The map of the asteroid

Only in 2022 will the Marco Polo-R mission have its first moment of fame with the launching of a space probe from the base of Kourou, in French Guiana. The target is a 450 metre diameter asteroid called 2008 EV5. For ESA, this is an opportunity to strengthen its position in Space. For INESC TEC, in Porto, the Marco PoIo-R can be the first real test for a 3D LIDAR device, which can be used to measure distances, map objects and surfaces in 3D, obtain the necessary coordinates for landing and collect samples. «We will create a consortium with EFACEC and participate in a call that the ESA will be launching for technology providers», explained Francisco Araújo, a researcher at INESC TEC’s Optoelectronics and Electronic Systems Unit.

Today, INESC TEC’s lab already has a 3D LIDAR prototype with enough capacity to produce 3D maps in a process that is similar to sonar, but using lasers instead of sound waves. At first, the goal with the 3D LIDAR was to create a solution that could be useful to analyse the quality of foods. Later, after talking to João Pereira do Carmo, who works on Spatial Technologies at ESA, Francisco Araújo realised that the solution developed by INESC TEC could also be used in space missions. It was there that the INESC TEC researchers decided to apply to the Innovation Triangle Initiative, promoted by ESA, to guarantee funding to develop the first prototype.
«Initially, the idea was to develop a LIDAR for a mission to Mars, but then there was this opportunity for us to apply to provide this solution for the Marco Polo-R. This doesn’t mean that the solution can’t be used later in missions to Mars», Francisco Araújo added.

The choice of the LIDAR supplier should be made available in the first trimester of 2014. At INESC TEC everyone is optimistic: competition worldwide is scarce, and it would force the ESA to go to North-American companies. Moreover, the prototype created at the Portuguese lab uses a single pixel sensor that can generate images where resolution is 300 times higher than that achieved by LIDAR systems used today in space missions. «Moreover, it is not necessary to perform sweeps on all points, which makes it easier to obtain information at a given location. Another important aspect is that the information is already compressed and requires less broadband to be transmitted», explained Filipe Magalhães, a researcher at INESC TEC’s Optoelectronics Unit who developed the technology used in the LIDAR prototype during his PhD.

João Pereira do Carmo recalls that the technology created by the institute located in the city of Porto is advantageous because it can be used «in various space applications»: «It can not only help us select the safest landing zones, but also navigate the rovers on planet surfaces or facilitate satellite detection and rendezvous – the specifications of each system vary significantly in accordance with the requirements of each application. In certain applications, the system’s design can be determined by the intended spatial resolution, by the maximum detection distance or by the speed at which the image is obtained». 

FOR SPACE AND OTHER APPLICATIONS

The prototype designed at INESC TEC was developed with components currently used in electronics labs and factories, and its total cost is about 30 thousand Euros. The INESC TEC researchers admit that this price can be competitive for the automotive, mobile phone or projector industries, but that will not be the determining factor for ESA’s decision. «In a space mission, it is necessary to develop electronics for each function, to have more resistant components and to create a more compact solution», Francisco Araújo pointed out.

Today, anyone can see the LIDAR operating at INESC TEC’s optoelectronics lab: the device emits laser pulses with a repetition rate of 50 MHz and a duration of 50 picoseconds. The short duration of each pulse is easily explained: the LIDAR can map a location or an object by capturing the reflexes that the pulses produce on the different surfaces. Because the duration is short, the system will not confuse the original pulses with the reflection of the pulses on the surfaces.

The INESC TEC researchers believe that they can develop a LIDAR capable of emitting 10 metres wide by 10 metres long projections, which can represent a space with resolutions of 1024 by 768 pixels. By combining pixels that switch on and off alternatively and randomly, the LIDAR can obtain the necessary 3D coordinates to map surfaces and objects.

The INESC TEC researchers highlight that, with the due adaptations, this technology can also be used to analyse works of art or to predict the occurrence of avalanches. «This technology can be deployed in conjunction with radiation technology, which operates with frequencies in the order of THz, to find what is under the surface of each mapped area», Francisco Araújo concluded.

WHAT IS A LIDAR MADE OF?

LIDAR means Light Detection And Ranging. Using a LIDAR it is possible to map an object or a surface in 3D, or conduct a spectral analysis of light and find phenomena which are not visible to the human eye (examples: verify the presence of pesticides or fruit ripeness at an agriculture unit). To head over to space, INESC TEC’s LIDAR will have to be perfected: according to ESA’s requirements, the LIDAR cannot weigh more than 4 kilos, and it should fit in a 25 by 30 x 25 centimetre box. Its energy consumption cannot exceed 35 W. The LIDAR should be able to take measurements at maximum distances of 5 kilometres, collect information to map the entire asteroid at a distance of 250 metres, or even collect the necessary information to choose the best landing zone for the probe that will be collecting samples.

Exame Informática, February 2014