ESA Document - Emits - ESA

s
4.5.2.1 Requirements and design drivers
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 367 of 422
The following requirements apply to the design of the GNC subsystem to fulfil the Rendezvous
and docking in Mars orbit:
• To execute a safe ascent of astronauts from the Martian soil to a parking orbit
• To be able to detect, follow, and dock with the orbiter
• To be the active chaser approaching a cooperative passive target (The term “passive target”
is meant from the actuation - position, attitude - point of view. Since the target – MAV –
will carry a beacon and be active from a RF point of view, the term “non-cooperative” target
is used instead.)
• The probability of collision between target and chaser shall be less than 0.001% over a 2
Earth days period
• To be able to establish the convenient selection of the MAV launch window
• To allow the possibility of re-trial the rendezvous in case of fail for up to 3 times
• To establish and perform the absorption of launch dispersions
• To be able to allow manual rendezvous overriding the automatic capability of the MAV.
• To be able to maintain at all times a three-axis stabilization
• To be able to accomplish all manoeuvres in less that 4 days (life support limit).
• To use as trajectory criteria the safety of the astronauts.
• To use as trajectory criteria the total rendezvous time (minimise the total time)
• To use as trajectory criteria the fuel consumption (minimum fuel consumption).
• Several sensors to be used are a radio frequency (RF) system, camera, and a LIDAR. For the
very far range a radio-frequency beacon (distances between 4000 km and 5 km) would be
used.
• The orbiter shall make use of data fusion between both sensors on the estimation process to
improve navigation accuracy
• The sensors camera and LIDAR shall be mounted fixed to the platform of the orbiter.
• The Camera shall be axially aligned with its docking pattern in the target during normal
operations.
• The accommodation of the LIDAR on the platform shall take into account the potential
dissymmetrical scanning capability of the instrument to enable tracking of the target as long
as possible (the origin of this remark is due to the fact that some LIDAR have dissymmetrical
scanning capabilities for example: Horizontal FOV: +/- 170 degrees, Vertical FOV: +/- 40).
• During the terminal phase of the experiment, the orbiter shall be able to impart a velocity
change manoeuvre of less than 1 m/s in any arbitrary direction without re-orienting its
attitude
The rendezvous mission arc should rely on:
• High-thrust chemical propulsion
• A fixed orbital altitude
• A maximum total maneuvering time
• A maximum total ∆V
• High accuracy sensing technology and high-precision actuation techniques