! $Id: 5361,v 7.1 1994/10/17 17:17:28 pepsa Exp $ coverpage: title_1: THE NUCLEUS OF COMET P/BORELLY AND ITS DUST title_2: AND GAS EMISSIONS CYCLE4MEDIUM sci_cat: SOLAR SYSTEM sci_subcat: COMETS proposal_for: GO pi_fname: PHILIPPE pi_mi: L pi_lname: LAMY pi_inst: 5446 pi_country: FRANCE pi_phone: 33 91055932 hours_pri: 0.78 num_pri: 1 wf_pc: Y time_crit: Y ! end of coverpage abstract: line_1: We propose to observe with the planetary camera (PC) of HST the short- line_2: period comet P/Borrelly during the month following its perihelion passage line_3: (1 November 1994) and ending with its closest approach to Earth at 0.62 line_4: AU (4 december 1994). The spatial resolution (2 pixels) will range from line_5: 48 to 41 km allowing to discriminate the nucleus against the coma, to line_6: image the possible dust and gas structures in the coma "down to the line_7: nucleus" and to follow their temporal evolution. It will be possible to line_8: obtain the magnitude of the nucleus and derive its projected cross- line_9: section as a function of time (assuming a constant albedo). Combined line_10: with ground-based observations and a model of the dust-gas expansion, line_11: it will also be possible to map the sources of dust and gas on the line_12: nucleus and constrain its rotational properties. HST will extend the line_13: present insight we have of a few comets (P/Halley, Levy, P/Faye ...) line_14: to another comet, an important step in the current exploration and line_15: understanding of primitive bodies in the solar system. line_16: Altered 10/3/94 to observe in one group, around closest approach, line_17: and to change the F702W to F675W and ATD-GAIN from 15 to 7 (ADS). ! ! end of abstract general_form_proposers: lname: LAMY fname: PHILIPPE mi: L inst: 5446 country: FRANCE esa: Y ! lname: GRUN fname: EBERHARD inst: 5544 country: GERMANY esa: Y ! lname: KELLER fname: UWE inst: 5540 country: GERMANY esa: Y ! lname: SEKANINA fname: ZDENEK inst: 2370 country: USA ! lname: TOTH fname: IMRE inst: 5720 country: HUNGARY ! lname: WEST fname: RICHARD inst: 5520 country: GERMANY esa: Y ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: Observation of a short-period comet of more than one apparition (to line_2: limit acquisition problems) coming sufficiently close to the Sun line_3: (q < 1.6 AU) for activity and to the Earth (Delta < 0.7 AU) for line_4: resolution, having an elongation larger than 50 degrees and apparent line_5: motion less than 0.21 arc sec per sec to satisfy HST conditions. line_6: An oustanding opportunity exists in the cycle 4 of HST, comet P/Borrelly line_7: 1987 XXXIII. During a period of about one month following its perihelion line_8: passage on 1 November 1994 (q = 1.365 AU), it will remain within 0.7 AU line_9: of the Earth reaching closest approach on 4 December (Delta = 0.618 AU). line_10: The elongation will vary from 106 to 122 deg. The observational program line_11: consists in imaging the coma with the PC and two filters line_12: - F702 W for the dust (this broad spectral region ensures a high signal line_13: for the continuum with only slight contamination by gas emissions) line_14: - F390 N for CN. line_15: The dust observations will be repeated 5 times (5 visits) while the CN line_16: observations will only be performed during 3 of the 5 visits. The 5 line_17: visits will be scheduled to cover a broad range of possible rotational line_18: periods of the nucleus and to monitor temporal variations of the coma. line_19: Past experience with comet P/Faye has shown the difficulty to select line_20: specific time intervals due ot the operational constraints of the HST. line_21: We shall closely work with the operators at ST ScI to optimize the line_22: time intervals of the observations. ! question: 3 section: 2 line_1: ! question: 4 section: 1 line_1: HST high spatial resolution makes it possible to directly detect the line_2: cometary nucleus and to resolve structures in its immediate proximity. line_3: Therefore confusion is minimal and structures may be directly traced back line_4: to the nucleus. Minimum sky background improves detectability of low- line_5: contrast features. Its low level and stability considerably improves the line_6: signal-to-noise ratio in the outer parts of the coma. line_7: As discussed in section 2, ground-based observations of cometary nuclei line_8: have been limited to a few cases where they are presumably dormant line_9: (Jewitt, in "Comets in the post-Halley era", p. 19, 1991). Near nucleus line_10: studies using both photographic and CCD techniques are more extended. line_11: However, due to limited resolution and other problems discussed in line_12: section 2, the results are not always firmly conclusive. The two kind line_13: of observations are sometime consistent (P/Temple 2) and sometime line_14: inconsistent (P/Encke). The best results obtained so far were the high line_15: resolution images of the nucleus and the inner most coma of P/Halley line_17: with the GIOTTO and VEGA space probes. ! question: 5 section: 1 line_1: The observations are time critical since they must be performed during line_2: a period of approximately one month extending roughly from 4 November line_3: 1994 (a few days after perihelion passage) to 4 December 1994 (closest line_4: approach to Earth). The precise timing of the 5 visits will be optimized line_5: with operators at ST ScI to satisfy the HST scheduling constraints line_6: (see section 3a). ! question: 6 section: 1 line_1: None ! ! question: 8 section: 1 line_1: Early observations of the selected comet will be performed for line_2: astrometric positions in order to refine the ephemeris.High-resolution, line_3: ground-based images will later be obtained over a period overlapping line_4: the HST observations in order to complement them and put them in a line_5: broader interval of cometary activity. ! question: 9 section: 1 line_1: The HST program P2231 entitled "Heterogeneity of dust and gas emissions line_2: on a cometary nucleus" carried out during cycle 1 pursued the same line_3: scientific objectives as the present proposal. line_4: The above program consisted in 7 visits to comet P/Faye while it was line_5: within 0.6 AU of the Earth, the spatial resolution (2 pixels) being 40 line_6: km. Each visit has provided two identical, well-exposed images in the line_7: continuum (F702W). C2 was not detected due to its very low abundance. line_8: The influence of the spherical aberrations has been more severe than line_9: anticipated as the wings of the PSF of the bright nucleus amount to line_10: roughly 10 % of the coma creating artificial structures at a level line_11: higher than possible real coma structures. All images have been line_12: presently restored using the Richardson-Lucy technique. line_13: The nucleus has a R magnitude varying between 16.5 and 17.0, fainter line_14: than the prediction. Assuming a constant albedo of 0.04, a standard line_15: phase law and projected circular cross-sections, its radius varies line_16: between 0.9 and 1.2 km suggesting a rather spherical body. The inner line_17: coma (within 500 km) is asymmetric suggesting a broad fan which is line_18: neither oriented in the solar or the anti-solar directions. The outer line_19: coma, on a scale of several thousands km presents also an asymmetry line_20: along direction different from that of the inner coma. A preliminary line_21: comparison with a standard model of steady-state coma expansion line_22: including the effect of radiation pressure does not appear compatible line_23: with the observed isophotes. ! question: 10 section: 1 line_1: All participating laboratories have extensive in-house image processing line_2: and data analysis capabilities. The european members have further access line_3: to the ST-ECF at ESO (FRG) Models of cometary comae have been developped line_4: and are available at JPL, MPIAe, MPIK. line_5: Specific research grants will be sought to support the HST activities line_6: of the team. ! !end of general form text general_form_address: lname: LAMY fname: PHILIPPE mi: L category: PI inst: 5446 addr_1: BP 8 city: MARSEILLE zip: 13376 country: FRANCE phone: 33 91055932 telex: (SPAN) LASM0A::LAMY ! lname: category: CON ! ! end of general_form_address records ! No fixed target records found solar_system_targets: targnum: 1 name_1: COMET-BORRELLY-1987XXXIII descr_1: COMET BORRELLY 1987XXXIII lev1_1: TYPE = COMET, Q = 1.3651154, lev1_2: E = 0.6228036, I = 30.26946, lev1_3: O = 74.73634, W = 353.34589, lev1_4: T = 01-NOV-1994:11:48:51, lev1_5: EQUINOX = B1950, lev1_6: EPOCH = 15-OCT-1994, lev1_7: A1 = 0.20E-8, A2 = -3.98E-10, A3 = 0.0, lev1_8: ACQ = 2.0 wind_1: WND1 = 05-NOV-1994 TO 05-DEC-1994 comment_1: FLUXVAL_1 IS THE PREDICTED VISUAL comment_2: MAGNITUDE OF THE COMET NUCLEUS, comment_3: FLUXVAL_2 IS THE PREDICTED TOTAL comment_4: MAGNITUDE OF THE EXTENDED COMA comment_5: IN A CIRCULAR APERTURE OF 60" DIAM comment_6: DURING THE SPECIFIED WINDOW. comment_7: A RADIAL BRIGHTNESS VARIATION 1/R comment_8: IS ASSUMED IN THE COMA. fluxnum_1: 1 fluxval_1: V = 16.4 +/- 0.3 fluxnum_2: 2 fluxval_2: V = 7.5 +/- 0.5 fluxnum_3: 3 fluxval_3: SIZE = 60 ! ! end of solar system targets ! No generic target records found exposure_logsheet: linenum: 1.000 sequence_1: DEFINE sequence_2: DUST targname: COMET-BORRELLY-1987XXXIII config: WFPC2 opmode: IMAGE aperture: PC1-FIX sp_element: F675W num_exp: 2 time_per_exp: 40S s_to_n: 80 s_to_n_time: 40S fluxnum_1: 1 fluxnum_2: 2 fluxnum_3: 3 priority: 1 param_1: CR-SPLIT = 0.25, param_2: CLOCKS = YES, param_3: ATD-GAIN = 7, req_1: GUID TOL 0.2" / 1-9 comment_1: S_TO_N CALCULATED IN ONE PIXEL AT comment_2: A DISTANCE OF 1000 KM FROM NUCLEUS ! linenum: 2.000 sequence_1: DEFINE sequence_2: DUSTGAS targname: COMET-BORRELLY-1987XXXIII config: WFPC2 opmode: IMAGE aperture: PC1-FIX sp_element: F675W num_exp: 2 time_per_exp: 40S s_to_n: 80 s_to_n_time: 40S fluxnum_1: 1 fluxnum_2: 2 fluxnum_3: 3 priority: 1 param_1: CR-SPLIT = 0.25, param_2: CLOCKS = YES, param_3: ATD-GAIN = 7 comment_1: S_TO_N CALCULATED IN ONE PIXEL AT comment_2: A DISTANCE OF 1000 KM FROM NUCLEUS ! linenum: 3.000 sequence_1: DEFINE sequence_2: DUSTGAS targname: COMET-BORRELLY-1987XXXIII config: WFPC2 opmode: IMAGE aperture: PC1-FIX sp_element: F390N num_exp: 2 time_per_exp: 400S s_to_n: 2.7 s_to_n_time: 400S fluxnum_1: 1 fluxnum_2: 2 fluxnum_3: 3 priority: 1 param_1: CR-SPLIT = NO, param_2: CLOCKS = YES, param_3: ATD-GAIN = 7 req_1: SEQ 2-3 NO GAP comment_1: S_TO_N CALCULATED IN ONE PIXEL AT comment_2: A DISTANCE OF 1000 KM FROM NUCLEUS ! linenum: 4.000 sequence_1: USE sequence_2: DUSTGAS req_1: CYCLE 4; req_2: AT 01-DEC-1994 +/- 3D ! linenum: 5.000 sequence_1: USE sequence_2: DUSTGAS req_1: CYCLE 4; req_2: AFTER 4 BY 192M +/- 20M ! linenum: 6.000 sequence_1: USE sequence_2: DUST req_1: CYCLE 4; req_2: AFTER 4 BY 384M +/- 20M ! linenum: 7.000 sequence_1: USE sequence_2: DUST req_1: CYCLE 4; req_2: AFTER 6 BY 96M +/- 10M ! linenum: 8.000 sequence_1: USE sequence_2: DUSTGAS req_1: CYCLE 4; req_2: AFTER 7 BY 96M +/- 10M ! linenum: 9.000 sequence_1: USE sequence_2: DUST req_1: CYCLE 4; req_2: AFTER 8 BY 96M +/- 10M ! ! end of exposure logsheet ! No scan data records found