Proposal_Information Title: Observation of short timescale variability of the Jovian UV aurora Proposal_Category: GO Scientific_Category: SOLAR SYSTEM Cycle: 6 Investigators PI_name: Jean-Cl. Gerard PI_Institution: Universite de Liege (Belgium) CoI_Name: Vincent Dols CoI_Institution: Universite de Liege (Belgium) Contact: N CoI_Name: Denis Grodent CoI_Institution: Universite de Liege (Belgium) Contact: Y CoI_Name: Gilda Ballester CoI_Institution: University of Michigan (USA/MI) Contact: N CoI_Name: John Clarke CoI_Institution: University of Michigan (USA/MI) Contact: N CoI_Name: John T. Trauger CoI_Institution: Jet Propulsion Laboratory (USA/CA) Contact: N Abstract: Previous FOC and WFPC2 observations have shown the very complex morphological structure of the Jovian UV aurora and its unexpectedly strong temporal variations. They (and other IUE and Voyager UVS observations) suggest that time variations occur on different timescales. Some of the auroral structures deduced from previous images may be the result of a time averaging of short-lived auroral features. We propose to image the short time variations (minutes) of the ultraviolet Jovian auroral morphology and brightness with WFPC2. Exposures will be made near central meridian longitudes (CMLs) = 180 degrees in order to get the best view of the northern auroral zone. The question of temporal variability is of major importance in understanding the origin and acceleration mechanisms of the auroral particles exciting the Jovian UV aurora. Questions Observing_Description: We propose to image the short timescale variability of the Jovian polar regions with WFPC2. Two visits of one orbit each covering CMLs around 180 degrees (lambda III) will be selected to give the best viewing geometry of the auroral region and to obtain statistically significant results. During the first visit, the PC1 chip will take : - 1 short exposure (4s) of the visible disk of Jupiter through the F673N filter in order to obtain a sharp limb determination. - 6 consecutive UV exposures of the auroral emission (200s) through the F160BW Wood's filter. This filter has proven to be perfectly suited to auroral observation as it provides good contrast between the UV emission (H2 Lyman and Werner bands) and the bright disk background. Analyses of previous WFPC2 auroral images show that a 100s exposure time is a good compromise between the pixel count rate and the signal dilution due to the planet's rotation. During the second visit, the WF3 chip will take : - 1 short exposure (1s) of the visible disk of Jupiter through the F673N filter in order to obtain a sharp limb determination. - 8 consecutive UV exposures of the auroral emission (160s) through the F160BN15 Wood's filter. The second visit will occur one Jovian rotation (~ 10 hours) after the beginning of the first visit in order to cover timescale variations ranging from minutes to hours, and to obtain images with comparable CMLs from one visit to the other. The program must be carried out near quadrature in order to include the complete Jovian disk in the PC1 field. Real_Time_Justification: The observations must be carried out (between 05 May 1997 and May 28 1997) or (between June 30 1997 and July 20 1997) Calibration_Justification: Additional_Comments: Solar_System_Targets Target_Number: 1 Target_Name: JUPITER-AURORA Description: PLANET JUPITER Level_1: STD=JUPITER Level_2:TYPE=TORUS, LONG=0, LAT=+30, RAD=66770, POLE_LAT=+90 Window: CML OF JUPITER FROM EARTH BETWEEN 155 215 OLG OF IO BETWEEN 110 250 Flux: SURF(V)=5.3+/-0.05 U-B=0.48 B-V=0.83 Comments: Jovian CMLs are expressed in System-III longitude. Visits Visit_Number: 1 Visit_Requirements: PCS MODE F BETWEEN 05-MAY-97 AND 28-MAY-97 BETWEEN 30-JUN-97 AND 20-JUL-97 On_Hold_Comments: Visit_Comments: Exposure_Number: 1 Target_Name: JUPITER-AURORA Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F673N Wavelength: Optional_Parameters: ATD-GAIN = 7 Number_of_Iterations: 1 Time_Per_Exposure: 4S Special_Requirements: SEQ 1-2 NON-INT Comments: Exposure_Number: 2 Target_Name: JUPITER-AURORA Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F160BW Wavelength: Optional_Parameters: ATD-GAIN = 7 Number_of_Iterations: 6 Time_Per_Exposure: 200S Special_Requirements: Visit_Number: 51 Visit_Requirements: PCS MODE F BETWEEN 28-JUL-97 and 11-aug-97 On_Hold_Comments: Visit_Comments: Exposure_Number: 1 Target_Name: JUPITER-AURORA Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: F673N Wavelength: Optional_Parameters: ATD-GAIN = 7 Number_of_Iterations: 1 Time_Per_Exposure: 1S Special_Requirements: SEQ 1-2 NON-INT Comments: Exposure_Number: 2 Target_Name: JUPITER-AURORA Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: F160BN15 Wavelength: Optional_Parameters: ATD-GAIN = 7 Number_of_Iterations: 8 Time_Per_Exposure: 160S Special_Requirements: Comments: Visit_Number: 2 Visit_Requirements: PCS MODE F On_Hold_Comments: Visit_Comments: To be done at quadrature. Visit #2 must start 1 Jovian rotation (~10H) after the beginning of visit #1, the viewing geometry of both visits will therefore be comparable (same CMLs). Exposure_Number: 1 Target_Name: JUPITER-AURORA Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: F673N Wavelength: Optional_Parameters: ATD-GAIN = 7 Number_of_Iterations: 1 Time_Per_Exposure: 1S Special_Requirements: SEQ 1-2 NON-INT Comments: Exposure_Number: 2 Target_Name: JUPITER-AURORA Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: F160BN15 Wavelength: Optional_Parameters: ATD-GAIN = 7 Number_of_Iterations: 8 Time_Per_Exposure: 160S Special_Requirements: Comments: Data_Distribution Medium: 8MM Blocking_Factor: 10 Ship_To: PI_Address ! Laboratoire de Physique ! Atmospherique et Planetaire ! Institut d'Astrophysique, ! 5 avenue de Cointe ! Liege ! B 4000 (Belgium) Ship_Via: UPS