Industries take a closer look at the Don Quijote concept
The preliminary industrial assessments of the Don Quijote mission scenario, which began in April 2006, are now complete. Three independent industrial consortiums (led by Alcatel Alenia Space (I), EADS Astrium (D) and QinetiQ (UK)) undertook a study focussing on the mission feasibility and the design of both spacecraft, together with the equipment and operations needed for the characterisation of the deflection resulting from the asteroid impact.
The executive summaries can be downloaded here:
Don Quijote is a precursor mission concept aimed at preparing and testing technology that could one day be needed for a real mitigation mission. The scenario comprises two spacecraft; the Sancho orbiter and an impactor named Hidalgo. Sancho would be launched first and would perform many observations whilst in orbit around the asteroid. Following this Hidalgo would then impact the asteroid transferring enough energy so as to modify its trajectory by an amount that would be measurable through a second Sancho observation campaign (more information). Previous internal studies performed at ESA's Concurrent Design Facility (CDF). provided a baseline scenario for the two selected asteroids, namely 2002AT4 and 1989ML.
In addition, the Don Quijote mission scenario has an important technology demonstration component, including in particular:
- Autonomous guidance and navigation for interplanetary cruise,
- Autonomous low relative velocity rendezvous operations,
- High-speed impact targeting
- Autonomous close-proximity operations (including collision avoidance)
The industrial studies had the following detailed objectives:
- To critically review the mission requirements, assess their implications on the design of the flight elements and establish mission design solutions,
- To provide a design of all flight segment elements, down to equipment level,
- To identify the development risks and the critical technologies necessary for achieving the required design performance,
- To provide programmatic, cost and schedule data for the subsequent phases.
All three industrial assessments have identified feasible solutions for both the Orbiter and Impactor. Although at present Don Quijote is simply a mission concept, the main findings of the three studies are summarised below:
- Can reach both targets thanks to the flexibility provided by the electric propulsion technology,
- The designed Radio Tracking Experiment (RTE) can determine the asteroid orbit variation (semi-major axis) as a consequence of the impact with an accuracy of 10 m,
- Can be launched on a small launcher (such as Vega or Dnepr),
- Autonomous terminal guidance found to be feasible,
- Impact models show that the required deflection is achievable (on the limit for the 1989ML case),
- The ability of the Impactor to autonomously navigate onto the target using an optical camera does not represent a significant propellant requirement or drive the processing power of the spacecraft computer,
- Current technologies (camera, processor and thrusters) can achieve the requirements.
In general, the tasks of the two spacecraft would be too different to allow the use of a common platform for the mission. Nevertheless strong commonalities were established at equipment level that could be used for joint unit procurement for both spacecraft in order to reduce the overall development and manufacturing costs should this mission concept ever be taken further.
If the Don Quijote mission concept is to be further developed the following recommendations and suggestions were given by the three industrial consortiums:
- Select an easier target for the Orbiter to reach on the basis of engineering constraints. These should allow for shorter flight time to reduce operations cost and total radiation dose, for lower mass NEOs in order to enhance the deflection at a given impact velocity, and retain near-ecliptic target to minimize the propellant consumption.
- To maximise the probability of impacting the NEO, a precise surface model of the NEO must be generated from the Orbiter data, for use by the Impactor in terminal guidance phase.
- Flexible operations planning architecture should be envisaged and automated Radio Tracking Experiments (RTE) campaigns would allow a significant saving on ground station resources.
- Increasing the level of onboard autonomy can efficiently reduce overall mission costs, provided the technologies are ready and not fully developed in the context of Don Quijote.