The Dawn spacecraft is scheduled to arrive in initial orbit around Ceres in February 2015 with a final planned orbital change in December to reduce its orbit to a 700km altitude.

At present I can't find any speculative information about an extended mission to be conducted afterwards. Is this just NASA not doing anything that far in advance to avoid a potential letdown if hardware failures end up precluding something planned; or will Dawns fuel supply be too highly depleted to depart from orbit and go somewhere else?

Assuming it is able to depart from Ceres, does it have enough fuel to enter orbit around any additional asteroids, or would it be limited to doing an occasional flyby past a target of opportunity?


NASA doesn't seem1 to currently have any plans for an extended mission so far. See this screenshot from this page:

enter image description here

Also from Wikipedia:

An extended mission following the completion of the Ceres study is also possible, although unlikely, as greater scientific returns may be attained by spending more time at Vesta and Ceres. Although 2 Pallas would have been a feasible extended target for the originally scheduled launch date, launch delays have meant that this may no longer be the case. Fuel was not specifically allocated to break orbit from Ceres, so doing this depends upon the details of the flight to Ceres.

1: This is very important that it only seems this way. Politics, for example, might get in the way of disclosing openly displaying such info, and instead may hide the info deep in the jungle of non-Google-indexed pages.


Dawn uses an ion drive which is very efficient but does still require xenon as a reaction mass. Dawn started with 425kg of xenon and used about 275kg to get to Vesta and will use about 110kg to get to Ceres. The remaining 40kg is for stationkeeping and margin. Dawn does not, nor was it planned to have, enough xenon left after arriving at Ceres to depart Ceres.

  • $\begingroup$ See my answer below - there was a feasible extended mission target, but launch delays made it no longer feasible. $\endgroup$
    – Undo
    Jul 20 '13 at 16:27
  • $\begingroup$ Probably true, but as of today, there isn't enough reaction mass left to leave Ceres. $\endgroup$
    – Erik
    Jul 20 '13 at 16:30
  • $\begingroup$ Yep - 'Fuel was not specifically allocated to break orbit from Ceres, so doing this depends upon the details of the flight to Ceres.' $\endgroup$
    – Undo
    Jul 20 '13 at 16:31
  • 1
    $\begingroup$ On Ceres surface, Dawn's 800 some kilogram dry mass would weigh about 240 newtons. The thrust of the xenon engines are about .1 newton. With thrust/weight much less than 1, Dawn wouldn't be able to get off the surface. $\endgroup$
    – HopDavid
    Jul 7 '14 at 9:46
  • 1
    $\begingroup$ By my arithmetic, 40 kg xenon with an exhaust velocity of 30 km/s would be able to impart about 1.4 km/s of delta V to Dawn's 815 kg dry mass. Ceres' escape velocity at a 375 km orbit is about .4 km/s. Will Dawn still have 40 kg of xenon after parking in that low orbit? I imagine it'd have somewhat less. Dawn might have enough to achieve Ceres escape, but not much else. $\endgroup$
    – HopDavid
    Jul 7 '14 at 9:56

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