! $Id: 5466,v 7.1 1995/01/04 14:22:33 pepsa Exp $ coverpage: title_1: THE INTERACTION BETWEEN IO AND THE PLASMA title_2: TORUS: DIRECT MEASUREMENT OF THE MASS LOADING RATE CYCLE4MEDIUM sci_cat: SOLAR SYSTEM sci_subcat: SATELLITES proposal_for: GO pi_fname: IMKE pi_lname: DE PATER pi_inst: 1500 pi_country: US pi_phone: 510-642-1947 hours_pri: 5.05 num_pri: 2 hrs: Y time_crit: Y funds_amount: 75000 funds_length: 12 ! end of coverpage abstract: line_1: We propose to make the first direct measurement of the slow-down of the Io line_2: plasma torus in the immediate vicinity of Io. The slow-down is a direct line_3: measure of the rate of ionization of neutral material from Io that will line_4: provide critical information about the origin and maintenance of the torus, line_5: about the details of the interaction between the torus and the satellite, line_6: and about the nature and coverage of the Io atmosphere. Current understanding line_7: in these areas is extremely tenuous due to the lack of concrete observations. line_8: We will unambiguously determine the slow-down at Io by measuring the rotation line_9: velocity of the torus from the Doppler shift of OII 2471 A emission observed line_10: with Io in the aperture as the torus plane passes through the satellite. line_11: This method has been used in our intensive ground-based study to measure line_12: the slow-down, and thus the mass loading rate, at almost all points in the line_13: torus, however no visible wavelength measurements are possible at the crucial line_14: point where the torus passes through Io because the satellite is far too line_15: bright at these wavelengths to allow detection of the ion emissions. By line_16: contrast, in the UV the Io continuum is negligible compared with the torus line_17: emissions, and the measurement of the slow-down is comparatively easy. The line_18: results coming from this observation will have a large and immediate impact line_19: on our knowledge of the Io atmosphere and of the physical mechanisms involved line_20: in the torus-Io interaction. ! ! end of abstract general_form_proposers: lname: DE PATER fname: IMKE inst: 1500 country: USA ! lname: BROWN fname: MICHAEL inst: 1500 country: USA ! lname: MCGRATH fname: MELISSA inst: 3470 country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: We propose high-resolution observations of OII 2471 A emission in the line_2: Io plasma torus using the GHRS echelle-B to precisely measure the line_3: Doppler shift of the emission line, from which the mass loading rate in the line_4: torus can be inferred. The emission line will be observed with Io line_5: in the aperture at dusk (western) elongation as the torus plane is line_6: passing through Io and also in the same spot but with Io far line_7: from the aperture and the torus in the same geometric configuration. line_8: A comparison of the velocity shift between these two spectra will yield line_9: a direct measure of the slow-down caused by mass loading line_10: in the immediate vicinity of the satellite. line_12: The OII line was chosen because it will give the most counts of any line_13: known torus emission line (the SII emission at 1729 A is brighter, line_14: but echelle-B is approximately twenty times less sensitive at that line_15: wavelength), and we will observe at western elongation because torus line_16: emissions are known to be brightest on that side. Ground-based observations line_17: of [SII] 6731 A emission show typical FWHM linewidths of about 25 km/s, line_18: so we expect a similar value for the OII emission. Filled-aperture line_19: resolution at 2471 A is about 0.17 A, or 20 km/s, so we expect this line_20: emission to be marginally resolved. For significant scientific results, line_21: we require the ability to distinguish velocity shifts of about 4 km/s, line_22: which should be achievable with moderate signal to noise at this resolution. ! question: 4 section: 1 line_1: The goal of this program is to observe the velocity of the Io plasma torus line_2: as it passes through Io. Because Io will be within the aperture of the HRS line_3: during the exposures, this observation can only be done in the UV. At visible line_4: wavelengths, continuum emission from Io swamps the relatively weak torus line_5: emission. This fact has been confirmed by our extensive ground based line_6: observations of the rotation velocity of the torus (Brown 1992); we have line_7: shown that even with long and repeated exposures and careful continuum line_8: subtraction it is impossible to obtain a usable visible wavelength spectrum line_9: as the torus plane passes through Io. In contrast, in the UV continuum line_10: emission from Io is negligible, so obtaining a good spectrum of the torus line_11: passing through Io is comparatively easy. The only other observatory with UV line_12: capability is the IUE, but it has neither the required sensitivity (no torus line_13: emissions are detectable at high resolution) nor the required spectral line_14: resolution to measure a small deviation from corotation velocity (on the line_15: order of 4 km/s) in the immediate vicinity of Io. The comparison spectrum, line_16: taken without Io in the aperture, could, in principle, be observed line_17: elsewhere, but we feel very strongly that because we require the ability line_18: to measure a velocity shift as small as 1/5 of a resolution element line_19: (filled-aperture resolution at 2471 A is about 20 km/s) precise and line_20: reliable scientific results can only be obtained by a line_21: direct comparison between two spectra of the same emission line taken with line_22: the same instrument under the same observing conditions. ! question: 4 section: 2 line_1: The brightness of the OII 2471 A emission has been measured by the line_2: GHRS at lower resolution to be about 50 R (McGrath et al. 1993). Using line_3: the most recent Echelle-B sensitivity and ripple correction we calculate line_4: a count rate of 1.0 X 10^-2 counts/diode-sec. For the S/N calculation line_5: we included an average dark count rate of 1.2 X 10^-2 counts/diode-sec, line_6: a value of 0.03 for the inter-order background grating scattered light, line_7: and 0.11 for the fraction of time spent measuring the inter-order line_8: background during the observation. Because these extended emissions line_9: will be oversampled by the large aperture, we will bin the data by a line_10: factor of two to increase S/N at no expense of resolution. We then find line_11: that an exposure time of 160 min is required to maintain a S/N of 6. line_12: It is crucial that these observations are made as Io is inside the line_13: central part of the torus. Io never stays within this region for more line_14: than 120 minutes, so an observation can never be made over more than line_15: two orbits. Including time for on-board acquisition during the first line_16: orbit, we assume that we will obtain about 40 minutes of on-target line_17: exposure during two orbits. Thus the observation with Io in the line_18: aperture will require four separate visits to complete a 160 minute line_19: exposure. Appropriate torus-Io geometric configurations occur line_20: approximately 10 times every 35 days. line_21: The exposures without Io in the aperture need to reproduce as closely line_22: as possible the torus configuration of the preceding observations, line_23: thus we also estimate four separate visits to complete the 160 minute exposure. ! question: 5 section: 1 line_1: This program is highly time-critical. The goal is to observe the Io line_2: plasma torus as the torus plane passes through Io at western elongation, line_3: so the observations must be scheduled carefully. (Correct torus-Io geometric line_4: configurations occur about once every 3.5 days.) Because Io only stays within line_5: the central part of the torus for about 120 minutes, each observation can line_6: last no more than two orbits. We will therefore require four separate line_7: visits, each at the appropriate torus-Io geometry, to complete the line_8: observation. The spectra will be compared with similar spectra taken line_9: with the torus in the same geometric configuration but with Io far from line_10: the field of view. These observations will need to be scheduled to line_11: reproduce as closely as possible torus configuration of the first line_12: observations in order to make a meaningful comparison between the two line_13: spectra. (Correct torus geometric configurations with Io far from the line_14: aperture occur about once every twenty hours). line_16: In addition, all observations should take place when the other line_17: Galilean satellites are far removed to avoid contaminating light. ! ! question: 9 section: 1 line_1: 1. GO 2627 - Io's Atmosphere and its Interaction with the Plasma Torus line_2: M. McGrath, co-I. line_4: 2. GO 2625 - Excitation Processes for the Outer Planet UV Emissions, M. line_5: McGrath co-I. line_7: 3. GO 3616 - The Upper Atmospheres of Uranus and Neptune, line_8: M. McGrath, PI. line_10: 4. GO 3617 - The Ultraviolet Emissions of Titan, M. McGrath, PI. line_12: 5. GO 3618 - Excitation Processes for the Outer Planet UV Emissions-- line_13: Cycle 2 Continuation, M. McGrath, PI. line_15: 6. GO 4353 - Hubble Space Telescope Imaging of Io, M. McGrath, PI. line_17: 7. GO 4600 - FUV Spectrscopy of Io's SO2 Atmosphere and Surface, line_18: M. McGrath, co-I. ! question: 9 section: 2 line_1: 1. GO 2627 - cycle 1 program, observations completed successfully in line_2: March and May 1992. Observations have resulted in the first detection of line_3: [OII]2471 emission from the Io plasma torus; the first UV detection of the line_4: Io SO2 atmospheric absorption bands (only the third time the SO2 atmosphere line_5: of Io has been detected directly) yielding a measurement of the atmospheric line_6: density, pressure, and coverage; and spatial scans of Io neutral S and O line_7: atmospheric emissions, resulting in a factor of 3 improvement in the spatial line_8: resolution of these constituents compared with previous IUE measurements. line_10: 2. GO 4353 - cycle 3 program, not yet completed. Some data obtained on line_11: May 10, 1993; remaining observations scheduled for week of May 24, 1993. line_12: No results to date. line_14: 3. GO 4600 - no data obtained to date. ! question: 10 section: 1 line_1: line_2: These observation fit into our ongoing ground-based (at Berkeley) and line_3: space-based (at STScI) programs to determine the interaction between line_4: Io and the plasma torus and the Jovian magnetosphere. The data will be line_5: analyzed using the same facilities and techniques that are being used line_6: in our current study of torus rotation velocities. We will provide line_7: extensive ground-based support from Lick Observatory during the periods line_8: of the observations to characterize the state of the torus and the line_9: neutral clouds, and we also hope to obtain observations of the Io-torus line_10: system from the Keck telescope during these times. ! !end of general form text general_form_address: lname: de Pater fname: Imke category: PI inst: 1500 addr_1: Department of Astronomy addr_2: University of California city: Berkeley state: CA zip: 94720 country: USA phone: 510-642-1947 telex: imke@bkyast.berkeley.edu ! ! end of general_form_address records ! No fixed target records found solar_system_targets: targnum: 1 name_1: TORUS-WITH-IO descr_1: TORUS JUPITER lev1_1: STD=JUPITER lev2_1: STD=IO wind_1: WND1=25-FEB-94 TO 22-JUN-94, wind_2: WND2=1-DEC-94 TO 1-JAN-99, wind_3: OLG OF IO BETWEEN 246 280, CML OF wind_4: JUPITER FROM EARTH BETWEEN 109 235 wind_5: SEP OF GANYMEDE IO FROM EARTH GT 5", wind_6: SEP OF EUROPA IO FROM EARTH GT 5", wind_7: SEP OF CALLISTO IO FROM EARTH GT 5" comment_1: EXPOSURE OF THE IO PLASMA TORUS AT comment_2: THE POSITION OF IO WITH IO AT comment_3: ELONGATION, AND THE TORUS AT A CML comment_4: OF NEAR 200 IN ORDER FOR IO TO BE comment_5: IN THE DENSEST REGION OF TORUS. comment_6: CML OF JUPITER BETWEEN 289 55 comment_7: IS ACCEPTABLE, AS LONG AS ALL comment_8: OBS ARE MADE IN THIS RANGE. fluxnum_1: 1 fluxval_1: V=5.02 fluxnum_2: 2 fluxval_2: W-LINE(2471)=0.21 +/- 0.05 fluxnum_3: 2 fluxval_3: SURF-LINE(2471)=13 +/- 4 E-15 fluxnum_4: 2 fluxval_4: SIZE=20 +/- 5 ! targnum: 2 name_1: TORUS-WITHOUT-IO descr_1: TORUS JUPITER lev1_1: STD=JUPITER lev2_1: TYPE=TORUS, lev2_2: LONG=90, lev2_3: LAT=0, lev2_4: RAD=4.22E05, lev2_5: POLE_LAT=+90 wind_1: WND1=25-FEB-94 TO 22-JUN-94, wind_2: WND2=1-DEC-94 TO 1-JAN-99, wind_3: OLG OF IO BETWEEN 0 180, wind_4: CML OF JUPITER FROM EARTH wind_5: BETWEEN 109 235 comment_1: EXPOSURE OF THE IO PLASMA TORUS WELL comment_2: AWAY FROM IO, BUT WITH THE SAME CML comment_3: OF TARGET 1. THE EXPOSURE SHOULD BE comment_4: IN THE ORBITAL PLANE OF IO, AND NOT comment_5: IN THE CENTRIFUGAL PLANE OF THE TORUS comment_6: (HENCE POLE_LATE= +90). comment_7: CML OF JUPITER BETWEEN 289 55 comment_8: IS ACCEPTABLE, AS LONG AS ALL comment_9: OBS ARE MADE IN THIS RANGE. fluxnum_1: 1 fluxval_1: W-LINE(2471)=0.21 +/- 0.05 fluxnum_2: 1 fluxval_2: SURF-LINE(2471)=13 +/- 4 E-15 fluxnum_3: 1 fluxval_3: SIZE=20 +/- 5 ! ! ! end of solar system targets ! No generic target records found exposure_logsheet: linenum: 1.000 targname: TORUS-WITH-IO config: HRS opmode: ACQ aperture: 2.0 sp_element: MIRROR-N2 num_exp: 1 time_per_exp: 10S fluxnum_1: 1 priority: 1 param_1: SEARCH-SIZE=5 param_2: BRIGHT=RETURN req_1: CYCLE 4; req_2: ONBOARD ACQ FOR 2; req_3: GROUP 1-11 WITHIN 120D; req_4: group 1-3 within 1 d; comment_1: FROM PREVIOUS IO ACQUISITIONS, WE comment_2: ESTIMATE A STEP TIME OF 0.4 SEC. comment_3: BECAUSE OF TEMPORAL CHANGES OBSERVED comment_4: WITHIN THE TORUS, ALL EXPOSURES comment_5: SHOULD BE WITHIN ONE JOVIAN comment_6: APPARITION. ! linenum: 2.000 targname: TORUS-WITH-IO config: HRS opmode: ACCUM aperture: 2.0 sp_element: ECH-B wavelength: 2471 num_exp: 8 time_per_exp: 5M s_to_n: 6 s_to_n_time: 160M fluxnum_1: 2 priority: 1 param_1: STEP-PATT=DEF param_2: FP-SPLIT=STD param_3: CENSOR=YES req_1: CYCLE 4 comment_1: GO IMMEDIATELY TO ACCUM MODE. comment_2: NO PEAKUP IS PERFORMED, BECAUSE comment_3: TARGET IS TORUS SURROUNDING IO, comment_4: SO CENTERING OF IO W/O APERTURE comment_5: IS UNIMPORTANT. ! linenum: 3.000 targname: TORUS-WITHOUT-IO config: HRS opmode: ACCUM aperture: 2.0 sp_element: ECH-B wavelength: 2471 num_exp: 11 time_per_exp: 4.4M s_to_n: 6 s_to_n_time: 160M fluxnum_1: 1 priority: 2 param_1: STEP-PATT=DEF param_2: FP-SPLIT=STD param_3: CENSOR=YES req_1: CYCLE 4 comment_1: TARGET IS IO PLASMA TORUS. BLIND comment_2: POINTING TO WITHIN A FEW ARC-SECS comment_3: SHOULD BE SUFFICIENT, comment_4: SO NO ACQUISITION IS PERFORMED. ! linenum: 4.000 targname: TORUS-WITH-IO config: HRS opmode: ACQ aperture: 2.0 sp_element: MIRROR-N2 num_exp: 1 time_per_exp: 10S fluxnum_1: 1 priority: 1 param_1: SEARCH-SIZE=5 param_2: BRIGHT=RETURN req_1: CYCLE 4; req_2: ONBOARD ACQ FOR 5; req_4: group 4-6 within 1 d; comment_1: FROM PREVIOUS IO ACQUISITIONS, WE comment_2: ESTIMATE A STEP TIME OF 0.4 SEC. comment_3: BECAUSE OF TEMPORAL CHANGES OBSERVED comment_4: WITHIN THE TORUS, ALL EXPOSURES comment_5: SHOULD BE WITHIN ONE JOVIAN comment_6: APPARITION. ! linenum: 5.000 targname: TORUS-WITH-IO config: HRS opmode: ACCUM aperture: 2.0 sp_element: ECH-B wavelength: 2471 num_exp: 8 time_per_exp: 5M s_to_n: 6 s_to_n_time: 160M fluxnum_1: 2 priority: 1 param_1: STEP-PATT=DEF param_2: FP-SPLIT=STD param_3: CENSOR=YES req_1: CYCLE 4 comment_1: GO IMMEDIATELY TO ACCUM MODE. comment_2: NO PEAKUP IS PERFORMED, BECAUSE comment_3: TARGET IS TORUS SURROUNDING IO, comment_4: SO CENTERING OF IO W/O APERTURE comment_5: IS UNIMPORTANT. ! linenum: 6.000 targname: TORUS-WITHOUT-IO config: HRS opmode: ACCUM aperture: 2.0 sp_element: ECH-B wavelength: 2471 num_exp: 11 time_per_exp: 4.4M s_to_n: 6 s_to_n_time: 160M fluxnum_1: 1 priority: 2 param_1: STEP-PATT=DEF param_2: FP-SPLIT=STD param_3: CENSOR=YES req_1: CYCLE 4 comment_1: TARGET IS IO PLASMA TORUS. BLIND comment_2: POINTING TO WITHIN A FEW ARC-SECS comment_3: SHOULD BE SUFFICIENT, comment_4: SO NO ACQUISITION IS PERFORMED. ! linenum: 7.000 targname: TORUS-WITH-IO config: HRS opmode: ACQ aperture: 2.0 sp_element: MIRROR-N2 num_exp: 1 time_per_exp: 10S fluxnum_1: 1 priority: 1 param_1: SEARCH-SIZE=5 param_2: BRIGHT=RETURN req_1: CYCLE 4; req_2: ONBOARD ACQ FOR 8; req_4: group 7-9 within 1 d; comment_1: FROM PREVIOUS IO ACQUISITIONS, WE comment_2: ESTIMATE A STEP TIME OF 0.4 SEC. comment_3: BECAUSE OF TEMPORAL CHANGES OBSERVED comment_4: WITHIN THE TORUS, ALL EXPOSURES comment_5: SHOULD BE WITHIN ONE JOVIAN comment_6: APPARITION. ! linenum: 8.000 targname: TORUS-WITH-IO config: HRS opmode: ACCUM aperture: 2.0 sp_element: ECH-B wavelength: 2471 num_exp: 8 time_per_exp: 5M s_to_n: 6 s_to_n_time: 160M fluxnum_1: 2 priority: 1 param_1: STEP-PATT=DEF param_2: FP-SPLIT=STD param_3: CENSOR=YES req_1: CYCLE 4 comment_1: GO IMMEDIATELY TO ACCUM MODE. comment_2: NO PEAKUP IS PERFORMED, BECAUSE comment_3: TARGET IS TORUS SURROUNDING IO, comment_4: SO CENTERING OF IO W/O APERTURE comment_5: IS UNIMPORTANT. ! linenum: 9.000 targname: TORUS-WITHOUT-IO config: HRS opmode: ACCUM aperture: 2.0 sp_element: ECH-B wavelength: 2471 num_exp: 11 time_per_exp: 4.4M s_to_n: 6 s_to_n_time: 160M fluxnum_1: 1 priority: 2 param_1: STEP-PATT=DEF param_2: FP-SPLIT=STD param_3: CENSOR=YES req_1: CYCLE 4 comment_1: TARGET IS IO PLASMA TORUS. BLIND comment_2: POINTING TO WITHIN A FEW ARC-SECS comment_3: SHOULD BE SUFFICIENT, comment_4: SO NO ACQUISITION IS PERFORMED. ! linenum: 10.000 targname: TORUS-WITH-IO config: HRS opmode: ACQ aperture: 2.0 sp_element: MIRROR-N2 num_exp: 1 time_per_exp: 10S fluxnum_1: 1 priority: 1 param_1: SEARCH-SIZE=5 param_2: BRIGHT=RETURN req_1: CYCLE 4; req_2: ONBOARD ACQ FOR 11; req_4: group 10-11 within 1 d; comment_1: FROM PREVIOUS IO ACQUISITIONS, WE comment_2: ESTIMATE A STEP TIME OF 0.4 SEC. comment_3: BECAUSE OF TEMPORAL CHANGES OBSERVED comment_4: WITHIN THE TORUS, ALL EXPOSURES comment_5: SHOULD BE WITHIN ONE JOVIAN comment_6: APPARITION. ! linenum: 11.000 targname: TORUS-WITH-IO config: HRS opmode: ACCUM aperture: 2.0 sp_element: ECH-B wavelength: 2471 num_exp: 8 time_per_exp: 5M s_to_n: 6 s_to_n_time: 160M fluxnum_1: 2 priority: 1 param_1: STEP-PATT=DEF param_2: FP-SPLIT=STD param_3: CENSOR=YES req_1: CYCLE 4 comment_1: GO IMMEDIATELY TO ACCUM MODE. comment_2: NO PEAKUP IS PERFORMED, BECAUSE comment_3: TARGET IS TORUS SURROUNDING IO, comment_4: SO CENTERING OF IO W/O APERTURE comment_5: IS UNIMPORTANT. ! ! ! linenum: 12.000 ! targname: TORUS-WITHOUT-IO ! config: HRS ! opmode: ACCUM ! aperture: 2.0 ! sp_element: ECH-B ! wavelength: 2471 ! num_exp: 8 ! time_per_exp: 4.4M ! s_to_n: 6 ! s_to_n_time: 160M ! fluxnum_1: 1 ! priority: 2 ! param_1: STEP-PATT=DEF ! param_2: FP-SPLIT=STD ! param_3: CENSOR=YES ! req_4: CYCLE 4 ! comment_1: TARGET IS IO PLASMA TORUS. BLIND ! comment_2: POINTING TO WITHIN A FEW ARC-SECS ! comment_3: SHOULD BE SUFFICIENT, ! comment_4: SO NO ACQUISITION IS PERFORMED. ! ! end of exposure logsheet ! No scan data records found