Mars Rover’s Instruments are in fact a US-Europe joint effort...
Both China’s Tianwen-1 mission and the UAE’s Hope Orbiter have successfully set off on their respective journeys to Mars in the last few days. Within a week, Nasa’s Mars 2020 mission is due to do the same, taking advantage of a small window where Earth and Mars are closer together than normal (this happens every 26 months). With China, the Middle East and USA represented, you might be forgiven for thinking Europe is sitting this round out. Not so – researchers from some of Europe’s top universities and research institutes have contributed to Nasa’s mission to land a new Mars rover on the surface in order to search for signs of historical life and help prepare for future manned missions.
The new Mars rover, Perseverance, is more than double the size of its circa-2011 predecessor Curiosity (which is still exploring the Martian surface). Perseverance includes 23 separate instruments used for a variety of tasks. Many of these instruments were developed by international teams of scientists from the US and across Europe.
The rover’s “head” contains Mastcam-Z and SuperCam instruments.
Mastcam-Z was developed by a mostly US-based team but in collaboration with scientists from UK, Austria, Denmark, Germany, and Canada. This stereo camera is the rover’s main imaging system and can zoom, focus, and take 3D pictures and videos to allow detailed examination of distant objects, including surface objects and features in the atmosphere. It’s mounted on the mast, 2m above the ground so should get a good view! It will collect about 148 megabits of data per sol (Martian day) – or about 2 megapixels per image.
SuperCam examines rocks and soil with optical cameras and laser spectroscopy – it can identify a rock the size of a grain of salt from 7 meters away. SuperCam will be looking for organic compounds as well as rocks, that could indicate historic Martian life. It uses the same laser induced breakdown spectroscopy capability as Curiosity, but can also perform additional types of spectroscopy that can provide mineralogy and molecular structure information. Many of the team members who worked on this system are from research instates in France and Spain, as well as some from Denmark and USA.
On the rover’s “body” are RIMFAX, MEDA and MOXIE systems.
The Radar Imager for Mars’ subsurFAce eXperiment (RIMFAX) team is led by researchers from the University of Oslo, and the team is from various Norwegian institutes as well as the US and Germany. This instrument is a ground-penetrating radar (150-1200 MHz) that will take a look at geological features below the Martian ground for the first time. It can “see” 10 metres into the ground, or more, depending on the material.
The Mars Environmental Dynamics Analyzer (MEDA) will investigate and record Martian weather, and the amount and size of dust in the atmosphere. It has two wind speed and direction sensors and five air temperature sensors, as well as sensors for radiation and dust, relative humidity, infrared and pressure. MEDA’s team is primarily from different research institutes in Spain, but also the US, Italy and Finland.
MOXIE, also known as the Mars Oxygen In-Situ Resource Utilization Experiment, will generate oxygen from carbon dioxide in the Martian atmosphere (the atmosphere is 96% carbon dioxide). This is a test run for equipment that may support future manned missions – teams will not only need oxygen for breathing, but also as rocket fuel to return home. The main part of MOXIE’s team is in USA, but it also includes collaborators from the UK and Denmark.
The rover’s robotic “arm,” home to PIXL and SHERLOC, will be used for drilling samples of Martian rock.
SHERLOC is short for Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals. This instrument uses spectrometers, a laser and a camera to look at rock samples to look for signs of historical life. SHERLOC’s systems were developed by a team mostly from US institutions, but with a couple of collaborators from Germany.
PIXL, Planetary Instrument for X-ray Lithochemistry, includes one collaborator from Denmark in its US-based team. PIXL uses an X-ray spectrometer to identify chemical elements in samples plus a camera that takes pictures of rock and soil textures to identify them.
EE Times Europe spoke to space electronics expert Minal Sawant, systems architect and marketing lead for space applications at Xilinx, to find out more about some of Perseverance’s electronic systems and the challenges they face.
FPGA maker Xilinx has long served the space market, and has parts in SHERLOC and Mastcam-Z (first- and second-generation Virtex products) and PIXL (Virtex 4). The company’s FPGAs are also used in the rover’s Electra-Lite UHF radio transceiver for relay telecommunications and navigation, and the spacecraft’s radar terminal descent sensor (TDS), a Ka-band radar system that provides range and velocity measurements from the moment the heatshield separates in the atmosphere to the moment the rover lands on Mars.
“Part of the reason they still use our older generation is if you have an instrument that has already been designed, JPL and Nasa don’t change the design too much,” explained Sawant. “They just add more different instruments – so if its design was already done with Virtex 2, they just take the same design and rebuild it for the next generation without having to redesign everything. So that’s why you see our Vertex 2s are still on [the rover]. We have Virtex 4 and Virtex 5 product on it too; as new boxes are designed, they’ve been using the latest generation products.”
Notably, the Virtex 5 is used in the lander vision system (LVS) as an image co-processor and as an interface for the camera and IMU (inertial measurement unit). According to Xilinx, running the visual odometry algorithms on previous generations of lander (Spirit or Opportunity, circa 2003) with their 20-MHz RAD6000 CPU meant algorithm took 160 seconds to estimate a relative pose change. On Perseverance, the visual odometry will be split between a faster 200-MHz RAD750 CPU and Virtex 5 FPGA, and the algorithm takes 8.8 seconds, an improvement of 18x.
A lot of engineering goes into making electronics resistant to radiation in space, and qualifying them, a process which takes 12-18 months.
“We built some hardness into the [Virtex 5] silicon that ensures that it doesn’t flip in a radiation environment,” she said. “The part can absorb radiation and not lose its propagation delay characteristics or increase in current, which could eventually lead to a functional failure… withstanding one mega rad total dose means it can go into any deep space application.”
Ceramic packaging is also typical for space chips, as it helps mitigate shock and vibration experienced during launch, not to mention G-forces. Space parts also experience extreme temperature cycling – the surface of Mars varies between about +20 to -150 °C, for example – and the extreme cold of outer space. While the various electronic systems on board Perseverance have heating and insulation systems to protect them from the worst of the Martian cold, ceramic chip packaging helps.
If all goes to plan, Perseverance will be trekking across the surface of Mars for years to come – just like its older brother Curiosity, who is still sending back pictures after 8 years in service so far.