Thursday, September 13, 2007

Constellation-X: There is good news and there is bad news

Last week the National Research Council's Space Studies Board finally published its conclusions assessing the feasibility and priorities for space missions in the NASA "Beyond Einstein" program. Basically this was a match-up to select between current political and fashion favorites going after dark energy, and the older-but-surer science missions like Constellation-X (and X-ray observatory, e.g. for understanding black holes, AGN, and anything else extremely hot in the universe) and LISA (gravitational wave detection).

The committee will be charged to address the following tasks:

1. Assess the five proposed Beyond Einstein missions (Constellation-X, Laser Interferometer Space Antenna, Joint Dark Energy Mission, Inflation Probe, and Black Hole Finder probe) and recommend which of these five should be developed and launched first, using a funding wedge that is expected to begin in FY 2009. The criteria for these assessments include:
a. Potential scientific impact within the context of other existing and planned space-based and ground-based missions; and
b. Realism of preliminary technology and management plans, and cost estimates.

2. Assess the Beyond Einstein missions sufficiently so that they can act as input for any future decisions by NASA or the next Astronomy and Astrophysics Decadal Survey on the ordering of the remaining missions. This second task element will assist NASA in its investment strategy for future technology development within the Beyond Einstein Program prior to the results of the Decadal Survey.

You can read the full report online here. Stein Sigurdsson already offered his take on the predictable outcome (a mission focused on dark energy) in a post last week that can be found here. The Constellation-X team is rather more upbeat in its assessment:

Dear Colleagues:

The BEPAC report provides both bad and good news for the Con-X project. Bad news is that Con-X was not chosen as the highest priority (JDEM was recommended as the first BE mission) or even as the 2nd highest priority (LISA was recommended for enhanced technology investment). Good news can be found in the BEPAC endorsement of the Con-X science and technical readiness. Specifically, "Con-X will make the broadest and most diverse contributions to astronomy of any of the candidate Beyond Einstein missions...the general observer program of Con-X will harness the ingenuity of the entire astronomical community", and "Con-X is one of the best studied and tested of the missions presented to the panel...much of this can be attributed to...strong community support". The panel recognized that "Con-X was ranked second only to the James Webb Space Telescope in the 2001 Decadal Survey".

Looking forward, the BEPAC recommends that "Con-X development activities need to continue aggressively in areas such as achieving the mirror angular resolution, cooling technology and x-ray micro-calorimeter arrays to improve the Con-X missions readiness for the next Astronomy and Astrophysics Decadal Survey." We will continue to pursue technology developments in these areas. All of your assistance in preparing the BEPAC presentations provides us with a very good start for the upcoming Decadal Survey. One of our tasks will be to expand upon the BEPAC material, which was very focused on BE science, in order to capitalize on the breadth and diversity of Con-X science (which was recognized by the BEPAC). We anticipate having the next Con-X FST meeting in mid-Feb 2008, following the release of the NASA budget request for FY2009.

Harvey Tananbaum, Nick White, Michael Garcia, Jay Bookbinder, and Ann Hornschemeier, for the Con-X Project Team.
I leave it as an exercise for the reader to compare the Constellation-X assessment with the officially stated goals of the assessment (1a and b above).

Speaking personally, I'm very disappointed in the selection. Getting the equation of state for dark energy is interesting, but very limited in scope, and this selection basically sacrifices the potential of lot of scientific progress and potential for new discoveries in many branches of astrophysics for a very limited advance in one specific area. Indeed, an area that has little practical impact for our understanding the broader nature of the Universe and how we came to be here (see Simon White's essay regarding dark energy and astronomy here).

Constellation-X is, furthermore, the only proposed instrument in the next 10-20 years with the potential to unambiguously answer the most fundamental unknowns regarding starburst-driven winds (my primary area of study): measuring the velocity of the hot and very hot metal-enriched X-ray-emitting gas. If we don't and won't know that for sure, then we'll never be quite sure about interstellar medium and intergalactic medium feedback processes. Forget about getting the full picture on galaxy formation, galactic chemical evolution, mass loss from galaxies, enrichment and heating of the IGM, and so on. But hey, instead we get to know whether a number called W is between -1 and 1. I'm sure the public is eager to know that, I'm positive they'll get very excited about that result.

Now Con-X isn't officially dead yet, but being third in line is a dangerous place to be. In another few years, if there are further assessments to rationalize and prioritize spending, will Con-X survive? And without Con-X, I feel like I might as well pack up and give in. Game over...

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