I asked Jonathan McDowell about the value of tracking the Ariane for as long as possible.
He responded that it would be very useful to get as good an orbit as possible so that it can more easily be recovered when it returns to this neck of the woods in 2047.
The astrometry is being co-ordinated by Bill Gray at http://projectpluto.com and I urge anyone here, especially the asteroids people, to follow it as long as possible.