Chandra's First Decade of Discovery

Future Missions

The Off-Plane X-ray Grating Spectrometer for the International X-ray Observatory

Suzanne Casement, Northrop Grumman Aerospace Systems
T. Johnson (NGAS), C. Lillie (NGAS), R. McEntaffer (University of Iowa), W. Cash (University of Colorado at Boulder)

The baseline configuration for the International X-ray Observatory (IXO) includes a soft x-ray grating spectrometer as part of its instrument complement to provide a spectral resolution of R >3000 over the 0.3 - 1 keV band with >1000 square cm effective collecting area. Using the current generation of reflection gratings flown on rocket experiments as a point of departure, an Off-Plane X-ray Grating Spectrometer (OP-XGS) is being proposed to the project to meet this need. These rocket experiments have demonstrated R of >100 with wire grid collimators and objective gratings that produce large point spread functions. Prototype gratings fabricated for the IXO project have achieved adequate throughput to obtain the IXO effective area requirement while resolution tests have demonstrated λ/δλ > 200 when used with a 3 arc minute (angular resolution) telescope. When combined with the IXO telescope performance, the resulting spectral resolution is well over the IXO requirement. The OP-XGS will thus provide higher spectral resolution (over a slightly smaller energy range) than the Chandra LETGS instrument but with a larger effective collecting area providing improved sensitivity. The conceptual design and predicted performance of this system is presented here, along with the technology developments that will be needed to achieve the desired performance.

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Enhancing the International X-Ray Observatory

Dean Dailey, Northrop Grumman
Rolf Danner (NGC), Chuck Lillie (NGC)

We present preliminary results of systems studies expected to significantly enhance the science utility and reduce technical as well as cost risks for the International X-ray Observatory (IXO). Our Northrop Grumman team draws on the experience of building and operating Chandra and others of NASA's premier astrophysical observatories (Compton Gamma Ray Observatory, James Webb Space Telescope) as well as our experience as a leading developer of deployable space structures. For IXO, we have developed (a) an optical bench concept that increases the focal length from 20 to 25 m within the current mass and stability requirements; (b) an instrument and system layout that increases the accessible field of regard; and (c) a number of design choices based on flight proven concepts that reduce cost risk. Our concept for the IXO deployable bench is a tensegrity structure formed by two telescoping booms (compression) and a hexapod cable (tension) truss. This arrangement achieves the required stiffness for the optical bench at minimal mass while employing only high TRL components and flight proven elements. While the overall concept is innovative and will require further evaluation, it is based on existing elements, can be fully tested on the ground and does not require any new technology. We have also explored the options opened by using hinged, articulating solar panels, and found that when used along with a fully enclosed MLI tent surrounding the optical bench, and an instrument module utilizing radially facing radiator panels, the enhanced configuration will enable us to greatly increase IXO's field of regard without distorting the optical bench beyond acceptable tolerances, making more of the sky accessible for observation at any given time.

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Partnering Science and Engineering: Lessons from Chandra for IXO

Rolf Danner, Northrop Grumman Aerospace Systems
Jonathan Arenberg (Northrop Grumman Aerospace Systems)

Successfully developing and launching the International X-ray Observatory in a cost constrained environment will require a close partnership between scientists and engineers in academia, government and industry. We outline a development approach based on our experience of building the Chandra observatory that enables breakthrough scientific capability while maintaining credible commitment to tight cost constraints. Our approach further preserves flexibility in a changing funding environment and responsiveness to new technologies.We begin with a frame work for the system engineering process and argue that including science goals in the trade space is critical in achieving the best science performance. In this frame work, scientists work side by side with engineers throughout the development optimizing the science return within the project constraints and technical feasibility. From the perspective of the builders of the Compton Gamma Ray Observatory, Chandra and the James Webb Spaces Telescope, we summarize our progress towards a robust yet flexible development model that will allow the International X-ray Observatory to move successfully from detailed concept studies to in orbit science operation.

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The Gravity and Extreme Magnetism Small Explorer (GEMS)

Philip Kaaret, University of Iowa
J. Swank, K. Jahoda, T. Kallman (NASA/GSFC) and the GEMS team

The Gravity and Extreme Magnetism Small explorer (GEMS) was recently selected for flight in 2014 by NASA and will make the first sensitive search for X-ray polarization across a wide set of source classes including stellar black holes, Seyfert galaxies and quasars, blazars, rotation and accretion-powered pulsars, magnetars, shell supernova remnants and pulsar wind nebulae. GEMS will observe 35 targets during the 9 month prime mission. A possible science enhancement option would extend the mission with a 15 month guest observer phase. GEMS is implemented using time projection chamber (TPC) polarimeters with high efficiency in the 2-10 keV band behind thin foil mirrors. It also allows a small Bragg reflection soft X-ray experiment to be included that can extend the sensitivity to 0.5 keV. The entire spacecraft, less the solar panels, is rotated to enable measurement and correction of systematic errors. We will discuss the design of GEMS and the planned science program.

Design Concepts for the Generation-X Mission

Charles F. Lillie, Northrop Grumman Aerospace Systems
D. Dailey, R. Danner, D. Shropshire, D. Pearson Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278

The Generation-X mission, proposed by Roger Brissenden at SAO, is one of the Advanced Strategic Mission Concepts that NASA is considering for development in the post-2020 time period. As currently conceived Gen-X would be a follow-on to the International X-ray Observatory (IXO), with a collecting area ≥ 50 m2, 60-m focal length and 0.1 arc-second spatial resolution, which would be launched in ~2030 with an Ares V Cargo Launch Vehicle to an L2 orbit. Our design concept assumes an Ares V with a 10-m diameter, 1,400 m3 volume fairing (or an equivalent launch vehicle) will be developed for NASA's exploration program. The key features of this design include a 16-m diameter deployable x-ray mirror provides a collecting area of 136 m2; a 60-m deployable optical bench which utilizes a Tensegrity structure to achieve high stiffness with low mass; and adaptive grazing incidence optics. Gen-X's combination of large collecting area and high spatial resolution will provide 4 to 5 orders of magnitude greater sensitivity than IXO, enabling scientists to study the formation and growth of the first black holes at z ≈ 8-15 with 0.1 to 10 keV fluxes of ≈ 10-20 erg cm-2s-1.

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