In December 1990, the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) on the Astro-1 shuttle Spacelab mission obtained approximately eight hours of pioneering ultraviolet spectropolarimetric observations on more than 20 galactic and extragalactic objects. WUPPE is a 0.5 m Cassegrain telescope coupled to a Monk-Gilleson spectrometer with a magnesium fluoride polarizing beamsplitter preceded by magnesium fluoride halfwave retarders. Two spectra from 135 to 330 nm with orthogonal polarization are detected simultaneously by a pair of intensified photodiode arrays. The first flight measured for the first time the ultraviolet polarization induced by interstellar dust, the UV intrinsic polarization of the rapidly rotating `Be' stars, and the large polarization in a `hidden' active galactic nucleus. A second flight of Astro is currently scheduled for 1994.

We briefly describe the Spectrum-X-Gamma spacecraft, scheduled for launch in late 1995. The emphasis is made on the principal possibility of simultaneous polarimetric observations with more conventional ways of investigation of celestial x-ray sources in a wide range of energies. We also describe our approach to the Monte-Carlo simulations of the instrument. These simulations are needed in order to understand the performance of the SXRP instrument in actual flight conditions. These conditions will include offsets of the focal point of SODART telescope from the SXRP symmetry axis, the converging beam from SODART and others. In order to get means of extracting polarization value under various conditions, distorting perfect modulation from polarized x-rays we are also creating analytical model. This model will permit to take into account the majority of such factors.

The Stellar X-ray Polarimeter (SXRP) will be the third orbiting stellar x-ray polarimeter, and should provide an order of magnitude increase in polarization sensitivity over its predecessors. The SXRP exploits the polarization dependence of reflection from a graphite Bragg crystal and scattering from a lithium Thomson scattering target to measure the linear polarization of x- rays from astrophysical sources. In this paper, we review the status of the SXRP instrument.

Two sounding rockets payloads under development at the Space Astronomy Laboratory are intended to explore different forms of ultraviolet astronomical polarimetry as a follow-up to the successful mission of the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE). The unknown territory of diffuse-object ultraviolet polarimetry is to be explored by the Wide- Field Imaging Survey Polarimeter (WISP). WISP is a quite unusual integrated fast telescope/polarimeter optimized for the wavelengths 135 - 260 nm. The first WISP flight is scheduled for Fall 1993, targeting the Pleiades reflection nebula. Just in its early development is another sounding rocket payload, the Far-Ultraviolet Spectropolarimeter. This instrument is to have a resolution of better than 0.1 nm and a spectral coverage from 105 to 145 nm. It will consist of a 0.4 m parabolic primary with polarimetric optics at the prime focus and a far ultraviolet spectrometer. The polarimetric analyzer will be a thin stressed-LiF waveplate, followed by a diamond Brewster-angle polarizer.

A large area thin graphite crystal and a lithium scattering block are used as the polarization sensitive elements of the Stellar X-Ray Polarimeter. We discuss the construction, selection and characterization of these two polarizing elements. In addition, we describe the plans for calibration of the completed instrument and the facility where it will be conducted.

We have measured the states of polarization of synchrotron radiation at a few beamlines at the Photon Factory using multilayer mirrors as a polarizer or an analyzer. Remarkable differences between the observed data and the theoretical prediction have been found for bending magnet radiation. It has been also found that changes of the states of polarization, especially the inclination of the major axis of the polarization ellipses is caused by the beamline optics both for bending and undulator radiation.

Scattering polarimetry is based on the detection of photons scattered by a target at angles close to 90 degree(s). For Astrophysical purposes in the hard X-ray band, where a large collecting area is needed and optics are ineffective, we suggest to produce a large array of very thin detectors made of scintillating fibers read by optical fibers. We computed, by means of MCNP code the response of some possible configurations with different thickness of plastic scintillator, CsI and CaF₂.

Reflecting multilayers (ML) are widely used and their linearly polarizing property is well known. In particular an angle of incidence of 45 degree(s) theoretically leads to reflection of only the s-component. Kimura et al. used the phase shifting properties of a reflecting ML to measure circular polarization at 97 eV. A transmitting ML as phase shifting element for the same energy has been described and measured. In this paper we report on the use of a transmission ML as a phase shifting element at photon energies near the carbon K edge. Such devices can have applications in detecting and perhaps generation of circularly polarized soft x-rays.

An analysis is presented of the stray light expected in a Coronagraph/Polarimeter operating at the H I Lyman (alpha) (Ly-(alpha) ) line ((lambda) 121.6 nm) and utilizing multilayer interference film optics and ultrasmooth substrates (i.e., rms-smoothness