A joint Fermilab/SLAC publication

Crunch time for Joint Dark Energy Mission

10/14/08

Last month's surprise cancellation of the competition to develop the Joint Dark Energy Mission left researchers stunned.  Now the former competitors have less than two months to come together and redefine what the mission should accomplish--a mission that will be developed and overseen not by a single, winning team but by JDEM's government sponsors, NASA and the US Department of Energy.

The two agencies have appointed a committee that meets for the first time on Wednesday in Washington, DC.  Called the Science Coordination Group, it includes representatives of each of the formerly competing teams and has the delicate task of determining broad science goals and observational requirements for the mission's new incarnation. They must include observations of at least three types of phenomena--supernovae, weak gravitational lensing, and baryon acoustic oscillation.

The group will also contribute to the design of an initial Reference Mission, to be delivered by the end of 2008. At that point the agencies will call for proposals for science investigations, with science teams to be selected next year.

"They've hit the reset button. It's a start anew," Michael Levi of Lawrence Berkeley National Laboratory told me. The Science Coordination Group "has six weeks to come up with a new mission, to take several lumps of clay and mush them together."

Kathy Turner, the JDEM program scientist in the DOE's Office of High Energy Physics, said one reason for the change of course was that none of the competing proposals included all the observational approaches NASA and the DOE considered essential. "The agencies have used those concepts to understand what kind of science can be done and for what kind of cost," she said, and will also consider "other concepts that will come forward."

Another concern, she said, was the need of each agency to control its own funding stream, to have "clean interfaces." And each wanted to have a hand in both the science instrumentation and science collaboration. NASA is taking the lead in the mission, with the DOE contributing about $200 million. Turner added that the life of the space-based mission may be extended from three years to five.

The goal is to launch JDEM by the middle of the next decade, according to an announcement posted on the mission's Web site on Sept. 12. It was the only public notification of the change in plan, which did not hit the news until Oct. 1 with a report in Nature News (subscription required.)

"No one I know had any advance notice that things were going to be this different,'' Aaron Roodman of Stanford Linear Accelerator Center told me. He's one of about 15 SLAC researchers involved with the proposal known as SNAP, for Supernova Acceleration Probe. "Even the leadership at SNAP didn't know."

NASA has set up a program office for the mission at Goddard Space Flight Center in Maryland. The DOE created its own program office at Lawrence Berkeley National Laboratory, and asked Levi--the co-principal investigator of the team formerly known as SNAP--to lead it.

The two other concepts whose development had been funded by NASA were the Advanced Dark Energy Physics Telescope, or ADEPT, and the Dark Energy Space Telescope, known as Destiny.

JDEM is the highest-priority mission in NASA's Beyond Einstein program. Its goal is to measure the properties of dark energy--a mysterious force thought to accelerate the expansion of the universe--at a total lifetime cost of about $600 million, not including the cost of launching it.

The final design "is not going to be all things to all people," Turner said. "There are going to have to be compromises to stay within the cost."

Toward that end, members of the Science Coordination Group were selected according to a number of criteria: People from each of the major concepts, and from several more that had not been funded for development. Theorists and experimentalists. People who know a lot about each of the observational approaches. Of 50-60 researchers who applied,  17 were selected (see the list here.)

"Of course we had to pick the team that could do the job and all work together," Turner said. "They have a big job to do over the next two months. They all have to get together and agree."

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