PARIS — The European Space Agency (ESA) expects to sign a contract for a radar Earth observation satellite in December despite unresolved financing and operational issues with its intended partners, the European Commission and Eumetsat, the head of ESA’s Earth observation program said.

Volker Liebig said the agency is obliged to move forward on a synthetic-aperture radar imager on a satellite called Sentinel 1 in order to make sure the satellite is ready to take over from the Envisat satellite, which now is expected to continue operations until 2010.

Astrium GmbH of Germany and Alcatel Alenia Space’s Italian component are competing for the Sentinel 1 business. The total cost of the satellite is expected to be around 220 million euros ($277 million), not including launch, Liebig said. The contract will be crafted on a cost-plus basis but with a ceiling price for the hardware-construction phase.

Sentinel 1 is part of Europe’s Global Monitoring for Environment and Security (GMES) project, a package of Earth observation missions co-funded by ESA and the European Commission.

Two other Sentinel missions, one carrying a superspectral imager for land and agricultural observation and one devoted to ocean altimetry, also are part of GMES. Liebig said requests for bids from industry for these two satellites are expected to be issued in December, with selection of a prime contractor early in 2007.

ESA has secured 255 million euros for GMES so far, and its member governments have said they will provide an additional 430 million euros, a commitment that is expected to be formalized in 2007.

A final tranche of 465 million euros will be solicited in 2008.

This package of 1.15 billion euros is supposed to be ESA’s half of the entire GMES program, which in addition to the first three Sentinel satellites has two other payloads, called Sentinel 4 and Sentinel 5, that are to fly on satellites planned by Europe’s Eumetsat meteorological satellite organization.

An identical amount had been expected from the European Commission as part of its Seventh Framework Program for Research for the period 2007-2013.

The problem for ESA is that the commission has been unable to say exactly how much it will spend on GMES — and in particular how much of its budget will go to sharing satellite construction costs with ESA, and how much will be reserved for stimulating GMES-related services among the European Commission.

Another problem is that the Brussels-based commission is not used to committing itself to contracts for more than one year without being able to cancel the work.

In an Oct. 18 interview, Liebig said ESA is taking account of these open issues by crafting the Sentinel satellite contracts in such a way that they can be cancel ed at a predefined point if necessary.

“We will have break points in the Sentinel 2 and Sentinel 3 contracts so that work can begin but, if funding is not available, the contract will stop. But the commission’s difficulty with multi year contracts is a problem we are still working on. It is clear I cannot manage a contract for satellite construction by telling manufacturers that we start at zero every year or two.”

Several ESA governments, especially Britain, have questioned the current approach to GMES, saying the unresolved funding issues should force ESA to cut back GMES to a single satellite. In this way, these governments argue, ESA and the commission will more likely be able to build follow-on satellites — a necessary component of GMES to assure user adoption of its services.

Liebig said he understands this reasoning but that ESA governments and the prospective users that ESA and the commission are working with have expressed clear support for all three Sentinel satellites.

He said ESA is still operating on the assumption that the European Commission, not ESA, will finance follow-on satellites to assure uninterrupted GMES services.

Eumetsat is ESA’s other partner in GMES, but not on the financing side. Eumetsat and ESA recently have agreed that Eumetsat will operate three of the five Sentinel missions — those dealing with ocean altimetry and two missions dealing with atmospheric monitoring, one from low Earth orbit and one from geostationary orbit.

Mikael Rattenborg, Eumetsat director of operations, said Eumetsat’s ruling council is expected to confirm Eumetsat’s GMES role at its next meeting, scheduled for Nov. 30.

In an Oct. 23 interview, Rattenborg said Eumetsat expects that ESA and the European Commission will finance the satellite hardware, with Eumetsat funding the costs of upgrading its ground network to receive, process and distribute the satellite data.

Rattenborg said Eumetsat’s bylaws permit the agency to manage services on behalf of third parties, and the GMES project falls easily into this category.

In addition to GMES, Eumetsat and the U.S. National Oceanic and Atmospheric Administration are still in discussions on how to share responsibility for a long-term ocean-altimetry mission now assured by the Jason-1 satellite and a Jason-2 follow-on scheduled for launch in June 2008.