Determination of Rotation Axis Project (drap)

From: Bart De Pontieu <BDP_at_MPE.MPE-GARCHING.MPG.DE>
Date: Mon, 13 Mar 1995 17:03:13 -0500

I would like to start a project aimed at determining the rotation axis of
a flashing satellite. The project would involve simultaneous timings of
as many flashes as possible by observers located at different sites.

Using these simultaneous timings it should be possible to determine the
rotation axis of a flashing satellite rather accurately. The experiments
in the last two months have shown promise (see my message on the Sampex
rocket and also the article in Flash 90), but have also demonstrated the
need for simultaneous observations.

Here are some details of what the project would be like :

1. The observer needs instruments that allow the accurate storage of
several dozen times (stopwatch with a memory, or tape-recorder),
as well as an accurate time signal. Accuracies of 0.1 seconds in
absolute time should be the goal. We need observers that are not too
far away from one another, since they need to be able to see the same
satellite at the same time. They should also not be too close to
one another, since they have to view the satellite in as different
geometries as possible. E.g. one of the observers sees it as a north-south
pass in the west, and the other sees it in the east.

2. One or several objects should be the focus of this project. Preferrably
one of the objects should be a payload with the following qualifications :

- active, so that the orientation of the rotation axis can be found out
  from the owners of the satellite (this need for information from the
  owners probably eliminates military satellites :-) A scientific satellite
  is probably better suited.

- the satellite should not be too faint and should have an easy flash pattern.

- the payload should preferrably be tumbling end-over-end and cylindrical.
  If that's not possible (i.e. if it's spinning, as lots of payloads do)
  the payload should have highly reflective booms that cause the flashes.

I have no idea if an object with the above qualifications exists. I need
help here. Anyone?

The goal of having this 'control' satellite is to check the validity of the
method used to determine the rotation axis.

The other satellite(s) followed in this project should be :

- bright

- nice flashers with an easy flash pattern, i.e. preferrably not too
  many secundary maxima.

I have not been active enough in observing during the last year to make
a decision on which objects belong to this category, so I would welcome
suggestions from the observers amongst you.

3. I can guarantee the subsequent analysis of the data using the se-software
I've developed. Coordination of the project could be done over seesat-l,
or personal mail, depending on the number of participants. The ultimate
goal of the project is to determine and understand the motion of the
rotation axis as a function of time. A secondary goal is to check the
predictions of the eddy-currents theory of the braking of the rotational
motion of cylinders in orbit (as put forward by Patrick Wils, and as it
was 'published' partially in Chapter 7 of the Introduction to Artificial
satellite Observing brochure). Full credit will be given to the observers
should the results of this project be worthwile and get published in a

I hope some of you will find this proposal interesting enough to
discuss it (on seesat-l, preferrably) and perhaps even participate in it.
I look forward to your reactions.

  Bart De Pontieu
Received on Mon Mar 13 1995 - 17:38:52 UTC

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