Written for the E&T magazine
Only one country has so far managed to land objects on Mars successfully – the USA. Not wanting to get left behind, Europe is building its own rover – the ExoMars. Its three prototypes are currently roaming a mock section of Mars built at Airbus’s facilities in Stevenage, UK.
Peering through the large windows that flank the corridors inside the Airbus Defence and Space complex in Stevenage, Hertfordshire, feels like entering a science-fiction movie set. Each of the metallic blocks glittering under the lights within enormous clean rooms will, in the not-so-distant future, shoot off towards the sky aboard a rocket reaching locations too distant for most humans even to comprehend.
Among the line-up of commercial telecommunication satellites, designed to reach a geostationary orbit about 36,000km away from the Earth’s surface, are some true pioneers. They may look quite the same as their serially-produced counterparts, but for the engineers involved they represent the real frontier of technology development.
“The one in the back is Solar Orbiter,” says Ralph Cordey, head of science, pointing towards a cube-like satellite at the end of the hall as we stop on a small visitors’ gallery overlooking the clean room. “It will orbit around the Sun closer than any mission before; it will have to withstand enormous temperatures.”
Technicians are working on Lisa Path Finder – an unusually shaped hexagonal spacecraft designed to measure gravitational waves, the ripples in space-time predicted in Einstein’s theory of general relativity.
However, the reason for my visit hasn’t yet made it into the clean room. In fact, its assembly will require the strictest regime and Airbus will need a dedicated clean room, cleaner than clean, to prevent it spreading earthly bugs at its destination – Mars.
The spacecraft I have come to see is having its design fine-tuned by engineers, driving its three prototypes across a giant sand pit, or should I say a Mars yard, which was opened a couple of months ago in Stevenage.
The sand-filled hall, which has rocks of different shapes and sizes scattered around, represents the Martian surface as we know it from images provided by vehicles that have already made it to Mars.
Searching for signs of past and present life
The ExoMars mission, approved by the European Space Agency (ESA) in 2005 and originally in cooperation with Nasa, is Europe’s second shot to land an object on the Red Planet’s surface. The first was the unfortunate British Beagle 2 lander, which failed to match the success of its parent spacecraft – orbiter Mars Express – and was lost during the landing attempt in 2003.
If successful, the ExoMars rover will land on Mars in January 2019 to search for signs of past and present life using its two-metre sub-surface drill. The drill, the researchers say, is the key instrument for the success of the ExoMars mission, as traces of Martian life will have most likely survived below the planet’s torrid surface.
“The surface environment of Mars is very harsh and it’s not a good place for chemical markers of life to survive for long periods of time,” explains Cordey. “The reason it is harsh is because Mars lacks a magnetic field. The Earth is protected from the radiation coming from the Sun by its magnetic field. That’s not true of Mars. Its surface is subject to extremely strong cosmic radiation, to particles, to ultra-violet radiation. It’s chemically very reactive as well. It’s not a good place for the survival of chemicals.”
However, there is no sign of this drill on any of the three prototypes I can see roaming around the Mars Yard at modest speeds that will amount to no more than 90m a day once on Mars. The scientific instruments, developed by ExoMars project partners around Europe, will be mounted onto the final rover before final testing.
For now, the team still has about a year and a half to refine the rover’s design to address the major technical challenges it faces – and there are quite a few of those.
Bruno, Bridget and Brian
With about 56 million kilometres between Mars and Earth at their closest and a mind-boggling 401 million kilometres at their furthest, any signal travelling from Earth to Mars would take too long for direct steering of the rover by Earth-based controllers.
The 300kg robot, about a third of the mass of the current Mars exploration superstar Curiosity, will therefore have to be highly autonomous, capable of making its own decisions to avoid disasters.
“Autonomy is really the key,” says Cordey. “That means allowing the rover enough knowledge of its own environment and of itself to be able to control itself, at least for going certain distances on Mars. It has to be able to look after itself, to ensure it is not going to hit obstacles or do something that would be potentially damaging.”
The rover, equipped with a stereoscopic eye-like camera on its long, thin metal neck, will be exploring the environment in real time, creating a 3D map and analysing the terrain.
“We will give it a goal and it will survey its terrain, calculate what’s in front of it and then pick the best route to drive to the goal and let us know once it gets there,” explains ExoMars structural engineer Abbie Hutty.
“We have to develop all the thinking processes, all the perception processes to make sure that our rover can see what’s in front of it to accurately build that map where it can or can’t travel and then pick the best route through. It’s going to be a really smart beast,” she says.
The three rovers I see, fondly named Bruno, Bridget and Brian, represent various steps on the way towards the final abilities of ExoMars not only autonomy-wise, but also when it comes to the undercarriage and wheel design or mass. No detail can be left unassessed as the €1.2bn venture will get only one shot at success.
“There are several really challenging aspects about the mission we don’t normally have on spacecraft flights,” explains Hutty. “For a start, there is the landing case. We are not normally doing that because we usually stay in space with satellites.
“Once you are on the surface it is not just that harsh landing, it’s the environment. There are really low temperatures, which pose structural challenges because materials don’t usually have to perform in those temperatures. We have to develop new materials and new systems of materials.”
There’s no doubt that going to Mars is a risky venture. Not only had the UK failed with the Beagle 2 lander, the Russians have a staggeringly poor track record with the Red Planet. Starting in the late 1960s as the former USSR, Russia tried to send 21 spacecraft to Mars, 18 of which failed in various stages. Of the three Soviet landers sent to Mars in the 1970s, none survived the landing and the ambitious Marsokhod, with a planned sample return mission programme, had to be cancelled as a super-rocket, designed to launch the heavy spacecraft, never performed a successful flight.
Probably the most epic and high-profile of Russia’s Martian disasters was the 2011 Fobos-Grunt fiasco. The project, intended to restore the reputation of Russia’s space industry as the world’s leader, was meant to land the first ever spacecraft on Mars’s moon Phobos, retrieve a rock sample and bring it back to Earth. However, the venture ended only a couple of hours after launch when an autonomous propulsion unit derived from the Fregat, or upper stage of the rocket, failed to ignite for its second burn.
Instead of shooting off triumphantly towards Mars, the ill-fated spacecraft remained trapped in the Earth’s orbit and eventually came crashing down into the Pacific Ocean, sparking panic because of the 7.51 metric tonnes of highly toxic hydrazine and nitrogen tetroxide on board.
The participation of Russia in the ExoMars project may raise concerns. In 2012, Nasa pulled out of the mission after its budget had been cut. ESA then turned to the Russian Federal Space Agency, commonly called Roscosmos, to save the project.
In March 2013 Russia became a full partner in the ExoMars mission, committing to provide the two Proton launchers needed to deliver to Mars not only the rover but also two stationary landers and an orbiter to secure communications. Russia will also develop a landing system to lower the rover onto the Martian surface, which will be tested during the first of the two ExoMars launches.
Other countries have also struggled with Mars. Even Nasa, so far the only conqueror of the Red Planet, lost the 1999 Mars Polar Lander, as well as two Deep Space 2 penetrators. Its 1998 Mars Climate Orbiter famously burned during its descent through the Martian atmosphere after confusion between Nasa and Lockheed Martin engineers over units of measurement.
With only two years to go before the first of ExoMars’ planned launches, scheduled for October 2016, questions still remain.
ESA has struggled to plug the funding gap after Nasa’s withdrawal and had to increase its financial contribution beyond original limits. Earlier this year, Russian Space Web, a site dedicated to the news and history of Russian space exploration, speculated that whereas the first part of the mission – to be launched in 2016 – was on schedule, the second part including the rover was facing a two-year delay or even a cancellation due to cost over-runs. The reason for the delay was supposed to be the innovative landing system jointly produced by Russia and Europe.
Although space cooperation has so far been exempt from sanctions against Russia in the wake of the crisis in Ukraine, further uncertainties remain as the political tension between the West and Russia grows ever deeper.
ExoMars – all systems go
The Trace Gas Orbiter, to be launched together with the Entry, Descent and Landing Demonstrator Module (EDM) in January 2016, will survey the atmosphere of Mars from its orbit about 400km above the planet’s surface. It will search for signs of methane – a tell-tale sign of life. The satellite will also provide communication links between Earth and both landers.
The EDM will be carried to Mars aboard the Trace Gas Orbiter. The lander, called Schiaparelli after Italian astronomer and science historian Giovanni Virginio Schiaparelli, will enter the atmosphere of Mars at an altitude of 120km and a speed five times greater than the speed of sound. It will test the landing concept for the rover, slowing itself down to Mach 2 before deploying its parachute. Schiaparelli will activate its Doppler radar altimeter and velocimeter to locate its position before soft-landing in a controlled manner, braking with a liquid propulsion engine.
Schiaparelli will remain active for two to eight days to measure wind speed and direction, humidity, pressure and surface temperature, and determine the transparency of the atmosphere. It will also take the first measurements of electrical fields at the planet’s surface.
The ExoMars rover will be launched with a surface platform inside a single aeroshell two years after the first mission. Shortly before reaching the Martian atmosphere, a descent module will separate, performing the same landing manoeuvre as tested by the EDM. After touchdown, the rover will depart from the surface platform to start its scientific mission. The ExoMars rover will generate its electrical power using solar panels.
What has previously landed on Mars?
Viking – 1976
Seven years after conquering the Moon, Nasa won the race to land a spacecraft on Mars and has stayed the unquestionable leader of Mars exploration ever since. The two Viking probes entered orbit around Mars in 1976, each releasing a lander module that made a successful soft landing on the planet’s surface. The two missions returned the first colour pictures of Mars and provided a wealth of scientific information.
Mars Pathfinder – 1997
The Mars Pathfinder spacecraft, carrying a small rover called Sojourner, landed on Mars in 1997. The spacecraft only remained active for three months but provided over 17,000 images of the Martian’surface. The tiny Sojourner, the first Martian rover, was able to travel a few metres around the landing site.
Spirit and Opportunity – 2003 and 2004
Spirit and Opportunity were launched as part of the Mars Exploration Rover Mission. Delivered separately to the Martian surface about six months apart, both vehicles exceeded their designed three-month life expectancy multiple times. Spirit’s contact with Earth only ceased in 2010 while Opportunity continues surveying the Martian terrain in the area of Meridiani Planum. The two spacecraft were reportedly contaminated with the Bacillus safensis bacterium before launch and might thus have brought life to Mars.
Phoenix – 2008
Phoenix was a stationary lander equipped with a robotic arm, the first spacecraft to successfully land near the North Pole of Mars. Although the mission only lasted about four months, it was deemed successful as it completed all of its scientific goals.
Curiosity – 2012
The superstar of Martian exploration, nuclear-powered Curiosity, part of the Mars Science Laboratory mission, landed in Mars’s Gale Crater in what engineers described as seven minutes of terror in August 2012. The landing, demonstrating a previously untested concept was anxiously watched by global audiences. Curiosity is about twice as long and five times as heavy as Spirit and Opportunity and carries over ten times the mass of scientific instruments.
ExoMars – Mission timeline
7-27 January 2016
The Trace Gas Orbiter and the Entry, Descent and Landing Demonstrator Module (EDM) launches on a Proton rocket in a mated configuration.
16 October 2016
The Trace Gas Orbiter and EDM arrives at Mars. The orbiter releases the EDM three days before reaching the Martian atmosphere.
19 October 2016
The EDM performs the demonstration landing, verifying mechanisms to be used to lower the rover safely two years later. Throughout its descent, the EDM will keep sending data to Earth through the Trace Gas Orbiter and Nasa’s Relay Orbiter.
23 October 2016
The EDM’s mission will end within eight days after the landing.
25 October 2016
The orbiter will be re-directed into its final orbit 400km above the Martian surface.
The Orbiter commences its scientific mission, searching for gases that could signal the existence of life.
The ExoMars rover is enclosed in a landing platform launched aboard a Russian-made Proton rocket.
The aeroshell carrying the rover and the landing platform arrives at Mars. The descent module will separate from the carrier shortly before reaching the Martian atmosphere. During the descent phase, a heat shield will protect the payload from the severe heat flux.
Parachutes, thrusters, and damping systems will reduce the speed, allowing a controlled landing on the surface of Mars. After touchdown, the 207kg rover will be released from the landing platform to start surveying the terrain. The rover’s mission will last at least six months.
Expected end of operations of the Trace Gas Orbiter.