Publication archive

Publication archive

The Interstellar Heliopause Probe (IHP) is one of four Technology Reference Studies (TRS) introduced by the Planetary Exploration Studies Section of the Science Payload & Advanced Concepts Office (SCI-A) at ESA. The overall purpose of the TRSs is to focus the development of strategically important technologies of likely relevance to future science missions. This is accomplished through the study of several technologically demanding and scientifically interesting missions, which are currently not part of the ESA science programme. The TRS baseline uses small satellites (~ 200kg), with highly miniaturized and highly integrated payload suites. By using multiple low resource spacecraft in a phased approach, the risk and cost, compared to a single, high resource mission can be reduced.

Equipped with a Highly Integrated Payload Suite the IHP will answer scientific questions concerning the nature of the interstellar medium, how the interstellar medium affects our solar system and how the solar system impacts the interstellar medium.

This paper will present an update to the results of the studies being performed on this mission. The current mission baseline and alternative propulsion systems will be described and the spacecraft design and other enabling technologies will be discussed.

Published: 29 April 2005
The European Space Agency is currently studying the Jovian Minisat Explorer (JME), as part of its Technology Reference Studies (TRS). TRS are model science-driven studies contributing in the ESA strategic development plan of technologies that will enable future scientific missions.

The JME focuses on the exploration of the Jovian system and particularly the exploration of its moon Europa. The Jupiter Minisat Orbiter (JMO) study, which is the subject of the present paper, concerns the first mission phase of JME that counts up to three missions spaced in time by 6 years using pairs of minisats. The scientific objectives are the investigation of Europa's global topography, the composition of its (sub)surface and the demonstration of existence of a subsurface ocean below Europa's icy crust.

The present paper describes the candidate JMO system concept, based on a Europa Orbiter (JEO) supported by a communications relay satellite (JRS), and its associated technology development plan. It summarizes an analysis performed in 2004 jointly by ESA and the EADS-Astrium Company in the frame of an industrial technical assistance to ESA.

It addresses the interplanetary transfer, the hostile radiation environment, the power generation issue, the communication system, as well as the need for high autonomy on-board.

Published: 26 April 2005
ESA's Science Payload and Advanced Concepts Office (SCI-A) has recently introduced the Technology Reference Studies (TRS) as a technology development tool to provide a focus for the development of strategically important technologies that are of likely relevance for future scientific missions. This is accomplished through the study of several technologically demanding and scientifically interesting missions, which are not part of the ESA science programme.

The goal of the Deimos Sample Return (DSR) TRS is to study the means of collecting a scientifically significant sample from Deimos' surface and returning it to Earth. The DSR mission profile consists of a small spacecraft, launched on a Soyuz-Fregat 2B. After transferring to the Martian system, the spacecraft will enter into a co-orbit with Deimos where it will perform remote sensing observations and ultimately perform a series of sampling maneuvers. Upon completion of sampling the spacecraft will return to Earth, where the sample canister will perform a direct Earth entry.

This paper will outline the preliminary mission architecture of the DSR TRS, as well as the critical technology drivers. This will include an outline of sampling tools and methods appropriate for a small, low gravity body, as well as planetary protection and re-entry technologies.

Published: 26 April 2005
ESA's Science Payload & Advanced Concepts Office (SCI-A) has introduced Technology Reference Studies (TRS) to focus the development of strategically important technologies of likely relevance to future science missions. This is accomplished through the study of several technologically demanding and scientifically interesting missions, which are not part of the ESA science programme. Presently the Planetary Exploration Studies Section of SCI-A is studying four TRS; the Venus Entry Probe, the Jovian Minisat Explorer, the Deimos Sample Return and the Interstellar Heliopause Probe. These TRS cover a wide range of mission profiles in the solar system with an even wider range of strategic important technologies.

All TRS mission profiles are based on small satellites, with miniaturized highly integrated payload suites, launched on Soyuz Fregat-2B.

This paper describes the current four TRS in further detail and shows how these missions are used to identify and prepare the development of enabling technologies.

Published: 26 April 2005
The interaction between broadband drift mode turbulence and zonal flows has been studied through the wave-kinetic approach. Simulations have been conducted in which a particle-in-cell representation is used for the quasiparticles, while a fluid model is employed for the plasma. The interactions have been studied in a plasma edge configuration which has applications in both tokamak physics and magnetopause boundary layer studies. Simulation results show the development of a zonal flow through the modulational instability of the drift wave distribution, as well as the existence of solitary zonal flow structures about an ion gyroradius wide, drifting towards steeper relative density gradients.
Published: 29 April 2005
We have studied the entry paths of solar wind plasma into the magnetosphere during an extended period of northward IMF using an OpenGGCM MHD simulation of the cold dense plasma sheet (CDPS) event observed on October 23, 2003 by the Cluster spacecraft. We find that high-latitude reconnection occurs tailward of both cusps between the IMF and geomagnetic field. The newly created closed magnetic flux tubes capture magnetosheath plasma, and subsequently sink and shrink into the magnetosphere, while convecting tailward. The plasma that enters near the reconnection site is driven sunward and toward the low latitude region initially; it then drifts to the flanks. The captured plasma is characterized by small flow velocity, and it is moderately heated in the reconnection region. In the present case study we find the cold plasma enters the plasma sheet in the near Earth tail where it is observed by Cluster.
Published: 29 April 2005
The October 22-24, 2003 interplanetary magnetic cloud was characterized by an exceptionally long interval (~32 hours) of nearly purely northward interplanetary magnetic field (IMF). Following the northward IMF turning Cluster observed a gradual transition to a cold (<1 keV) and dense (~1-2 cm-3) plasma sheet (CDPS). Cluster observed CDPS continuously for the following ~30 hours while passing through the neutral sheet from the northern to the southern hemisphere. DMSP observations mapped to the equatorial plasma sheet reveal that the CDPS extended to all nightside local times. The FAST satellite observed reversed ion dispersion signatures in the cusp indicative of poleward-of-cusp reconnection, and nearly no polar cap. The CDPS observations show good agreement with a global MHD simulation where the CDPS is formed by poleward-of-cusp reconnection capturing magnetosheath plasma and convecting it to the tail. The process shrinks the size of the lobes (and therefore the polar cap) significantly, as observed.
Published: 29 April 2005
XMM-Newton EPIC observations of PSR B0656+14, PSR B1055-52, and Geminga have substantially increased the collection of statistics available for these three isolated neutron stars, so apparently similar to deserve the nickname of the Three Musketeers, given to them by Becker & Trumper. Here we take advantage of the EPIC statistics to perform phase-resolved spectroscopy for all three objects. The phase-averaged spectrum of the Three Musketeers is best described by a three-component model. This includes two blackbody components -a cooler one, possibly originating from the bulk of the star surface, and a hotter one, coming from a smaller portion of the star surface (a "hot spot") -plus a power law. The relative contributions of the three components are seen to vary as a function of phase, as the stars' rotation brings into view different emitting regions. The hot spots, which have very different apparent dimensions (in spite of the similarity of the three neutron stars polar cap radii) are responsible for the bulk of the phase variation. The amplitude of the observed phase modulation is also markedly different for the three sources. Another striking aspect of our phase-resolved phenomenology is the apparent lack of any common phase alignment between the observed modulation patterns for the two blackbody components. They are seen to vary in phase in the case of PSR B1055-52 but in antiphase in the case of PSR B0656+14. These findings do not support standard and simplistic models of neutron star magnetic field configuration and surface temperature distribution.
Published: 21 April 2005
The origin of the solar wind in solar coronal holes has long been unclear. We establish that the solar wind starts flowing out of the corona at heights above the photosphere between 5 megameters and 20 megameters in magnetic funnels. This result is obtained by a correlation of the Doppler-velocity and radiance maps of spectral lines emitted by various ions with the force-free magnetic field as extrapolated from photospheric magnetograms to different altitudes. Specifically, we find that Ne7+ ions mostly radiate around 20 megameters, where they have outflow speeds of about 10 kilometers per second, whereas C3+ ions with no average flow speed mainly radiate around 5 megameters. Based on these results, a model for understanding the solar wind origin is suggested.
Published: 23 April 2005
We report the discovery of persistent hard X-ray emission extending up to 150 keV from the soft gamma-ray repeater SGR 1806-20 using data obtained with the INTEGRAL satellite in 2003-2004. Previous observations of hard X-rays from objects of this class were limited to short duration bursts and rare transient episodes of strongly enhanced luminosity ("flares''). The emission observed with the IBIS instrument above 20 keV has a power law spectrum with photon index in the range 1.5-1.9 and a flux of 3 milliCrabs, corresponding to a 20-100 keV luminosity of ~1036 erg s-1 (for a distance of 15 kpc). The spectral hardness and the luminosity correlate with the level of source activity as measured from the number of emitted bursts.
Published: 02 March 2005
The scientific objectives of an advanced NeUtral Atom Detector Unit (NUADU) designed for the Chinese Double Star Polar Mission, which is scheduled for launch in July 2004, are described. The potential during this mission to realize, hitherto unprecedented, integrated studies of global dynamic magnetospheric processes through combining with NUADU data contemporaneous measurements made aboard the CLUSTER II, IMAGE and TWINS spacecraft is also discussed and a short technical account of NUADU provided.
Published: 15 January 2005
We present the analysis of XMM-Newton observations of three X-ray weak quasars: PG 1001+054, PG1535+547 and PG 2112+059. All objects are absorbed by ionized material showing high column densities, NH = 2.9 x 1022 cm-2 to NH = 1.9 x 1023 cm-2, and ionization parameters, xi = 147 erg cm s-1 to xi = 542 erg cm s-1. The spectra of PG1535+547 requires an additional partial covering by neutral material with a column density of NH approx 9 x 1022 cm-2 at a covering factor of approx 0.96. The spectra of PG1535+547 show systematic residuals in the energy range from sim 4 keV to sim 6 keV, which are inconsistent with Kalpha-fluorescence-emission of neutral or ionized iron under the assumption of a Gaussian line profile. They can be described with a relativistic disk line (Laor) and establish therefore the second X-ray weak quasar with such a spectral characteristic. Our results together with the findings of Brinkmann et al. (2004) and Piconcelli et al. (2004a), indicate that warm absorbers characterized by high column densities and ionization parameters are typical of X-ray weak quasars. The occurrence of a variable relativistic broad Fe Kalpha fluorescence line in two out of the five well studied X-ray weak quasars might indicate a second general characteristic of the entire object class. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.
Published: 07 April 2005

This report of the ESA-ESO working group on Extra-Solar Planets, produced by the first joint ESA-ESO working group (Chairman: M. Perryman, ESA, Co-chair: O. Hainaut, ESO), summarises the direction of exo-planet research that can be expected over the next 10 years or so, identifies the roles of the major facilities of the two organisations in the field, and concludes with some recommendations which may assist development of the field.

Published: 04 March 2005
It is believed that core-collapse supernovae (CCSN), occurring at a rate ~once per century, have seeded the interstellar medium with long-lived radioisotopes such as 60Fe (half-life 1.5 Myr), which can be detected by the gamma-rays emitted when they beta-decay. Here we report the detection of the 60Fe decay lines at 1173 keV and 1333 keV with fluxes 3.7 ± 1.1 × 10-5 photons cm-2 s-1 per line, in spectra taken by the SPI spectrometer on board INTEGRAL during its first year. The same analysis applied to the 1809 keV line of 26Al yielded a line flux ratio 60Fe/26Al = 0.11 ± 0.03. This supports the hypothesis that there is an extra source of 26Al in addition to CCSN.
Published: 02 March 2005
GRB 040403 is one of the faintest gamma-ray bursts for which a rapid and accurate localization has been obtained. Here we report on the gamma-ray properties of this burst, based on observations with the IBIS instrument aboard INTEGRAL, and the results of searches for its optical afterglow. The steep spectrum (power law photon index = 1.9 in the 20-200 keV range) implies that GRB 040403 is most likely an X-ray rich burst. Our optical limit of R > 24.2 at 16.5 h after the burst, indicates a rather faint afterglow, similar to those seen in other relatively soft and faint bursts.
Published: 02 March 2005
Very high energy gamma-rays probe the long-standing mystery of the origin of cosmic rays. Produced in the interactions of accelerated particles in astrophysical objects, they can be used to image cosmic particle accelerators. A first sensitive survey of the inner part of the Milky Way with the High Energy Stereoscopic System (HESS) reveals a population of eight previously unknown firmly detected sources of very high energy gamma-rays. At least two have no known radio or x-ray counterpart and may be representative of a new class of "dark" nucleonic cosmic ray sources.
Published: 25 March 2005
We present a 30 ks XMM-Newton observation of the z = 2.35 Type II radio quiet quasar RXJ1343.4+0001. These data provide the first good quality X--ray spectrum for this object. We measured a continuum slope Gamma = 1.85+/-0.10 with only an upper limit on the column density of the absorbing material of Nh <~ 10e22 cm-2 as well as a Fe K_alpha emission line at the 3sigma confidence level. We do not find therefore a highly absorbed object neither a truly flat spectrum as suggested on the basis of previous less sensitive ROSAT and ASCA measurements.
Published: 20 March 2005
Images from the Mars Express HRSC (High-Resolution Stereo Camera) of debris aprons at the base of massifs in eastern Hellas reveal numerous concentrically ridged lobate and pitted features and related evidence of extremely ice-rich glacier-like viscous flow and sublimation. Together with new evidence for recent ice-rich rock glaciers at the base of the Olympus Mons scarp superposed on larger Late Amazonian debris-covered piedmont glaciers, we interpret these deposits as evidence for geologically recent and recurring glacial activity in tropical and mid-latitude regions of Mars during periods of increased spin-axis obliquity when polar ice was mobilized and redeposited in microenvironments at lower latitudes. The data indicate that abundant residual ice probably remains in these deposits and that these records of geologically recent climate changes are accessible to future automated and human surface exploration.
Published: 17 March 2005
The majority of volcanic products on Mars are thought to be mafic and effusive. Explosive eruptions of basic to ultrabasic chemistry are expected to be common, but evidence for them is rare and mostly confined to very old surface features. Here we present new image and topographic data from the High Resolution Stereo Camera that reveal previously unknown traces of an explosive eruption at 30° N and 149° E on the northwestern flank of the shield volcano Hecates Tholus. The eruption created a large, 10-km-diameter caldera ~350 million years ago. We interpret these observations to mean that large-scale explosive volcanism on Mars was not confined to the planet's early evolution. We also show that glacial deposits partly fill the caldera and an adjacent depression. Their age, derived from crater counts, is about 5 to 24 million years. Climate models predict that near-surface ice is not stable at mid-latitudes today, assuming a thermo-dynamic steady state. Therefore, the discovery of very young glacial features at Hecates Tholus suggests recent climate changes. We show that the absolute ages of these very recent glacial deposits correspond very well to a period of increased obliquity of the planet's rotational axis.
Published: 17 March 2005
It is thought that the Cerberus Fossae fissures on Mars were the source of both lava and water floods two to ten million years ago. Evidence for the resulting lava plains has been identified in eastern Elysium, but seas and lakes from these fissures and previous water flooding events were presumed to have evaporated and sublimed away. Here we present High Resolution Stereo Camera images from the European Space Agency Mars Express spacecraft that indicate that such lakes may still exist. We infer that the evidence is consistent with a frozen body of water, with surface pack-ice, around 5° north latitude and 150° east longitude in southern Elysium. The frozen lake measures about 800 x 900 km in lateral extent and may be up to 45 metres deep - similar in size and depth to the North Sea. From crater counts, we determined its age to be 5 ± 2 million years old. If our interpretation is confirmed, this is a place that might preserve evidence of primitive life, if it has ever developed on Mars.
Published: 17 March 2005
28-Sep-2020 20:06 UT

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