Ted, Are your magnitude estimates based only on the small box-like body? I would think the 32 m solar array would contribute a fair amount of light in its own right, even without a specular reflection. I suspect that the phase angle will be much larger during the close fly-by, with the solar arrays more edge-on, in which case your formula could be more in line with observations. Regards, --Bill Dillon Ted Molczan wrote: > Joseph A. Dellinger posted obs by Bill Dillon at the George Observatory near > Houston, Texas: > > Rosetta C2005 03 01.18294 11 06 40.09 +02 24 00.0 17.0 R 735 > Rosetta C2005 03 01.19055 11 06 37.60 +02 24 03.7 17.0 R 735 > Rosetta C2005 03 01.19689 11 06 35.47 +02 24 06.6 17.0 R 735 > > >>the mags are really "unfiltered", but "R" is a good approximation. > > > Mag 17 is very bright for the range, about 0.0089 A.U. (1.33 million km). See > appended ephemeris. My formula predicts mag 21. Had the object been only 1000 km > away, it would have been mag 1.4, unlikely for Rosetta's non-specular, 2.8 x 2.1 > x 2.0 m box-like body. > > Rosetta's low phase angle, 6.8 deg (see S-T-O column in ephemeris), meant that > the observer was almost directly between it and the Sun. Since its large solar > array (32 m span) is aimed at the Sun, it seems likely to have been flaring, > i.e. sending a bright specular reflection toward the observer. Imagine an > observer on Earth between the Sun and Rosetta in this artist's conception: > > http://satobs.org/seesat_ref/Rosetta/Rosetta.jpg > > The unusually bright obs at Czechia, some 22 h later, was made under similar > conditions, with phase angle near 5.8 deg: > > http://satobs.org/seesat/Mar-2005/0022.html > > Ted Molczan > > > Target Body: Rosetta (Spacecraft) > Observer Location: Houston, TX > Coordinates: 95°21'37.1''W, 29°45'25.9''N > > From: A.D. 2005-03-01 04:23 UT > To: A.D. 2005-03-01 04:44 > > ******************************************************************************* > Date__(UT)__HR:MN R.A._(ICRF/J2000.0)_DEC delta deldot S-T-O > ******************************************************************************* > 2005-Mar-01 04:23 11 06 39.86 +02 23 54.2 0.0089222014 -4.19264 6.8419 > 2005-Mar-01 04:24 11 06 39.64 +02 23 54.6 0.0089205194 -4.19124 6.8406 > 2005-Mar-01 04:25 11 06 39.42 +02 23 54.9 0.0089188379 -4.18984 6.8393 > 2005-Mar-01 04:26 11 06 39.19 +02 23 55.2 0.0089171571 -4.18843 6.8380 > 2005-Mar-01 04:27 11 06 38.97 +02 23 55.5 0.0089154768 -4.18702 6.8367 > 2005-Mar-01 04:28 11 06 38.74 +02 23 55.9 0.0089137970 -4.18560 6.8354 > 2005-Mar-01 04:29 11 06 38.51 +02 23 56.2 0.0089121179 -4.18418 6.8341 > 2005-Mar-01 04:30 11 06 38.29 +02 23 56.5 0.0089104393 -4.18275 6.8328 > 2005-Mar-01 04:31 11 06 38.06 +02 23 56.9 0.0089087613 -4.18132 6.8315 > 2005-Mar-01 04:32 11 06 37.83 +02 23 57.2 0.0089070838 -4.17988 6.8302 > 2005-Mar-01 04:33 11 06 37.60 +02 23 57.5 0.0089054070 -4.17844 6.8289 > 2005-Mar-01 04:34 11 06 37.37 +02 23 57.8 0.0089037307 -4.17700 6.8276 > 2005-Mar-01 04:35 11 06 37.14 +02 23 58.2 0.0089020550 -4.17555 6.8263 > 2005-Mar-01 04:36 11 06 36.90 +02 23 58.5 0.0089003799 -4.17410 6.8250 > 2005-Mar-01 04:37 11 06 36.67 +02 23 58.8 0.0088987054 -4.17264 6.8237 > 2005-Mar-01 04:38 11 06 36.44 +02 23 59.1 0.0088970314 -4.17118 6.8224 > 2005-Mar-01 04:39 11 06 36.20 +02 23 59.5 0.0088953581 -4.16971 6.8211 > 2005-Mar-01 04:40 11 06 35.97 +02 23 59.8 0.0088936853 -4.16824 6.8198 > 2005-Mar-01 04:41 11 06 35.73 +02 24 00.1 0.0088920132 -4.16676 6.8184 > 2005-Mar-01 04:42 11 06 35.50 +02 24 00.4 0.0088903416 -4.16529 6.8171 > 2005-Mar-01 04:43 11 06 35.26 +02 24 00.7 0.0088886707 -4.16380 6.8158 > 2005-Mar-01 04:44 11 06 35.02 +02 24 01.1 0.0088870003 -4.16232 6.8145 > > > > ------------------------------------------------------------------------- > Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: > http://www.satobs.org/seesat/seesatindex.html > > -- __________________________________________________________________ Bill Dillon Note that my email address has changed: Schlumberger-SIS dillon1@houston.oilfield.slb.com (713) 513-2162 __________________________________________________________________ ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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