Of some interest in the context of the Herschel/Planck "UFOs":

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THE ASTRONOMER Electronic Circular No 2553 2009 May 24 11.47UT
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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.
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(This is a paid-subscription-only electronic newsletter but given the intense
work many on MPML have put into following the HP aftermath, re-distributing
it "for scholarly use only" here seems more than fair. Comments welcome!)

Dan