ESA Embraces In-Orbit Demos with 2 More Proba Flights Planned

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PARIS — The European Space Agency (ESA) expects to assemble the financing this year to develop a pair of small satellites to demonstrate formation flying as part of its in-orbit technology-demonstration program that launched its most recent satellite in November, according to ESA officials.

With an initial impetus from the Belgian government, which was seeking a prime contractor’s role for its industry, ESA’s Proba series of satellites is taking on the appearance of a regular series of missions that once were considered too small for the 18-nation ESA.

Proba-1 was launched in October 2001 on a two-year mission featuring a spectrometer and a panchromatic Earth observation camera as well as a series of spacecraft-autonomy experiments.

More than eight years later, the 94-kilogram Proba-1 continues to operate. Several of its technologies have begun to flow into the regular production lines of Europe’s satellite builders, according to Michel Courtois, ESA’s director of technical and quality management.

“The Proba program’s goal is to get new technologies onto in-orbit demonstration programs to prove things we’ve been working on in the laboratory,” Courtois said in a Jan. 26 interview on Proba-2’s in-orbit status. “We have seen a number of Proba-1 technologies developed for use in later satellites that are now being built.”

The 130-kilogram Proba-2, which was also built with a major contribution from the Belgian government and with Verhaert Design & Development of Belgium as prime contractor, was launched in November with two solar-observation sensors and two space-weather experiments.

Perhaps more important, Proba-2 is carrying 17 demonstration technologies covering a wide range of satellite functions. They include a new design of lithium-ion battery from Saft of France; an experimental data-processing system from Verhaert; a digital sun sensor from TNO of the Netherlands; a newly designed star tracker, designed by Galileo Avionica of Italy and intended to prove a technology for ESA’s BepiColombo mission to Mercury; and an experimental solar panel with a deployable solar-flux concentrator from CSL of Belgium.

Courtois said the solar power concentrators are intended to solve some of the problems encountered by Boeing when it launched a new generation of solar panels fitted with concentrators in the first six 702-model commercial telecommunications satellites launched between 1999 and 2001. All were launched before a design defect in the concentrators was discovered that will reduce their in-orbit service lives. Boeing has since stopped using the concentrator technology.

ESA Science Director David Southwood said the Proba-2 star tracker’s performance will be taken into account as ESA prepares to build the BepiColombo mission to Mercury, now scheduled for launch in 2014. In a Jan. 26 interview, Southwood said ESA’s science missions will increasingly make use of technologies proved on technology-demonstration satellites as a way of reducing risk.

In an unusual move, ESA’s science division is launching a technology-demonstration satellite of its own, called LISA Pathfinder, whose mission is to prove technologies to be used on the follow-on LISA, or Laser Interferometer Space Antenna, mission.

Courtois said all 17 Proba-2 technology experiments have been switched on to prove at least initial functionality, as have the four observation sensors.

Two more Proba missions are being planned. Proba-V, to be launched in 2012, will continue observations made on the Belgian-built Vegetation sensor, which measures Earth’s plant cover, placed on the French Spot 4 Earth observation satellite launched in 1998, and the Spot 5 satellite launched in 2002.

Spot 5 is already past its contracted service life, and the Vegetation sponsors — Belgium, France, Italy, Sweden and the European Commission — view Proba-V as providing post-Spot 5 Vegetation data continuity.

A more complex Proba-3 mission featuring two satellites that will test formation-flying techniques is now in the design phase, with several nations, including France and Sweden, discussing financial contribution levels.

Proba-3 mission backers had hoped to use the success of Sweden’s own formation-flying demonstration, the two-satellite Prisma mission, to facilitate Proba-3 financing. But Prisma’s launch has been delayed because of a Russian-Kazakh dispute over rocket debris from Russia’s Yasny launch site.

Christer Nilsson, Prisma program manager at the Swedish National Space Board, said Dnepr managers have agreed to transfer the launch to the Russian-run Baikonur Cosmodrome in Kazakhstan if no drop-zone approval is given by late February. A Baikonur launch likely would not occur before August at the earliest, Nilsson said.