ESA Science & Technology - Publication Archive

This note summarises the status of the Gaia project at the end of 2004, describing the progress achieved in 2004, and summarising the major ongoing and planned activities. An important development was the appointment of the Gaia Project Team within the Projects Department of the ESA Directorate of Science, signifying the transition from study to project phase. The target launch date is 1 December 2011. Compared to the target 1 year ago, this represents a delay of more than 1 year. On the positive side, this corresponds to a technical feasibility assessment of the newProject Team, and may still be compared with the 'not later than 2012' launch target mandated by the Science Programme Committee when the project was accepted by ESA in 2000.

During Nov. 26-29, 2003 XMM-Newton observed soft (0.2-2 keV) X-ray emission from Jupiter for 69 hours. The low-latitude X-ray disk emission of Jupiter is observed to be almost uniform in intensity with brightness that is consistent with a solar-photon driven process. The simultaneous light curves of Jovian equatorial X rays and solar X rays (measured by the TIMED/SEE and GOES satellites) show similar day-to-day variability. A large solar X-ray flare occurring on the Jupiter-facing side of the Sun is found to have a corresponding feature in the Jovian X rays. These results support the hypothesis that X-ray emission from Jovian low-latitudes are solar X rays scattered from the planet's upper atmosphere, and suggest that the Sun directly controls the non-auroral X rays from Jupiter's disk. Our study also suggests that Jovian equatorial X rays can be used to monitor the solar X-ray flare activity on the hemisphere of the Sun that is invisible to space weather satellites.

The presentation was given at the SPC meeting in Paris on 10 February 2005 and presented the status of the SMART-1 mission, as well as a case for a 1 year mission extension.

Author: Bernard Foing et al.

Link to Publication	[pdf, 7.9 Mb]
Additional Slides	[pdf, 4.5 Mb]

The center of our Galaxy is a known strong source of electron-positron 511 keV annihilation radiation. Thus far, however, there have been no reliable detections of annihilation radiation outside of the central radian of our Galaxy. One of the primary objectives of the INTEGRAL (International Gamma-Ray Astrophysics Laboratory) mission, launched in 2002 October, is the detailed study of this radiation. The Spectrometer on INTEGRAL (SPI) is a high-resolution, coded-aperture gamma-ray telescope with an unprecedented combination of sensitivity, angular resolution, and energy resolution. We report results from the first 10 months of observation. During this period a significant fraction of the observing time was spent in or near the Galactic plane. No positive annihilation flux was detected outside of the central region (|l|>40°) of our Galaxy. In this paper we describe the observations and data analysis methods and give limits on the 511 keV flux.

The massive cluster of galaxies Abell 2219 (z=0.228) with two spectacular gravitational lensing arcs was observed at 14.3mu (hereafter 15mu) with the Infrared Space Observatory and results were published by Barvainis et al.(1999). These observations have been reanalyzed using a method specifically designed for the detection of faint sources that had been applied to other clusters.

Five new sources were detected and the resulting cumulative total of ten sources all have optical counterparts. The mid-infrared sources are identified with three cluster members, three foreground galaxies, an Extremely Red Object, a star and two galaxies of unknown redshift. The spectral energy distributions (SEDs) of the galaxies are fit with models from a selection, using the program GRASIL. Best-fits are obtained, in general, with models of galaxies with ongoing star formation. Infrared luminosities and star formation rates are obtained for six sources_ the cluster members and the foreground galaxies. For the three cluster members the infrared luminosities derived from the model SEDs are between 5.7x10e10 L_sol and 1.4x10e11 L_sol, corresponding to infrared star formation rates between 10 and 24 M_sol/yr. The two cluster galaxies that have optical classifications are in the Butcher-Oemler region of the colour-magnitude diagramme. The three foreground galaxies have infrared luminosities between 1.5x10E10 L_sol and 9.4x10e10 L_sol, yielding infrared star formation rates between 3 and 16 M_sol/yr. Two of the foreground galaxies are located in two foreground galaxy enhancements (Boschin et al.2004). Including Abell 2219, six distant clusters of galaxies have been mapped with ISOCAM and luminous infrared galaxies (LIRGs) have been found in three of them. The presence of LIRGs in Abell 2219 strengthens the association between luminous infrared galaxies in clusters and recent or ongoing cluster merger activity.

We report a detection of methane in the martian atmosphere by the Planetary Fourier Spectrometer onboard the Mars Express spacecraft. The global average methane mixing ratio is found to be 10 +/- 5 parts per billion by volume (ppbv). However, the mixing ratio varies between 0 and 30 ppbv over the planet. The source of methane could be either biogenic or nonbiogenic, including past or present subsurface microorganisms, hydrothermal activity, or cometary impacts.

The Analyzer of Space Plasma and Energetic Atoms (ASPERA) on board the Mars Express spacecraft found that solar wind plasma and accelerated ionospheric ions may be observed all the way down to the Mars Express pericenter of 270 kilometers above the dayside planetary surface. This is very deep in the ionosphere, implying direct exposure of the martian topside atmosphere to solar wind plasma forcing. The low-altitude penetration of solar wind plasma and the energization of ionospheric plasma may be due to solar wind irregularities or perturbations, to magnetic anomalies at Mars, or both.

On 14 January 2005, after a marathon seven-year journey through the Solar System aboard the Cassini spacecraft, ESA's Huygens probe successfully descended through the atmosphere of Titan, Saturn's largest moon, and landed safely on its surface. It was mankind's first successful attempt to land a probe on another world in the outer Solar System. Following its release from the Cassini mothership on 25 December, Huygens reached Titan's outer atmosphere after 20 days and a 4 million kilometre cruise. The probe started its descent through Titan's hazy cloud layers from an altitude of about 1270 km at 09:06 UTC. During the following three minutes, Huygens had to decelerate from 18 000 to 1400 km per hour.

Contents

• 3rd Announcement of Opportunity
• Mission Status
• INTEGRAL science workshop
• Science Operations - Highlights
• ISOC at ESAC - latest news
• List of approved open time AO-3 observations

We present Chandra and XMM-Newton observations of a small sample (11 objects) of optically-selected Seyfert 2 galaxies, for which ASCA and BeppoSAX had suggested Compton-thick obscuration of the Active Nucleus (AGN). The main goal of this study is to estimate the rate of transitions between "transmission-" and "reprocessing-dominated" states. We discover one new transition in NGC4939, with a possible additional candidate in NGC5643. This indicates a typical occurrence rate of at least 0.02/year. These transitions could be due to large changes of the obscuring gas column density, or to a transient dimming of the AGN activity, the latter scenario being supported by detailed analysis of the best studied events. Independently of the ultimate mechanism, comparison of the observed spectral dynamics with Monte-Carlo simulations demonstrates that the obscuring gas is largely inhomogeneous, with multiple absorbing components possibly spread through the whole range of distances from the nucleus between a fraction of parsecs up to several hundreds parsecs. As a by-product of this study, we report the first measurement ever of the column density covering the AGN in NGC3393, and the discovery of soft X-ray extended emission, apparently aligned along the host galaxy main axis in NGC5005. The latter object hosts most likely an historically misclassified low-luminosity Compton-thin AGN.

In the last decade star clusters have been found in the centers of spiral galaxies across all Hubble types. We here present a spectroscopic study of the exceptionally bright (10⁶10⁸ L_Sun) but compact (r_e ~ 5 pc) nuclear star clusters in very late type spirals with the Ultraviolet and Visual Echelle Spectrograph at the VLT. We find that the velocity dispersions of the nine clusters in our sample range from 13 to 34 km s^-1. Using photometric data from the Hubble Space Telescope WFPC2 and spherically symmetric dynamical models, we determine masses between 8 x 10⁵ and 6 x 10⁷ M_Sun. The mass-to-light ratios range from 0.2 to 1.5 in the I band. This indicates a young mean age for most clusters, in agreement with previous studies.

We report the XMM-Newton discovery of a X-ray bright AGN pair in the interacting galaxy system ESO509-IG066. Both galaxies host an X-ray luminous (L_X ~ 10⁴³ erg/s) obscured nucleus with column densities N_H ~ 7x10²² and N_H ~ 5 x 10²¹ atoms.cm^-2. The optical morphology is only mildly disturbed, suggesting a merging system in the early stage of its evolution. Still, the pair is probably gravitationally bound, and might eventually evolve into a compact, fully gas embedded systems such as NGC6240.

Temporal and spatial characteristics of intense quasi-static electric fields and associated electric potential structures in the return current region are discussed using Cluster observations at geocentric distances of about 5 Earth radii. Results are presented from four Cluster encounters with such acceleration structures to illustrate common as well as different features of such structures. The electric field structures are characterized by (all values are projected to 100 km altitude) peak amplitudes of ~1V/m, bipolar or unipolar profiles, perpendicular scale sizes of ~10km, occurrence at auroral plasma boundaries associated with plasma density gradients, downward field-aligned currents of ~10 microA/m², and upward electron beams with characteristic energies of a few hundred eV to a few keV. Two events illustrate the temporal evolution of bipolar, diverging electric field structures, indicative of positive U-shaped potentials increasing in magnitude from less than 1kV to a few kV on a few 100s time scale. This is also the typical formation time for ionospheric plasma cavities, which are connected to the potential structure and suggested to evolve hand-in-hand with these. In one of these events an energy decay of inverted-V ions was observed in the upward field-aligned current region prior to the acceleration potential increase in the adjacent downward current region, possibly suggesting that a potential redistribution took place between the two current branches. The other two events were characterized by intense unipolar electric fields, indicative of S-shaped potential contours and were encountered at the polar cap boundary. -- abstract truncated --

Using the Fourier Transform Spectrometer at the Canada France Hawaii Telescope, we observed a spectrum of Mars at the P-branch of the strongest CH₄ band at 3.3 Œm with resolving power of 180,000 for the apodized spectrum. Summing up the spectral intervals at the expected positions of the 15 strongest Doppler-shifted martian lines, we detected the absorption by martian methane at a 3.7 sigma level which is exactly centered in the summed spectrum. The observed CH₄ mixing ratio is 10+/-3 ppb. Total photochemical loss of CH₄ in the martian atmosphere is equal to 2.2x10 cms, the CH₄ lifetime is 340 years and methane should be uniformly mixed in the atmosphere. Heterogeneous loss of atmospheric methane is probably negligible, while the sink of CH₄ during its diffusion through the regolith may be significant. There are no processes of CH₄ formation in the atmosphere, so the photochemical loss must therefore be balanced by abiogenic and biogenic sources. - Remainder of abstract truncated -

Data obtained with the NICMOS instrument on board the Hubble Space Telescope (HST) have been used to determine the H-band luminosity function (LF) and mass function (MF) of three stellar fields in the globular cluster M15, located ~7' from the cluster centre. The data confirm that the cluster MF has a characteristic mass of ~0.3 Msolar, as obtained by Paresce & De Marchi (2000) for a stellar field at 4.6' from the centre. By combining the present data with those published by other authors for various radial distances (near the centre, at 20" and at 4.6'), we have studied the radial variation of the LF due to the effects of mass segregation and derived the global mass function (GMF) using the Michie-King approach.

Both amateur and professional meteor groups more and more use Low-Light level TV (LLTV) systems to record meteors. Double-station observations can yield orbit data. However, data analysis normally is still done by hand and thus time consuming. This paper addresses the question whether available automated tools can be used to determine reasonably accurate orbits with minimum human intervention.

The European Space Agency performed several observing campaigns to observe the Leonid meteor stream. In November 1999, the ESA meteor group was stationed at two locations in Southern Spain, in November 2001 at two stations close to Broome in North-Western Australia. Double-station observations with LLTV systems were conducted. The data was recorded on S-VHS video tapes. The tapes were digitized using automatic detection software. Meteor heights, velocities and radiants were computed. This paper shows the results for the two maximum nights. The radiants determined in 1999 show a very large scatter due to unfortunate observing geometry and inaccurate position determination since one of the cameras was moving because of the wind. The 2001 data is excellent and the radiant was determined to be at RA = 153.96°±0.3° and Dec = 21.09°±0.2°. The error bars for individual meteor radiants are about 0.2° to 0.4°. This demonstrates that is indeed possible to determine good radiant positions using totally automated tools. Orbits, on the other hand, are not well defined due to the fact that the velocity of individual meteors shows large errors. Reasons for this are described.

Cassini-Huygens, named after the two celebrated scientists, is the joint NASA/ESA/ASI mission to Saturn and its giant moon Titan. It is designed to shed light on many of the unsolved mysteries arising from previous observations and to pursue the detailed exploration of the gas giants after Galileo's successful mission at Jupiter. The exploration of the Saturnian planetary system, the most complex in our Solar System, will help us to make significant progress in our understanding of planetary system formation and evolution, which is also a key step in our search for extra-solar planets.

The change of year is the opportunity to look back over the events of the previous twelve months, and to consolidate one's plans for the year that lies ahead. 2003 was certainly a year of great contrasts for ESA, with unfortunate failures, even dramatic catastrophes, but also some very welcome successes paving the way to the future.

Contents

• 3rd Announcement of Opportunity (AO-3)
• Science Highlights
• Mission Status
• INTEGRAL Public Data Archive