European Space Agency Selects Orbital Observatories for Next Major Space Missions

On 31 October, European Space Agency (ESA) director of science and robotic exploration, Alvaro Giménez, put forward the “hot and energetic Universe” and the “gravitational Universe” as the two themes that will shape the agency’s next large (L-class) projects —the €1-billion (US$1.4-billion) L2 and L3 missions, scheduled for launch in 2028 and 2034, respectively. ESA’s Science Programme Committee, composed of member-state representatives, will consider the recommendation and announce a decision at a meeting on 28–29 November. It would be rare for the committee not to endorse the science director’s advice.

The first of the themes is good news for Athena+ (the Advanced Telescope for High Energy Astrophysics), an X-ray observatory that would be the front runner in a formal call — planned for next year — for mission proposals to probe the hot and energetic aspects of the Universe. The observatory, which will carry a telescope and instruments to measure the energy of X-ray sources and image them with unprecedented precision, would study how hot gas evolves into galaxy clusters and how black holes grow. Luigi Piro, a member of the Athena+ instrument and optics working group at Italy’s National Institute for Astrophysics in Rome, says that half of all visible matter is in this ‘hot phase’, but is poorly understood. “We will now be able to tackle questions about how the Universe is actually working and what is the role of hot plasma and black holes in shaping the Universe,” he explains.

The second theme would focus on gravitational-wave astronomy, a field never before studied in space. The planned space-based mission eLISA (evolved Laser Interfero­meter Space Antenna) would detect the low-frequency gravitational waves that are thought to stretch the fabric of space-time. Gravitational waves have not been directly detected at ground-based observatories. eLISA would bounce lasers between three spacecraft at least one million kilometres apart, and spot a passing wave when it alters the precise positioning of one of the spacecraft.

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