NEOTwIST: Changing the Spin State of (25143) Itokawa

Predicting the total momentum delivered onto a target asteroid constitutes one of the challenges of kinetic impactor-based orbit deflection methods. In spite of numerous laboratory experiments and considerable modeling efforts, uncertainties in the direction and magnitude of the momentum carrying material excavated during the impact remain uncomfortably large. Field-testing of kinetic impactors is, therefore, crucial to verifying ejecta models and credible momentum enhancement factor (β) predictions. The NEOTωIST mission concept could deliver such a validation by changing the spin state of the asteroid (25143) Itokawa. Targeting a well-characterized object off-center yields a change in the rotation state that is proportional to the momentum enhancement factor. Consisting of an impactor, a flyby vehicle and CubeSat chasers, the NEOTωIST concept would constrain β through direct observation of the ejected material, as well as through a complementary tracking of changes in the asteroid's spin state via ground-based observations. In this contribution, we show that the currently envisioned impact scenario would alter Itokawa's principle rotation period by several minutes - well above the detection limit of ground-based facilities. We, furthermore, present optimum potential impact locations on Itokawa that would allow for an accurate determination of the momentum enhancement factor. This information about the NEOTωIST concept is pre-decisional and is presented for planning and discussion purposes only.