A. M. Cruise

The Coronal Diagnostic Spectrometer for the Solar and Heliospheric Observatory

The Coronal Diagnostic Spectrometer is designed to probe the solar atmosphere through the detection of spectral emission lines in the extreme ultraviolet wavelength range 150–800 A. By observing the intensities of selected lines and line profiles we may derive temperature, density, flow and abundance information for the plasmas in the solar atmosphere. Spatial and temporal resolutions of down to a few arcseconds and seconds, respectively, allow such studies to be made within the fine-scale structure of the solar corona. Furthermore, coverage of large wavelength bands provides the capability for simultaneously observing the properties of plasmas across the wide temperature ranges of the solar atmosphere.

The Bragg Crystal Spectrometer for SOLAR-A

The Bragg Crystal Spectrometer (BCS) is one of the instruments which makes up the scientific payload of the SOLAR-A mission. The spectrometer employs four bent germanium crystals, views the whole Sun and observes the resonance line complexes of H-like Fexxvi and He-like Fexxv, Caxix, and Sxv in four narrow wavelength ranges with a resolving power (λ/Δλ) of between 3000 and 6000. The spectrometer has approaching ten times better sensitivity than that of previous instruments thus permitting a time resolution of better than 1 s to be achieved. The principal aim is the measurement of the properties of the 10 to 50 million K plasma created in solar flares with special emphasis on the heating and dynamics of the plasma during the impulsive phase. This paper summarizes the scientific objectives of the BCS and describes the design, characteristics, and performance of the spectrometers.

LISA Pathfinder: the experiment and the route to LISA

LISA Pathfinder (LPF) is a science and technology demonstrator planned by the European Space Agency in view of the LISA mission. As a scientific payload, the LISA Technology Package on board LPF will be the most precise geodesics explorer flown as of today, both in terms of displacement and acceleration sensitivity. The challenges embodied by LPF make it a unique mission, paving the way towards the space-borne detection of gravitational waves with LISA. This paper summarizes the basics of LPF, and the progress made in preparing its effective implementation in flight. We hereby give an overview of the experiment philosophy and assumptions to carry on the measurement. We report on the mission plan and hardware design advances and on the progress on detailing measurements and operations. Some light will be shed on the related data processing algorithms. In particular, we show how to single out the acceleration noise from the spacecraft motion perturbations, how to account for dynamical deformation parameters distorting the measurement reference and how to decouple the actuation noise via parabolic free flight.

Sirius B: A New, More Accurate View*

Long-standing questions regarding the temperature, gravity, mass, and radius of the well-known white dwarf Sirius B are considered in light of new data. Recently obtained Extreme Ultraviolet Explorer (EUVE) observations and reprocessed IUE NEWSIPS data have produced a new, well-defined effective temperature of 24,790 ± 100 K and a surface gravity of log g = 8.57 ± 0.06 for Sirius B. A new Hipparcos parallax for the Sirius system of π = 037921 ± 000158 is used in conjunction with the above spectroscopic results and the previously published gravitational redshift to yield a mass of 0.984 ± 0.074 M☉ and a radius of R = 0.0084 ± 0.00025R☉ for the white dwarf. Combining these results with the existing astrometric mass for Sirius B gives a refined mass estimate of M = 1.034 ± 0.026 M☉. The mass and radius for Sirius B are found to be consistent with the theoretical mass-radius relation for a carbon-core white dwarf. The EUVE spectrum is also used to determine a firm upper limit of He/H = 1.8 × 10-5 for the helium mixing ratio in the photosphere of Sirius B. IUE echelle spectra of Sirius B provide an estimate of log NH I = 17.72 ± 0.1 for the interstellar H I column to this star.

An electromagnetic detector for very-high-frequency gravitational waves

An interaction between a gravitational wave and the polarization vector of an electromagnetic wave is described in which the polarization vector rotates about the direction of propagation. If a resonant condition can be established with the electromagnetic wave always experiencing the same phase of the gravitational wave then the effect is cumulative and can be enhanced linearly by repeated circuits of a closed loop. When implemented with realistic experimental apparatus, a detector sensitive to gravitational waves at very high frequencies can be envisaged, in a frequency range where the signals are expected to be from cosmological sources at very early moments in the Universe.

The AMPTE UKS Spacecraft

The decision to include a third spacecraft, the UKS, in the AMPTE mission was made in 1981. The reasons for this are presented, together with a description of the spacecraft, its subsystems, and a summary of its early orbit performance. The UKS scientific instruments, and early results from them, are described in companion papers in this issue.

Results from the first stage of a UK Galactic dark matter search using low background sodium iodide detectors

Abstract Low-energy background spectra from 1.3 kg and 6.2 kg NaI(TI) crystal scintillators operating in the shielded Boulby underground facility were measured. Upper limits to the scattering interaction rates and cross-sections of Galactic dark matter in the form of Weakly Interacting Massive Particles (WIMPs) are calculated from these data. This work provides an improved limit for spin-dependent interactions for WIMP masses above 10 GeV.

Construction and testing of the optical bench for LISA Pathfinder

eLISA is a space mission designed to measure gravitational radiation over a frequency range of 0.1–100 mHz (European Space Agency LISA Assessment Study Report 2011). It uses laser interferometry to measure changes of order 10 pm/ √ Hz in the separation of inertial test masses housed in spacecraft separated by 1 million km. LISA Pathfinder (LPF) is a technology demonstrator mission that will test the key eLISA technologies of inertial test masses monitored by laser interferometry in a drag-free spacecraft. The optical bench that provides the interferometry for LPF must meet a number of stringent requirements: the optical path must be stable at the few pm/ √ Hz level; it must direct the optical beams onto the inertial masses with an accuracy of better than ±25 μm, and it must be robust enough not only to survive launch vibrations but to achieve full performance after launch. In this paper we describe the construction and testing of the flight optical bench for LISA Pathfinder that meets all the design requirements.

A prototype gravitational wave detector for 100 MHz

A prototype gravitational wave detector has been constructed for observations at 100 MHz. The device uses an interaction between an electromagnetic wave and the curved spacetime of the gravitational wave. A resonance effect is used to improve the sensitivity by a factor of ~2000 over a narrow bandwidth. Two prototype detectors have been constructed and their outputs used in a correlation experiment to improve the sensitivity by one or more orders of magnitude, giving a noise spectral density of ~10−14 Hz−1/2 at 100 MHz. Target sources for an improved detector would include the stochastic gravitational wave background from energetic events in the very early universe and black hole interactions in higher dimensional gravitational theories. Possible technological pathways for improving the sensitivity are suggested.

A correlation detector for very high frequency gravitational waves

Several processes active in the very early universe are thought capable of generating gravitational waves at frequencies above 1 MHz. These include parametric amplification of quantum fluctuations during inflation and bubble cavitation during first-order phase changes. Predictions of the likely spectra of such radiation often show peaks in the MHz to GHz region, far beyond the range of either bar detectors or interferometers and so other detection methods must be developed. A correlation detector based on these principles is being commissioned at Birmingham.