PARIS — Europe’s first Mars rover and lander, ExoMars, is increasingly likely to be launched aboard a Russian Proton rocket as part of a no-exchange-of-funds agreement with the Russian Space Agency, a decision that would permit European scientists to launch most, if not all, of their proposed experiment package, European Space Agency (ESA) Science Director David Southwood said Jan. 16.

Speaking with reporters here after addressing the inaugural ceremony of the International Year of Astronomy at Unesco headquarters, Southwood said he is meeting with Russian Space Agency officials in the week of Jan. 19 and that a broad collaboration with on Mars exploration is at the top of the agenda.

“We are working on agreements with NASA on long-term Mars exploration and I would like to see what the Russians want to do along these lines,” Southwood said. “But underneath this broad dialogue there is clearly” the ExoMars issue.

European scientists and an industry team led by ThalesAlenia Space have produced an ExoMars proposal that would cost around 1.2 billion euros ($1.62 billion) including some 150 million euros for a launch aboard 5 rocket.

ESA governments have told the agency they cannot afford to spend more than 1 billion euros, and perhaps less, on ExoMars, now scheduled for launch in 2013. They asked ESA managers to seek participation outside United States and

Launching ExoMars aboard a Proton vehicle from ‘s BaikonurCosmodrome would spare ESA the additional cost of having to modify ‘s French Guiana to handle nuclear heaters needed to keep ExoMars’ payload warm on the martian surface.

ESA has been negotiating with Russian companies on the commercial purchase of nuclear heaters.

Southwood said the Russian Space Agency already has agreed to finance a preliminary design review relating to a Proton launch of ExoMars, a decision that ESA officials take to mean is serious about offering Proton for the mission.

A decision is likely by midyear, Southwood said.

ESA’s Science Program Committee, which decides what science satellites will be built within ESA’s budget and technology guidelines, is set to meet the week of Feb. 2 to begin the process of selecting two so-called Medium-class and one Large- class science mission for launches between 2017 and 2020.

The current six Medium-class missions in the competition all have costs estimated at well above the 300 million euro limit. Southwood said he assumes that the agency can take advantage of delays in Large-class mission selection to build two Medium-class missions, each costing around 420 million euros. Whether they will be built at the same time or staggered by a couple of years is a decision the Science Program Committee likely will make this year.

ESA and NASA are jointly reviewing a possible Outer Planets mission to either Saturn or Jupiter. The two agencies are scheduled to decide by the end of this month which will be selected. The winning choice then will be placed into ESA’s usual competitive process in which scientists, and ultimately the Science Program Committee, determine a winner for launch around 2020. Southwood said ESA’s contribution to this mission, if it is selected, would total around 650 million euros.

A review of ESA’s science budget in 2006 proposed that the Science Program Committee agree to make the difficult decision to stop spending on missions that run well beyond their scheduled in-orbit lifetimes. The review argued that ESA was at risk of draining its budget on missions that, while of interest, had exhausted most of their science potential.

The result has been a decision to classify in-service missions by several criteria, with an automatic switch-off date decided as a result.

Southwood said the Science Program Committee will have the difficult job — nobody likes to shut down a healthy science satellite — of implementing the policy this year.

Peter B. de Selding was the Paris bureau chief for SpaceNews.