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Mission design 
ESA's Don Quijote is an asteroid deflection precursor mission, designed to assess and validate the technology that one day could be used to deflect an asteroid threatening the Earth... Overview ESA's Don Quijote mission consists of two spacecraft which are to be launched in separate interplanetary trajectories:
Mission objectives The primary objective of the Don Quijote mission is to impact the target Near-Earth Asteroid (NEA) and to be able to determine the deflection resulting from the impact. To achieve this, it will measure with extreme accuracy the asteroid's position in space before and after impact. There is also a secondary objective, involving the so-called Autonomous Surface Package Deployment Engineering eXperiment (ASP-DeX). In this experiment a small device, an Autonomous Surface Package or ASP, would be released from the Orbiter spacecraft while it's on orbit about the asteroid. It would then passively free-fall towards the asteroid surface after its release, and touchdown within a certain distance of a target landmark, most likely the crater resulting from the impact of the Hidalgo spacecraft.
In
addition, part of the mission secondary goals are to and study the
asteroid's surface chemical composition and the characterization of the
thermal and mechanical properties of the asteroid surface.
The mission of the Impactor spacecraft is a peculiar one: the spacecraft should remain in a dormant state during most of its lifetime until the last days of asteroid approach where the autonomous guidance takes over and targets it toward the asteroid. During the cruise phase only minimum functions are required but before the impact all the sub-systems have to be up and functional with high level of reliability. A major system design constraint is also on the spacecraft mass that (contrarily what normally is required) shall be above a certain threshold to achieve the required asteroid orbit deflection and lower than the launch system escape performance. In order to increase the impact mass, the propulsion module is not jettisoned at escape but is kept attached during the whole mission until impact as a ballast. The major design drivers for the Impactor spacecraft are:
The mass budget for the Impactor spacecraft is:
For the design of the Orbiter, a re-use of the SMART-1 bus was considered during the internal mission feasibility studies. Though this approach provides a good reference case to assess mission costs and the maturity of the technologies, there are some limitations, mainly given by the availability of a single PPS-1350 engine, a fixed Xenon tank capacity that limits the propellant mass, and finally a given bus structure. In order to accomplish the mission, some modifications need to be performed on the SMART-1 bus.
The seven years required mission lifetime for Don Quijote is far longer than the one of SMART-1 (2.5 years by design). However, an analysis showed that the SMART-1 design can in principle be compatible with the extended required lifetime considering the encountered radiation dose levels, the qualification of the equipment and the thrusters lifetime. The mass budget for the Orbiter spacecraft, with the extended payload set (see below), is:
Orbiter payload The payload of the Orbiter spacecraft plays a major role in the mission. Not only it will allow to charaterise the target and determine its position, shape, mass, and gravity field, but it will also meaure the deflection caused by the Impactor spacecraft to the asteroid.
A basic
payload (made up by the navigation camera, the Radio Science Experiment
and a LIDAR) addressing the primary objective of the mission would be
complemented by a set of scientific instruments dedicated to the
secondary mission goal, as shown in the accompanying figure.
The ASP
would be thus part of the payload of the Orbiter, which would carry and
deliver it to the surface at the end of the mission, from an orbit
about the asteroid. This approach has been taken to minimise the
uncertainties related to the orbiter operations during its deployment.
In the 2002 AT4 asteroid scenario, deployment would take place from an
orbit of 1 km in radius, a ΔV of 16 cm/s being required for the release
and deorbit of the ASP. The duration of the drift towards the asteroid
surface would be of around 2 hours and the impact velocity would range
between 11 and 21 cm/s. After deployment the ASP should reach
autonomously its preferred location, which would most likely be the
interior of the impact crater.
In addition to this the ASP would most likely carry a set of scientific instruments, including at least the following instruments:
Last update: 19 September 2007
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