! File: 3769C.PROP ! Database: PEPDB ! Date: 19-FEB-1994:18:55:17 coverpage: title_1: THE STRUCTURE OF THE INNER COMA OF COMET CHIRON: IMAGING THE EXOPAUSE sci_cat: SOLAR SYSTEM sci_subcat: COMETS proposal_for: GO pi_fname: KAREN pi_mi: J. pi_lname: MEECH pi_inst: INSTITUTE FOR ASTRONOMY, UNIVERSITY OF HAWAII pi_country: USA pi_phone: 808-956-6828 hours_pri: 7.00 num_pri: 2 wf_pc: Y time_crit: Y funds_amount: 94721 funds_length: 12 off_fname: MOHEB off_mi: A. off_lname: GHALI off_title: DIRECTOR OF RESEARCH off_inst: UNIVERSITY OF HAWAII off_addr_1: OFFICE OF RESEARCH AND ADMINISTRATION off_addr_2: SPALDING 253 off_addr_3: 2540 MAILE WAY off_city: HONOLULU off_state: HI off_zip: 96822 off_country: USA off_phone: (808) 956-8612 ! end of coverpage abstract: line_1: We propose to use the Planetary Camera to obtain a series of images of line_2: 2060 Chiron. The radial brightness distribution obtained from these images line_3: will be used (i) to locate an exopause structure which would indicate line_4: gravitational control by the nucleus over the structure of the inner coma, and line_5: (ii) to explore the inner coma for indications of active regions which will line_6: reveal the number and location of major sources on the nucleus. The line_7: detection of the exopause, when combined with particle size information line_8: obtained from ground-based observations of color gradients in the outer coma, line_9: will constrain models of the structure of the dust coma and allow us to make a line_10: rough estimate of the mass of Chiron. The exopause is expected to be located line_11: between 0.3-0.4 arcseconds from the nucleus during 1993 (Cycle 2), thus the line_12: resolution capabilities of HST are required for this project. ! ! end of abstract general_form_proposers: lname: MEECH fname: KAREN title: PI mi: J. inst: INSTITUTE FOR ASTRONOMY country: USA esa: N ! lname: BELTON fname: MICHAEL mi: JS inst: NATIONAL OPTICAL ASTRONOMY OBSERVATORIES country: USA esa: N ! lname: BUIE fname: MARC mi: W. inst: LOWELL OBSERVATORY country: USA esa: N ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: The light we receive from Chiron will have contributions from 3 line_2: sources: (i) the nucleus, effectively a point source (angular size line_3: probably no larger than 0.035 arcsec during the cycle 2 observations); line_4: (ii) the unbound coma of small dust grains (typically 0.1 microns in line_5: size; the brightness profile is a power law with an index >2); and line_6: (iii) from the gravitationally bound dust atmosphere which may be line_7: approximated to first order by a power law. The signature of the line_8: exopause, or boundary of this dust atmosphere, will be a change in line_9: power law slope of the surface brightness distribution of Chiron's line_10: coma, probably occurring between 0.3-0.4 arcsec from the nucleus. We line_11: propose to obtain a series of images of Chiron using the PC through line_12: the F555W filter, which was chosen because it will minimize the exposure line_13: time and its properties are well-understood (i.e. it is already widely line_14: used). Finally, because the accurate deconvolution of the stellar line_15: point spread function (PSF) is critical to the success of this line_16: proposal, and the fact that the PSF is a function of time and position line_17: on the chip we feel it is essential that the PSF's be taken as part line_18: of this investigation. We note that the bright halo in the PSF line_19: has a relative maximum at about 0.75 arcsec and so should not cause line_20: much problem for the exopause detection. Additionally, the high line_21: resolution core and it first two Airy rings seem well behaved and line_22: should subtract adequately. ! question: 3 section: 2 line_1: We have estimated exposure times for the F555W filter to be 2 minutes line_2: for Chiron (15.76 mag) at the core of the image. This will produce line_3: about 14000 e- at the core of the image (the full-well is about 3000 line_4: e-). At the position expected for the exopause we estimate a line_5: brightness of 18.9 mag/arcsec^2 which gives a count of about 1 e- s^-1 line_6: pixel^-1, or about 120 e^- in a 2 minute exposure roughly 0.4 to 0.5 line_7: arcsec out from the nucleus in 1993. These signal-to-noise (S/N) line_8: calculations indicate that to detect a change of +/-1 in the power line_9: law slope at the expected exopause we need only achieve S/N of 10% in line_10: this region. This is accomplished in a single image in a 3 minute line_11: exposure. However, because Chiron will cover an area of roughly 200 x line_12: 200 pixels (10 x 10 arcsec), cosmic ray hits will be a problem. Based line_13: on a previously observed rate of 1.65 hits/sec we expect between 10 - line_14: 20 hits to contaminate the Chiron information. Therefore each image line_15: will be acquired at least twice to remove the hits. line_17: In addition, we plan to obtain good coverage over rotational phase to line_18: fully explore the inner coma structure. This will be accomplished in line_19: 2 visits, with a total of 36 images in 6 orbits. A second epoch of line_20: observation is possible within our time allocation and this will follow line_21: the first epoch by approximately 2 weeks. Chiron is known for its short- line_22: term variability on timescales of days; this second epoch maximizes line_23: the liklihood of detecting inner coma structure related to sources on ! question: 3 section: 3 line_1: the nucleus. Because it is necessary to subtract the core PSF from the line_2: images to reveal the nature of the coma we must deal with the noise of line_3: PSF function itself. Each epoch of observation will require 4 line_4: exposures of the PSF star to obtain good S/N in the wings of the PSF. line_5: Finally, all observations will be made while tracking at planetary line_6: rates. We need high data-rate positional information during the line_7: exposures in order to create a jittered PSF. ! question: 4 section: 1 line_1: For resolving the inner coma - line_3: Because of the distance to Chiron and the image degradation due to the line_4: Earth's atmosphere, resolution of the inner coma of Chiron (estimated line_5: extent has been between 0.1 and 0.5 arcsec) has not been possible from line_6: ground-based observations. However, there has been a recent interest line_7: in the development of adaptive optics (AO) to improve the ground-based line_8: resolution. AO is a technique which can reduce the image degredation line_9: introduced by the Earth's turbulent atmosphere. The technique involves line_10: a real time compensation of the errors in the wavefronts introduced by line_11: the atmosphere, to first order by driving a deformable mirror for line_12: correcting tip and tilt in the x and y directions. line_14: The summit of Mauna Kea, where the median seeing is typically 0.7-0.8 line_15: arcsec, is beginning to employ AO at its telescopes. The High line_16: Resolution camera (HRCAM) at the Canada-France-Hawaii Telescope (CFHT) line_17: uses a system of fast-guiding (equivalent to tip/tilt corrections) to line_18: improve the resolution. Although the image quality has been improved line_19: in this manner, yielding a typical resolution of 0.5-0.6 arcsec (and line_20: sometimes as good as 0.4 arcsec), theory predicts that the achievable line_21: resolution should be between 0.3-0.4 arcsec. Ground-based resolution line_22: at this level will be ideal for studying the outer coma from about 1 line_23: arcsec outwards, but is still insufficient to assure detection of the ! question: 4 section: 2 line_1: exopause nor is it sufficient to study features which might be present line_2: in the inner coma. line_4: The NASA Infrared Telescope Facility (IRTF) on Mauna Kea line_5: also has a proposal in to implement tip/tilt corrections, but the line_6: probable time scale for completion will be 1995, if funded. line_7: Furthermore, near IR arrays are not as sensitive as the optical arrays, line_8: so the best chance of detection is in the visible. Additionally, the line_9: Univ. of Hawaii (UH) 2.2m has received funding for a new secondary line_10: mirror for a similar tip/tilt correction and this should be installed line_11: sometime during the fall of 1991. However, funding has not yet been line_12: obtained for the guider. If funded, this system could be operational line_13: within a year, but again, the expected peak resolution should be no line_14: better than 0.3-0.4 arcsec. At optimal conditions, with the relatively line_15: large pixel sizes on the most sensitive UH CCD, the pixel scale of 0.22 line_16: arcsec / pixel will be undersampling the PSF. There is one telescope line_17: which is achieving 0.3 arcsec resolution with ground-based optical line_18: imaging; this is the New Technology Telescope (NTT) at La Silla. The line_19: telescope utilizes a system of active optics to correct for flexure and line_20: coma in the telescope, but does not correct for the wavefront line_21: distortions due to the atmosphere (Wilson, 1989; Wilson et al., line_22: 1985). However, U.S. observers generally cannot get access to this line_23: telescope. Therefore, at present, the HST is the only facility capable ! question: 4 section: 3 line_1: of achieving the resolution needed for this project. line_3: For the mass / radius determination of Chiron line_5: Although there has been no way in which to image the inner coma of Chiron line_6: from the ground, there have been many attempts to determine the radius of line_7: Chiron using the techniques of thermal radiometry. The first published line_8: attempt by Lebofsky (et al., 1984) yielded only a 2 sigma detection and line_9: according to Sykes and Walker (1991) based on IRAS observations, may not have line_10: been a detection at all. The IRAS observations were only able to place 3 line_11: sigma detection upper limits on the thermal flux from Chiron. There have line_12: been 2 further observations were made by Cruikshank et al. (1990, private line_13: communication) and Meech and Spencer (unpublished, 1990) which yielded line_14: detections of only 2 sigma or less. The thermal flux from Chiron is too low line_15: for Earth-based detection with the present technology. Furthermore, the line_16: interpretation of the radius of Chiron from such measurements is highly line_17: uncertain (Spencer et al., 1990; Sykes and Walker, 1991), therefore the line_18: technique is not a good method for the mass determination of Chiron because line_19: it is highly model dependent. line_21: There is the possibility that the ISO observatory will be able to obtain a line_22: good thermal flux from Chiron, but even excluding the difficulties with the line_23: model-dependent interpretation of the data, the activity in Chiron has been ! question: 4 section: 4 line_1: such that the coma contribution to the thermal flux in the observing aperture line_2: may well exceed that of the nucleus, so that a reliable estimate of the line_3: nucleus size is impossible at this point by using infra-red techniques (Meech line_4: and Belton, 1990). ! question: 5 section: 1 line_1: The especially time critical aspect of this program is to distribute the line_2: images in rotational phase. The images should be taken at phases separated line_3: by 0.1 of a rotational period. A rotational period of 5.9178 hours should be line_4: assumed. The pattern of visits in the exposure logsheet is designed to give line_5: dense sampling in rotational phase. We are requesting that the line_6: observations at different rotational phase be made in either the same or line_7: adjacent rotational periods so that we can isolate activity due to discrete line_8: vents from activity changes due to changing heliocentric distance etc. line_10: Although the observations of Chiron are not particularly time-critical in an line_11: absolute sense, the best chance of detecting the gravitationally bound coma line_12: will be during early 1993 February when Chiron is at opposition and the line_13: geocentric distance is at a minimum, thus giving a maximum angular extent for line_14: the exopause. ! question: 7 section: 1 line_1: All images will first undergo standard reduction (using STSDAS/IRAF) line_2: including bias and dark removal and flat-fielding. The source of these line_3: calibration frames will be the existing WF/PC library of frames. Cosmic ray line_4: hits will be removed by comparing exposures in successive frames using the line_5: cosmic ray algorithm in IRAF. The images will be treated in four ways: (i) line_6: they will be deconvolved using the Lucy-Richardson algorithm and then the line_7: core image will be subtracted to reveal the coma; (ii) the images will also line_8: be de-convolved using state-of-the-art Maximum Entropy image reconstruction line_9: techniques (iii) the observed stellar PSF will be matched to the core of line_10: each image and then subtracted to reveal the coma and then the coma will be line_11: deconvolved using the Lucy-Richardson and MaxEnt algorithms; and finally, line_12: (iv) the central core will be removed as in (iii) then the remaining coma line_13: will be compared with models of the coma/exopause convolved with the PSF. line_15: The products from the above processing steps will be analyzed for the line_16: presence of an exopause and the results from the different procedures line_17: compared for accuracy. The signature of an exopausal boundary will line_18: be given as a discontinuity in the slope of the surface brightness line_19: profile. We note that at opposition (phase angle = 0.76 degrees) line_20: that the unbound coma should be fairly circularly symmetric with line_21: respect to the nucleus. line_23: A theoretical modelling program will be developed in parallel with the ! question: 7 section: 2 line_1: observing effort to provide comparisons with the data. The theoretical basis line_2: and some aspects of the modelling will be accomplished under different line_3: auspices prior to the observations. Simulations of the coma will consist of line_4: monte carlo simulations of Chiron's dust coma under a variety of assumptions line_5: about the release of particles into the coma and their loss from the same. In line_6: particular, work has already begun on initial monte carlo models for generic line_7: comets which do not exert gravitational control on the inner coma. In the line_8: present model, particles are injected into the coma from a source or sources line_9: on the nucleus. The injection velocity is taken to be the grain terminal line_10: velocity in a gas flow, which is dependent upon the sublimating gas and the line_11: particle size. The model allows for a distribution of grain sizes as well as line_12: sublimation from the grains. The only force acting upon the particles once line_13: reaching terminal velocity in this initial model is that from solar radiation line_14: pressure. The optical constants of dirty dielectrics (silicates), good comet line_15: dust candidates, are used to calculate the scattering cross sections, hence line_16: beta. This will be the basis for more sophisticated models in which the line_17: nucleus does exert gravitational control on a portion of the grains. The line_18: capture of particles into satellite orbits, and their subsequent loss into line_19: the unbound coma (possibly through grain charging, fragmentation, etc.) will line_20: alter the source function for particles entering the outer coma and hence line_21: change its appearance. The results of the modelling will allow us to line_22: constrain the scattering properties of the grains (beta), and from this we line_23: will determine a rough mass for Chiron. ! question: 7 section: 3 line_1: The complementary ground-based observations will be pursued so that we can line_2: best interpret the HST observations. In particular, we will need to know the line_3: rotational phase of Chiron. The current period of rotation is 5.91780 +/- line_4: 0.00005 hr (Luu and Jewitt, 1990) and was last measured in 1990 January. This line_5: makes the absolute phase uncertain by 20% of the rotational period in early line_6: 1993. Our observations prior to the proposed HST program will be analysed line_7: with existing Fourier Transform technique programs so that we will have an line_8: accurate knowledge of Chiron's rotational state at the time of the HST line_9: observations. In addition, we will be attempting to observe the outer line_10: unbound coma in several different wavelength regions, to develop better line_11: models of the scattering properties of the grains. Our model predicts line_12: core region should be relatively neutral, whereas the outer unbound line_13: coma should be bluer. ! question: 8 section: 1 line_1: We plan to maintain an extensive ground-based observing program to monitor line_2: the brightness, extent of coma and level of activity in Chiron to better line_3: estimate the HST fluxes and to more fully interpret the coma structure in the line_4: context of sporadic versus long term activity. The ground-based observations line_5: will be carried out by the PI and Co-I's using facilities on Mauna Kea, the line_6: Kitt Peak National Observatory, the Cerro Tololo Interamerican Observatory line_7: and Lowell Observatory to which we have routine access on a competitive line_8: basis. Specifically, in addition to the long-term monitoring program (which line_9: has already begun), we plan to begin the characterization of the outer coma line_10: (>0.5 arcsec) by using the high resolution techniques discussed previously line_11: at the CFH telescope on Mauna Kea. This will enable us to begin the detailed line_12: modelling of the coma (as discussed above) prior to the receipt of the line_13: HST data. Furthermore, we will attempt to obtain extensive observations line_14: of Chiron just prior to the HST observations in addition to nearly line_15: simultaneous groundbased photometry of Chiron during the HST observations so line_16: that we will know the exact rotational phase, amplitude and location of the line_17: odd harmonics in the light curve for comparison with inner coma structure. line_19: Astrometry has been and will continue to be reported for all Chiron line_20: observations in order to obtain the best possible orbital accuracy prior to line_21: the HST observations. The ground-based research will be supported by our line_22: individual NASA and NSF grants. ! question: 9 section: 1 line_1: No previous HST observing time has been granted to either the PI or M.Buie. line_2: M.J.S. Belton is co-investigator on a HST Cycle 1 GO program entitled line_3: "Integrated Dynamical and Spectroscopic Observations of Jupiter, Saturn, and line_4: Titan" for which Dr. R. Beebe (NMSU) is the principal investigator. The line_5: proposal number is 2560. This project is not related to the current proposal line_6: in any manner. ! question: 10 section: 1 line_1: Meech - (i) Meech expects to be able to successfully compete for ground-based line_2: observations on the UH 2.2m telescope in support of the project, (ii) an 11- line_3: month salary is provided by the University, therefore only 1 summer month of line_4: salary is being requested, and (iii) University Research Council seed money line_5: funds will be solicited to cover 50 percent of the costs of the workstation line_6: upgrade. Support for the workstation will be provided by the computer line_7: staff at the Institute for Astronomy. Meech will require graduate assistant line_8: support (50% time) to assist with the reduction and modelling of the data. line_10: Belton - The National Optical Astronomy Observatories will provide full line_11: salary support for Belton, in addition to all of the computer resources for line_12: the project. It is anticipated that ground-based telescope time in support line_13: of this project will be readily obtainable through the usual competitive line_14: processes, and that the ground-based work will be supported by NOAO. Belton line_15: will require support for a half-time assistant to program dynamical line_16: simulations of the coma of Chiron and analytical comparisons with the ST line_17: data. line_19: Buie - Lowell Observatory will provide the computer support required by Buie line_20: for the project, however, he will need to purchase MEMSYS to support the line_21: Maximum Entropy reconstructions as well as obtain partial salary support (1.2 line_22: months) for his 10% effort on the project. It is anticipated that line_23: ground-based telescope time in support of this project will be readily ! question: 10 section: 2 line_1: obtainable through the usual competitive processes, and that the ground-based line_2: work will be supported by the observatory. ! !end of general form text general_form_address: lname: MEECH fname: KAREN mi: J. category: PI inst: INSTITUTE FOR ASTRONOMY addr_1: 2680 WOODLAWN DRIVE city: HONOLULU state: HI zip: 96822 country: USA phone: (808) 956-6828 telex: 723-8459 UHAST HR ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: HD946160-CALIB name_2: BD-00D2389 name_3: GSC4914-1028 descr_1: J,702,704 pos_1: RA = 10H 55M 25.262S +/- 0.022S, pos_2: DEC = -00D 48' 46.94" +/- 0.33" equinox: 2000 fluxnum_1: 1 fluxval_1: V=8.890 +/- 0.0047 fluxnum_2: 2 fluxval_2: B-V=0.4 ! ! end of fixed targets solar_system_targets: targnum: 10 name_1: 2060-CHIRON descr_1: ASTEROID 2060 CHIRON lev1_1: STD=2060 wind_1: OLG OF 2060 BETWEEN 345 15 comment_1: IMAGING OF CHIRON NEAR OPPOSITION, comment_2: OPPOSITION PURELY TO MAXIMIZE THE comment_3: SCALE OF THE IMAGES. fluxnum_1: 1 fluxval_1: V=15.76 +/- 1.0 fluxnum_2: 2 fluxval_2: B-V=0.6 +/- 0.05 ! ! end of solar system targets ! No generic target records found exposure_logsheet: linenum: 1.100 targname: 2060-CHIRON config: PC opmode: IMAGE aperture: PC6 sp_element: F555W num_exp: 3 time_per_exp: 120S s_to_n: 100 fluxnum_1: 1 priority: 1 req_1: CYCLE 2; PCS MODE C; req_2: SEQ 1.1-1.4 NO GAP; comment_1: TAKE IMAGES IN FOUR CONSECUTIVE comment_2: ORBITS, EACH SET OF 5 MUST FIT IN comment_3: ONE TARGET VISIBILITY WINDOW. ! linenum: 1.200 targname: 2060-CHIRON config: PC opmode: IMAGE aperture: PC6 sp_element: F555W num_exp: 5 time_per_exp: 120S s_to_n: 100 fluxnum_1: 1 priority: 1 req_1: CYCLE 2; PCS MODE C; ! linenum: 1.300 targname: 2060-CHIRON config: PC opmode: IMAGE aperture: PC6 sp_element: F555W num_exp: 5 time_per_exp: 120S s_to_n: 100 fluxnum_1: 1 priority: 1 req_1: CYCLE 2; PCS MODE C; ! linenum: 1.400 targname: 2060-CHIRON config: PC opmode: IMAGE aperture: PC6 sp_element: F555W num_exp: 5 time_per_exp: 120S s_to_n: 100 fluxnum_1: 1 priority: 1 req_1: CYCLE 2; PCS MODE C; ! linenum: 2.000 targname: HD946160-CALIB config: PC opmode: IMAGE aperture: PC6 sp_element: F555W num_exp: 4 time_per_exp: 0.3S s_to_n: 100 fluxnum_1: 1 priority: 1 req_1: CYCLE 2; PCS MODE C; req_2: AFTER 1.1 BY 48H +/- 24H; ! linenum: 3.100 targname: 2060-CHIRON config: PC opmode: IMAGE aperture: PC6 sp_element: F555W num_exp: 3 time_per_exp: 120S s_to_n: 100 fluxnum_1: 1 priority: 1 req_1: CYCLE 2; PCS MODE C; req_2: SEQ 3.1-3.4 NO GAP; req_3: AFTER 1.1 BY 40.0H +/- 24.1H; comment_1: TAKE IMAGES IN THREE CONSECUTIVE comment_2: ORBITS, EACH SET OF 5 MUST FIT IN comment_3: ONE TARGET VISIBILITY WINDOW. ! linenum: 3.200 targname: 2060-CHIRON config: PC opmode: IMAGE aperture: PC6 sp_element: F555W num_exp: 5 time_per_exp: 120S s_to_n: 100 fluxnum_1: 1 priority: 1 req_1: CYCLE 2; PCS MODE C; ! linenum: 3.300 targname: 2060-CHIRON config: PC opmode: IMAGE aperture: PC6 sp_element: F555W num_exp: 5 time_per_exp: 120S s_to_n: 100 fluxnum_1: 1 priority: 1 req_1: CYCLE 2; PCS MODE C; ! linenum: 3.400 targname: 2060-CHIRON config: PC opmode: IMAGE aperture: PC6 sp_element: F555W num_exp: 5 time_per_exp: 120S s_to_n: 100 fluxnum_1: 1 priority: 1 req_1: CYCLE 2; PCS MODE C; ! linenum: 4.100 targname: 2060-CHIRON config: PC opmode: IMAGE aperture: PC6 sp_element: F555W num_exp: 4 time_per_exp: 120S s_to_n: 100 fluxnum_1: 1 priority: 1 req_1: CYCLE 2; PCS MODE C; req_2: SEQ 4.1-4.2 NO GAP; req_3: AFTER 1.1 BY 21D +/- 7D; comment_1: TAKE IMAGES IN TWO CONSECUTIVE comment_2: ORBITS, EACH SET OF 4 MUST FIT IN comment_3: ONE TARGET VISIBILITY WINDOW. ! linenum: 4.200 targname: 2060-CHIRON config: PC opmode: IMAGE aperture: PC6 sp_element: F555W num_exp: 4 time_per_exp: 120S s_to_n: 100 fluxnum_1: 1 priority: 1 req_1: CYCLE 2; PCS MODE C; ! linenum: 5.000 targname: HD946160-CALIB config: PC opmode: IMAGE aperture: PC6 sp_element: F555W num_exp: 4 time_per_exp: 0.3S s_to_n: 100 fluxnum_1: 1 priority: 1 req_1: CYCLE 2; PCS MODE C; req_2: AFTER 4.1 BY 12H +/- 12H; ! ! end of exposure logsheet ! No scan data records found