3: PCS MODE F; req_4: POS TARG -4.2,0.0 /1.1-1.5 comment_1: RED IMAGES OF URANUS WITH SAME GUIDE comment_2: STARS AS IN LINENUM 1.2 TO comment_3: IDENTIFY LIMB OF PLANET. ! linenum: 1.200 targname: URANUS-AUR1 config: WFPC2 opmode: IMAGE aperture: WF4-FIX sp_element: F160BW, F165LP num_exp: 1 time_per_exp: 1000.0 S s_to_n: 3 fluxnum_1: 3 fluxnum_2: 4 priority: 1 param_1: ATD-GAIN = 7 param_2: CR-SPLIT=NO req_1: CYCLE 4; req_2: PCS MODE F comment_1: IMAGE OF URANUS' BACKGROUND UV comment_2: SCATTERED LIGHT TO SUBTRACT FROM FUV comment_3: IMAGES OF AURORA. ! linenum: 1.300 targname: URANUS-AUR1 config: WFPC2 opmode: IMAGE aperture: WF4-FIX sp_element: F160BW num_exp: 4 time_per_exp: 1000.0 S s_to_n: 10 fluxnum_1: 2 fluxnum_2: 3 fluxnum_3: 4 priority: 1 param_1: ATD-GAIN = 7 param_2: CR-SPLIT=NO req_1: CYCLE 4; req_2: PCS MODE F comment_1: FUV IMAGE OF URANUS' AURORA/AIRGLOW comment_2: H AND H2 EMISSIONS. DARK TIME. ! linenum: 1.400 targname: URANUS-AUR1 config: WFPC2 opmode: IMAGE aperture: WF4-FIX sp_element: F160BW, F165LP num_exp: 1 time_per_exp: 1000.0 S s_to_n: 10 fluxnum_1: 2 fluxnum_2: 3 fluxnum_3: 4 priority: 1 param_1: ATD-GAIN = 7 param_2: CR-SPLIT=NO req_1: CYCLE 4; req_2: PCS MODE F comment_1: FUV IMAGE OF URANUS' AURORA/AIRGLOW comment_2: H AND H2 EMISSIONS. DARK TIME. ! linenum: 1.500 targname: URANUS-AUR1 config: WFPC2 opmode: IMAGE aperture: WF4-FIX sp_element: F673N num_exp: 1 time_per_exp: 12.0 S s_to_n: 120 fluxnum_1: 5 fluxnum_2: 6 priority: 1 param_1: ATD-GAIN = 15 param_2: CR-SPLIT=NO req_1: CYCLE 4; req_2: PCS MODE F comment_1: RED IMAGES OF URANUS WITH SAME GUIDE comment_2: STARS AS IN LINENUM 1.4 TO comment_3: IDENTIFY LIMB OF PLANET AND TELESCOPE comment_4: POINTING. ! ! end of exposure logsheet ! No scan data records found