------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 2553 2009 May 24 11.47UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074 INTERNET: GUY@TAHQ.DEMON.CO.UK Backup: gmh@wdcc1.bnsc.rl.ac.uk WORLD WIDE WEB http://www.theastronomer.org ------------------------------------------------------------------- PHOTOMETRY OF OBJECTS IN THE HERSCHEL-PLANCK LAUNCH CONSTELLATION 1212 observations of objects that for the Herschel-Planck launch cluster up to May 21.35 have been reported on DASO Circulars #213-230. Initially there was some confusion about the precise identity of each the objects, firm identifications have now been published on DASO #226 (http://www.cfa.harvard.edu/~gwilliams/DASO/000000/DASO_000226.txt) The four brightest objects in the constellation are the Ariane upper stage and, forming a tight cluster about a third of a degree away, Herschel, Planck and the Sylda support that covered Planck during launch. Other, fainter, objects of uncertain identification, designated 2009-026E and 2009-02F, have been sighted around the Ariane upper stage: the latter has a large non-gravitational component of motion and has been shown to have separated from the Ariane upper stage shortly after launch. The photometry has been converted to R assuming a solar colour index of V-R=+0.53 and that unfiltered photometry is equivalent to R. Identifications and absolute magnitudes are in the table: Provisional Formal Absolute Designation Identification Designation magnitude Notes HP03 Ariane upper stage 2009-026C 28.7 Planck Planck Planck 29.2 HP02 Herschel Herschel 28.8 HP01 Sylda 2009-026D 30.3 HP04 Unidentified 2009-026E 30.7 Fading HP05 Unidentified 2009-026F 31.4 Fading Planck, the upper stage, the Sylda and, apart from one excursion in brightness that may have been due either to a small change of aspect angle, or to wrongly identified observations, Herschel, all show good fits to a pure reflection light curve of constant absolute magnitude. In contrast, 2009-026E and 2009-026F show a persistent fade consistent with a cross-section that has decreased in diameter by a factor of 2. Light curves for these objects can be found at the url: http://www.observadores-cometas.com/Herschel/Image_of_the_day/HER04_05-09 0522.jpg and an image archive at http://www.observadores-cometas.com/Herschel/images/images.htm The strong non-gravitational motion of 2009-026F and the fact that it separated from the Ariane upper stage shortly after launch suggest that this may be an object of low mass and large surface area, with high albedo, however the fading appears inconsistent with a refractory nature (such as shed insulation) unless there is a slow aspect angle change with time, something not seen in the upper stage or the Sylda. Herschel commissioning is proceeding extremely smoothly. The satellite is in excellent health and the four days of check-out observations have already been made. Real-time updates on the progress of Herschel testing can be obtained from the Herschel Twitter account (http://twitter.com/), ESAHerschel. The Herschel Team is buoyant at the tremendously successful progress to date and the success of the commissioning activities carried-out so far. TA METEOR COLUMN Tony Markham reports that his Internet address is changing and now with immediate effect to: tonymarkham832@btinternet.com Guy M Hurst