SIMPLE  =                    T / Standard FITS format                           BITPIX  =                    8 / Character information                          NAXIS   =                    0 / No image data array present                    EXTEND  =                    T / Standard extensions                            OBJECT  = 'P/HALLEY'           / Object of investigation                        FILE-NUM=               089007 / File number                                    DATE-OBS= '13/03/86'           / Date of mid-observation                        TIME-OBS= '.98     '           / Mid-time of observation                        LONG-OBS= '999/99/99'          / Longitude of observatory                       LAT-OBS = '+99/99/99'          / Latitude of observatory                        DATE-REL= '01/07/90'           / Date of release                                DISCIPLN= 'GIOTTO/DID'         / Giotto DIDSY experiment data                   SYSTEM  = '05009983'           / Observation system                             OBSERVER= 'MCDONNELL,J.A.M/ET AL.' / Giotto DIDSY team (as A&A, 1987)           SUBMITTR= 'GREEN,S.F/PANKIEWICZ,G.S' / Submitters to IHW                        SPEC-EVT=                    F / No special events inserted or deleted                                                                                          DAT-FORM= 'ASCII   '           / Data in tabular ASCII form                     ORIGIN  = 'UNIV.KENT,U.K'      / Site at which tape was written                 DATE    = '08/05/90'           / Date tape was written                          COMMENT  GIOTTO DUST IMPACT DETECTION SYSTEM (DIDSY) DATA                       COMMENT  UNIT FOR SPACE SCIENCES, UNIVERSITY OF KENT,                           COMMENT  CANTERBURY, KENT, CT2 7NR.                                             COMMENT  FILE 089007                                                            COMMENT  CUMULATIVE FLUXES FROM DISCRETE DATA FOR 10 TIME PE                    COMMENT                                                                         COMMENT                                                                         COMMENT  ADD. OBS. ALEXANDER,W.M/BURTON,W.M/BUSSOLETTI,E/EVANS,G.C/             COMMENT  ADD. OBS. EVANS,S.T/FIRTH,J.G/GRARD,R.J.L/GREEN,S.F/GRUN,E/            COMMENT  ADD. OBS. HANNER,M.S/HUGHES,D.W/IGENBERGS,E/KISSEL,J/                  COMMENT  ADD. OBS. KUCZERA,H/LINDBLAD,B.A/LANGEVIN,Y/MANDEVILLE,J.C/            COMMENT  ADD. OBS. NAPPO,S/PANKIEWICZ,G.S/PERRY,C.H/SCHWEHM,G.H/                COMMENT  ADD. OBS. SEKANINA,Z/STEVENSON,T.J/TURNER,R.F/WEISHAUPT,U/             COMMENT  ADD. OBS. WALLIS,M.K/ZARNECKI,J.C                                      END                                                                                                                                                             XTENSION= 'TABLE   '           / Table extension                                BITPIX  =                    8 / Character                                      NAXIS   =                    2 / 2-D matrix                                     NAXIS1  =                   45 / Number of characters per row                   NAXIS2  =                  167 / Number of rows                                 PCOUNT  =                    0 / No random parameters                           GCOUNT  =                    1 / Only one group                                 TFIELDS =                    8 / Number of fields per row                       EXTNAME = 7 DIDSY DISCRETE     / Name of file                                   EXTVER  =                    4 / Extension version number                                                                                                       TTYPE1  = 'MEAN HR '           / Mean ground received time (hr)                 TBCOL1  =                    1 / Start in column 1                              TFORM1  = 'I2      '           / Integer nn                                     TUNIT1  = 'HOUR    '           / Hours                                                                                                                          TTYPE2  = 'MIN     '           / Mean ground received time (min)                TBCOL2  =                    4 / Start in column 4                              TFORM2  = 'I2      '           / Integer nn                                     TUNIT2  = 'MIN     '           / Minutes                                                                                                                        TTYPE3  = 'SEC     '           / Mean ground received time (sec)                TBCOL3  =                    7 / Start in column 7                              TFORM3  = 'F4.1    '           / Real xx.x                                      TUNIT3  = 'SEC     '           / Seconds                                                                                                                        TTYPE4  = 'MEAN DISTANCE'      / Cometocentric distance                         TBCOL4  =                   12 / Start in column 12                             TFORM4  = 'I6      '           / Integer nnnnnn                                 TUNIT4  = 'KM      '           / Kilometres                                                                                                                     TTYPE5  = 'COUNTS  '           / Discrete counts > mass                         TBCOL5  =                   20 / START IN COLUMN 20                             TFORM5  = 'I2      '           / Integer nn                                                                                                                     TTYPE6  = 'MASS    '           / Mass threshold                                 TBCOL6  =                   23 / Start in column 23                             TFORM6  = 'E9.3    '           / Real x.xxxE+xx                                 TUNIT6  = 'KG      '           / Kilogrammes                                                                                                                    TTYPE7  = 'FLUX    '           / Derived particle flux                          TBCOL7  =                   33 / Start in column 33                             TFORM7  = 'E9.3    '           / Real x.xxxE+xx                                 TUNIT7  = 'M-2.SEC-1'          / PER SQUARE METRE PER SECOND                                                                                                    TTYPE8  = 'ERROR   '           / Statistical error from counts                  TBCOL8  =                   43 / Start in column 43                             TFORM8  = 'I3      '           / Integer nnn                                    TUNIT8  = '%       '           / Percentage                                                                                                                     COMMENT  DIDSY DISCRETE DATA ARE A SUBSET OF THE LARGE MASS PARTICLES DETECTED. COMMENT  THEY CONSIST OF UP TO FOUR IMPACTS PER DATA GATHERING INTERVAL (1.13S) COMMENT  FOR WHICH SIGNALS FROM 2 OR MORE SENSORS ARE AVAILABLE.  THIS ALLOWS ANCOMMENT  ACTUAL MASS TO BE DERIVED. THE UNCERTAINTY IN MASS FOR AN INDIVIDUAL   COMMENT  PARTICLE MAY BE HIGH, BUT FOR >10 IMPACTS THE DISTRIBUTION OF MASSES ISCOMMENT  REPRESENTATIVE OF THE TRUE POPULATION (C.PERRY PHD). DATA ARE PRESENTEDCOMMENT  IN 10 TIME PERIODS (~50% OVERLAP) AS GIVEN IN TABLE:                   COMMENT  PERIOD      START TIME         END TIME            NO OF IMPACTS       COMMENT    1     22:59:50 (-4272S)   00:08:52 (-130S)            20             COMMENT    2     00:04:32 (-390S)    00:09:52 (-70S)             20             COMMENT    3     00:08:53 (-129S)    00:10:19 (-43S)             21             COMMENT    4     00:09:53 (-69S)     00:10:36 (-26S)             20 *           COMMENT    5     00:10:20 (-42S)     00:10:47 (-18S)             19 *           COMMENT    6     00:10:37 (-25S)     00:10:47 (-15S)             18 *           COMMENT    7     00:11:18 (+16S)     00:11:41 (+39S)             15 *           COMMENT    8     00:11:28 (+26S)     00:12:42 (+100S)            14 *           COMMENT    9     00:11:42 (+40S)     00:13:02 (+120S)            12             COMMENT   10     00:12:43 (+100S)    01:01:02 (+3000S)            8             COMMENT  PERIODS MARKED * HAVE LARGER UNCERTAINTIES IN MASS DUE TO THE HIGH FLUXCOMMENT  OF SMALLER PARTICLES WHICH CAN CAUSE FALSE COINCIDENCE.                HISTORY  MASSES FOR EACH DISCRETE IMPACT WERE CALCULATED WITH MOMENTUM ENHANCEM-HISTORY  ENT OF E=11 FOR NON-PENETRATING PARTICLES: P(MEASURED)=E*P(TRUE).      HISTORY  FOR PARTICLES WHICH PENETRATE THE FRONT SHIELD THE MEASURED MOMENTUM ISHISTORY  DERATED: P(MEASURED)=E*P(TRUE)*(MPEN/M)**G                             HISTORY  WHERE MPEN=PENETRATION MASS (3E-9KG) AND G=MOMENTUM DERATING EXPONENT. HISTORY  A VALUE OF G=0.4 WAS USED HERE. MEAN TIME AND DISTANCE QUOTED ARE MEANSHISTORY  IN LOG(DISTANCE) SPACE. FLUXES FOR TIMES WITHIN 60 SECONDS OF ENCOUNTERHISTORY  ARE CORRECTED FOR INCOMPLETE SAMPLING BY COMPARISON WITH BINNED DATA.  END