! Proposal 6818, submission 1 ! PI: Dr. Heidi Hammel ! Received Fri Feb 9 14:50:11 EST 1996 ! From: pi47@stsci.edu ! Name of Phase I Proposal: archive-1095.hammel.prop ! Date generated: Fri Dec 22 16:25:03 EST 1995 ! Date of current version of this Phase II proposal = 17 January 1996 Proposal_Information Title: The Atmosphere of Uranus: Vertical Aerosol Structure and Horizontal Inhomogeneity Proposal_Category: GO Scientific_Category: SOLAR SYSTEM Cycle: 6 Investigators PI_name: Dr. Heidi Hammel PI_Institution: Massachusetts Institute of Technology CoI_Name: Kathy Rages CoI_Institution: Space Physics Research Institute Contact: N CoI_Name: Wes Lockwood CoI_Institution: Lowell Observatory Contact: N Abstract: In the past few years, evidence is emerging that the atmosphere of the distant gas giant Uranus may be beginning to undergo interesting changes as the planet moves away from southern summer solstice in 1986 toward equinox in 2007. The planet's equatorial region is now moving into sunlight after being in darkness for many years, and historical data along with recent HST images suggest that discrete cloud structure may become more common over the next decade. In Cycle 6, we propose to image Uranus to document these changes. The goal is to model the present distribution of vertical aerosols. Uranus is getting darker, but current vertical aerosol models cannot reproduce this secular change without invoking very large and unlikely variations in color and/or distribution of vertical aerosols. It is not clear whether seasonal or latitudinal effects (or both) are creating this discrepancy. We will separate these possibilities by modeling the yearly observed aerosol distribution using both the center-to-limb reflectivity as a function of latitude and the wavelength-dependent reflectivity of the atmosphere (and of individual features if any are detected). Observations will be coordinated with groundbased imaging and photometry, linking the HST data to a 22-year record of photometry. Questions Observing_Description: To fully map Uranus in longitude, three "samples" are required. Two samples (one of each hemisphere) are insufficient, because limb effects (e.g., foreshortening of features, limb-brightening, limb-darkening) render identification and interpretation of any putative discrete features near the limb ambiguous, if not impossible. The first two "samples" are separated in time by about 9 hours, which is roughly 1/2 of the planet's atmospheric rotation period (about 17 hours on average). The third "sample" is about 16 hours after the second "sample," to reacquire any discrete features and hence determine rotation periods, and to characterize limb effects. To cover all wavelengths, 2 orbits per "sample" are be required. For S/N better than 1000, the exposure times for F336W, F467M, F547M, F673N, F953N, FQCH4N15 (619 nm), and FQCH4P15 (890 nm) are 120, 8, 10, 120, 60, 240, and 600 seconds, respectively. These exposures (plus overhead) fit into one orbit (about 23 m integration + 21 m overhead + 8 m GS acquisition = 52 m). We propose to add the F255W filter, and calculate a required exposure time of 1500 seconds (note: Uranus is darker in the UV than Neptune). Because this will necessarily be in a second orbit, we will also measure the color of the aerosols in the remainder of the orbit: integrate at F467 (8 s) and take slightly shorter integrations at 619 nm (180 s) and 890 nm (480 s) (i.e., 36 m integration + 11 m overhead + 6 m reacq = 53 m). Therefore, one complete map (three "samples" with two orbits per "sample") requires 6 orbits. Real_Time_Justification: None. We will attempt to coordinate the HST observations with groundbased observing (imaging, photometry, and spectroscopy) at several sites. In the past, we have used the UH 2.2-m telescope and the NASA Infrared Telescope Facility (both on Mauna Kea, HI), and facilities at Lowell Observatory (Flagstaff, AZ). Use of supporting groundbased data minimizes the amount of HST time needed to characterize the atmosphere, and provides more detailed understanding of Uranus by adding wavelengths which are not accessible to HST's Planetary Camera (e.g. the intermediate methane band at 727 nm, and IR wavelengths longward of 2 microns). Through this coordination, the HST data can be tied into the longterm ground-based data taken over the past 22 years by the Co-I Lockwood. Hammel has also obtained Uranus imaging periodically during the past 9 years, most recently in August 1995 at the IRTF. These data will be included in the analysis where appropriate. Some funds will be requested for the PI to make supporting observations, and for minimal support of the data analysis. Calibration_Justification: Additional_Comments: Fixed_Targets Solar_System_Targets Target_Number: 1 Target_Name: URANUS Description: PLANET URANUS Level_1: STD = URANUS Window: OLG OF URANUS BETWEEN 320 40 Flux: V = 5.52 B-V = 0.56 U-B = 0.28 Comments: THE WINDOW AROUND OPPOSITION (OLG NEAR 0) IS REQUESTED TO COORDINATE WITH GROUNDBASED OBSERVATIONS. IF THIS WINDOW IS UNAVAILABLE, THEN WE CAN RELAX THE CONSTRAINT SOMEWHAT. CONTACT PI H. B. HAMMEL (MIT) FOR INFO. Visits Visit_Number: 01 Visit_Requirements: ! AFTER [BY [TO ]] Visit_Comments: Uranus Visit 1 Exposure_Number: 01 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F336W Number_of_Iterations: 1 Time_Per_Exposure: 26S Special_Requirements: SEQ 01-08 NON-INT Exposure_Number: 02 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F467M Number_of_Iterations: 1 Time_Per_Exposure: 10S Exposure_Number: 03 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F547M Number_of_Iterations: 1 Time_Per_Exposure: 2.6S Exposure_Number: 04 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F673N Number_of_Iterations: 1 Time_Per_Exposure: 100S Exposure_Number: 05 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F953N Number_of_Iterations: 1 Time_Per_Exposure: 50S Exposure_Number: 06 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: FQCH4N15 Sp_Element: FQCH4N15 Wavelength: 6211.0 Number_of_Iterations: 1 Time_Per_Exposure: 100S Exposure_Number: 07 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: FQCH4P15 Sp_Element: FQCH4P15 Wavelength: 8922.0 Number_of_Iterations: 1 Time_Per_Exposure: 350S Exposure_Number: 08 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: FQCH4P15 Sp_Element: FQCH4P15 Wavelength: 8922.0 Number_of_Iterations: 1 Time_Per_Exposure: 350S Exposure_Number: 09 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F255W Number_of_Iterations: 1 Time_Per_Exposure: 1300S Special_Requirements: SEQ 09-10 NON-INT Exposure_Number: 10 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F953N Number_of_Iterations: 1 Time_Per_Exposure: 50S Exposure_Number: 11 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: FQCH4P15 Sp_Element: FQCH4P15 Wavelength: 8922.0 Number_of_Iterations: 1 Time_Per_Exposure: 350S ! VISIT 02 - SHOULD START 8.0 HOURS AFTER START OF VISIT 01 Visit_Number: 02 Visit_Requirements: AFTER 01 BY 7.5H TO 8.5H Visit_Comments: Uranus Visit 2 Exposure_Number: 01 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F336W Number_of_Iterations: 1 Time_Per_Exposure: 26S Special_Requirements: SEQ 01-08 NON-INT Exposure_Number: 02 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F467M Number_of_Iterations: 1 Time_Per_Exposure: 10S Exposure_Number: 03 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F547M Number_of_Iterations: 1 Time_Per_Exposure: 2.6S Exposure_Number: 04 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F673N Number_of_Iterations: 1 Time_Per_Exposure: 100S Exposure_Number: 05 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F953N Number_of_Iterations: 1 Time_Per_Exposure: 50S Exposure_Number: 06 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: FQCH4N15 Sp_Element: FQCH4N15 Wavelength: 6211.0 Number_of_Iterations: 1 Time_Per_Exposure: 100S Exposure_Number: 07 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: FQCH4P15 Sp_Element: FQCH4P15 Wavelength: 8922.0 Number_of_Iterations: 1 Time_Per_Exposure: 350S Exposure_Number: 08 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: FQCH4P15 Sp_Element: FQCH4P15 Wavelength: 8922.0 Number_of_Iterations: 1 Time_Per_Exposure: 350S Exposure_Number: 09 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F255W Number_of_Iterations: 1 Time_Per_Exposure: 1300S Special_Requirements: SEQ 09-10 NON-INT Exposure_Number: 10 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F953N Number_of_Iterations: 1 Time_Per_Exposure: 50S Exposure_Number: 11 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: FQCH4P15 Sp_Element: FQCH4P15 Wavelength: 8922.0 Number_of_Iterations: 1 Time_Per_Exposure: 350S ! VISIT 03 - SHOULD START 24.0 HOURS AFTER START OF VISIT 01 ! TO HAVE LONGITUDE MATCHED TO VISIT 02 Visit_Number: 03 Visit_Requirements: AFTER 01 BY 23.5H TO 24.5H Visit_Comments: Uranus Visit 3 Exposure_Number: 01 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F336W Number_of_Iterations: 1 Time_Per_Exposure: 26S Special_Requirements: SEQ 01-08 NON-INT Exposure_Number: 02 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F467M Number_of_Iterations: 1 Time_Per_Exposure: 10S Exposure_Number: 03 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F547M Number_of_Iterations: 1 Time_Per_Exposure: 2.6S Exposure_Number: 04 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F673N Number_of_Iterations: 1 Time_Per_Exposure: 100S Exposure_Number: 05 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F953N Number_of_Iterations: 1 Time_Per_Exposure: 50S Exposure_Number: 06 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: FQCH4N15 Sp_Element: FQCH4N15 Wavelength: 6211.0 Number_of_Iterations: 1 Time_Per_Exposure: 100S Exposure_Number: 07 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: FQCH4P15 Sp_Element: FQCH4P15 Wavelength: 8922.0 Number_of_Iterations: 1 Time_Per_Exposure: 350S Exposure_Number: 08 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: FQCH4P15 Sp_Element: FQCH4P15 Wavelength: 8922.0 Number_of_Iterations: 1 Time_Per_Exposure: 350S Exposure_Number: 09 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F255W Number_of_Iterations: 1 Time_Per_Exposure: 1300S Special_Requirements: SEQ 09-10 NON-INT Exposure_Number: 10 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F953N Number_of_Iterations: 1 Time_Per_Exposure: 50S Exposure_Number: 11 Target_Name: URANUS Config: WFPC2 Opmode: IMAGE Aperture: FQCH4P15 Sp_Element: FQCH4P15 Wavelength: 8922.0 Number_of_Iterations: 1 Time_Per_Exposure: 350S Data_Distribution Medium: 8MM Blocking_Factor: 10 Ship_To: 54-416 77 Massachusetts Avenue Cambridge, MA 02139 Ship_Via: UPS