ESA Science & Technology - ESA Science Newsletter No. 35

Message from the Director of the Science Programme

The year 1998 is now at a turning point and all our missions are proceeding on schedule, but their fate depends on a number of decisions expected to be taken in the near future. However, the horizon is darkening!

The Council Meeting at Ministerial Level has been delayed probably until next year, and all important programmatic decisions will have to wait. Also, there is little chance that the Ministers of the Member States will send a signal to the ordinary Council when it will discuss the level of resources of the mandatory scientific programme, before the end of this year.

The prospects here are gloomy! We stand to lose more buying power, since there are no signs that some Member States in particular will agree to stop the decrease which affects the science budget since the ministerial meeting of 1995 in Toulouse. Even the strongest supporters of Space Science are now resigned and do not seem to will to fight anymore.

The science programme has however prepared itself in many ways:

1. With your collaborations, we are experiencing success in all our missions, from ISO, which ended its operations on 16 May, to SOHO, which stands out as a competitor to HST in the media, to Huygens, which is now on its way to Saturn and Titan. XMM is to be launched in August 1999 and its mirrors are the best ever produced for x-ray astronomy. Our missions are becoming much cheaper and not necessarily smaller, offering much more science for the money available. They are outstanding: results like those of Hipparcos, ISO and SOHO will not be straw-fires at the border of PR and science, but will yield solid knowledge.
2. We have been making extraordinary economies, innovating in managing our missions and inducing restless and continuous efforts to achieve more efficiency gains and economies. The selections of the payloads for FIRST, Planck, Mars Express and SMART have been carried at the fastest pace ever, with outstanding professionalism. I can only express thanks to the working groups, the SSAC, the SPC and to all those who were involved.
3. We have started an effort in science communication, bringing out a clear message both to the society at large and to the decision makers, that space science is an essential cultural, educational, technological and industrial asset for Europe. You might have noticed that the quality of our Internet pages has improved, some of them being among the best on the whole Web, and I promise even greater improvements shortly.

I cannot say that we have succeeded in all our efforts but our willingness to pursue improvements has no frontiers. As I promised in my last message, we are not giving up! Unfortunately, the times to come are cloudy because Europe, contrary to the US, is not investing in its scientific future at the right level! We run the risk of losing our leadership, so fiercefully achieved, and the control of our future may not be in our hands anymore. As was clearly evidenced at the last SPC, the science of our missions or their launch dates is now directly affected by decisions taken on the Level of Resources and any cost escalation of a mission will have programmatic consequences on all the others.

In this context, the role of the science community is crucial in understanding and explaining the sacrifices that are confronting us. Fighting among yourselves or for your own interests would create no room for improvement. The science community should be unified in this very delicate situation!

Consider that all of space science is in for a fight for survival, along with all of basic science. All scientists are allied in this fight, not enemies.

R.M. Bonnet
Director of Scientific Programme

News from SPC

The 83th Science Programme Committee (SPC) was held at ESA on 16-17 February 1998 and the 84th meeting on 28-29 May 1998. Important decisions were taken then.

FIRST/Planck Mission

WWW address:http://sci.esa.int/herschel and http://sci.esa.int/planck

Three scenarios for the "combination" of the FIRST and Planck missions resulted from industrial studies which ended at the beginning of April 1998, their aim being to reduce the cost of both missions combined to a level of # 655 MECU (1997 ec):

1. Merged mission (one spacecraft, one launcher), 36 MECU above ceiling
2. "Carrier" mission (two spacecraft, one launcher), 103 MECU above ceiling
3. Separate missions (two spacecraft, two launchers), 183 MECU above ceiling

The scientific output was accepted to be the same in all three scenarios.

The SSAC recommended that the SPC approve the FIRST/Planck mission, to be implemented for a launch in mid-2006 with a financial envelope of 654 MECU (1997 e.c.), and to take note that probably only the "merged" option is compatible with this envelope.

After in depth discussion, made more acute by the gloomy prospects for the budget until 2010, the SPC approved the FIRST/Planck mission, to be implemented preferably according to the carrier option, however with a target launch date of 2007 and a target cost of 654 MECU (1997 e.c).

Also the SPC unanimously endorsed the FIRST and Planck Payload pre-selection as indicated in the following two tables.

Table 1: Pre-Selected payload - Planck Mission

Table 2: Pre-Selected payload - FIRST Mission

The Chairman requested the delegations to express themselves on the availability of payload support for the FIRST/Planck mission. Six delegations expressed unqualified support; two delegations stated their priorities; four delegations will confirm their support at the end of the year; for one delegation the case had to be decided and in any case no expenditure is possible before 2000.

At its meeting on 6 May, the SSAC unanimously endorsed the selection made by the FIRST Mission Scientist Evaluation Committee, Chaired by Dr. W. Hermsen (NL).

The selected Mission Scientists are:

• Prof. P. Encrenaz (F),
• Prof. J. Cernicharo (E),
• Dr. P. Barthel (NL),
• Prof. P. Harvey (USA),
• Prof. M. Harwit (USA).

The mission scientists will be appointed for a term of 3 years.

Mars Express

WWW address:http://sci.esa.int/marsexpress

During the last three months the responses to the Announcement of Opportunity were received and evaluated and the design of the spacecraft has been consolidated. In the meanwhile, preparations for the issue of the Industrial Phase B Invitation to Tender are in progress.

ALENIA, Dornier Space Systems and Matra-Marconi (France) are involved in competitive studies which will lead to a bid for the Phase B/C/D of the project (if approved at the next SPC in November). These companies have assisted ESA with the technical evaluation of the proposed instruments and have shown how the proposed payload could be accommodated in their respective spacecraft design.

Table 3: Mars Express Payload

The SPC unanimously endorsed the scientific payload of Mars Express as proposed by the Peer Review Committee and recommended by the SSWG and SSAC. The launch date is fixed to 2003.

The SPC also agreed to keep open the concept that a 60 kg (at launch) lander could be carried on Mars Express. The tentative deadline for proposal submission was set at 3rd July 1998.

International Cooperation on Mars Exploration

The Mars Express mission must also be seen in the international context of missions to Mars.

Within this framework, NASA is the most important contributor, with a series of Orbiters and Landers to be launched nearly every 18 months. ISAS (Japan) will for its own part launch a mission in 1998.

The International Mars Exploration Working Group (IMEWG) and the Inter-Agency Coordination Group for Space Science (IACG) are active in coordinating technical and scientific issues. ESA is represented in both groups.

The Italian Space Agency (ASI) has expressed its strong interest to support Mars Express with the specific aim to embed the mission into the NASA-lead effort to return a sample from the planet. NASA asked ESA to consider the possibility to provide the spacecraft as data relay Orbiter from 2003 to 2007, two years after the nominal mission lifetime. The implications of the consequent mission extension have been studied by industry and it appears feasible to carry enough consumables on board to extend the mission lifetime for one Martian year, i.e. two calendar years. The only required additional hardware capability would be a transponder including a multi-channel telecommunication package for the Orbiter/Lander communications. This package would also be required if European Landers were to be served. ASI offered to contribute this package to Mars Express.

If Mars Express will be carrying the data relay package, it will also be able to provide data relay services to NASA for its sample return mission in 2005 and also for its Lander mission in 2003. In return, NASA may offer access for European scientists to data from both missions and possibly to samples brought back in 2007.

Additional contributions to Mars Express by ASI concern the possibility of using the new ground station to be built in Sardinia. In view of its much larger dish diameter, this would result in a significant increase in the scientific return of the mission if compared with the currently based Perth station, and to guarantee continuous contact with the spacecraft.

As the mission extension must be carried out within the currently foreseen cost cap of 150 MECU to ESA, ASI was lead to propose the contribution of manpower to ESOC. The resulting economies to ESOC would be used to finance the mission extension.

Should the French offer of an Ariane 5 to launch the NASA sample return mission in late 2004/2005 be confirmed, an opportunity would be created to launch a French-led network mission on the same launcher. ESA is considering coordinating the efforts for the definition and implementation of such a mission and would make the Mars Express orbiter available for communications and data acquisition.

All collaboration with ASI, NASA and CNES, will be worked out in detail during the coming summer, and submitted to approval after the final mission confirmation by SPC in November 1998.

Collaboration was also proposed by the Russian Space Agency. ESA has accepted the participation of Russian scientists and will facilitate the implementation of their responsibilities as Co-Investigators.

SMART-1 Mission Definition and Payload Selection

The mission is in an intensive phase with the start of the industrial activity in the Swedish Space Corporation (SSC) and the issue of AO's for the scientific and technical payload items.

While SSC takes the overall system responsibility, ESA has particular responsibility for the design of the Solar Electric Primary Propulsion (SEPP) stage, the key technological element of the SMART mission. The aim is to demonstrate that

such a stage can be operated in the continuous controlled manner that will be needed for deep space missions. Such a stage could be of value for the Mercury and IRSI cornerstone missions as it would allow more flexibility in the mission planning and the mass in orbit capability. Three candidate technologies are under consideration; the PPS1350 Stationary Plasma Thruster developed by SEP in France; the RIT 10 Ion Thruster developed by DASA in Germany; and the UK10 Ion Thruster developed by DERA in the United Kingdom. The final choice will be made on technical and programmatic grounds, based on the mission needs.

Subject to the approval of Council at the end of 1998, the phase C/D of the project is planned to start in January 1999 with launch foreseen for October 2001.

Fourteen science proposals involving hardware were received and rated following the criteria outlined in the AO issued on 6 March 1998. A core science payload as presented in the attached table was defined by SSWG, AWG and SSAC, fulfilling science and technology priorities. The core science payload mass is compatible with different asteroid rendezvous missions launched in 2001.

Table 4: SMART-1 Recommended Science Core Payload

Two mission scenarios have been envisaged:

1. to Near Earth Objects, if possible after Lunar Gravity assist flyby. The lunar gravity assist would allow enhanced payload as well as an opportunity for lunar polar science flyby. Different NEO targets for RdV have been identified and a decision will be taken after an exhaustive search and optimization.
2. near-polar orbit (1000-10 000 km orbit).

The choice will be based on cost and technology/scientific consideration and is foreseen at the time of the next SPC in November 1998.

The SPC took note of the mission scenarios and unanimously approved the scientific payload complement as indicated in Table 4.

In the meantime the selection of the Technological payload is on-going. The AO was released on 27 April 1998 and 25 proposals were received by the deadline of 5 June 1998. This response demonstrates the interest within the technological community in this new ESA initiative. The selection will be made by a joint inter-directorate group including a representative of the prime contractor and will be approved by IPC during the fall 1998.

Other decisions

• The SPC unanimously approved the transfer of the IUE Final Archive to INTA IUE/LAEFF (E)
• The SPC unanimously approved the new 72-hour Integral orbit .

Satellites in Orbit

Six spacecraft are presently operated in orbit (including ISO).

Hubble Space Telescope (HST)

Information on HST can be found at the address: http://sci.esa.int/hubble

Ulysses

Further information on the Ulysses mission can be found on Internet at the address: http://sci.esa.int/ulysses

On 17 April, after travelling for more than seven years and covering 3.8 billion kilometres, Ulysses completed its first orbit of the Sun. All spacecraft subsystems and experiments continue to perform extremely well, and the recent MIDAS (Multi-project Investigation during Alignment of Spacecraft) campaign involving Ulysses, SOHO, ACE and Wind was very successful in obtaining near-continuous coverage at high bit-rate over a period of several weeks. Moving slowly southward on its post-aphelion trajectory, Ulysses crossed the ecliptic in mid-May at a distance of 5.4 astronomical units from the Sun.

After an extended period of quiet solar conditions, two major solar flares occurred in quick succession at the beginning of November. These events, which produced significant interplanetary disturbances, have been the subject of a number of comparative studies involving Ulysses and the fleet of spacecraft at 1 AU, including SOHO. By studying these phenomena in detail, it is hoped to gain a better understanding of the global structure of the disturbances and their influence on particle transport. Such multi-spacecraft studies will play an increasingly important role in the analysis of

Ulysses data as the solar cycle develops.

Another topic addressed by Ulysses relates to the much larger-scale issue of cosmic ray confinement. By measuring the isotopic composition of cosmic ray aluminium and chlorine with high precision, Professor John Simpson and his co-workers on the COSPIN experiment have derived a cosmic ray "age" of 20 Myrs, requiring that the cosmic ray particles spend a significant fraction of their lifetime in the low-density galactic halo. These and many other findings were reported at the recently held Ulysses Science Working Team and European Geophysical Society meetings.

The ESA Ulysses archive is accessible via the World Wide Web at URL: http://helio.estec.esa.nl/ulysses/archive/

Infrared Space Observatory (ISO)

Information on ISO, is available at: http://sci.esa.int/iso

Depletion of ISO's supply of liquid helium was formally declared at 21:07 UT on 8 April 1998. This marked the end of the highly successful routine operations phase of the world's first true orbiting infrared observatory. This phase had lasted nearly 1 year longer than specified and enabled over 26 000 individual observations (instead of the expected 16000) to be successfully obtained, including two visits to the Taurus/Orion region.

The first indication of imminent helium depletion occurred on 8 April at 03:31 UT when there was a decrease in the pressure of the helium gas in the vent line. The helium bath temperature also started to increase above its nominal value of 1.75K, going out of limits, i.e. above 2.21K, by 05:17 UT. Even though the temperatures of the instruments were increasing, the normal planned observation programme was continued during the day until the instruments reached 4.2K at 21:07 UT. At that time, the instruction to switch off all instruments was given.

Starting on 20 April, spacecraft activities focussed on a 1-month period of calibrations and a technology test programme, including - among other activities - testing the operation of the star trackers at low altitudes, i.e. in the radiation belts, use of the on-board redundant units that were not needed during the routine operations, and evaluation of the software intended to overcome multiple gyro failures. The satellite was switched off on 16 May at 14:00 UT, after changing the orbit to a lower perigee one, with an expected lifetime of about 20 year.

During the few days immediately following helium loss, tests were carried out which showed that the shortest-wavelength detectors - covering the wavelength range from 2.4 to 4 microns - of the Short Wavelength Spectrometer could still be used on some sources. Anticipating this possibility, a specific scientific programme, aimed at extending the MK spectral classification scheme into the infrared, had been prepared to fill any gaps before and during the technology tests.

On 5-6 March a team of 10 people from NASA's SIRTF Science Center and operations visited Vilspa to receive a detailed briefing on the very successful ISO operations.

To mark the successful conclusions of the ISO mission, some of ISO's latest results were announced to the Press at a briefing, organized with PPARC, in London (7 April 1998). Among these discoveries were the finding of water vapour on Saturn's moon Titan (complementing ISO's many detections of water throughout the cosmos), detections of young stars in the Orion region of the sky and measurements of infrared galaxies at immense distances. This press briefing plus associated ESA Information Notes led to very extensive radio, TV and Press coverage of the successes of ISO. In parallel to the London press briefing, ISO scientists and Project Staff gathered at Villafranca on 2-3 April 1998 to celebrate the successful conclusion of the ISO mission.

It is planned to open the ISO archive to the community in early autumn. Approximately 25% of the ISO data will be in the public domain at that time and will be retrievable by use of a new WWW- based interface.

Solar and Heliospheric Observatory (SOHO)

Information on SOHO can be found on Internet at the address:http://sci.esa.int/soho and related pages.

SOHO has just completed its nominal mission lifetime, with all instruments working and obtaining excellent data. The spacecraft is also working well with all its subsystems operating within specification.

The MDI helioseismology experiment has made the first observation of seismic waves from a solar flare. During the impulsive phase of the X2.6 class flare of July 1996 a high-energy electron beam heated the chromosphere, triggering a series of phenomena which eventually excited propagating waves in the solar interior. The seismic waves propagated to at least 120,000 km from the flare epicenter with an average speed of about 50 km/s on the solar surface and was about 3 km high.

The solar-wind instrument CELIAS/MTOF has made the first in-situ determination of the solar wind calcium isotopic composition. The isotopic ratios 40Ca/42Ca and 40Ca/44Ca measured in the solar wind are consistent with terrestrial values.

Results from a joint observing campaign of the SUMER spectroheliometer and Big Bear Solar Observatory provide strong evidence that transition-region explosive events are a manifestation of magnetic reconnection occurring in the quiet Sun.

On 28 April SOHO results were presented to the European media at a Press Conference held at Rutherford Appleton Laboratory, on the occasion of the end of the nominal lifetime of the satellite and to mark the start of the mission which will take SOHO into the solar maximum. The press Conference resulted in an extensive coverage of SOHO results in the written press as well as on European TV.

The SOHO Data Archive currently holds the full sets of data of SUMER, CDS, EIT, LASCO, and VIRGO as well as MDI full disk magnetograms and continuum images, and UVCS data from launch to April 1997 (all adding up to 315000 files and 350 Giga-Byte). In addition to these science-processed data sets, the archive also holds the mission ancillary data and a set of daily synoptic observations from other solar observatories from around the world.

Cassini/Huygens

Information on the Huygens mission can be found at the Internet address: http://sci.esa.int/huygens

Cassini's first planetary gravity assist occurred on April 26 at Venus. Cassini/Huygens flew at the planned altitude of 284 km above the Venusian surface at 15:52:14 UT. Two science instruments were switched on during the Venus flyby: the radar, for an end-to-end signal bounce test on the surface of Venus, and the Radio and Plasma Wave Subsystem, to search for lightnings in the atmosphere of Venus.

It should be noted that the Venus flyby was so accurate that the correction manoeuvres planned for 14 May are no longer needed.

The 2nd in-orbit Huygens Probe checkout was executed on March 27 and the results of the preliminary analysis of the data were discussed at ESOC on April 17. All the Probe subsystems and instruments performed well. On the two Huygens radio receivers noise interference was detected, which was thought to relate to the need to point Cassini's high-gain antenna (HGA) towards the Sun. A test of the hypothesis was made at the end of May 1998 and gave a positive result. Noise levels are now back to normal and we may be confident in the good functioning of all Huygens subsystems.

Satellites under Development

XMM

Information on the XMM mission can be found at the Internet address: http://sci.esa.int/xmm

The test campaign on the structural & thermal model of the satellite was successfully completed in early March. In parallel, the last integrated system tests are being run at Dornier (D) on the engineering model before shipment of the service module to Alenia for re-use on Integral.

Flight equipment was delivered in time and the integration of the flight satellite has started. At the same time flight acceptance tests are being conducted at MMS (UK) on the attitude and orbit control sub-system before final integration into the spacecraft, planned for this summer.

Work on the ground segment development has progressed nominally with the detailed design phase. Delivery of the first version of the control software took place in March.

Tests at Centre Spatial de Liège (CSL) on X-ray Mirrors continued without interruption: The flight spare mirror module is now under acceptance testing. The third flight mirror module together with the second flight model of the reflection grating assembly as well as the associated X-ray baffle was transported to Munich where calibration tests are being conducted at the Max Planck X-ray facility (PANTER). The two first flight mirror modules are being prepared for final wide-angle stray-light tests that will run at IABG in Munich. It has to be noted that the mirror performances are better than specification. The XMM mirrors have been shown to have an angular resolution of about 14 arcsec (Half Energy Width), comfortably better than the formal specifications to the Prime Contractor (30 arcsec at 8 KeV and 20 arcsec at 3 KeV), and precisely in the range desired by the community at the start of the development.

The Flight Model delivery of the experiments, foreseen in early January 1998 had been rescheduled for the period March to July. The Agency, fully supported by the Prime Contractor Dornier, continues to try accommodating these delays without impact on the spacecraft launch date.

The project is working together with Arianespace and Dornier on the detailed definition of a launch campaign leading up to the scheduled launch date on the 3 August 1999.

CLUSTER II

Information on Cluster II is available at the WWW address: http://sci.esa.int/cluster

The manufacture of all spacecraft equipment is progressing according to plan, consistent with the start of integration of the first new Cluster II Spacecraft in the third quarter of 1998. Nearly all parts for all spacecraft have been delivered to the sub-contractors.

The rebuild of the payload is also progressing satisfactorily. Functional tests of the experiments, comprising the Wave Experiment Consortium (WEC), have been successfully performed. These included all new elements necessary, due to unavailability of processors and parts, and also the modifications and updates of the software.

The launch is foreseen on 21 January 2000 with Soyuz launchers. ESA is presently discussing the overall launcher situation with the Starsem Consortium.

INTEGRAL

Information on the INTEGRAL mission can be found at the Internet address: http://sci.esa.int/integral

The industrial work of the spacecraft contractor Alenia (I) is progressing. The integration of the Structural Thermal Model (STM) of the satellite is completed and the start of the thermal tests is imminent.

All instrument teams delivered the instrument STMs and started the development of the instrument engineering models.

The ESA/RSA INTEGRAL Arrangement on the launch by a Proton rocket has not yet entered into force and discussions on launcher adaptations and ESA's contributions to it are still ongoing.

Technical discussions on launch adaptation have led to scrutiny of the old INTEGRAL Proton orbit. As an outcome and in close co-operation with the INTEGRAL scientists the orbit has been changed to a more eccentric orbit which maximizes the time above a height of 60,000 km and avoids a long coast phase.

ROSETTA

Information on the Rosetta mission can be found at the Internet address: http://sci.esa.int/rosetta

The AIV major subcontractor (Alenia Aerospazio) has been successfully negotiated and kicked off early February.

The design activities have been refined with effort concentrated on mass, thermal aspects and dust environment around the comet.

The payload design has made progress which permits a better assessment of the mass Situation, which is a subject of concern. The Experiment Intermediate Design Review objectives and organisation have been documented and sent to the Principal Investigators.

The draft Space Ground Interface Control Document has been issued and distributed to the parties with the objective the release of the formal issue 1 by end May 1998.

An Independent review is being set up in coordination with DLR to examine the progress of the Germany-France-Italy provided Lander from the technical, scientific, and managerial point of view. The plan is to have the review in September.

FIRST/PLANCK

See SPC above.

Future Cornerstone studies

Gaia

Information on the Gaia mission can be found at the Internet address: http://sci.esa.int/gaia

The two contractors of the Gaia studies (Matra-Marconi Space -France and Alenia Spazio) are both busy with the final phase of their study activities. The final results of their studies will be presented at ESTEC on 2 July and 14 October 1998 respectively. The technology activities required for the Gaia mission have been identified and preliminarily described in a technical document, to be finalised and rationalised after the completion of the two studies and the selection of the baseline satellite and payload configuration for the Gaia mission. This document will be used as the reference for later technological developments.

IRSI - The Infrared Space Interferometer

The IRSI study is being performed by Aerospatiale in Cannes.

The study has two major scientific objectives:

• The planet detection Mission. To design a nulling interferometer mission capable of the direct detection of Earth-like planets around other stars and to characterise them spectroscopically.
• The imaging Mission. To study an interferometric imaging mission working in the spectral band 1 micron to 30 micron and which has one order-of- magnitude better spatial resolution than NGST.

LISA

Information on the LISA mission can be found at the Internet address: http://sci.esa.int/lisa

The FPAG reviewed the LISA payload during its seventh meeting on April 10th and concluded that the payload a 3 spacecraft option is preferable to the 6 spacecraft option which was previously proposed. It was agreed that the payload definition has reached a sufficient level of maturity for the industrial system definition study phase. The FPAG also recommended that a technological demonstration mission (ELITE) should be flown in a timely way for technology demonstration.

Mercury Orbiter

Information can be found at the Internet address: http://sci.esa.int/bepicolombo

The 1st Progress Meeting of the Mercury cornerstone system and technology study was held at Alenia Spa., Turin, on 30/04/98. Progress has been made in the area of mission analysis and in modeling the Mercury transfer using electric propulsion. The planned enhanced version of Ariane 5 is also being considered, as this would improve the mission capability. The status of work on the Orbiter and Subsatellite was presented and the main critical issues were identified has being related to thermal analysis and design. The 1st meeting of the Mercury CS SWG is to be convened during first week of June '98 to review the Orbiter, Sub-Satellite and Surface Package payload requirements.

NGST

Information can be found at the Internet address: http://sci.esa.int/jwst

In order to identify possible ESA contributions to the NGST project and to define follow-on activities in Europe compatible with the NASA schedule, industrial studies will be executed between July this year and July 1999 on:

• a study of a spectrograph with multi-object/integral field
• a combined payload/telescope study including the definition and design of a complete instrument suite and the study of a deployable telescope

European scientific institutes are encouraged to participate in the spectrograph study (possibly as prime contractor) and in the combined payload/telescope study (as sub-contractor(s) to an industrial prime). A call for "Letters of Interest" was issued to the scientific community. The high interest of the community is reflected by the large number (15) of responses that were received, mostly from broad consortia of scientific institutes.

Venus Sample Return Assessment Study

An in-house study of a Venus Sample Return mission was made over the period January-April 1998. Several options were considered ranging form an atmospheric sample return to a full surface sample return mission. Briefly the conclusions were that although feasible, considerable technology development would be needed before such a mission could be undertaken. A full report of the study is in preparation. A symposium on Solar System exploration jointly organized by ESA and CNES will be announced later this year.

Timetable of forthcoming events (as of 8 June 1998)