Newsletter No. 99, December 2011

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10. The Next NASA X-ray Astronomy Mission, or the Mission Formerly Known as IXO
Michael Garcia (SAO) & Rob Petre (GSFC)

As we noted in our last HEAD newsletter, the results of the US Decadal Survey and ESA Cosmic Visions process, as well as fiscal resources have made it clear that IXO will not go forward this decade. The IXO study team has therefore been directing its efforts at a NASA-only, simplified and lower cost version of IXO dubbed AXSIO, the Advanced X-ray Spectroscopic Imaging Observatory. AXSIO has an effective area is 1m2 as compared to the 2.5m2 envisioned for IXO, but is able to address the majority of the IXO key science objectives. Many of the simplifications come directly from recommendations made by the Decadal Survey in the evaluation of IXO, including a reduction in the focal length to 10m, removing the extendable bench which allowed a 20m focal length, and relaxing the angular resolution requirement to 10 arc sec HPD (while retaining a goal of 5 arc sec).

In order to help direct X-ray astronomy technology and mission study efforts in the near term, NASA has released a Request for Information (RFI) entitled 'Concepts for the Next NASA X-ray Astronomy Mission'. Quoting from this RFI, "NASA is seeking information that can be used to develop concepts that meet some or all of the scientific objectives of the International X-ray Observatory (IXO). Information being sought includes relevant mission concepts, instrument concepts, enabling technologies, or any aspect of flight, ground or launch systems architecture." Responses were due Oct. 28, 2011, and a total of 28 (including AXSIO) were received.

The replies will be presented and discussed at a 2 day workshop hosted by the PCOS Program Office, which will take place on Dec. 14 --15 at the Maritime Institute, Linthicum, MD, near the BWI Airport. The workshop is open to all, but registration is required by Dec. 9, 2011. Based on community input at the workshop and the RFI responses, several mission concepts will be selected for further study. Further details on the workshop and the RFI responses can be found at:

Progress continues on key IXO technologies, including both the slumped glass mirrors and micro-calorimeter. Mirror substrates are now being consistently made at the 6.5 arc sec HPD level (two reflections) and the best substrates have 3.9 arc sec HPD. The ability to align and mount mirror pairs to achieve better than 10 arc sec HPD has now been demonstrated repeatedly.

Progress on small TES (transition edge sensor) micro-calorimeters has allowed them to operate at higher rates than envisioned for IXO. These were initially developed for solar physics applications, and 57 micron pixel devices have now reached energy resolution of 1.6 eV at 6 keV.

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