Ariane 5 and ODD-star experiment.

Neil Clifford (
Mon, 7 Apr 1997 13:16:13 +0100 (BST)

Hello folks!

I have news of an experiment that may interest a number of you. 

Summary: In early March I was contacted by the Uffe Mortensen, Head of
the Mathematics and Software Division (ESA, ESTEC). The next Ariane 5
test flight will involve an experiment which aims to provide data
concerning orbital decay and de-orbiting trajectories from GTO
(geosynchronous transfer) orbits. This will involve both radar and
visual observation of various objects deployed during the mission - it
was suggested that subscribers to this list (hereafter refered to as VSO
[visual satellite observers] for the purposes of this experiment) might
like to participate in this activity.

Details: I enclose here a message I received today providing more
information concerning the experiment:

|>  Hi Neil,
|> my name is Gerhard Drolshagen and I work at the ESTEC establishment of ESA
|> in the Netherlands.
|> I am involved in some experiments which will likely be flown with the
|> next Ariane 5 flight.
|> I heard from our Head of division, Uffe Mortensen, that you are connected
|> to the VSO network of amateur astronomers.
|> I believe the upcoming Ariane 5.02 flight could be an interesting opportunity
|> for some optical observations. It is planned to use that flight and the
|> payloads to be released (inter alia) to study the capabilities of optical
|> telescopes for space debris observations.
|> Several objects of various sizes will be released.
|> The biggest is a cylindrical structure of about 2.5 m diameter and 2.5 m
|> height. We have painted it in black (25 percent) and white (75 percent
|> of surface area, 80 percent reflectivity) to have a well defined body for
|> optical observations. That should be easily visible
|> (I hope) with even relatively small telescopes. It is expected that also
|> the spinning or tumbling motion of the spacecraft can be seen and deduced as
|> it is covered with the  contrasting paint.
|> There are a few other smaller objects ranging in size from 2.4 X 1.5 m
|> to 1 X 0.8 m  or smaller. Those are mainly unpainted Aluminium on the
|> outside.
|> I will provide more detailed information on the geometries later.
|> All the objects will be in a Geostationary transfer orbit with a perigee
|> around 600 km, an apogee of 36000 km and 7 degrees inclination.
|> Launch is presently foreseen at 16 September 1997 but that date could still
|> be shifting (backwards).
|> The orbit has a period of about 10.6 hours what means that the objects will
|> be visible from different locations on the Earth for each orbit.
|> We hope to follow the objects over a long period but some  of the experiments
|> will only be active during the first week after launch and that is when we
|> would like to have as much observing support around the world as possible.
|> The locations of best visibilty of the spacecraft during the first week
|> will only be known after the exact time of launch has been fixed. That has
|> not yet happened but I will inform you once it is known.
|> I hope you and the VSO network will find this an interesting activity. It
|> will also tell you and us exactly what size objects can be seen at what
|> distance with a given size telescope.
|> Please let me know if you need further initial information. Perhaps you could
|> provide me at some time with a list of the main sites and telescope sizes
|> which are part of your observing network and which might participate in the
|> observation campaign.
|> Actually, we called the painted cylinder the 'ODD-star' experiment (ODD
|> stands here for 'Orbiting Debris Device').
|>   with best regards,  Gerhard Drolshagen

Suggestion: Would those persons interested in participating get in
contact with me? As indicated above I am looking for geographical
location with a description of available equipment. I can then channel
the information back to Gerhard (I shall attempt to act as some sort of

Bear in mind that these will be GTO objects. I don't know what the
geographical distribution of seesat-l subscribers actually is (but am
willing to bet a huge bias to N. America/W. Europe, with a few others
scattered across Australia/NZ/Japan/S. Africa) - ie the majority of this
audience will probably only be able to view these objects around apogee
and thus require telescopic aid (a quick calculation suggests that the
largest object may be around mag +13-+15 around apogee, climbing to mag
+5/+6 at perigee).

Looking forward to your suggestions etc,


Neil Clifford                                 <>