PARIS — The European Space Agency on Jan. 15 said its 2016 budget of 5.25 billion euros ($5.71 billion) is up 18.4 percent compared to last year on the strength of higher contributions by several member governments, especially Italy, and substantially increased investment by the European Commission.

The Brussels, Belgium-based commission has become ESA’s biggest paymaster, mainly because of the Galileo positioning, navigation and timing network and the Copernicus Earth observation program and its fleet of Sentinel satellites. Both have entered satellite-deployment phase.

The commission owns both these programs and has hired ESA to perform technical and contract oversight.

Given the manufacturing and deployment schedule of the Galileo and Copernicus satellites, it is not surprising that the commission’s 2016 spending at ESA is up sharply – by nearly 29 percent, to 1.35 billion euros ($1.44 billion).

But it’s not just the commission. In what may come as a surprise to some, Italy’s payments to ESA in 2016 are scheduled to total 512 million euros – up 55 percent from 2015. The main reason: the Italian-led Vega rocket.

The current-version Vega small-satellite launch vehicle has just completed its early demonstration and validation phase, but ESA governments in December 2014 agreed to a package of rocket-related spending that in the coming years will result in a new Ariane 6 heavy-lift rocket and a more-powerful Vega-C.

Italy has a large majority stake in Vega.

Just a few years ago, it appeared as though Britain, which in 2012 agreed to a sizable increase in ESA spending, might surpass Italy as ESA’s No. 3 contributor among national governments, after Germany and France.

But with Britain’s ESA contribution this year scheduled to be about 325 million euros, Italy has clearly re-established itself as a top-three ESA backer.

Germany remains the top contributor, at about 873 million euros for 2015 – up 9 percent from 2015; with France just behind at 845 million euros. French spending will increase by nearly 18 percent from 2015. France has a majority stake in the Ariane 6 program, whose development cost will ratchet up this year.

The big increase in spending on rockets – up 72 percent, to 1.05 billion euros in 2016 – still leaves launch vehicles in second place among ESA priorities after Earth observation, which accounts for nearly 31 percent of ESA’s total planned spending.

The impression given is of an agency awash in cash, but at ESA this is rarely the case. Its member governments attempt to tailor outlays based on the precise status of given programs.

A prime contractor falls behind schedule, a launch is delayed — lots of reasons can result in a given nation withholding some of the spending that appeared necessary at the beginning of the year because it is not immediately needed for a program.

In fact, ESA is struggling to fund two high-profile programs that have yet to secure the necessary commitments.

The first is the International Space Station. ESA Director-General Johann-Dietrich Woerner told a press briefing here Jan. 15 that he would do his utmost to persuade his member governments — starting with Germany, France and Italy — that Europe should join the other station partners and commit to using the facility to 2024.

The German Aerospace Center, DLR, recently completed an assessment of space station costs and benefits. DLR officials said they would withhold the release of the report until Germany’s Ministry of Economy — which has principal DLR oversight —weighs in with its own opinion.

ESA governments are scheduled to meet in December to determine their future space station roles. Gerd Gruppe, head of space programs at DLR, said here Jan. 15 that while he personally hoped Germany would continue to use a facility in which German taxpayers had invested so much, he could not guarantee a decision one way or another.

The other program struggling financially is the Euro-Russian ExoMars mission, a two-part program with a first launch, in March, of a telecommunications relay satellite, atmospheric-gas sensor and lander. A European rover is scheduled for launch in 2018.

Both are being launched by Russian Proton rockets.

In surprisingly downbeat terms, Woerner openly speculated that ExoMars 18 may have to be delayed by two years to give time to find the missing funding — a scenario that would only increase total program cost.

Asked if Russia’s government budget cutbacks posed a threat to Russia’s ExoMars contributions, Woerner said:

“I met recently with our Roscosmos colleagues and there is no indication of any delays or other issues,” Woerner said. “So we are not considering a Plan B. In fact, if there is a problem it is on the European side.”