Grant, The upper stage was 16.5 last night. It will be passive now so optical astrometry is useful to determine where it is going. JWST will be injected into a halo orbit around L2 and will require periodic station keeping to keep it there. Since L2 is unstable the upper stage will move off into a heliocentric orbit with a period of around 380 days. Using astrometry from Peter Carson and myself I’ve integrated this forward and it is likely to return to the Earth’s vicinity in the summer of 2047 when it will be around mag 20 (see plot attached). The more accurately we can get astrometry as it departs the better we can predict where it will be in 2047 so surveys in 25 years time will know what it is.
