Dark Energy Top Priority, But Astronomers Ask if Both US and European Space Missions Are Needed

Dark Energy Top Priority, But Astronomers Ask if Both US and European Space Missions Are Needed

Discovering the nature of dark energy is the top scientific priority for astronomy and astrophysics as indicated in the National Research Council’s Astro2010 Decadal Survey released last month. It set both a space mission, the Wide Field InfraRed Survey Telescope (WFIRST), and a ground-based telescope, Large Synoptic Survey Telescope (LSST), as the top priorities for space- and ground-based astronomy respectively. Both would search for answers about dark energy, a mysterious force that is causing the universe to expand at an accelerated rate. At the same time, the European Space Agency (ESA) is set to decide next summer on whether its dark energy probe, Euclid, will get the nod for one of its upcoming space missions.

Today, members of the NASA Advisory Council’s Astrophysics Subcommittee heard from Astro2010 chairman Roger Blandford, as well as from NASA Astrophysics Division Director Jon Morse and Jet Propulsion Laboratory’s Jason Rhodes about the space-based dark energy missions and raised questions about potential overlap between them. The Astrophysics Subcommittee reports to NAC’s Science Committee, which in turn makes recommendations to NAC and the NASA Administrator.

Subcommittee members asked penetrating questions about why WFIRST and Euclid could not be combined, with 50-50 participation by each side. Dr. Morse told the subcommittee that current ESA-NASA discussions envision NASA as a one-third contributor to the Euclid mission if ESA proceeds with it. However, he stressed that while top level descriptions of WFIRST and Euclid indicate the two have similar goals in dark energy studies, a more detailed understanding of the instruments might show significant differences in the approaches being taken. Dr. Blandford also emphasized that dark energy is only one of three scientific objectives for WFIRST. The other two are looking for Earth-like planets (exoplanets) and an infrared sky survey, neither of which would be addressed by Euclid.

In a cost constrained environment made all that more difficult due to cost overruns on the James Webb Space Telescope (JWST), subcommittee members clearly were looking for ways to address the highest priority scientific questions in the most cost-effective manner. JWST and WFIRST are both “flagship” missions within the purview of the NASA Astrophysics Division. Dr. Morse emphasized repeatedly that flagship missions must wait their turn and WFIRST cannot proceed until JWST is launched.

The current launch date for JWST is 2014, but Dr. Eric Smith of NASA’s Astrophysics Division briefed the subcommittee on JWST and intimated that the date is likely to slip. The program is currently scheduled to go before an agency Program Management Council (PMC) at the end of November where a decision on its schedule is expected. Repeated cost overruns and schedule slips have led to a number of JWST program reviews, including one demanded by Senator Barbara Mikulski (D-MD), who chairs the Senate appropriations subcommittee that funds NASA.

A strong supporter of NASA and especially its Goddard Space Flight Center in her state of Maryland, which manages JWST, Sen. Mikulski nonetheless became concerned about additional problems with JWST identified during its mission Critical Design Review (CDR) earlier this year. She wrote a sharp letter to NASA in June telling the agency to create an independent panel to look at several issues including the root causes of JWST’s problems. That review is due to NASA Administrator Charlie Bolden next month. Dr. Smith was unable to answer most of the questions posed by subcommittee members about JWST pending completion of that review and the agency PMC.

The subcommittee meeting continues tomorrow.

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