Josef Polny

JEM-X: The X-ray monitor aboard INTEGRAL ?

The JEM-X monitor provides X-ray spectra and imaging with arcminute angular resolution in the 3 to 35 keV band. The good angular resolution and the low energy response of JEM-X plays an important role in the identification of gamma ray sources and in the analysis and scientific interpretation of the combined X-ray and gamma ray data. JEM-X is a coded aperture instrument consisting of two identical, coaligned telescopes. Each of the detectors has a sensitive area of 500 cm 2 , and views the sky through its own coded aperture mask. The two coded masks are inverted with respect to each other and provides an angular resolution of 3 0 across an eective field of view of about 10 diameter.

X-ray calibration of the SODART flight telescopes

The on- and off-axis imaging properties and effective area of the two SODART flight telescopes have been measured using the expanded beam x-ray facility at the Daresbury synchrotron. From on-axis measurements the encircled power distribution and the point spread function at three energies 6.627 keV, 8.837 keV and 11.046 keV have been measured using a one-dimensional position sensitive detector. We found that the point spread function can be presented well by a function which is a sum of a Gaussian divided by the radius and two exponential terms where the first has a 1/e value close to 2 arcmin and the other a 1/e value of ca. 15 arcmin. The data have been used to calculate the half power diameter (HPD) for three different SODART focal plane detectors, the high energy proportional counter (HEPC) with a field of view (FOV) of 65 arcmin, the low energy proportional counter (LEPC) with a FOV of 33 arcmin and the 19 element solid state detector array (SIXA) with a FOV of 18 arcmin. We found that the HPD decreases with increasing energy due to poorer figure of the outermost mirrors. The HPD falls in the range from 2.4 to 3.8 arcmin depending on energy and FOV. Data have also been obtained on the on- and off-axis effective area at all three energies and compared to that obtained from a raytracing of an ideal telescope configuration. We found that the measured on-axis effective area integrated over a FOV of 105 arcmin is ca. 65% of the area predicted from an ideal geometry. Finally the one- dimensional detector data has been used to obtain the radial dependence of the on-axis HPD and the on-axis effective area and the data from the two-dimensional position sensitive detector has been used to obtain the azimuthal dependence of the on-axis HPD and the on-axis effective area.

JEM-X inflight performance

We summarize the inflight performance of JEM-X, the X-ray monitor on the INTEGRAL mission during the initial ten months of operations. The JEM-X instruments have now been tuned to stable operational conditions. The performance is found to be close to the pre-launch expectations. The ground calibrations and the inflight calibration data permit to determine the instruments characteristics to fully support the scientific data analysis.

X-ray facility for the ground calibration of the X-ray monitor JEM-X on board INTEGRAL

We describe the X-ray facility developed for the calibration of the X-ray monitor JEM-X on board the INTEGRAL satellite. The apparatus allowed the scanning of the detector geometric area with a pencil beam of desired energy over the major part of the passband of the instrument. The monochromatic radiation is obtained with the use of a double crystal monochromator at fixed exit. We discuss the facility performance.

Optical measurements of the XSPECT mirrors and the assembled mirror modules for the SODART x-ray telescope on the Spectrum-X-Gamma satellite

The Danish Space Research Institute is supplying high- throughput x-ray mirror modules (MM) for the SODART telescopes to be flown on the Russian Spectrum-X-Gamma mission. We have finished the process of building two flight units and one spare unit. We have measured 5500 flight quality single mirrors using laser scanning. Edge deformations have been found to be a persistent phenomenon giving rise to reduced effective area and alignment accuracy. The degree of foil straightness is a function of the radius of curvature. Detailed optical measurements of the MMs is a control of the mechanical alignment achieved by repeated adjustments between the stages of assembly. The results of these investigations are discussed and compared with x-ray calibration measurements. A combination of the optical results and x ray results is fed into a raytracing code resulting in a reliable prediction of the imaging capabilities of the SODART telescopes.

JEM-X: the x-ray monitor on INTEGRAL

The INTEGRAL X-ray monitor, JEM-X, (together with the two gamma ray instruments, SPI and IBIS) provides simultaneous imaging with arcminute angular resolution in the 3-35 keV band. The good angular resolution and low energy response of JEM-X plays an important role in the detection and identification of gamma ray sources as well as in the analysis and scientific interpretation of the combined X-ray and gamma ray data. JEM-X is a coded aperture X-ray telescope consisting of two identical detectors. Each detector has a sensitive area of 500 cm2, and views the sky through its own coded aperture mask. The coded masks are located 3.4 m above the detector windows. The detector field of view is constrained by X-ray collimators (6.6° FOV, FWHM).

TopHat series of top mounted balloon-borne telescopes

We describe the engineering design and operational concept for a series of three complementary top mounted balloon- borne experiments to measure the Cosmic Microwave Background Radiation anisotropy, culminating in a two week circumpolar flight from McMurdo Station, Antarctica. Each experiment is designed to provide a maximum science return in addition to acting as a pathfinder to the successor flights of top- mounted balloon-borne experiments. The experiment program, named TopHat, will involve the launch and operation of the first far-infrared and microwave telescope flown entirely from the top of a 28 million cubic foot balloon. It utilizes a two axis gimbal pointing system, a one meter Cassegrain optical system with a chopping secondary mirror, and a 3He evaporation cryostat designed to maintain a bolometer detector temperature of 0.25 K for 30 days without cycling. The series of flights will begin with an engineering test flight scheduled for launch in July 1996 from Palestine, Texas, followed by a pointing experiment to be flown from Ft. Sumner, New Mexico in April 1997. A spinning experiment will be launched from Ft. Sumner in April 1998 and Antarctica in December 1998.

SODART optical block of the SRG satellite: design and integration

This paper describes the design and the successful integration of the optical block of the SODART telescopes to be flown on the Spectrum Roentgen Gamma satellite. The integration involves both the integration of the two high throughput x-ray telescopes as well as the objective crystal spectrometer. The integrated unit meets all mechanical, thermal and optical specifications and it is now in safe storage in Moscow and awaits further integration procedures with the remaining satellite structure.

Production, assembly, and alignment of the XSPECT mirror modules for the SODART x-ray telescope on the Spectrum Roentgen Gamma satellite

Danish Space Research Institute is supplying the high throughput x-ray concentrators, the so called SODART telescopes, to be flown on the Spectrum Rontgen-Gamma (SRG) satellite. We have completed the process of the developing, building, testing and calibrating the two flight units and one spare unit. Their design is based on the principle of multiple, concentrically nested foil mirrors constituting a conical approximation of the Wolter I geometry. We describe some aspects of the mechanical design, alignment and production process. The optical characteristics of the thin foil telescopes are partly determined by the optical characteristics of the foil mirrors and partly by the assembly and alignment tolerances. The influence of the mirror manufacture processes on some aspects of its optical characteristics is discussed. The concept and the steps of the assembly and alignment procedure are given. The process of obtaining the required accuracy involves a number of technological processes that need optimization in order to reduce the mechanical errors. The overall alignment was tested and improved by optical methods. The experience gained during the development and building of the SODART telescopes shows the potential for improvements in the utilization of the foil mirrors optical characteristics and in future thin foil telescope design and manufacture.

X-ray study of a SODART flight telescope using the expanded beam x-ray optics beamline at the Daresbury synchrotron

The on- and off-axis imaging properties of the first of two SODART flight telescopes have been studied using the expanded beam x-ray facility at the Daresbury synchrotron. From on- axis measurements the encircled power distribution and the point spread function at three energies 6.627 keV, 8.837 keV, and 11.046 keV have been measured using a one dimensional position sensitive detector. The data have been used to calculate the half power diameter (HPD) for three different SODART focal plane detectors, the high energy proportional counter (HEPC), the low energy proportional counter (LEPC) and the 19 element solid state array detector (SIXA). We found that the HPD decreases with increasing energy due to poorer figure error of the outermost mirrors. The HPD falls in the range from 2.3 to 3 arcmin for all detectors. Residual misalignment of the individual quadrants of the telescope was found to contribute to the HPD by approximately 10%. If 33% of the geometric telescope area near the edges of the quadrants are covered a reduction of 10% of the HPD can be obtained. On- and off-axis images generated from the one dimensional intensity distribution are presented. Finally the data have been used to calculate the variation of the effective area versus the off- axis angle.