The Imaging X-ray Polarimetry Explorer (IXPE) is an exciting international collaboration for a scientific mission that dramatically brings together the unique talents of the partners to expand observation space by simultaneously adding polarization measurements to the array of source properties currently measured (energy, time, and location). IXPE uniquely brings to the table polarimetric imaging. IXPE will thus open new dimensions for understanding how X-ray emission is produced in astrophysical objects, especially systems under extreme physical conditions-such as neutron stars and black holes. Polarization singularly probes physical anisotropies-ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin-that are not otherwise measurable. Hence, IXPE complements all other investigations in high-energy astrophysics by adding important and relatively unexplored information to the parameter space for studying cosmic X-ray sources and processes, as well as for using extreme astrophysical environments as laboratories for fundamental physics.

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The Imaging X-ray Polarimetry Explorer (IXPE)

A method of forming a discrete track recording pattern on a soft magnetic underlayer of a perpendicular magnetic recording disk. In one embodiment, the soft magnetic underlayer is continuous throughout the discrete track recording pattern.

Perpendicular magnetic discrete track recording disk

The XMM-Newton Observatory is a cornerstone mission of the European Space Agency's Horizon 2000 programme, and is the largest scientific satellite it has launched to date. This paper summarises the principal characteristics of the Observatory which are pertinent to scientific operations. The scientific results appearing in this issue have been enabled by the unprecedentedly large effective area of the three mirror modules, which are briefly described. The in-orbit performance and preliminary calibrations of the observatory are briefly summarised. The observations from the XMM-Newton calibration and performance verification phase, which are public and from which most papers in this issue have been derived, are listed. The flow of data from the spacecraft, through the ground segment, to the production of preliminary science products supplied to users is also discussed.

XMM-Newton observatory*: I. The spacecraft and operations. Commentary

In this paper we present the enhanced X-ray Timing and Polarimetry mission - eXTP. eXTP is a space science mission designed to study fundamental physics under extreme conditions of density, gravity and magnetism. The mission aims at determining the equation of state of matter at supra-nuclear density, measuring effects of QED, and understanding the dynamics of matter in strong-field gravity. In addition to investigating fundamental physics, eXTP will be a very powerful observatory for astrophysics that will provide observations of unprecedented quality on a variety of galactic and extragalactic objects. In particular, its wide field monitoring capabilities will be highly instrumental to detect the electro-magnetic counterparts of gravitational wave sources. The paper provides a detailed description of: (1) the technological and technical aspects, and the expected performance of the instruments of the scientific payload; (2) the elements and functions of the mission, from the spacecraft to the ground segment.

The enhanced X-ray Timing and Polarimetry mission - eXTP

Instrumental background in balloon-borne gamma-ray spectrometers is presented. The calculations are based on newly available interaction cross sections and new analytic techniques, and are the most detailed and accurate published to date. Results compare well with measurements made in the 20 keV to 10 MeV energy range by the Goddard Low Energy Gamma-ray Spectrometer (LEGS). The principal components of the continuum background in spectrometers with GE detectors and thick active shields are: (1) elastic neutron scattering of atmospheric neutrons on the Ge nuclei; (2) aperture flux of atmospheric and cosmic gamma rays; (3) beta decays of unstable nuclides produced by nuclear interactions of atmospheric protons and neutrons with Ge nuclei; and (4) shield leakage of atmospheric gamma rays. The improved understanding of these components leads to several recommended techniques for reducing the background.

Instrumental background in balloon-borne gamma-ray spectrometers and techniques for its reduction

An electrolytic plating process is provided for electrodepositing a nickel or nickel cobalt alloy which contains at least about 2% to 25% by atomic volume of phosphorous. The process solutions contains nickel and optionally cobalt sulfate, hypophosphorous acid or a salt thereof, boric acid or a salt thereof, a monodentate organic acid or a salt thereof, and a multidentate organic acid or a salt thereof. The pH of the plating bath is from about 3.0 to about 4.5. An electroplating process is also provided which includes electroplating from the bath a nickel or nickel cobalt phosphorous alloy. This process can achieve a deposit with high microyield of at least about 84 kg/mm 2 (120 ksi) and a density lower than pure nickel of about 8.0 gm/cc. This process can be used to plate a deposit of essentially zero stress at plating temperatures from ambient to 70° C.

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Nickel cobalt phosphorous low stress electroplating

A dispersed release of neutrons is generated from a source. A portion of this dispersed neutron release is reflected by surfaces of a plurality of nested, axisymmetric mirrors in at least an inner mirror layer and an outer mirror layer, wherein the neutrons reflected by the inner mirror layer are incident on at least one mirror surface of the inner mirror layer N times, wherein N is an integer, and wherein neutrons reflected by the outer mirror are incident on a plurality of mirror surfaces of the outer layer N+i times, where i is a positive integer, to redirect the neutrons toward a target. The mirrors can be formed by a periodically reversed pulsed-plating process.

Compact neutron imaging system using axisymmetric mirrors

The Astronomical Roentgen Telescope (ART) instrument is a hard x-ray instrument with energy response up to 30 keV that is to be launched on board of the Spectrum Roentgen Gamma (SRG) Mission. The instrument consists of seven identical mirror modules coupled with seven CdTe strip focal-plane detectors. The mirror modules are being developed at the Marshall Space Flight Center (MSFC.) Each module has approximately 65 sq. cm effective area and an on-axis angular resolution of 30 arcseconds half power diameter (HPD) at 8 keV. The current status of the mirror module development and testing will be presented.

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ART-XC/SRG: Status of the X-ray Optics Development

The Spectrum-Rontgen-Gamma (SRG) mission is a Russian-German X-ray astrophysical observatory that carries two co-aligned and complementary X-ray telescope systems The primary instrument is the German-led extended ROentgen Survey with an Imaging Telescope Array (eROSITA), a 7-module X-ray telescope system that covers the energy range from 02-12 keV The complementary instrument is the Russian-led Astronomical Roentgen Telescope -- X-ray Concentrator (ART-XC or ART), a 7-module X-ray telescope system that provides higher energy coverage, up to 30 keV (with limited sensitivity above 12 keV)

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The Marshall Space Flight Center development of mirror modules for the ART-XC instrument aboard the Spectrum-Roentgen-Gamma mission

MSFC is fabricating x-ray optics for the Astronomical Roentgen Telescope – X-Ray Concentrator (ART-XC or ART for short) instrument under agreements with the Russian Space Research Institute (IKI). ART-XC is one of two instruments that will be launched on the Russian-German Spectrum-Roentgen-Gamma (SRG) Mission to be launched in 20161. Delivery of the flight optics for ART-XC (7 mirror modules) is currently scheduled for summer/fall of 20142. MSFC has to date completed assembly of four modules and has performed extensive calibration on two of these. These calibrations show that the modules meet effective area requirements and greatly exceed the angular resolution requirements. Details of the calibration procedure and an overview of the results obtained to date are presented here.

B. Ramsey

Papers

Nickel cobalt phosphorous low stress electroplating

Compact neutron imaging system using axisymmetric mirrors

ART-XC/SRG: Status of the X-ray Optics Development

The Marshall Space Flight Center development of mirror modules for the ART-XC instrument aboard the Spectrum-Roentgen-Gamma mission

The calibration of flight mirror modules for the ART-XC instrument on board the SRG mission