an unusual observation

Johannes Mueller (
Sat, 2 Aug 1997 21:42:20 -0400

Hello everybody,

on 29 July 1997 at 20:44 UTC my friend Josef Mueller and I made an
unusual observation from Irmtraut/Germany (50.55417N 8.05917E)
through 10x70 binoculars. An object was moving slowly in the eastern
sky from the constellation Cygnus down to the horizon.

Its brightness changed from an estimated magnitude between 3 and 4 to
invisibility about 2 to 3 times per second. The brightness did not
vary gradually between minimum and maximum but abruptly, much like a
stroboscopic lamp. The colour of the light was definitely more =

blueish than with satellites or rocket bodies who often have a =

slight yellow or even reddish tint.

The object has been identified unambiguously by Bruno Tilgner in
Paris, France as COSPAR 86061A (EGP). According to "The R.A.E. =

Table of Earth Satellites 1957-1989" this satellite, also called
"Ajisai" (hydrangea in English, Hortensie in German, hortensia in =

French), was launched on 12 August 1986 into a 1479 km x 1497 km
orbit with 50.01 deg inclination and an estimated lifetime of =

10 000 years. The satellite is a sphere of 2.15 m diameter and 685 kg
mass. It is an experimental geodetic satellite and to this effect it
is outfitted with laser retroflectors. In Ted Molczan's elements list
its standard magnitude is given as 6.7.

We believe that we saw reflected sunlight at a very favourable phase
angle. The light flashes could be explained by the rotation of the =

satellite and the colour of the light by the optical properties of =

the retroflectors.

We wonder if somebody else has made similar observations of satellites
with retroreflectors and if our explanation appears plausible. It
would also be interesting to know if such satellites are still in use
by laser ranging stations so that one might be able to see a =

reflected laser beam.

On behalf of the "team"

Johannes Mueller

Johannes Mueller Irmtraut/Germany
Location: 50d33m15s N, 8d03m33s E, 354m, UT+2=