• development of a novel optical sensor architecture merging imaging technologies and time-of-flight measurements,


• applicability evaluation of the sensor for object relative robotic navigation according to space mission scenarios,


• design and realization of standardized assessment protocols reproducing reliably and realistically missions' conditions.

Figure 1. Typical application of the flash optical sensor: soft-landing.

Figure 2. Scanning versus flash LIDAR.

• complex optomechanical scanning sub-system is absent, allowing to reduce drastically 3D image acquisition time,
• matrix detector (or focal plane array) is used and coupled with the laser source modulated continuously by a pseudo-random sequence.

Figure 3. Main characteristics of the flash optical sensor architecture.

1. To provide specifications for flash optical sensor and define applicability assessment protocols extracted from the investigation of real exploration future missions term of requirement.


2. To design and assemble a prototype of the flash optical sensor obeying the specifications of point 1 and ready to be used in applicability test facilities.


3. To assess the operation and capabilities for relative navigation of the flash optical sensor in ground-test facilities (Figures 4 and 5) reproducing down-scaled dynamics and exploration conditions of missions with either soft-landing or docking phases.


4. To disseminate information including evaluation results on the sensor concept, the project approach in the interested communities and ensure the exploitation in terms of availability of the technology for implementation by European industry and research.

Figure 4. Schematic view of the Testbed for Robotic Optical Navigation (TRON) at DLR.

Figure 5. Free-range high speed testing at airfield near Bremen.

1. Derivation of the specifications of the flash sensor from missions’ terms of requirement while taking into account current limitations of the technologies entering in the imaging LiDAR architecture. Several planned missions have been investigated by the project team: Mars Sample Return, Marco Polo and Lunar landing scenarios.


2. Part of the preliminary design of the sensor prototype.


3. Description of the test facilities and definition of test plan.

• Extensive review of missions involving either rendezvous or landing.
• Following the extended review of missions’ scenari and requirements three modes of operation have been defined for the sensor. In short, they permit to optimize the use of the limited energy available for the sensor. This is especially important for the part of this energy that is converted in optical power by the illumination head. The general guideline is to maintain the optical power available in the smallest divergence angle to ensure the best possible signal-to-ratio on the sensor’s detector and consequently to maintain the statistical error of the measurement of the distance between the sensor and the target as small as possible.
• In close relation with the three modes of operation, a sensor architecture has been studied and confirmed. It is innovative compared with other flash sensor from the point of view of the controllable target illumination chosen (modulated continuous wave multiple lasers source) and the type of matrix detector used (integrated demodulation pixels).
• Elaboration of sensor models allowing at the same time full GN&C system simulation and the support of the design of the sensor. The definition of the model varies whether it is of interest for experts in image processing or GN&C systems (denominated imager model), or for scientists designing LiDAR systems (called performance model). For the first group it is capital to get an image at the output of the model while for the second it is more about calculating the optical power budget emitted by the laser head and then reflected back and detected by the sensor receiver.
• Determination and detailed description of the test facilities that will be used to assess the sensor’s prototype.

Expected final results and their potential impact and use

• To identify and summarize the key requirements coming from missions’ planners for future missions that might involve flash sensors.
• To derive from the missions’ requirements a concept for the flash sensor that may potentially fulfill them.
• To build a functional sensor prototype based on an innovative flash LiDAR architecture that can be tested on real GN&C testbenches.
• To demonstrate that this sensor architecture is applications for rendezvous and landing space applications.
• To generate a database of DEM coupled with trajectory data of the sensor for further investigations in future activities related to flash optical sensors. The aim is to constitute a database of 3D images acquired while the prototype is moved on test-benches to allow in the future the development of a complete system including software elements comprising for example algorithms for hazard recognition and detection, GN&C information extraction, craft attitude and motion compensation, etc.

Following the demonstration of applicability of the sensor architecture, the expected long technical and economic impact expected is to trigger larger development activities that would allow the flash technology to be further developed in Europe to a level comparable with the development of the most advanced flash solutions from the USA.

1. Development of more efficient and miniaturized continuous-wave laser head.
2. Development of imager technology for space and for long range applications. In FOSTERNAV, an imager developed for motion detection for video games or microscopy is used. New imagers with better sensitivity, in-pixel demodulation capability to extract distance from phase difference and able to sustain space vibrational, thermal and radiation should be developed.
3. Development of imager for any semi-autonomous or fully-autonomous systems such as driver assistance systems.
4. Development targeting a drastic miniaturization of system’s building-blocks such as: the opto-mechanical part (transmitter and receiver).
5. Development of the algorithms needed to process efficiently DEM and to allow data fusion of flash sensors and other GN&C sensors (IMU, accelerometer, passive camera, etc.). With such activities Europe might compensate seriously the backwardness observed with the most advanced nations.