Conference warhed::astronomy

                  I N T E R O F F I C E   M E M O R A N D U M

                                        Date:     28-Jan-1997 03:05am GMT 
                                        From:     VMSmail User "astro@store-forw
                                                  "[email protected]"@VBORMC@MRGATE@RDGMTS
                                        Dept:      
                                        Tel No:    

TO:  [email protected]@VBORMC@MRGATE@RDGMTS

Subject: Comet Hale-Bopp Orbit and Ephemeris Information

Orbit and Ephemeris Information for Comet 1995 O1 Hale-Bopp

Don Yeomans - JPL
January 27, 1997

Additional observations through Jan. 19, 1997 have been used to
update the orbit, ephemeris, and error analysis.


 Object: Comet C/1995 O1 (Hale-Bopp)
 JPL Ref. Solution: 48
 Planetary Ephemeris: DE403
 No. Observations:  1772
 Observation Arc:  1993 Apr 27 - 1997 Jan 19

 ---- Residual Summary ----       RA        Dec      Total
 Mean                             .004      .007      .008
 RMS, unweighted                  .641      .818      .735

 ---- Corrected Elements (J2000):  Solution 48
   Epoch  2450571.50000 = 1997 May  3.00000
                        Post-Fit Std.Dev.
 e    0.995107808       .000001002
 q    0.914103842       .000001861
 Tp   2450539.6353558   .0002557    1997 Apr  1.13536
 Node 282.4708075       .0000054
 w    130.5910110       .0000886
 i     89.4293189       .0000336


ORBITAL ELEMENTS FOR COMET HALE-BOPP (1995 O1)
The following (J2000) osculating orbital elements can be used to
generate ephemeris data using two body programs.  However, care must
be taken to select an orbital element set with an epoch close to
the desired ephemeris output times.


Elements at other epochs:
  Epoch (TDB)     e        q       Node      w         i           Tp
1996 Oct  5.0  .9952196 .9142922 282.47235 130.57623  89.43236  1997 Apr  1.125624
1997 Jan 12.0  .9950907 .9141164 282.47088 130.58980  89.42959  1997 Apr  1.134909
1997 Mar 13.0  .9950949 .9141041 282.47069 130.59092  89.42945  1997 Apr  1.135287
1997 May  2.0  .9951077 .9141039 282.47081 130.59101  89.42932  1997 Apr  1.135355
1997 Sep 30.0  .9950804 .9140236 282.46924 130.58587  89.42802  1997 Apr  1.134290

e:      Eccentricity
q:      Perihelion passage distance (AU)
Node:   Longitude of the ascending node (deg.)
w:      Argument of perihelion (deg.)
i:      Inclination (deg.)
Tp:     Perihelion passage time (TDB)


Original and Future Orbital periods
By integrating the above orbit forward and backward in time until the comet
leaves the planetary system and then referring the osculating orbital elements
to the solar system barycenter, the following orbital periods result:

Original orbital period before entering planetary system = 4200 years
Future orbital period after exiting planetary system     = 2380 years



Ephemeris data at 1 day steps (O hours UTC)

Ephemeris computed using JPL orbital solution No. 48 dated Jan. 27, 1997
The given magnitude estimates correspond to the more conservative of two
estimates given by Charles Morris.


Absolute (inertial) plane-of-sky ephemeris uncertainties (1-sigma)
over this interval are as follows:

   1996 Aug. - Sep.    < 1"
   1997 Jan. - Feb.    < 1"
   1997 Mar.           < 3"
   1997 Apr.           < 2"


Ephemeris (with perturbations) for Comet Hale-Bopp (1995 O1)
JPL Ref. Orbit 48 by D.K. Yeomans, Jan. 27, 1997

 Date (UT)       R.A. J2000  Dec.     Delta Deldot    r   Theta Beta Moon PsAng PsAMV TMag
1997 Feb  1  19 40 32.57 +15 28 44.9  2.004 -34.13  1.368  37.9  26.3  77 328.6 200.2  2.5
1997 Feb  2  19 42 59.75 +15 57 49.9  1.985 -34.18  1.356  38.3  26.7  67 328.2 201.2  2.5
1997 Feb  3  19 45 30.19 +16 27 33.9  1.965 -34.21  1.344  38.6  27.2  57 327.8 202.2  2.4
1997 Feb  4  19 48 04.04 +16 57 57.6  1.945 -34.23  1.332  39.0  27.8  47 327.4 203.2  2.4
1997 Feb  5  19 50 41.45 +17 29 01.7  1.925 -34.22  1.320  39.4  28.3  40 327.0 204.1  2.3
1997 Feb  6  19 53 22.59 +18 00 46.8  1.906 -34.19  1.309  39.7  28.8  35 326.7 205.1  2.3
1997 Feb  7  19 56 07.64 +18 33 13.5  1.886 -34.15  1.297  40.1  29.3  35 326.4 206.2  2.2
1997 Feb  8  19 58 56.79 +19 06 22.2  1.866 -34.08  1.286  40.4  29.8  39 326.1 207.2  2.2
1997 Feb  9  20 01 50.23 +19 40 13.5  1.846 -33.98  1.274  40.8  30.4  47 325.9 208.2  2.1
1997 Feb 10  20 04 48.18 +20 14 47.6  1.827 -33.86  1.263  41.1  30.9  57 325.7 209.2  2.1
1997 Feb 11  20 07 50.85 +20 50 04.9  1.807 -33.72  1.251  41.4  31.5  68 325.5 210.2  2.0
1997 Feb 12  20 10 58.49 +21 26 05.4  1.788 -33.55  1.240  41.8  32.0  78 325.3 211.3  2.0
1997 Feb 13  20 14 11.34 +22 02 49.4  1.769 -33.35  1.229  42.1  32.6  88 325.2 212.3  1.9
1997 Feb 14  20 17 29.69 +22 40 16.6  1.749 -33.12  1.218  42.4  33.1  98 325.2 213.4  1.9
1997 Feb 15  20 20 53.80 +23 18 26.9  1.730 -32.87  1.207  42.7  33.7 107 325.1 214.5  1.8
1997 Feb 16  20 24 24.00 +23 57 20.0  1.711 -32.58  1.196  43.0  34.3 116 325.2 215.6  1.8
1997 Feb 17  20 28 00.58 +24 36 55.2  1.693 -32.26  1.186  43.3  34.8 123 325.2 216.7  1.7
1997 Feb 18  20 31 43.89 +25 17 11.8  1.674 -31.91  1.175  43.5  35.4 130 325.3 217.8  1.6
1997 Feb 19  20 35 34.29 +25 58 08.8  1.656 -31.52  1.164  43.8  36.0 135 325.4 218.9  1.6
1997 Feb 20  20 39 32.15 +26 39 45.0  1.638 -31.11  1.154  44.0  36.6 138 325.6 220.0  1.5
1997 Feb 21  20 43 37.85 +27 21 58.7  1.620 -30.65  1.144  44.3  37.1 140 325.8 221.2  1.5
1997 Feb 22  20 47 51.82 +28 04 48.1  1.602 -30.16  1.134  44.5  37.7 139 326.1 222.4  1.4
1997 Feb 23  20 52 14.48 +28 48 11.1  1.585 -29.63  1.124  44.7  38.3 136 326.4 223.6  1.4
1997 Feb 24  20 56 46.27 +29 32 04.9  1.568 -29.06  1.114  44.9  38.9 131 326.8 224.8  1.3
1997 Feb 25  21 01 27.66 +30 16 26.5  1.552 -28.45  1.104  45.1  39.4 125 327.2 226.0  1.3
1997 Feb 26  21 06 19.13 +31 01 12.4  1.535 -27.80  1.095  45.3  40.0 119 327.7 227.3  1.2
1997 Feb 27  21 11 21.17 +31 46 18.6  1.519 -27.11  1.086  45.5  40.6 112 328.3 228.6  1.2
1997 Feb 28  21 16 34.30 +32 31 40.4  1.504 -26.38  1.076  45.6  41.1 104 328.9 229.9  1.1
1997 Mar  1  21 21 59.01 +33 17 12.8  1.489 -25.61  1.067  45.7  41.7  96 329.5 231.3  1.1
1997 Mar  2  21 27 35.82 +34 02 50.0  1.474 -24.79  1.059  45.9  42.2  88 330.3 232.7  1.0
1997 Mar  3  21 33 25.25 +34 48 25.5  1.460 -23.93  1.050  46.0  42.7  80 331.1 234.1  1.0
1997 Mar  4  21 39 27.80 +35 33 52.3  1.447 -23.03  1.042  46.0  43.3  72 331.9 235.6   .9
1997 Mar  5  21 45 43.95 +36 19 02.5  1.434 -22.08  1.033  46.1  43.8  64 332.9 237.1   .9
1997 Mar  6  21 52 14.15 +37 03 47.6  1.421 -21.09  1.025  46.2  44.3  57 333.9 238.7   .8
1997 Mar  7  21 58 58.84 +37 47 58.5  1.409 -20.06  1.018  46.2  44.7  51 335.0 240.3   .8
1997 Mar  8  22 05 58.36 +38 31 25.1  1.398 -18.99  1.010  46.2  45.2  47 336.2 241.9   .8
1997 Mar  9  22 13 13.04 +39 13 57.0  1.387 -17.88  1.003  46.2  45.7  45 337.5 243.7   .7
1997 Mar 10  22 20 43.07 +39 55 22.8  1.377 -16.73   .996  46.2  46.1  46 338.8 245.4   .7
1997 Mar 11  22 28 28.60 +40 35 30.7  1.368 -15.54   .989  46.2  46.5  50 340.2 247.2   .6
1997 Mar 12  22 36 29.62 +41 14 08.6  1.360 -14.31   .982  46.2  46.9  55 341.8 249.1   .6
1997 Mar 13  22 44 46.01 +41 51 03.9  1.352 -13.05   .976  46.1  47.2  62 343.4 251.0   .6
1997 Mar 14  22 53 17.48 +42 26 03.8  1.344 -11.76   .970  46.0  47.6  69 345.1 253.0   .5
1997 Mar 15  23 02 03.60 +42 58 55.6  1.338 -10.45   .964  46.0  47.9  76 346.8 255.1   .5
1997 Mar 16  23 11 03.72 +43 29 26.7  1.332  -9.10   .959  45.9  48.1  83 348.7 257.1   .5
1997 Mar 17  23 20 17.03 +43 57 24.9  1.328  -7.74   .953  45.7  48.4  90 350.6 259.3   .5
1997 Mar 18  23 29 42.49 +44 22 38.6  1.323  -6.35   .948  45.6  48.6  97 352.6 261.5   .4
1997 Mar 19  23 39 18.89 +44 44 57.2  1.320  -4.96   .944  45.5  48.8 104 354.7 263.7   .4
1997 Mar 20  23 49 04.80 +45 04 11.1  1.318  -3.55   .940  45.3  48.9 110 356.8 266.0   .4
1997 Mar 21  23 58 58.62 +45 20 12.0  1.316  -2.13   .936  45.2  49.0 117 359.0 268.3   .4
1997 Mar 22  00 08 58.59 +45 32 53.1  1.315   -.72   .932  45.0  49.1 123   1.3 270.6   .4
1997 Mar 23  00 19 02.84 +45 42 09.4  1.315    .70   .929  44.8  49.1 129   3.6 273.0   .4
1997 Mar 24  00 29 09.38 +45 47 57.5  1.316   2.11   .926  44.6  49.1 134   5.9 275.4   .3
1997 Mar 25  00 39 16.18 +45 50 16.2  1.318   3.51   .923  44.4  49.1 138   8.2 277.7   .3
1997 Mar 26  00 49 21.21 +45 49 06.0  1.320   4.89   .921  44.1  49.0 140  10.6 280.1   .3
1997 Mar 27  00 59 22.47 +45 44 29.4  1.323   6.26   .919  43.9  48.9 141  13.0 282.5   .3
1997 Mar 28  01 09 18.03 +45 36 30.6  1.327   7.60   .917  43.7  48.7 138  15.3 284.8   .3
1997 Mar 29  01 19 06.07 +45 25 15.6  1.332   8.92   .916  43.4  48.5 134  17.7 287.1   .3
1997 Mar 30  01 28 44.92 +45 10 51.9  1.338  10.21   .915  43.1  48.3 128  20.0 289.4   .3
1997 Mar 31  01 38 13.11 +44 53 28.3  1.344  11.46   .914  42.9  48.0 120  22.3 291.7   .4
1997 Apr  1  01 47 29.30 +44 33 14.7  1.351  12.68   .914  42.6  47.7 111  24.6 293.9   .4
1997 Apr  2  01 56 32.42 +44 10 21.8  1.359  13.87   .914  42.3  47.4 101  26.9 296.1   .4
1997 Apr  3  02 05 21.54 +43 45 01.1  1.367  15.01   .915  42.0  47.0  91  29.1 298.2   .4
1997 Apr  4  02 13 55.96 +43 17 24.2  1.376  16.11   .916  41.7  46.6  80  31.3 300.3   .4
1997 Apr  5  02 22 15.17 +42 47 43.2  1.385  17.16   .917  41.4  46.2  69  33.4 302.3   .4
1997 Apr  6  02 30 18.84 +42 16 10.0  1.396  18.17   .918  41.1  45.7  57  35.5 304.2   .4
1997 Apr  7  02 38 06.77 +41 42 56.3  1.406  19.14   .920  40.7  45.2  46  37.6 306.1   .5
1997 Apr  8  02 45 38.94 +41 08 13.8  1.418  20.06   .922  40.4  44.7  37  39.6 308.0   .5
1997 Apr  9  02 52 55.43 +40 32 13.3  1.430  20.93   .925  40.1  44.2  29  41.5 309.8   .5
1997 Apr 10  02 59 56.45 +39 55 05.5  1.442  21.75   .928  39.7  43.6  26  43.4 311.5   .6
1997 Apr 11  03 06 42.28 +39 17 00.3  1.455  22.53   .931  39.4  43.1  29  45.3 313.2   .6
1997 Apr 12  03 13 13.28 +38 38 07.0  1.468  23.26   .935  39.0  42.5  35  47.1 314.8   .6
1997 Apr 13  03 19 29.87 +37 58 34.4  1.482  23.94   .938  38.7  41.9  43  48.9 316.4   .6
1997 Apr 14  03 25 32.50 +37 18 30.3  1.496  24.58   .943  38.3  41.3  52  50.6 317.9   .7
1997 Apr 15  03 31 21.69 +36 38 02.3  1.510  25.18   .947  37.9  40.6  62  52.3 319.4   .7
1997 Apr 16  03 36 57.93 +35 57 17.1  1.525  25.73   .952  37.6  40.0  72  54.0 320.8   .8
1997 Apr 17  03 42 21.75 +35 16 20.7  1.540  26.24   .957  37.2  39.4  82  55.6 322.1   .8
1997 Apr 18  03 47 33.69 +34 35 18.6  1.555  26.71   .962  36.8  38.7  92  57.2 323.5   .8
1997 Apr 19  03 52 34.29 +33 54 15.9  1.571  27.15   .968  36.4  38.0 102  58.7 324.8   .9
1997 Apr 20  03 57 24.06 +33 13 16.8  1.586  27.54   .974  36.1  37.4 113  60.3 326.0   .9
1997 Apr 21  04 02 03.52 +32 32 25.4  1.602  27.89   .980  35.7  36.7 124  61.8 327.2  1.0
1997 Apr 22  04 06 33.18 +31 51 44.9  1.619  28.21   .987  35.3  36.0 135  63.3 328.4  1.0
1997 Apr 23  04 10 53.52 +31 11 18.6  1.635  28.50   .994  34.9  35.4 146  64.8 329.5  1.0
1997 Apr 24  04 15 05.01 +30 31 08.8  1.651  28.75  1.001  34.5  34.7 156  66.2 330.6  1.1
1997 Apr 25  04 19 08.12 +29 51 18.0  1.668  28.98  1.008  34.1  34.0 165  67.7 331.6  1.1
1997 Apr 26  04 23 03.26 +29 11 48.0  1.685  29.17  1.015  33.7  33.4 167  69.1 332.7  1.2
1997 Apr 27  04 26 50.86 +28 32 40.5  1.702  29.33  1.023  33.3  32.7 159  70.5 333.6  1.2
1997 Apr 28  04 30 31.31 +27 53 56.7  1.719  29.47  1.031  32.9  32.1 148  71.9 334.6  1.3
1997 Apr 29  04 34 04.99 +27 15 37.9  1.736  29.58  1.039  32.5  31.4 136  73.3 335.5  1.3
1997 Apr 30  04 37 32.26 +26 37 44.8  1.753  29.66  1.048  32.1  30.8 123  74.7 336.4  1.4
1997 May  1  04 40 53.44 +26 00 18.2  1.770  29.72  1.056  31.8  30.1 110  76.1 337.3  1.4
1997 May  2  04 44 08.88 +25 23 18.6  1.787  29.76  1.065  31.4  29.5  96  77.5 338.2  1.5
1997 May  3  04 47 18.85 +24 46 46.3  1.804  29.77  1.074  31.0  28.9  82  78.9 339.0  1.5
1997 May  4  04 50 23.66 +24 10 41.5  1.822  29.77  1.083  30.6  28.3  69  80.3 339.8  1.6
1997 May  5  04 53 23.56 +23 35 04.4  1.839  29.74  1.092  30.2  27.7  55  81.7 340.6  1.6
1997 May  6  04 56 18.81 +22 59 54.8  1.856  29.70  1.102  29.8  27.1  41  83.1 341.3  1.7
1997 May  7  04 59 09.65 +22 25 12.7  1.873  29.64  1.111  29.4  26.5  28  84.5 342.1  1.7
1997 May  8  05 01 56.30 +21 50 57.9  1.890  29.56  1.121  29.1  25.9  15  85.9 342.8  1.8
1997 May  9  05 04 38.97 +21 17 10.0  1.907  29.47  1.131  28.7  25.4   4  87.3 343.5  1.8
1997 May 10  05 07 17.85 +20 43 48.8  1.924  29.37  1.141  28.3  24.8  12  88.8 344.1  1.9
1997 May 11  05 09 53.14 +20 10 53.8  1.941  29.25  1.151  28.0  24.3  23  90.2 344.8  1.9
1997 May 12  05 12 25.02 +19 38 24.6  1.958  29.12  1.161  27.6  23.8  35  91.7 345.4  1.9
1997 May 13  05 14 53.64 +19 06 20.7  1.975  28.97  1.172  27.3  23.3  47  93.2 346.0  2.0
1997 May 14  05 17 19.16 +18 34 41.6  1.992  28.82  1.183  26.9  22.8  58  94.7 346.6  2.0
1997 May 15  05 19 41.74 +18 03 26.8  2.008  28.66  1.193  26.6  22.3  70  96.2 347.2  2.1
1997 May 16  05 22 01.52 +17 32 35.7  2.025  28.49  1.204  26.3  21.8  81  97.7 347.8  2.1
1997 May 17  05 24 18.62 +17 02 07.8  2.041  28.31  1.215  25.9  21.3  92  99.2 348.4  2.2
1997 May 18  05 26 33.18 +16 32 02.5  2.057  28.12  1.226  25.6  20.9 104 100.8 348.9  2.2
1997 May 19  05 28 45.31 +16 02 19.2  2.074  27.92  1.237  25.3  20.5 116 102.4 349.4  2.3
1997 May 20  05 30 55.12 +15 32 57.3  2.090  27.72  1.248  25.0  20.0 128 104.0 350.0  2.3
1997 May 21  05 33 02.72 +15 03 56.2  2.106  27.51  1.259  24.7  19.6 140 105.6 350.5  2.4
1997 May 22  05 35 08.21 +14 35 15.3  2.121  27.30  1.271  24.4  19.2 152 107.2 350.9  2.4
1997 May 23  05 37 11.69 +14 06 54.0  2.137  27.08  1.282  24.2  18.9 165 108.9 351.4  2.5
1997 May 24  05 39 13.24 +13 38 51.7  2.153  26.85  1.294  23.9  18.5 175 110.6 351.9  2.5
1997 May 25  05 41 12.95 +13 11 07.9  2.168  26.62  1.305  23.7  18.1 167 112.3 352.3  2.5
1997 May 26  05 43 10.91 +12 43 41.9  2.183  26.39  1.317  23.4  17.8 154 114.0 352.8  2.6
1997 May 27  05 45 07.18 +12 16 33.1  2.199  26.15  1.329  23.2  17.5 141 115.8 353.2  2.6
1997 May 28  05 47 01.84 +11 49 41.1  2.214  25.90  1.340  23.0  17.2 127 117.5 353.7  2.7
1997 May 29  05 48 54.96 +11 23 05.1  2.228  25.65  1.352  22.8  16.9 114 119.3 354.1  2.7
1997 May 30  05 50 46.61 +10 56 44.6  2.243  25.40  1.364  22.6  16.6 100 121.2 354.5  2.8
1997 May 31  05 52 36.83 +10 30 39.2  2.258  25.15  1.376  22.4  16.3  86 123.0 354.9  2.8
1997 Jun  1  05 54 25.70 +10 04 48.1  2.272  24.89  1.388  22.3  16.1  73 124.8 355.2  2.9
1997 Jun  2  05 56 13.25 +09 39 10.9  2.287  24.62  1.400  22.1  15.8  60 126.7 355.6  2.9
1997 Jun  3  05 57 59.54 +09 13 47.1  2.301  24.36  1.412  22.0  15.6  46 128.6 356.0  2.9
1997 Jun  4  05 59 44.61 +08 48 36.1  2.315  24.09  1.424  21.9  15.4  34 130.5 356.4  3.0
1997 Jun  5  06 01 28.51 +08 23 37.3  2.329  23.82  1.437  21.8  15.2  22 132.4 356.7  3.0
1997 Jun  6  06 03 11.28 +07 58 50.4  2.342  23.55  1.449  21.7  15.0  12 134.3 357.1  3.1
1997 Jun  7  06 04 52.95 +07 34 14.8  2.356  23.28  1.461  21.6  14.8  12 136.2 357.4  3.1
1997 Jun  8  06 06 33.56 +07 09 50.1  2.369  23.01  1.473  21.6  14.7  21 138.2 357.7  3.1
1997 Jun  9  06 08 13.14 +06 45 35.7  2.382  22.73  1.486  21.6  14.5  32 140.1 358.0  3.2
1997 Jun 10  06 09 51.73 +06 21 31.3  2.395  22.46  1.498  21.5  14.4  43 142.0 358.4  3.2
1997 Jun 11  06 11 29.36 +05 57 36.3  2.408  22.18  1.510  21.5  14.3  54 144.0 358.7  3.3
1997 Jun 12  06 13 06.05 +05 33 50.4  2.421  21.91  1.523  21.6  14.2  65 145.9 359.0  3.3
1997 Jun 13  06 14 41.84 +05 10 13.1  2.434  21.63  1.535  21.6  14.1  77 147.8 359.3  3.3
1997 Jun 14  06 16 16.75 +04 46 44.0  2.446  21.36  1.548  21.6  14.0  88 149.8 359.6  3.4
1997 Jun 15  06 17 50.81 +04 23 22.8  2.458  21.08  1.560  21.7  13.9  99 151.7 359.8  3.4
1997 Jun 16  06 19 24.04 +04 00 09.1  2.470  20.81  1.573  21.8  13.9 111 153.6    .1  3.4
1997 Jun 17  06 20 56.46 +03 37 02.4  2.482  20.54  1.585  21.9  13.8 122 155.4    .4  3.5
1997 Jun 18  06 22 28.09 +03 14 02.4  2.494  20.27  1.598  22.0  13.8 134 157.3    .7  3.5
1997 Jun 19  06 23 58.97 +02 51 08.8  2.506  20.00  1.610  22.1  13.7 145 159.2    .9  3.5
1997 Jun 20  06 25 29.10 +02 28 21.2  2.517  19.73  1.623  22.3  13.7 156 161.0   1.2  3.6
1997 Jun 21  06 26 58.52 +02 05 39.2  2.528  19.46  1.636  22.4  13.7 163 162.8   1.4  3.6
1997 Jun 22  06 28 27.23 +01 43 02.6  2.540  19.19  1.648  22.6  13.7 161 164.6   1.7  3.7
1997 Jun 23  06 29 55.26 +01 20 31.0  2.551  18.92  1.661  22.8  13.7 151 166.3   1.9  3.7
1997 Jun 24  06 31 22.62 +00 58 04.1  2.561  18.66  1.673  23.0  13.7 139 168.1   2.2  3.7
1997 Jun 25  06 32 49.34 +00 35 41.5  2.572  18.39  1.686  23.2  13.7 126 169.8   2.4  3.8
1997 Jun 26  06 34 15.42 +00 13 23.0  2.583  18.13  1.699  23.4  13.8 113 171.5   2.6  3.8
1997 Jun 27  06 35 40.88 -00 08 51.7  2.593  17.86  1.711  23.7  13.8 100 173.1   2.9  3.8
1997 Jun 28  06 37 05.73 -00 31 03.0  2.603  17.60  1.724  23.9  13.8  87 174.7   3.1  3.9
1997 Jun 29  06 38 29.99 -00 53 11.1  2.613  17.34  1.737  24.2  13.9  74 176.3   3.3  3.9
1997 Jun 30  06 39 53.66 -01 15 16.3  2.623  17.07  1.749  24.5  13.9  62 177.9   3.5  3.9
1997 Jul  1  06 41 16.75 -01 37 19.0  2.633  16.81  1.762  24.7  14.0  50 179.4   3.7  3.9
1997 Jul  2  06 42 39.27 -01 59 19.2  2.643  16.55  1.775  25.0  14.0  39 180.9   3.9  4.0
1997 Jul  3  06 44 01.23 -02 21 17.4  2.652  16.30  1.787  25.3  14.1  29 182.4   4.1  4.0
1997 Jul  4  06 45 22.64 -02 43 13.8  2.662  16.04  1.800  25.7  14.2  23 183.9   4.3  4.0
1997 Jul  5  06 46 43.49 -03 05 08.6  2.671  15.79  1.813  26.0  14.2  22 185.3   4.5  4.1
1997 Jul  6  06 48 03.80 -03 27 02.0  2.680  15.53  1.825  26.3  14.3  26 186.7   4.7  4.1
1997 Jul  7  06 49 23.57 -03 48 54.3  2.689  15.28  1.838  26.7  14.4  34 188.0   4.9  4.1
1997 Jul  8  06 50 42.81 -04 10 45.6  2.697  15.04  1.851  27.0  14.5  44 189.4   5.1  4.2
1997 Jul  9  06 52 01.52 -04 32 36.3  2.706  14.79  1.863  27.4  14.5  54 190.7   5.3  4.2
1997 Jul 10  06 53 19.70 -04 54 26.4  2.715  14.55  1.876  27.8  14.6  64 192.0   5.5  4.2
1997 Jul 11  06 54 37.35 -05 16 16.2  2.723  14.31  1.889  28.2  14.7  75 193.2   5.6  4.2
1997 Jul 12  06 55 54.49 -05 38 05.9  2.731  14.07  1.901  28.6  14.8  85 194.4   5.8  4.3
1997 Jul 13  06 57 11.12 -05 59 55.6  2.739  13.84  1.914  28.9  14.9  96 195.6   6.0  4.3
1997 Jul 14  06 58 27.23 -06 21 45.6  2.747  13.61  1.927  29.4  15.0 107 196.8   6.2  4.3
1997 Jul 15  06 59 42.83 -06 43 35.9  2.755  13.38  1.939  29.8  15.1 118 198.0   6.3  4.4
1997 Jul 16  07 00 57.93 -07 05 26.8  2.763  13.15  1.952  30.2  15.2 128 199.1   6.5  4.4
1997 Jul 17  07 02 12.53 -07 27 18.5  2.770  12.93  1.965  30.6  15.3 139 200.2   6.6  4.4
1997 Jul 18  07 03 26.63 -07 49 11.0  2.777  12.71  1.977  31.0  15.4 148 201.3   6.8  4.4
1997 Jul 19  07 04 40.23 -08 11 04.5  2.785  12.50  1.990  31.5  15.5 153 202.3   7.0  4.5
1997 Jul 20  07 05 53.34 -08 32 59.2  2.792  12.28  2.002  31.9  15.6 153 203.4   7.1  4.5
1997 Jul 21  07 07 05.96 -08 54 55.3  2.799  12.07  2.015  32.3  15.6 146 204.4   7.3  4.5
1997 Jul 22  07 08 18.09 -09 16 52.8  2.806  11.86  2.028  32.8  15.7 136 205.4   7.4  4.5
1997 Jul 23  07 09 29.74 -09 38 52.0  2.813  11.66  2.040  33.2  15.8 124 206.4   7.6  4.6
1997 Jul 24  07 10 40.91 -10 00 53.0  2.819  11.45  2.053  33.7  15.9 112 207.4   7.7  4.6
1997 Jul 25  07 11 51.60 -10 22 55.8  2.826  11.25  2.065  34.1  16.0  99 208.3   7.8  4.6
1997 Jul 26  07 13 01.80 -10 45 00.8  2.832  11.05  2.078  34.6  16.1  87 209.3   8.0  4.6
1997 Jul 27  07 14 11.52 -11 07 07.9  2.839  10.86  2.091  35.1  16.2  75 210.2   8.1  4.7
1997 Jul 28  07 15 20.75 -11 29 17.4  2.845  10.66  2.103  35.5  16.3  64 211.1   8.3  4.7
1997 Jul 29  07 16 29.49 -11 51 29.3  2.851  10.47  2.116  36.0  16.4  54 212.0   8.4  4.7
1997 Jul 30  07 17 37.75 -12 13 43.9  2.857  10.28  2.128  36.5  16.5  44 212.9   8.5  4.7
1997 Jul 31  07 18 45.51 -12 36 01.1  2.863  10.10  2.141  37.0  16.6  37 213.7   8.7  4.8
1997 Aug  1  07 19 52.77 -12 58 21.0  2.869   9.91  2.153  37.5  16.7  32 214.6   8.8  4.8



R.A. J2000  Dec. = Geocentric astrometric right ascension and declination
                   referred to the mean equator and equinox of J2000.
                   Light time corrections have been applied

Delta            = Geocentric distance of object in AU

Deldot           = Geocentric radial velocity of object in km/s

r                = Heliocentric distance of object in AU

Theta            = Sun-Earth-Object angle in degrees

Beta             = Sun-Object-Earth angle in degrees

Moon             = Moon-Earth-Object angle in degrees

PsAng            = Position angle of extended radius vector in degrees
                   This will be the approximate position angle of an ion tail

PsAMV            = Position angle of minus velocity vector in degrees.
                   A dust tail will have an approximate position angle
                   located between the position angles defined by PsAng and PsAMV.

TMag             = Total magnitude
                 = 0.0 + 5.00*log(Delta) +  7.5*log(r)


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% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: Comet Hale-Bopp Orbit and Ephemeris Information
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    Hale-Bopp is pretty easy to spot in the early morning sky if you know
    where to look.  I saw it again at 5AM just looking out the kitchen widow
    while making coffee.  Isn't it going to be at it's brightest around
    March?  If that's the case, it should be spectacular in another 4
    weeks.
                                                      

    Yeah, it's pretty bright right now.  I'd say it's living up to
    expectations.  I caught it around 5, just below the eastward 
    trailing tip of Cygnus's wing.  Not quite as bright as Deneb,
    I'd guess, but brighter than the stars that make up the wings
    of the constellation.  Given the washed out sky of the just
    past full moon, I couldn't make out much of a tail by naked
    eye, but there was a nicely fanned out tail in the binoculars.
    Just a hint of that ion (?) tail.  March 22nd is closest
    approach to earth (still over an AU away) and April 1st is the
    closest approach to the sun (perihelion?  I can never keep
    peri- and apihelion(sp?) straight).  Given the distance and
    angle we see it at, we may never get as nice a tail as Hyakutake,
    but I'd say it's easily brighter now than Hyakutake got.
    
    PeterT
    

Well I had a chance to see Hale-Bopp this past weekend on Sunday
morning. I checked the weather report, and heard it was going to
be clear enough in the morning for the first time in a couple of
weeks. I set my alarm for around 4:30am got up, and went out
equipped with my 7X50 binocs into my back yard.
I looked towards the northeast, and within 2-3 seconds spotted it
naked-eye. there was certainly no mistaking that it was a comet! :-)
It had a magnitude of maybe 1.5, and with just my un-aided eye, I
could see a bit of tail of maybe 1-2 degrees. I pulled my 7X50's up
to my eyes, and could definitely make out a bright central core with
a fan-shaped tail (or double tail), and using averted vision, it had
a length of maybe 3-5 degrees.
The comet was just about ENE and at an altitude of 20-25 degrees up
from the horizon.
Late last summer I had also spotted it on one real clear night evening
over in the southern sky with my binoculars. Back then, it was nothing
more than a fuzz ball of magnitude 5+ or so.
Having also seen comet Hyakutake (hope I got the spelling correct),
last spring, I was impressed with this one. This one can only get better.
I'm going to try get some photos this time around as I missed the
opportunity to do so with last springs visitor.
Anybody else had a chance to make some sightings yet?
For those interested my location is here in the USA in Westford,
Massachusetts.

Bob

Re -2
>    March 22nd is closest
>    approach to earth (still over an AU away) and April 1st is the
>    closest approach to the sun (perihelion?  I can never keep
>    peri- and apihelion(sp?) straight).

Aphelion. I spent years trying to remember which was which before it occurred to
me that the "a" in aphelion, apogee etc. can stand for "away". If I could just
think of a synonym for "close" that begins with a "p"!

>Anybody else had a chance to make some sightings yet?

I've see it a couple of times in recent weeks, but I'm not a morning person, 
and it's a real effort to leave the warmth and comfort of my bed in the 
ungodly pre-dawn hours. It's worth it though! HB's a lovely sight in binoculars,
and shows a lot of detail when viewed with a 'scope. If my photos come out I'll
be a very happy bunny! The good news is that HB's now visible in the early 
evening, though you need a good west horizon. 

		Ian G.

    I'm not a morning person either, but if you drink enough tea before 
    bedtime, you can find yourself getting up every now and then during
    the night ;-)  I don't really want to set my alarm and wake others
    up.  My wife is not usually very appreciative of this...
    
    as far as it swinging into the evening sky, that may depend
    on your lattitude.  I read in S&T that H-B would become an all night
    object at some point for observers above 50 degrees North.  So it
    might be showing up in the UK evening skies before it does here in
    the US.
    
    Been cloudy most mornings recently.  Sigh...
    
    PeterT
    

Re: .18
>Aphelion. I spent years trying to remember which was which before it 
occurred to
>me that the "a" in aphelion, apogee etc. can stand for "away". If I could 
just
>think of a synonym for "close" that begins with a "p"!

	How about "proximity"?

	Mike

Re -1
>	How about "proximity"?

Pure genius! Thank you!

		Ian G.

Re .19    
>    as far as it swinging into the evening sky, that may depend
>    on your lattitude.  I read in S&T that H-B would become an all night
>    object at some point for observers above 50 degrees North.  So it
>    might be showing up in the UK evening skies before it does here in
>    the US.

I've just seen an observing report of HB as an evening object from someone in
the US, at 44d N.

		Ian G.

Well, when we get a clear sky, and I can find an appropriate horizon, 
I'll let you know ;-)

PeterT

    I saw H-B last nite just after sunset(about 6:30pm EST).  H-B was about
    20 deg above the horizon in the WNW sky.  I live 10 miles NW of Boston
    Mass.  I couldn't see much of a tail due to light polution in that
    direction(Street lights, the city of Lowell Mass etc).   H-B is much
    nicer in the AM.
    	

Got another view this morning, 4:30 to 5 or so before I crawled back into
bed.  I could make out a hint of the double tail in the binoculars,
and by using averted vision without the binocs.  Pretty sight.  Almost
considered pulling the scope out, but I think I would have woken
too many people in the house stumbling around pulling things together. 
I think I'll set the tripod in the yard near where I can catch it best
and prepare that way.  Bought some 400 speed film to try and catch it 
for posterity one of these mornings.

PeterT

    I knew it was going to be clear this morning, but forgot to
    set my alarm 45 minutes earlier than it usually goes off, so
    I missed an opportunity to see it under clear conditions. I'll
    be looking for it this evening though. There have been many
    newsgroup reportings of seeing it in the evening sky roughly
    an hour after sunset during the past week, though it may require
    a good horizon to see it in the northwest in the evening.
    
    Bob

    Hale Bopp is visible (make that detectable) with the naked eye in 
    downtown DC a half hour to an hour after sunset.  With binoculars, you
    can detect a bit of a tail.
    
    H-B is dramatic in the morning here, an hour before sunrise.  You can
    see a bit of the tail with the naked eye and it is "text book"
    beautiful with 7x50's.
    
    FJP

    I've glimpsed it briefly on the way home twice.  Rather low on the
    horizon.  Not at all visible from my house in the evening.  Though
    it's starting to dip low towards my effective horizon (of house and
    trees) in the morning too.  Have been taking pictures the last 
    few times out.  Might get something worthwile.  It has been 
    a very nice sight, and now is brighter than Deneb, the nearest 1st mag
    star.
    
    It looks pretty decent through the finder scope and through the 8"
    itself, using the 40mm eyepiece.  But I notice at the best focus I
    can achieve, it appears that there are concentric arcs in the 
    dust cloud surrounding the comet head.  I imagine this is an artifact
    of my scope, rather than a real phenomenom.  I say arcs, rather than
    circles, as they appear only in the sunward side of the dust cloud.
    The other side seems almost flat, as if it's in shadow from the
    rest of the cloud. It almost appears like Airy(?) rings, but I thought
    those showed up only out of focus, and the few stars in the same frame
    are as close to pin pricks as I can make them.  I suppose an attempt
    at collimation might be worthwile, but maybe it's something in the 
    mirror?  Any ideas?
    
    Thanks,
    PeterT  (having a good time anyway ;-)

Re -1    
>    It looks pretty decent through the finder scope and through the 8"
>    itself, using the 40mm eyepiece.  But I notice at the best focus I
>    can achieve, it appears that there are concentric arcs in the 
>    dust cloud surrounding the comet head.  I imagine this is an artifact
>    of my scope, rather than a real phenomenom.

They're real alright! I've read several reports, and seen them myself a couple
of times. If you increase the magnification you may see some structure in
the bright bands. Conventional wisdom has it that comets are best viewed at
low magnifications, but it looks like HB's been reading all the wrong books!

		Ian G.

Last night (12th), I got my scope out along with the 20x80 binoculars and had a
very good view of the comet. It was about 7pm before the sky was dark enough and
the comet was about 15� above the horizon (3 fist widths at arm's length).

While I was out I called over the boy from next door who's about 6 and keen as
mustard. He thought it was the best thing since sliced bread and ran back home
to get his mother and sister who called to the girl on the other side who
brought her parents who ...

Before I knew it I was holding an impromptu star party for a dozen people. I was
really quite surprised by the level of interest and keenness shown by the
neighbours. Perhaps I ought to do this again sometime.

I did notice that as the sky darkened, Hale-Bopp was the first thing to become
naked-eye visible. Another thing, I found the view far better through binoculars
than through the scope.

That's my two penn'orth.

Chris.

Re .29
> Conventional wisdom has it that comets are best viewed at
>low magnifications, but it looks like HB's been reading all the wrong books!

I've just had the error of my ways pointed out to me! What I meant to say was
that, unusualy, HB is worth looking at with high magnifications, AS WELL as 
low ones.

		Ian G.

> They're real alright! I've read several reports, and seen them myself a couple
> of times. If you increase the magnification you may see some structure in
> the bright bands.

Cool!  Where are these reports you've seen?  I'm guessing in sci.astro.*?
I've seen some mention of some other types of bands, but those were
in the tail, away from the head.  That was from the Hale-Bopp home page
from a Japanese site.

This morning I just poked my head out the bedroom porch door, saw a real
nice tail, longer and brighter than I think I've seen yet, and then
headed back to bed.  Last night I caught it before twilight had faded,
from a supermarket parking lot, with the crescent moon above and to 
the left of it.  I figured I'd go for one of the more light polluted
sites I could find, and still had no trouble picking it out.
Still behind the trees by the time I made it home about 15-20 minutes
later.

PeterT

    What magnification do have with your 8" & 40 mm? (? Primary focal
    length?).  I just got in a 30 mm and ultrablock filter for my 2.5"
    (60mm) x  900mm and was hoping to see something useful.  My 20mm was
    just too much magnification.
    
    I don't expect the overall picture will be as good as my 7x50
    binoculars, but wondered what the difference would be a slightly higher
    magnification..
    
    FJP
    
    

Re .32

>Cool!  Where are these reports you've seen?  I'm guessing in sci.astro.*?

I get this sort of stuff from the ASTRO listserver, I'm told the s/n ratio on 
sci.astro makes it a pain.

		Ian G. 

    Magnification??  Sigh...  I rarely think about this.   I think the
    focal length of your typical C8 is 2000mm.  And actually I realized
    I was using the 30mm eyepiece, so I think that works out to be 
    roughly 2000/30 = 200/3 = 67X or so.  Does that sound right to 
    others?  From the 30, I drop down to a 7mm and 4mm, which are 
    usually too high for me to focus very well, and tend to 
    be too susceptible to vibration.  The 7mm came with the scope, and
    the 4mm was given by a friend when he donated his scope to our
    old high school.  I'd love to get an eyepiece somewhere about 15 or
    20mm.  I think that would be more useful for my setup.
    
    PeterT

    Well I had a chance to see it both in the morning and evening
    sky yesterday. The morning sky is still a better view for now.
    The eveing view last night, I had in a school parking lot where
    there were abundant sodium flood lights. I took advantage of
    where I was at the time (about 7:15pm est), in the school 
    parking lot to take a look with my 7x50 binoculars. Even with
    the glare of the building floodlights, which I was able to 
    block to a certain degree, by positioning myself with my car 
    between myself and the floodlight, revealed a growing tail
    from what I recall seeing earlier this week. Crummy weather 
    this coming weekend precludes viewing or picture-taking.
    
    Bob

    >    I was using the 30mm eyepiece, so I think that works out to be
    >    roughly 2000/30 = 200/3 = 67X or so.  Does that sound right to
    >    others? 
    
    Yep, that's correct.

    I made some more evening and morning obs this past weekend.
    I also saw the comet again this morning. this morning, my perception
    was that the fainter tail had increased in length. In my somewhat
    light-polluted eastern sky, I could still ascertain with averted
    vision a faint tail of perhaps 12 degrees, and the brighter short
    tail is now perhaps 4-6 degrees. I've seen reports of people in
    darker skies that improve on those tail estimates by 30-50%.
    My perception also is that the fainter tail isn't angled off to
    one side as much as it was a couple of weeks ago. it seems more
    in-line now with the brighter shorter tail. My guestimate of magnitude
    of the comet core is about -.5
    I pulled a message off of sci.space.news of a preliminary report
    by the European Space Agency Infrared Space Observatory on observations 
    made last fall and spring of 1996 on Comet Hale-Bopp. I'll post it
    in a following reply. It's quite interesting.
    
    Bob
    

European Space Agency
Press Information Note N=A1 08-97
Paris, France=09=09=09=09=0914 March 1997

ISO's analysis of Comet Hale-Bopp

If you had infrared eyes, Comet Hale-Bopp would look quite different from
the streaky visible object now examined by astronomers' telescopes and
amateurs' binoculars all around the world, as the comet approaches its close
encounter with the Sun. You would see not just the very fine dust thrown out
by the comet, which makes its head and tail conspicuous to ordinary human
eyes, but larger particles of dust. The colour or dominant wavelength of the
infrared glow would tell you the temperature of the dust cloud. And infrared
hues at other wavelengths would reveal the nature of the dust, and let you
see what vapours emanate from the comet's nucleus as the Sun's rays warm its
chilly surface.

The European Space Agency's Infrared Space Observatory ISO inspected Comet
Hale-Bopp during the spring and autumn of 1996. The need to keep ISO's
telescope extremely cold restricts the spacecraft's pointing in relation to
the Sun and the Earth and it ruled out observations at other times. The
analyses of the 1996 observations are not yet complete, but already they
give new insight into the nature of comets.

Comet Hale-Bopp is believed to be a large comet with a nucleus up to 40
kilometres wide. It was discovered in July 1995 by two American astronomers
working independently, Alan Hale and Thomas Bopp. At that time, the comet
was a billion kilometres away from the Sun, but 200 times brighter than
Halley's Comet was, when at a comparable distance. Comet Hale-Bopp will make
its closest approach to the Earth on 22 March, and its closest approach to
the Sun (perihelion) on 1 April 1997.

Some scientific results from ISO

The discovery of Comet Hale-Bopp occurred before ISO's launch in November
1995. When first observed by ISO in March and April 1996, the comet was
still 700 million kilometres from the Sun, and almost as far from the Earth
and ISO. With its privileged view of infrared wavebands inaccessible from
the Earth's surface, ISO's photometer ISOPHOT discovered that carbon dioxide
was an important constituent of the comet's emissions of vapour. ISOPHOT
measured the temperature of the dust cloud around Comet Hale-Bopp. In March
1996, when the comet was still more than 700 million kilometres from the
Sun, the dust cloud was at minus 120 degrees C. When ISOPHOT made similar
observations in October 1996, the comet was 420 million kilometres from the
Sun, and the dust cloud had warmed to about minus 50 degrees C.

Intensive observations of Comet Hale-Bopp were also made by ISO's Short-Wave
Spectrometer SWS, the Long-Wave Spectrometer LWS, and the ISOPHOT
spectrometer PHOT-S. Results are due for publication at the end of March.
They will give details about the composition of the comet's dust and vapour,
and also rates of escape of vapour, which will help in assessing the loss of
material from Comet Hale-Bopp during this visit to the Sun's vicinity.

"Watch out for some fascinating news," says Thijs de Graauw of Groningen
University, who is in charge of the SWS instrument used in this study. "What
excites me is the opportunity we shall have to compare dusty Comet
Hale-Bopp, seen in the Solar System, with dusty objects far away among the
stars which seem to be made of similar materials. Infrared astronomy has a
special ability to unify cosmic chemistry at all scales from little dust
grains in the Earth's vicinity to vast and distant galaxies."

The dust itself interests the infrared astronomers, not least because their
view of the Universe at large is spoiled to some extent by dust left behind
by comets. Together with fine debris from asteroids, the comet dust makes a
bright infrared band around the sky, which corresponds with the zodiacal
light sometimes seen by eye, slanting above the horizon at twilight. ISO's
predecessor, the US-Dutch-UK infrared astronomical satellite IRAS, found
trails of comet dust much longer and more persistent than the familiar comet
tails. ISO has seen a trail from Comet Kopff. By detecting dust grains that
are typically much larger than those seen by visible light, ISO scientists
hope to learn more about the dust's long-term behaviour in the Solar System.

A series of images of Comet Hale-Bopp, obtained by the camera ISOCAM in
October 1996, is the subject of continuing analysis. Leading this work in
progress is Philippe Lamy of Marseille, France. "We hope to unveil the
nucleus of the comet," Professor Lamy explains. "In principle, the Hubble
Space Telescope can see finer details by visible light, but the contrast of
the nucleus against the bright surrounding coma is superior at infrared
wavelengths. This is because the thermal emission from the nucleus is very
large and can be detected thanks to the high spatial resolution of ISO. We
have a long time coverage of the comet, so we hope to determine the
light-curve of the nucleus -- which, in turn, will reveal its gross shape
and an estimate of its rotation period."

A commanding role in comet research

As comets are relics from the construction of the Solar System, and played
a major role in the formation of the planets, they are a link between the
Earth and the wider Universe of stars. The carbon compounds contained in
comets probably contributed raw materials for the origin of life on the
Earth, and according to one theory the Earth's oceans were made from comet
ice. Growing knowledge of the composition and behaviour of comets is
therefore crucial for a fuller understanding of our cosmic origins.

ESA has a commanding role in space research on comets. Its Giotto spacecraft
was the most daring of the international fleet of spacecraft that visited
Halley's Comet in March 1986. Giotto obtained exceptional pictures and other
data as it passed within 600 kilometres of the nucleus. Dust from the comet
badly damaged the spacecraft, but in a navigational tour de force Giotto
made an even closer approach to Comet Grigg-Skjellerup in July 1992. Now ESA
is planning the Rosetta mission that will rendezvous with Comet Wirtanen and
fly in company with it, making observations far more detailed than the fast
flybys of Halley's Comet and Comet Grigg-Skjellerup could achieve.

As for space astronomy, the International Ultraviolet Explorer, in which ESA
was a partner, made unrivalled observations of Halley's Comet by ultraviolet
light. ESA is also a partner in the Hubble Space Telescope, which saw the
historic impacts of Comet Shoemaker-Levy 9 on Jupiter in July 1994, and has
recently observed Comet Hyakutake as well as Hale-Bopp. The SOHO spacecraft,
built by ESA for a joint ESA-NASA project to examine the Sun, has a
distinctive view of comets. It has observed the hydrogen coronas of comets
with its SWAN instrument. SOHO's coronagraph LASCO observed Comet Hyakutake
rounding the Sun (when it was invisible to ground-based observers) and has
discovered seven new comets very close to the Sun.

Only ISO provides astronomers with information from comets across a very
wide range of infrared wavelengths unobservable from the ground. Besides
Comet Hale-Bopp, ISO has examined Comets Schwassmann-Wachmann 1, Chiron,
Kopff, IRAS 1 and Wirtanen. The last of these, Comet Wirtanen, is the target
of the Rosetta mission and is now making one of its six-yearly visits to the
Sun's vicinity.

Dietrich Lemke of Heidelberg, Germany, who is in charge of the ISOPHOT
instrument in ISO, summarizes ISO's unique contribution.

"By measuring the extremely weak heat rays from these frosty objects at
different distances," Professor Lemke says, "we have a thermometer to gauge
a comet's growing fever when it nears the Sun. As the temperature rises,
first one kind of ice evaporates, and then another, producing various
chemical signatures in the infrared spectrum. We can also characterize the
mineral dust coming out of the comet. So ISO offers a vivid impression of
comets in action which no other instrument can match."

Photos are available on the ESA home page on Internet :
http://www.estec.esa.nl/spdwww/iso/html/hale-bopp.htm


---
Andrew Yee
[email protected]

PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Contacts:
Diane Ainsworth, Jet Propulsion Laboratory
Jim Scott, University of Colorado, Boulder, 303-492-3114

FOR IMMEDIATE RELEASE                              March 19, 1997

ULYSSES SCIENTISTS BEGIN CAPTURING UNIQUE VIEW OF HALE-BOPP

     Scientists on a joint NASA-European Space Agency mission to 
study the poles of the Sun are using the Ulysses spacecraft's 
unique, high latitude orbit to help understand changes in comet 
Hale-Bopp as it nears the lower latitudes of the Sun while 
spewing its outer layers of gas and dust.     

     Using solar wind data from the spacecraft, a team of 
interdisciplinary scientists at NASA's Jet Propulsion Laboratory, 
the University of Colorado at Boulder and an international group 
of amateur astronomers known as the "Ulysses Comet Watch" have 
been observing other comets in the same way as they return from 
the far reaches of space. This unique, collaborative research 
effort focuses specifically on what happens to comets as they are 
exposed to different solar wind conditions at various solar 
latitudes. 

     "Until recently, no spacecraft had flown through high 
latitudes above the Sun's equator and the properties of the solar 
wind at these latitudes could only be surmised," said Dr. Edward 
Smith, project scientist of the Ulysses mission at JPL. "In the 
last two years, Ulysses has studied the steady, high-speed winds 
at high latitudes, and alternating, slow and fast winds near the 
Sun's equator. Hale-Bopp is about to enter the lower latitude 
zone, where the disturbed solar wind resides, and where dramatic 
changes in the comet's plasma tail are expected to occur." 

     The Ulysses Comet Watch group, spearheaded by Drs. John C. 
Brandt and Martin Snow of the University of Colorado's Laboratory 
for Atmospheric and Space Physics, and Carolyn Collins Petersen, 
now of Sky Publishing Corp. in Cambridge, MA, will provide 
worldwide observations of the returning comet as it descends from 
the polar regions of the Sun. Images from more than 200 observers 
around the world will be posted on the Ulysses Comet Watch home 
page on the Internet at http://lasp.colorado.edu/ucw/index.html. 
Observations will continue to be posted well after the comet 
makes its closest approach to the Sun on April 1.

     The Ulysses group is not watching for changes in the comet's 
more visible, wider and yellowish dust tail, though, but rather 
for changes in its narrower, paler, often bluish plasma tail, 
which consists of ionized gas being emitted by the comet and 
picked up by the magnetic field being swept along by the solar 
wind. 

     "We are particularly interested in the comet's plasma tail, 
which 'turned on,' or began to outgas, when Hale-Bopp was about 
1.5 astronomical units (140 million miles) from the Sun, the 
equivalent of 1.5 times the distance between the Earth and the 
Sun," Brandt said.

     Cometary plasma tails change constantly due to their 
interactions with slow and high-speed solar wind. One of the more 
dramatic changes that can occur is the abrupt disconnection of 
the tail, which then drifts away. Often a new tail will form 
within hours.

     "Comets lose their plasma tails when they are subjected to 
abrupt reversals in the direction of the solar wind magnetic 
field," Smith said. "This magnetic field reversal typically 
happens in the equatorial regions twice per solar rotation, or 
about every 13 days. They don't occur at high latitudes."  

     Consequently, Brandt and his team expect to see such 
dramatic changes in the comet's plasma tail only in the 
equatorial regions of the solar wind -- between 20 degrees north 
and 20 degrees south of the Sun's equator. 

     Modeled after the very successful international Halley Watch 
observation networks, which operated during 1985 and 1986, the 
Ulysses Comet Watch network has been operating since late 1992. 
Observers have studied a number of comets, and have supplied 
sequences of high-quality images of comets de Vico, which 
returned in September 1995, and Hyakutake, which was discovered 
and observed last year.  

     Scientists first discovered that the plasma tails of these 
comets change and drop off according to their latitudes with 
respect to the Sun during these two comet returns.  Observers are 
now beginning to submit early images of Hale-Bopp, which, 
according to Brandt, are looking equally as promising. "In fact, 
we expect the network's output of Hale-Bopp images to be 
fantastic," he said. 

     "At equatorial latitudes, the solar wind moves at an average 
speed of about 450 kilometers per second (970,000 miles per hour) 
with large variations in speed and density," Brandt continued. 
"This type of wind apparently comes from the equatorial streamers 
so clear at solar eclipses. The plasma tail of a comet 
experiencing this part of the solar wind has a distinctly 
disturbed appearance which varies over time, and undergoes 
disconnection events as it experiences reversals of the magnetic 
field.   

     "By contrast, when the same comet travels through the polar 
latitudes, it encounters a more steady, less dense and faster 
solar wind, moving at about 750 kilometers per second or 1.6 
million miles per hour," Brandt said. "There are smaller 
variations in speed and density and no magnetic field reversals. 
Consequently, the plasma tail looks much less turbulent and does 
not have disconnection events.  So, the comet, by acting as a 
'solar wind sock,' can be used to map the conditions in different 
latitudes of the solar wind."

     Comet Hale-Bopp is ideally suited to show these types of 
tail changes because of its high-latitude orbit. Ulysses' 
measurements of the solar wind from the same latitude, combined 
with ground-based observations of comet tails, will help 
scientists better understand the physics involved in cometary 
gases and their interaction with the outward-flowing solar wind. 
>From this information, they may be able to understand the solar 
wind in regions that have never been accessible to spacecraft 
before, such as very close to the Sun or at much higher latitudes 
above and below the Sun's equator. 

     Astronomers interested in further information about the 
Ulysses Comet Watch network may contact John C. Brandt at his e-
mail address: [email protected],
or write to him at the Laboratory for Atmospheric and Space 
Physics, Campus Box 392,
University of Colorado, Boulder, CO 80309. His office telephone 
number: (303) 492-3215, or by fax at (303) 492-6946.

     Ulysses is managed jointly by NASA and the European Space 
Agency to study the regions above and below the Sun's poles. The 
Jet Propulsion Laboratory manages the U.S. portion of the mission 
for NASA's Office of Space Science, Washington, D.C.

                           #####

[Note to Editors: NASA TV will broadcast a Ulysses video file 
featuring brief interviews with Drs. Bruce Goldstein, Ulysses 
deputy project scientist at JPL, and Jack Brandt, Ulysses Comet 
Watch team leader at the University of Colorado, during its 
regularly scheduled video file programming at 9 a.m., 12 noon, 3 
p.m. and 6 p.m. Pacific Standard Time today, March 19. The 
program also includes animation of a comet losing its plasma tail 
and footage of the Ulysses mission to the poles of the Sun. NASA 
Television has switched to a new satellite and is available on 
GE-2, transponder 9C, 85 degrees longitude, vertical 
polarization, audio frequency 3880 megahertz, audio 6.8 
megahertz.]


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% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: Ulysses Scientists Begin Capturing Unique View of Comet Hale-Bopp
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    re: .30
    
    I was out tonight with my 8x40 binoculars... I live in a condo, 
    and I also ended up with quite a gathering. Even with various
    house/street lights, and the nearly full moon, it was awesome.
    
    Dave

From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 21-MAR-1997 20:32:58.89
To:	[email protected]
CC:	
Subj:	Comet Hale-Bopp - When and Where to Watch


COMET HALE-BOPP - WHEN AND WHERE TO WATCH

March 1-10. The comet is up before the first light of dawn. Set your alarm
clock for about an hour and 45 minutes before sunrise (look up your local
sunrise time in a local newspaper). Step outdoors and look east-northeast.
Comet Hale-Bopp is shining there moderately high. It's about as bright as the
brightest stars, with a hazy head and a dimmer, filmy tail extending to the
upper left.

March 10-19. The comet remains fairly high in the predawn sky. It is shifting
a little left toward the northeast and gradually brightening.  But by now the
comet is also becoming visible low in the evening sky too! Look low in the
northwest just as the last glow of twilight is fading out. Again, look for a
hazy star with a dim tail. When the comet is seen in the evening sky, its
tail extends to the upper right. Each night Comet Hale-Bopp gains altitude
and becomes a little easier to find after dusk.  Moonlight starts flooding
the evening sky around March 16th, compromising the view of the dim outer
parts of the tail. But the comet's increasing height and brightness may just
about make up for the worsening effect of moonlight. If you want a moonless
view as late as the night of March 19-20, continue looking just before dawn.

March 20-22. The ever-brightening comet is now easy to spot fairly high in
the northwest after dusk. Meanwhile before the first light of dawn, it has
started to sink a bit lower in the northeast -- so that it's now balanced
equally high at both times. A bright Moon is in the sky at both times as
well.

March 23. This is a big night for skywatchers! The full Moon undergoes a deep
partial eclipse that will be visible throughout most of the Americas (and
western Europe on the morning of the 24th). Above or to the upper right of
the eclipsed Moon will be the bright orange planet Mars, separated from the
Moon by a little more than the width of your fist at arm's length. For more
on this spectacular lunar eclipse, including a timetable of events, see the
March issue of Sky & Telescope, page 82.  Comet watchers on the West Coast,
especially the Pacific Northwest, get an added bonus. The eclipse will
cleanse the sky of most moonlight from about 8:15 to 9:00 p.m. Pacific
Standard Time, right in prime comet-watching time.

March 24 - April 10. This is the peak of Comet Hale-Bopp's performance. Look
well up in the northwestern sky after the end of evening twilight. The Moon
is low in the east at the end of twilight on March 24th and is just rising on
the 25th. Then the sky is moonless for the next two weeks.  During this time
Comet Hale-Bopp is high enough that it will remain in good view for well over
an hour after the end of twilight -- though the earlier you look after
twilight, the higher it will be. (In fact the comet doesn't actually set
until almost three hours after twilight ends as seen from near 40 degrees
north latitude.)

The comet's head may shine at about magnitude 0, as bright as the star
Capella (which is sparkling much higher in the
west-northwestern sky). Anyone able to get away from glary city lights should
be treated to an awe-inspiring spectacle: the comet's brilliant, starlike
pseudo-nucleus in a hood-shaped head or coma trailed by a thin, bluish ion
(gas) tail and a broad, curved, yellowish dust tail, both extending upward.

April 11-15. The comet has moved a little to the left; look west-northwest
now after the end of twilight.  The waxing crescent Moon returns to the
western evening sky during this period, growing thicker and brightening each
night.  At first its light has little or no effect. But as the days go by the
moonlight will increasingly brighten the sky.

April 16 - 23. Comet Hale-Bopp is fading now and getting somewhat lower in
the west-northwest, and moonlight fills the evening sky, washing out our view
of celestial objects. Even so, the comet should still be plainly visible to
the naked eye.

April 24 - May 7. The comet continues to fade and sink lower in the
west-northwest at the end of twilight, but now the Moon is gone. How late
into the spring can you follow the comet with the naked eye? With binoculars?

May 8. The last hurrah. This evening the thin crescent Moon could form a
dramatic tableau with Comet Hale-Bopp -- which, however, may have become
increasingly difficult to see low in the fading glow of sunset. First spot
the Moon in the western sky in late twilight. The comet is 4 or 5 degrees to
the Moon's upper right -- about as far from the Moon as the width of three
fingers held at arm's length. Both objects will fit into a typical
binocular's field of view (appearing on opposite sides of the view).

During the next week or two, try following the fading comet right down into
the sunset with the naked eye or binoculars.

THE VIEW FROM THE SOUTHERN HEMISPHERE

While Comet Hale-Bopp is sinking out of good view from northern latitudes,
observers in South America, South Africa, Australia, and New Zealand -- who
have not seen the comet since last November -- begin to have their turn to
witness the show.

By about the end of April, viewers there should be able to catch sight of the
comet very low in the northwest in early evening hours.  As April progresses
into May, the comet climbs higher into far-southerners' evening skies. By
late May, when their northern counterparts are losing sight of it, Southern
Hemisphere watchers will still find the comet fairly high above the horizon
well after dusk's end. Although Hale-Bopp will have faded substantially from
its peak brightness, a fairly long tail may still be visible.

Thus, there is a possibility that observers below the equator will be treated
to a decent display after all.  And Southern Hemisphere viewers with
telescopes will be well placed to follow the comet's slow recession into the
distant outer solar system for the next couple of years.

James Musser
UCLA Astronomy


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% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: Comet Hale-Bopp - When and Where to Watch
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon"  6-MAY-1997 09:05:42.06
To:	[email protected]
CC:	
Subj:	[ASTRO] Spacecraft Watch For Comet Hale-Bopp Tail Disruption

Donald Savage
Headquarters, Washington, DC               May 5, 1997
(Phone:  202/358-1547)

William Steigerwald
Goddard Space Flight Center, Greenbelt, MD 
(Phone:  301/286-1085)

RELEASE:  97-89

SPACECRAFT WATCH FOR COMET HALE-BOPP TAIL DISRUPTION 

     A fleet of spacecraft for the International Solar Terrestrial 
Physics (ISTP) program is watching for a break in Comet Hale-
Bopp's plasma ion tail.

     "Preliminary estimates indicate that it may happen in the next few
days," said Dr. Mario Acuna, lead scientist for ISTP at NASA's Goddard
Space Flight Center (GSFC), Greenbelt, MD.  Goddard is the focal point 
for many of the ISTP investigations.

     Amateur astronomers around the world were put on watch last 
week when Dr. Bill Farrell, co-investigator for NASA's Wind spacecraft at 
GSFC, placed a notice on an Internet E-mail list, after scientists 
studying data from ISTP spacecraft estimated that Comet Hale-
Bopp's ion tail likely would be disrupted when it enters a region 
around the Sun known as the "current sheet."  Observations from 
amateur astronomers monitoring changes in the comet's tails will 
provide near-real-time data to scientists to complement 
observations from spacecraft.

     Scientists explain the disruption as a complicated 
interaction between the comet and the Sun's influence and magnetic 
fields.  As a comet comes closer to the Sun, ices from the nucleus 
(a porous structure of dust and ice composed of frozen gases) are 
continually vaporized, dislodging the dust, which is formed by the 
comet's weak gravity into a cloud, called a coma, surrounding the 
comet.  While pressure from the visible sunlight "pushes" the coma 
dust into a diffuse dust tail, the ultraviolet portion of the 
sunlight gives the coma an electrical charge, or ionizes it, 
turning it into a plasma of electrically charged particles of ions 
and electrons.

     The solar wind (also a plasma), flowing from the Sun at 
speeds from 240-450 miles per second and carrying an embedded 
magnetic field, smashes into the coma gas, causing additional 
ionization.  The magnetic field in the solar wind picks up comet 
ions and accelerates them into a long, blue plasma tail.  Since 
this tail is stretched very long, it is much fainter than the dust 
tail and consists mostly of long-lived (stable) ionized carbon 
monoxide.  The magnetic field is draped around the comet coma and 
controls the formation of the plasma tail.  If the magnetic field 
is disrupted, the plasma tail may be disconnected.

     Hale-Bopp's orbit is tilted relative to the Sun's equator 
with the comet moving from the Sun's northern hemisphere to its 
southern hemisphere, crossing the Sun's equatorial plane.  This 
plane is the location of the "current sheet," a place where the 
Sun's magnetic field lines change direction.  As Hale-Bopp passes 
through this plane, its ion tail may disconnect because of the 
change in direction of the magnetic field. 

     "Other events on the Sun may disrupt Hale-Bopp's tail," adds 
Dr. Farrell.  "For example, at any time, the Sun may eject large 
amounts of hot, electrically charged material in the form of 
plasma, called Coronal Mass Ejections, or CME's.  The magnetic 
fields associated with a CME may disrupt the ion tail, 
particularly if the CME is from the Sun's eastern limb in the 
direction of Hale-Bopp.  Also, the solar wind is more gusty around 
the equatorial regions, and this could cause a disruption as 
well," he said.

     "Monitoring this comet tail disruption is more than 
anticipating an intriguing astronomical phenomenon," said Dr. 
Farrell.  "The stronger solar events can have a tremendous impact 
on Earth.  The plasma ejected by these events smashes into the 
Earth's magnetic field and compresses it.  This generates a 
magnetic storm which can disrupt power grids and radio 
communications.  Additionally, the effects can damage 
microcircuits in satellites.  With ISTP, if we can monitor 
disruption events for comets, we can do the same for Earth, 
providing a warning when they occur," he said.

     When Hale-Bopp crosses the current sheet, it will provide 
additional data about its structure where no ISTP spacecraft 
exist.  "It could cost about a billion dollars to build and place 
a spacecraft where Hale-Bopp is," said Dr. Adam Szabo, senior 
scientist with Hughes STX on the Wind project.  "Comet Hale-Bopp 
will give us interesting information about this region of space 
for virtually no cost, except our time to watch and study it.  
It's a bonus which can really help us understand the most powerful 
forces which are affecting the Earth." 

     The ISTP spacecraft involved in this study are NASA's Polar 
and Wind missions and the European Space Agency/NASA Solar and 
Heliospheric Observatory mission.

                          -end-


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% Date: Mon, 5 May 1997 22:36:01 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: [ASTRO] Spacecraft Watch For Comet Hale-Bopp Tail Disruption
% Sender: [email protected]
% Precedence: bulk
% Reply-To: [email protected]

  Has Hale-Bopp crossed the sun's equator yet?

  Is it still visible in the evening or will there come a time when it's
better viewed in the morning before sunrise?

  At any event, where would it be around sunset at this point? I went out
around sunset with my binocs but had no luck finding it. Found Venus, that
looks neat but no comet.

  George

    It's crossed the suns equator and is now coming into view for
    south hemisphere viewers. It's permanently out of the view of
    those living in the northern hemisphere.
    If you hang around for (I think), about 4,000 years you may get
    to see it again in the northern hemisphere. :-)
    
    Bob

    Well, I think it's only about 2400 years he has to wait, due to orbital
    changes from Jupiter.  And I saw something over on the Hale-Bopp web
    page about it being visible for northern viewers in the fall.  But you
    have to be below 30 degrees northern lattitude, or something like
    that.  Definitely gone for New England viewers without southern
    travel plans.
    
    PeterT

From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 27-MAY-1997 04:37:59.67
To:	[email protected]
CC:	
Subj:	[ASTRO] SPACECRAFT WATCH FOR COMET HALE-BOPP TAIL DISRUPTION

SPACECRAFT WATCH FOR COMET HALE-BOPP TAIL DISRUPTION

     A fleet of spacecraft for the International Solar Terrestrial
Physics (ISTP) program is watching for a break in Comet Hale-
Bopp's plasma ion tail.

     "Preliminary estimates indicate that it may happen in the next few
days," said Dr. Mario Acuna, lead scientist for ISTP at NASA's Goddard
Space Flight Center (GSFC), Greenbelt, MD.  Goddard is the focal point
for many of the ISTP investigations.

     Amateur astronomers around the world were put on watch last
week when Dr. Bill Farrell, co-investigator for NASA's Wind spacecraft at
GSFC, placed a notice on an Internet E-mail list, after scientists
studying data from ISTP spacecraft estimated that Comet Hale-
Bopp's ion tail likely would be disrupted when it enters a region
around the Sun known as the "current sheet."  Observations from
amateur astronomers monitoring changes in the comet's tails will
provide near-real-time data to scientists to complement
observations from spacecraft.

     Scientists explain the disruption as a complicated
interaction between the comet and the Sun's influence and magnetic
fields.  As a comet comes closer to the Sun, ices from the nucleus
(a porous structure of dust and ice composed of frozen gases) are
continually vaporized, dislodging the dust, which is formed by the
comet's weak gravity into a cloud, called a coma, surrounding the
comet.  While pressure from the visible sunlight "pushes" the coma
dust into a diffuse dust tail, the ultraviolet portion of the
sunlight gives the coma an electrical charge, or ionizes it,
turning it into a plasma of electrically charged particles of ions
and electrons.

     The solar wind (also a plasma), flowing from the Sun at
speeds from 240-450 miles per second and carrying an embedded
magnetic field, smashes into the coma gas, causing additional
ionization.  The magnetic field in the solar wind picks up comet
ions and accelerates them into a long, blue plasma tail.  Since
this tail is stretched very long, it is much fainter than the dust
tail and consists mostly of long-lived (stable) ionized carbon
monoxide.  The magnetic field is draped around the comet coma and
controls the formation of the plasma tail.  If the magnetic field
is disrupted, the plasma tail may be disconnected.

     Hale-Bopp's orbit is tilted relative to the Sun's equator
with the comet moving from the Sun's northern hemisphere to its
southern hemisphere, crossing the Sun's equatorial plane.  This
plane is the location of the "current sheet," a place where the
Sun's magnetic field lines change direction.  As Hale-Bopp passes
through this plane, its ion tail may disconnect because of the
change in direction of the magnetic field.

     "Other events on the Sun may disrupt Hale-Bopp's tail," adds
Dr. Farrell.  "For example, at any time, the Sun may eject large
amounts of hot, electrically charged material in the form of
plasma, called Coronal Mass Ejections, or CME's.  The magnetic
fields associated with a CME may disrupt the ion tail,
particularly if the CME is from the Sun's eastern limb in the
direction of Hale-Bopp.  Also, the solar wind is more gusty around
the equatorial regions, and this could cause a disruption as
well," he said.

     "Monitoring this comet tail disruption is more than
anticipating an intriguing astronomical phenomenon," said Dr.
Farrell.  "The stronger solar events can have a tremendous impact
on Earth.  The plasma ejected by these events smashes into the
Earth's magnetic field and compresses it.  This generates a
magnetic storm which can disrupt power grids and radio
communications.  Additionally, the effects can damage
microcircuits in satellites.  With ISTP, if we can monitor
disruption events for comets, we can do the same for Earth,
providing a warning when they occur," he said.

     When Hale-Bopp crosses the current sheet, it will provide
additional data about its structure where no ISTP spacecraft
exist.  "It could cost about a billion dollars to build and place
a spacecraft where Hale-Bopp is," said Dr. Adam Szabo, senior
scientist with Hughes STX on the Wind project.  "Comet Hale-Bopp
will give us interesting information about this region of space
for virtually no cost, except our time to watch and study it.
It's a bonus which can really help us understand the most powerful
forces which are affecting the Earth."

     The ISTP spacecraft involved in this study are NASA's Polar
and Wind missions and the European Space Agency/NASA Solar and
Heliospheric Observatory mission.



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