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[vsnet-be 115] Galileo Data - delta Sco
Delta Scorpii Observations from the Galileo Star Scanner
Visual magnitude estimates from the Galileo spacecraft’s star scanner
of delta Scorpii are listed below. Over 6000 observations taken over 13
weeks have been distilled down to the daily averages (the 25 previous and
25 subsequent observations centered on midnight UT).
yyyy-ddd (UT) V(mag)
2002-285 1.97
2002-286
1.94
2002-287
1.94
2002-288
1.93
2002-289 1.93
2002-291 1.91
2002-292 1.92
2002-293 1.90
2002-294 1.88
2002-295 1.87
2002-296 1.86
2002-297 1.85
2002-298 1.84
2002-299 1.83
2002-300 1.82
2002-301 1.81
2002-302 1.80
2002-303 1.79
2002-304 1.80
2002-305 1.80
2002-306 1.79
2002-307 1.78
2002-308 1.78
2002-310 1.79
2002-311 1.80
2002-312 1.80
2002-313 1.80
2002-314 1.79
2002-315 1.77
2002-316 1.79
2002-317 1.80
2002-318 1.80
2002-319 1.80
2002-320 1.79
2002-321 1.80
2002-322 1.80
2002-323 1.80
2002-324 1.79
2002-325 1.79
2002-326 1.80
2002-327 1.80
2002-328 1.80
2002-329 1.80
2002-330 1.79
2002-331 1.78
2002-332 1.78
2002-333 1.79
2002-334 1.77
2002-335 1.78
2002-336 1.79
2002-337 1.79
2002-338 1.79
2002-339 1.78
2002-340 1.79
2002-348 1.79
2002-349 1.80
2002-350 1.80
2002-351 1.79
2002-352 1.79
2002-353 1.80
2002-354 1.81
2002-355 1.80
2002-356 1.79
2002-357 1.80
2002-358 1.81
2002-359 1.81
2002-360 1.82
2002-361 1.80
2002-362 1.80
2002-363 1.81
2002-364 1.80
2002-365 1.80
2003-001 1.82
2003-002 1.83
2003-003 1.82
2003-004 1.82
2003-005 1.83
2003-006 1.82
2003-007 1.81
2003-008 1.82
2003-009 1.82
2003-010 1.83
2003-011 1.83
2003-012 1.83
2003-013 1.82
2003-014 1.84
Some days are not reported due to gaps in Galileo’s telemetry.
The star scanner does not directly report visual magnitudes but rather
reports relative intensities which must then be scaled to a visual
magnitude. The starting point in the data was an observation of v = 1.97
on Oct 11 by S. Otero (personal communication). As a check, the
star scanner response was calibrated using about 10 stars of various
colors. Two stars spectrally similar to d Sco were then chosen ( b Cen
and b Cru) that had been measured by the star scanner just prior to the d
Sco observations. From this, visual magnitudes for d Sco of 1.976 and
1.959 were calculated which matches Otero’s observation well.
After this starting point was established, d Sco magnitude estimates were
calculated by comparing it to three calibration stars (a Cen, a Lup and a
Cep) all of which were frequently in the star scanner’s rotating field of
view during the entire period while d Sco data was gathered. Calibration
curves were generated for each star assuming that it was non-variable in
brightness. Each curve was checked by verifying that it could scale the
other two calibration stars to a constant mean intensity. These three
curves were then used to scale the d Sco raw data points into three sets
of visual magnitude estimates. At no point did a magnitude estimate
differ from the other two by more than 0.031 magnitude units.
The three sets of magnitude estimates derived from the three separate
curves were averaged. These averaged data were further smoothed by taking
the mean of the 50 of these points nearest to and centered on midnight
UT. These are the data listed above.
Note that the method used to compute the visual magnitudes relies on the
assumption that d Sco was not changing its color significantly during
these observations. The star scanner closely follows the B transmission
curve in the Johnson-Morgan UVB system.
For more information, visit the star scanner home-page at
http://www.mindspring.com/~feez
This work was partially performed at the Jet Propulsion
Laboratory, California Institute of Technology under contract to
NASA.
-Paul D. Fieseler
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