ESA Science & Technology - Publication Archive

The superconducting differential accelerometers both for the Equivalence Principle experiment and geodesy within the European STEP mission have common design principles. The test masses are suspended by stable superconducting magnetic levitation. The suspension design makes all the degrees of freedom of the masses stiff, except for the axial differential mode which is made compliant in order to obtain a high intrinsic sensitivity of the differential accelerometer, < 10^-14m s^-2Hz^-1/2. Trimming of persistent currents circulating in the levitation system allows to achieve rejection ratios for the unwanted common and radial accelerations > 10⁶. Two separate superconducting circuits couple the axial displacements of the test masses to two SQUIDs. Persistent currents are stored in the two circuits such that one SQUID is only coupled to the differential displacement while the other only senses the common one. By differencing the signal before its detection, one highly reduces the dynamic range needs of the SQUIDs, of the following amplifiers and of the final A/D converters.

Few facts in science are more surprising and none has had a longer history than the apparent equivalence of the two kinds of mass in physics, gravitational and inertial. From Galileo and Newton to Eötvös and Einstein, it has been a compelling issue both theoretically and experimentally. Ground-based tests have now a precision of about 1 part in 10¹². Even with this extraordinary agreement, there are profound theoretical reasons for carrying the measurements further. Our generation has the unique oppurtunity to make an advance of a factor of a million in testing the Equivalence Principle in space.

A special ESA publication to coincide with the 1st annivsary of the launch of the INTEGRAL spacecraft. Contribution were made by various members of the entire mission and project teams to give a unique account of a year in the life of a spacecraft.

Electric and magnetic field observations on the Polar satellite at the subsolar magnetopause show that the magnetopause current is often striated. The largest of the resulting current channels are interpreted as electron diffusion regions because their widths are several electron skin depths and the electron flow U_e within them does not satisfy E + U_e x B = 0. The data suggest that the magnetopause contains many such electron diffusion regions and that they are required because E x B/B² drifting electrons cannot carry the large filamentary currents imposed on the local plasma. The most probable interpretation of E + U_e x B is not equal to 0 is that the pressure term on the right side of the generalized Ohm's law balances this inequality.

In November 1993, the International Rosetta Mission was approved as a Cornerstone Mission in ESA's Horizons 2000 Science Programme. Since then, scientists and engineers from all over Europe and the United States have been combining their talents to build an orbiter and a lander for this unique expedition to unravel the secrets of a mysterious mini ice world – a comet.

Table of contents:

• Rosetta: Europe's comet chaser
• Why 'Rosetta'
• Life and survival in deep space
• The cosmic billiard ball
• The long trek
• Rendezvous with a comet
• Debris of the Solar System: asteroids
• Debris of the Solar System: Comet 67P/Churyumov-Gerasimenko
• The Rosetta orbiter
• Science from the orbiter
• The Rosetta lander
• Long-distance communication
• Rosetta overview

Note: a more recent Rosetta mission brochure (ESA BR-321) is available here.

We report the detection with the BeppoSAX Wide Field Cameras of a superburst from 4U 1254-69. The superburst is preceded by a normal type-I X-ray burst, has a decay time that is the longest of all eight superbursts detected so far and a peak luminosity that is the lowest. Like for the other seven superbursts, the origin is a well-known type-I X-ray burster with a persistent luminosity level close to one tenth of the Eddington limit. Based on WFC data of all persistently bright X-ray bursters, the average rate of superbursts is 0.51 +/- 0.25 per year per persistently bright X-ray burster. Some systems may have higher superburst rates. For all superbursters, we present evidence for a pure helium layer which is burnt in an unstable as well as a stable manner.

We describe the "Monitor e Imageador de Raios-X" (MIRAX), an X-ray astronomy satellite mission proposed by the high-energy astrophysics group at the National Institute for Space Research (INPE) in Brazil to the Brazilian Space Agency. MIRAX is an international collaboration that includes, besides INPE, the University of California San Diego, the University of Tubingen in Germany, the Massachusetts Institute of Technology and the Space Research Organization Netherlands.

The ESA Annual Report 2002 contains a summary of all the activities undertaken by ESA during 2002.

This Special Letters Issue features the INTEGRAL observatory. About one year after its successful launch, this series of 75 publications describe the mission, the various instruments and their performance, as well as first scientific results from the spacecraft, ranging from gamma-ray bursts to Galactic sources.

Several important INTEGRAL events took place during the last two months.

We celebrated the first launch anniversary, on 17 October, with the spacecraft in excellent shape. Unfortunately, recent high solar activity substantially interrupted the observing programme, for the first time.

Although the research of cosmic rays began nearly 100 years ago much is still unknown especially with regard to their origins and the mechanisms providing the particles nearly the speed of light. That is why the cosmic ray research continues to be one of the most fascinating adventures of modern space science. This article is based on publications of the International Space Science Institute on cosmic rays, which are strongly recommended for further reading.

The Lynx arc, with a redshift of 3.357, was discovered during spectroscopic follow-up of the z=0.570 cluster RX J0848+4456 from the ROSAT Deep Cluster Survey. The arc is characterized by a very red R-K color and strong, narrow emission lines. Analysis of HST WFPC2 imaging and Keck optical and infrared spectroscopy shows that the arc is an H II galaxy magnified by a factor of ~10 by a complex cluster environment. The high intrinsic luminosity, the emission-line spectrum, the absorption components seen in Lyalpha and C IV, and the rest-frame ultraviolet continuum are all consistent with a simple H II region model containing ~10⁶ hot O stars. The best-fit parameters for this model imply a very hot ionizing continuum (T_BB~= 80 000 K), a high ionization parameter (logU~=-1), and a low nebular metallicity (Z/Z_solar~=0.05). The narrowness of the emission lines requires a low mass-to-light ratio for the ionizing stars, suggestive of an extremely low metallicity stellar cluster. The apparent overabundance of silicon in the nebula could indicate enrichment by past pair-instability supernovae, requiring stars more massive than ~140 M_solar.

Presentation given during the 5th IAA International Conference on Low Cost Planetary Missions on 24th September 2003 by Bernard Foing

Proceedings of the Fifth IAA International Conference on Low-Cost planetary Missions

Geosail is a small, low cost, innovative mission designed to exploit the versatility of solar sail propulsion for the exploration of magnetic reconnection and electron dynamics in the earth's magnetotail. The GeoSail mission requires only a very low performance solar sail to precess the major axis of an otherwise inertially fixed orbit, thus maintaining payload alignment within the geomagnetic tail. This constant rotation enables a near continuous observation window with the opportunity to probe the rapid dynamic evolution of energetic particle distributions in this critical region of geospace. An end-to-end system design study has been concluded and the key performance requirements identified. The level of solar sail performance required for GeoSail is typical of that currently being discussed within Europe for a near-term technology demonstration mission. GeoSail is therefore capable of providing both technology validation within the cost restrictions of a SMART mission while also returning unique science data from a first solar sail mission.

The last few months have proved to be a time when both the Hubble project and the ST-ECF are considering the transition period when Hubble will end its life and the James Webb Space Telescope (JWST) will begin operations.

Planck is the third Medium-Sized Mission (M3) of ESA's Horizon 2000 Scientific Programme. It is designed to image the anisotropies of the Cosmic Microwave Background (CMB) over the whole sky, with unprecedented sensitivity (DeltaT/T ~ 2 x 10^-6) and angular resolution (better than 10 arcminutes). Planck will provide a major source of information relevant to several cosmological and astrophysical issues, such as testing theories of the early universe and the origin of cosmic structure. The ability to measure to high accuracy the angular power spectrum of the CMB fluctuations will allow the determination of fundamental cosmological parameters such as the density parameter (Omega₀) and the Hubble constant H₀, with an uncertainty of order a few percent. In addition to the main cosmological goals of the mission, the Planck sky survey will be used to study in detail the very sources of emission which "contaminate" the signal due to the CMB, and will result in a wealth of information on the properties of extragalactic sources, and on the dust and gas in our own galaxy. One specific notable result will be the measurement of the Sunyaev-Zeldovich effect in many thousands of galaxy clusters. We will present an overview of the Planck mission, its scientific objectives, the key elements of its technical design, and its current status.

In this paper we define and describe morphological features that have colloquially been termed "spiders" and map their distribution in the south polar region of Mars. We show that these features go through a distinct seasonal evolution, exhibiting dark plumes and associated fan-shaped deposits during the local defrosting of the seasonal cap. We have documented the seasonal evolution of the cryptic region and have found that spiders only occur within this terrain. These observations are consistent with a geyser-like model for spider formation. Association with the transparent (cryptic) portion of the seasonal cap is consistent with basal sublimation and the resulting venting of CO₂ gas. Also consistent with such venting is the observation of dark fan-shaped deposits apparently emanating from spider centers. Spiders are additionally confined to the polar layered deposits presumably due to the poorly consolidated and easily eroded nature of their upper surface.

Eds. Marsden, R., Scherer, K. and Heber, B.

Launched from Cape Canaveral more than 13 years ago, Ulysses is well on its way to completing two full circuits of the Sun in a unique orbit that takes it over the north and south poles of our star. In doing so, the European-built space probe and its payload of scientific instruments have added a fundamentally new perspective to our knowledge of the bubble in space in which the Sun and the Solar System exist, called 'the heliosphere'.