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Meet IXO scientists at Explore@NASA Goddard on Saturday, May 14, 11am – 5pm rain or shine.


Read an update on IXO from Nick White and Jay Bookbinder »


Presentations for the IXO Science Team Meeting, held on March 14–16, 2011 in Rome, are available for download


A new schedule for Cosmic Vision selections was announced at the IXO Science Meeting in Rome


Read about IXO on the BBC's Science and Technology blog page »


IXO Science Team Meeting, March 14—16, 2011, Rome, Italy »


217th AAS meeting

Mike Garcia´s talk "IXO Absolute Astrometry Requirements" is available for download.


IXO will take part in the AAS # 217 meeting held on January 9—13, 2011 in Seattle, WA. Please come by to see us at our booth # 218.


New IXO response matrices are available for download »


The IXO team will make an initial presentation on October 6th to the ESA Cosmic Vision review


Astro2010 Update

The Decadal report recommends IXO as one of three defined flight missions. Read more »


Randall Smith gave a talk on "The Potential of Future X-ray Missions" at the Accretion Processes Workshop

More news »

+ Image credits

Prior to its termination the International X-ray Observatory (IXO) was ranked fourth among large missions in the 2010 Astrophysics Decadal Survey, "New Worlds, New Horizons." In response, NASA has undertaken an X-ray mission concepts study to determine if alternative approaches exist to accomplish IXO's high ranking scientific objectives over the next decade. The primary goal of the study is to determine the degree to which missions in various cost ranges from $300M to $2B could fulfill these objectives. A secondary goal will be to assess relevant near-term technology plans in light of potential mission concepts.

NASA released a Request for Information in October 2011, seeking mission concepts and enabling technology ideas from the community, as well as soliciting membership for a Community Science Team (CST) to guide the process. A workshop was held in December 2011 in which the mission concepts and technology were presented and discussed. The CST membership and all RFIs and presentations at the workshop are posted at Based on the RFI responses and the workshop, the CST chose two notional mission concepts, representing several cost points, for further study. These notional missions concepts are being developed through NASA mission design laboratory activities, which provide systems engineering and costing assessment, in early 2012. The results of all these activities will be captured in the final X-ray mission concepts study report, to be submitted to NASA and the National Academy of Sciences Committee on Astronomy and Astrophysics in June 2012.

An Update on IXO

From Nick White and Jay Bookbinder

April 8, 2011

US IXO Team,

This is an update on the discussions with the European Space Agency (ESA) at the recent ESA-NASA bilateral meeting. This was reported by Jon Morse (HQ Astrophysics Division Director), first, to the IXO and LISA teams on Tuesday, and then, at the Astrophysics NASA Advisory Committee (NAC) sub-committee meeting on Thursday afternoon.

IXO was one of three candidates competing for the L1 opportunity in ESA´s Cosmic Vision Program (2015-2025). The Astrophysics and Planetary decadal rankings and NASA´s constrained out-year resources projected in the President's FY12 budget request led ESA to conclude that none of the three mission concepts were feasible within the Cosmic Vision L1 schedule. Consequently, ESA has ended consideration of IXO and the other concepts as partnerships at the scale proposed in the New Worlds New Horizons decadal survey (NWNH) and EJSM/Laplace in Visions and Voyages for Planetary Science.

Instead, ESA has begun a rapid definition effort that includes the formation of a new science team (to be announced shortly). That effort will identify science goals and a mission concept that can be implemented as part of an ESA-led mission launching in the early 2020´s for a cost to ESA of about 800M Euro. Revised mission concepts from the three science areas will be considered in a selection process tentatively foreseen in February 2012.

A future minor role for NASA in the new ESA-led X-ray mission, in particular contributions at the instrument level, has not been ruled out. NASA will participate in the new ESA science team through a "NASA HQ-empowered scientist." This will be a NASA civil servant scientist who will be the conduit for any engagement with the new ESA team.

Currently the decadal survey recommendations are centered on the IXO (and LISA) concept and partnerships. NASA HQ will NOT disband the current NASA IXO (and LISA) teams immediately, but will follow a deliberate path towards redirecting the NASA efforts in the context of the decadal survey recommendations. Read more »

Former IXO concept and science performance requirements

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IXO Science Team Meeting, March 14—16, 2011, Rome, Italy


IXO Astro2010 Decadal submissions available here.

Recent Technology Milestones

The XPOL team is continuing to investigate how different gas mixtures impact on the sensitivity of the X-ray polarimeter on-board of IXO. Read more »


Spectrum of monochromatic photons at 2.6, 5.2 and 7.8 keV. The energy resolution is 32.1% at 2.6 keV, 24.5% at 5.2 keV and 23.5% at 7.8 keV (Muleri et al., 2010). Read more »

Recent Publications

International X-ray Observatory (IXO) Assessment Study Report for the ESA Cosmic Vision 2015—2025,
X. Barcons et al.
More publications »