NASA's funding woes continue to have an impact on the European Space Agency (ESA) as it presses ahead with plans to launch a next-generation solar probe in 2017.
NASA was expected to provide up to four instruments and a launch vehicle to ESA's Solar Orbiter Collaboration, a robotic sun probe designed to help scientists understand the causes of space weather and provide the closest-ever view of the sun during the spacecraft's seven-year design life.
But rising launch costs coupled with flat spending in the U.S. forced NASA last year to pare back its Solar Orbiter commitment, leaving ESA to fund two instruments – the Suprathermal Ion Spectrograph and Spectral Imaging of the Coronal Environment – on its own.
Together the sensors added about €25 million ($33 million) to ESA's tab for Solar Orbiter, a project that will cost the agency close to €500 million. NASA expects to spend about $400 million through 2017 for its de-scoped Solar Orbiter contribution, which includes a U.S. Air Force Evolved Expendable Launch Vehicle and two science instruments: The Solar Orbiter Heliospheric Imager, provided by the U.S. Naval Research Laboratory, which will measure solar wind disturbances, shock formation and turbulence; and the Southwest Research Institute's Heavy Ion Sensor to will measure heavy ions in the solar wind.
Other missions dinged by flagging U.S. spending include ESA's ExoMars campaign, which NASA backed out of as ESA's industrial partners set to work building a methane-detecting orbiter for the two-pronged mission to the red planet in 2016 and 2018. The U.S. withdrawal left ESA to forge a partnership with Russia to launch the mission and help develop an entry, descent and landing capability, adding as much as €200 million to ESA's estimated €1 billion contribution to ExoMars, a program for which ESA member states have so far committed only €850 million.
More recently, NASA's wavering support influenced ESA's selection of its next large-class space science mission. Among the three L-class candidates, ESA opted for the Jupiter Icy Moons Explorer in part because the robotic mission to the Jupiter system planned for early next decade could be easily reconfigured to proceed absent NASA participation.
Regardless, says Thomas Passvogel, department head of ESA science missions, ESA is confident NASA will fulfill its commitment to Solar Orbiter, the first of ESA's Cosmic Vision missions to enter the implementation phase.
“We are as solid as we can be,” he says, adding that the two agencies recently signed a Memorandum of Understanding affirming a common line in implementing Solar Orbiter. “I have not seen a Memorandum of Understanding being broken.”
In April ESA awarded €300 million to EADS-Astrium to lead Solar Orbiter development as prime contractor. Passvogel says the mission is on track though technical challenges remain, including testing and development of the spacecraft's heat shield and solar arrays.
Passvogel says the heat shield has been in development for a number of years and is at an “advanced stage” in terms of design and test preparation.
“This is not yet manufactured, not yet tested, but it is going in the right direction,” he says.
For the solar arrays, ESA will rely on technologies being developed for Europe's BepiColombo mission, a pair of orbiters designed to investigate Mercury that are slated to fly two years before Solar Orbiter.
“This is a technology that is in ongoing testing and development, but it is something that will be there,” he says of the BepiColombo solar arrays, which are designed to withstand ten times the radiation power received by a satellite in orbit around Earth.