The European Space Agency is opting to send its first rover to the Red Planet two years later than originally planned.
After careful consideration, European and Russian officials have decided to postpone the launch of the second ExoMars mission to the next window of opportunity in 2020.
The first ExoMars mission launched this past March: the ExoMars Trace Gas Orbiter and the Schiaparelli lander are en route to Mars with an expected arrival in October. The second ExoMars mission, which will carry a rover, was originally set for launch in 2018.
The delay comes after the presentation of a detailed analysis of technical delays from a joint European Space Agency (ESA) and Roscosmos team in late 2015. The ESA press release that announced the decision cites the move as the “best solution” as they urged their “project teams to develop, in cooperation with industrial contractors, a new baseline schedule aiming towards a 2020 launch.”
Working a two-phase mission for ExoMars presents a unique challenge, as scientists and engineers have been working on the ExoMars Trace Gas Orbiter and the rover in parallel. "The same team that was working on the second mission was also working on the first," says project scientist Jorge Vago (ESA).
Holding to a 2018 launch would have forced the team to build the final spacebound rover before completing its prototype and finishing engineering tests: an unacceptable situation. According to Vago, officials pushed back the rover mission to reintroduce an acceptable schedule.
The ExoMars rover mission is an ambitious one. It seeks to deploy a Russian-built Mars lander, including a descent stage and surface science package provided by Roscosmos, as well as a European rover.
Set to launch atop a Proton rocket from the Baikonur Cosmodrome, the mission will be the first rover deployed on the surface of Mars by a space agency other than NASA. ESA's Mars rover will carry a suite of instruments specifically designed to answer the question of whether life ever existed on Mars. The ExoMars rover will be the first rover equipped with a drill capable of reaching two meters in depth (Curiosity's drill reaches only several centimeters in depth). The ExoMars rover will also be the first to carry a ground-penetrating radar package.
Though an early proposal called for a nuclear-powered rover similar to Curiosity, the ESA rover will use solar power. Russia certainly could have provided the plutonium — as they did for Curiosity — but European import restrictions on nuclear fuel made such a proposal problematic.
Four sites were considered for the ExoMars rover, with the equatorial Oxia Planum site still considered primary for the new launch date. But with the slip back to 2020, the Mawrth Vallis and Aram Dorsum locations are once again under consideration.
The ExoMars mission is unfurling in two stages. The ExoMars Trace Gas Orbiter launched from Baikonur on March 14, 2016. Currently in good health, the ExoMars Trace Gas Orbiter will release the Schiaparelli Entry, Descent and landing demonstrator Module (EDM) three days prior to orbital insertion. Schiaparelli will touch down at Meridiani Planum — the current home of NASA's Opportunity rover — on October 19, 2016, testing key technologies crucial to the delivery of the ExoMars rover to the surface in 2020.
Meanwhile, the ExoMars Trace Gas Orbiter will study the atmosphere of the Red Planet from high above. It will serve as a data link to Earth after the rover's arrival in 2020.
Getting to Mars
The two year delay is a function of orbital mechanics. Mars reaches opposition — its closest approach to the Earth — roughly once every 26 months. The optimal window to launch a mission, in terms of energy needed versus transit time, opens up a few months prior.
In 2016, Mars reaches opposition on May 22nd, and comes closest to Earth on May 30th, just 75.3 million kilometers (46.8 million miles) away. (The eight-day discrepancy happens because of the two planets' elliptical orbits: Mars comes to perihelion in October, while Earth heads towards aphelion in early July.) We're currently in a favorable cycle of Martian oppositions: the 2018 approach comes nearly as close as the historic close-approach in 2003.
Only the ExoMars Trace Gas Orbiter is making the trip to Mars during the 2016 launch window. Earlier this year, NASA decided to slip the Mars InSight launch, originally scheduled for March this year, back to 2018. The team cited time needed to fix a persistent vacuum leak on the Seismic Experiment for Interior Structure (SEIS) seismometer.
Another interesting mission may accompany Mars InSight's launch in 2018, as SpaceX recently announced plans to send its Dragon capsule to Mars during the same launch window. The feasibility of this plan rests on the first test launch of the company's Falcon Heavy rocket, set for this November. NASA's next still-unnamed Mars rover and the United Arab Emirates Mars mission probe will accompany the ExoMars rover during the 2020 launch window.
Caution is the watchword when it comes to Mars exploration, as the legendary “Galactic Ghoul of Mars” loves tasty spacecraft. It will be fascinating to watch as the ExoMars Trace Gas Orbiter and Schiaparelli lander both arrive at the Red Planet later this year, followed by the project's rover in 2020.