SOLAR SYSTEM NEWS

Newsletter of the Solar System Division

SOHO is back in full scientific operations. Follow the happy end of a drama in this newsletter.

Ulysses and Cassini-Huygens continue their journeys smoothly. Ulysses has ascended to 24°S heliographic latitude by end of March. Cassini-Huygens is on course for the second Venus encounter in June and the Earth flyby in August.

The rebuilding of the Cluster II spacecraft and the development of the Rosetta mission progress on schedule. Mars Express, ESA's first mission to the red planet to be launched in mid-2003, has entered its detailed design phase (Phase B) in early January. This important step permits an early definition of the payload interfaces.

Vicente Domingo, our long-term colleague and ESA SOHO Project Scientist, will retire in April. We thank him for all his efforts and wish him the best for his future.

We are in the process of providing a new and improved set of Web pages for the Solar System Division. When it is completed in the next few months, users will be directed to it from our current Web site at http://helio.estec.esa.nl/

We solicit applications for several ESA internal research fellowships to be awarded this summer for positions within our Division. Please send your application to the Division by 15 June. For details please consult the last page of this newsletter.

The response to our questionnaire in the last issue of the Solar System News was very good. We thank our readers for their help and for all the encouraging remarks we received and hope that you will continue enjoying our Newsletters in the future. We will certainly do our best to fill them with interesting articles from our projects and areas of research.

In order to make sure that all our readers get a copy of the Solar System News, this issue will be sent out as a paper copy to everyone as well as an email notification to those of you who indicated that choice in the questionnaire. From the next issue on, your choice will be implemented fully and you will receive future issues as email notification OR as the familiar green paper copy.

In the last issue of Solar System News we described the loss of contact with SOHO and the successful recovery up to the return to normal sun pointing attitude on 16 September. Since then, SOHO has challenged the skills of engineers and scientists more than once.

Following the attitude recovery and a busy week of recommissioning activities of the various spacecraft subsystems, SOHO was finally brought back to normal mode on 25 September. Remarkably, the only equipment failure at spacecraft level were two of the three gyroscopes. All other subsystems worked as well as they did before the loss of contact. From thermal models, confirmed by housekeeping data received in August, we know that the instruments went through an ordeal of extreme temperatures: some were being baked at almost +100°C, while others were subjected to a deep freeze of less than -120°C.

A detailed experiment recommissioning plan worked out by the SOHO Science Operations Coordinators, in close cooperation with the technical experts and operations personnel of the twelve instruments, was then implemented in October. While the recommissioning of the smaller instruments usually was a matter of a few days, sometimes even a single day, the large instruments like MDI, UVCS, LASCO, EIT, SUMER and CDS usually required many days of intense efforts to check out and revalidate all the software, electronics and mechanisms, followed by a thorough recalibration of the sensors, spectrometers, and cameras.

The recommissioning of the instruments, completed on 5 November, went smoothly, proving that, even after more than three months of forced inactivity, the experiment operations teams worked as effectively and collaboratively as they did before the SOHO mishap. Miraculously, all twelve instruments (with the exception of the LASCO C1 coronagraph, which is still being tested, and the SWAN +Z sensor which suffered some degradation and therefore required serious recalibration efforts) work as well as they did before the unfortunate loss-of-contact, and sometimes even better, despite the extremes in heat and cold that they have been subjected to.

The fact that both the spacecraft as well as all instruments survived this ordeal with minor scars constitutes a great tribute to the skill, dedication and professionalism of the scientists and engineers who designed and built these instruments and this spacecraft.

So far so good. On 21 December, however, the situation changed. During the setup phase of a planned momentum management and station keeping manoeuvre, just as the spacecraft was meant to enter a gyro-dependent attitude, SOHO went into Emergency Sun Reacquisition (ESR) mode again. The third and last gyro had failed, presumably due to some damage suffered during the deep summer freeze. As the mode to escape ESR requires a gyro output, it was clear that SOHO would have to remain in this mode until new software for a gyroless mode of operation had been developed.

In "ESR safe hold", the sun-pointing attitude is maintained by intermittent thruster firings which are actuated and controlled by on board sun sensors. The roll rate of the spacecraft was controlled using open-loop (ground-commanded) thruster firings. Since the thrust from the ESR firings pushed the spacecraft towards the Sun, frequent station keeping manoeuvres were required to maintain the proper orbit. Early estimates indicated that SOHO was consuming its fuel at a rate of about 10 kg per week as a result of all these thruster activities. As of end of December, SOHO had about 180 kg of fuel left. It was clear that we had no time to waste.

In a race against time, engineers at ESTEC and industry, while working on the design of a fast method to exit ESR mode, successfully conceived a method to reduce the heavy fuel consumption due to the ESR firings. This "yaw breaking" method was applied for the first time on 8 January. Finally, after 40 days of intense work designing, coding and testing software patches to the Attitude Control Unit (ACU), and following three orbit correction manoeuvres (while in ESR mode!), SOHO was brought out of ESR and back to a reaction wheel controlled (RMW) mode on 30 January. The ESR escape manoeuvre was immediately followed by the first gyroless momentum management and the first gyroless station keeping manoeuvre on 1 February.

The SOHO team had requested, and were granted, additional support from the Deep Space Network to support all these activities. We would like to thank all our colleagues, in particular those of the Ulysses mission, who have sacrificed some of their DSN time to support the SOHO recovery activities.

It took another five weeks (interrupted by yet another transition to ESR mode on 14 February due to a single event upset [SEU] in the Star Sensor Unit [SSU]), until procedures were developed to roll SOHO back to nominal roll attitude with solar north "up" on 8 March. On 13 March the 3-months continuous contact for the MDI dynamics programme began. We hope to get through this special campaign without too many interruptions. In the meantime, the engineers are working on an improved, more robust implementation of a gyroless mode of operation.

Thanks to the extraordinary efforts of the recovery team, crowned by this astounding accomplishment of successful recovery of the mission, the SOHO teams can now look forward to an exciting and scientifically rewarding Solar Maximum.

For information on the next SOHO workshops visit:

SOHO-8: http://soho8www.medoc-ias.u-psud.fr

SOHO-9: http://quake.Stanford.EDU:80/~SOHO-9/

The Ulysses Aphelion Workshop was held in Oxnard, CA on 27-30 October and was attended by about 50 scientists, mainly from the Ulysses and ACE communities. The Workshop, while focusing on data acquired at 1 and 5 AU during the period corresponding to Ulysses' aphelion passage (April/May 1998), also addressed three other themes: Science goals for solar maximum; Shocks, waves, particles and turbulence; Interstellar/astrophysical aspects of Ulysses. Separate Working Groups, lead by one or more members of the Ulysses science team, were established in advance of the workshop for each of the themes, and participants were encouraged to provide input prior to the meeting. This was facilitated by the creation of dedicated Workshop Web pages on the Ulysses ESA Web site, which will continue to be used to provide progress reports on activities that were initiated as a result of the workshop.

Working Group 1 (Data comparisons at 1 and 5 AU) focused on the period September 1997 to May 1998, during which Ulysses was close to the ecliptic at a radial distance of ~5 AU from the Sun. Within this period, specific intervals were selected in order to study the evolution of the solar wind and energetic particle populations between 1 and 5 AU. The main objective of Working Group 2 (Science Goals for Solar Maximum) was to refine the list of scientific questions that are unique to Ulysses in the framework of the forthcoming solar maximum epoch and beyond. Clearly, many of these questions concern the nature of the high-latitude heliosphere under conditions of high solar activity. It was also apparent the role of the solar magnetic field, which will reverse its polarity in 2000/2001, will be crucial, particularly for the years beyond 2001. As its name suggests, Working Group 3 focused on the topic of interplanetary shocks as observed by Ulysses. The fourth Working Group was devoted to the perhaps less well-known achievements of the Ulysses mission that bear upon the region beyond the heliosphere, namely the interstellar medium, high energy phenomena in the galaxy, the origins of matter and constraints on cosmological models of our Universe.

Although no formal proceedings of the workshop will be produced, it is anticipated that the meeting, which was highly successful, will result in a large number of papers appearing in the literature.

During the last year both the ESA Ulysses Home Page http://helio.estec.esa.nl/ulysses/ and the ESA Archive for Ulysses data http://helio.estec.esa.nl/ulysses/archive/ have been completely re-designed. Both sets of pages now provide an attractive and easily navigable collection of up-to-date information on the Ulysses Mission, its science and data. The Home Page (shown in Fig. 1) includes the latest Ulysses news, detailed background information on the Mission, an image gallery with many pictures not seen on the Web before, a directory of Ulysses scientists, and a list of related publications. Of particular note is the animation of the Ulysses trajectory, where the user can watch the spacecraft travel around its orbit, pan and zoom in the spacecraft, and learn about the key events in the mission via a text window. The new-look ESA Ulysses Home Page was successful enough to reach number one in the Lycos Web ratings under the category 'Space Missions' during September 1998, against major competition from top NASA sites and MIR!

The ESA Archive for Ulysses Data provides all the public release data from the Ulysses Mission, as well as 26-day, 1-year and whole mission summary plots of most the data products. The top page presents the user with a scrollable list of instruments and a clickable image map of the spacecraft (Fig. 2). Following a link to an instrument presents the user with a picture of the instrument and links to the data, plots and home page for that instrument. The data is in the form of downloadable zip files. The plots appear in GIF format and the user has the option of downloading a PostScript version. The user may also navigate backwards and forwards through the plots, select another type, or select another data product for the period of interest.

The integration of the first Cluster II spacecraft has been completed by Dornier Satellitensysteme (Germany). The spacecraft is now at the IABG test facility near Munich, where it will undergo environmental testing in the next three and a half months: acoustic tests, thermal vacuum test, when the instrument high voltages will be switched-on, and magnetic tests, when the magnetic cleanliness of the spacecraft will be verified.

The second Cluster II spacecraft is in its final stage of the payload integration. The shipment to IABG for the environmental tests is planned for mid June. The integration of the two following spacecraft will be finished in October and November, followed by the environmental tests. All four spacecraft will be ready by March 2000 for the two launches in June and July 2000.

The Science Operation Working Group has re-started its regular meetings to prepare the Cluster II commissioning and science operations phase. The increased capacity of the on-board memory (7.5 Gbit) and the possibi-lity to perform partial dumps allow the mission operations to be implemented with a single ground-station. Preliminary studies by ESOC have shown that the data return can also be increased by about 15 %. The Master Science Plan will be updated accordingly by the Joint Science Operation Centre (JSOC).

The Cluster Science Data System (CSDS) went out of hibernation after successfully passing the CSDS status review in November. The first task performed by the eight Data Centres (DCs) was to test the performance of public internet connections. In view of the significant improvement of public internet connections, the implementation working group decided to use public internet for the exchange of data between the DCs, replacing the dedicated CSDS network. The public internet will be monitored up to the start of Cluster II operations.

The first version of the Cluster Data Management System (CDMS), which controls the data exchange between the DCs and allows a scientific user to access the data through the Web, will be delivered to the DCs at the end of March. JSOC is actively preparing this delivery.

A CSDS Web page is being built to give the scientific user all information required to access the Cluster II data. The latest data, a few hours up to a few days old, will be accessible. It is also planned to include a 3D tool to display the position and configuration of the four spacecraft with respect to the scientific regions of interest.

Bi-weekly updates of the status of the Cluster II project can be found on the ESA Science Web pages at: http://sci.esa.int/cluster

Last year ended with an extremely busy period for Rosetta. The programme passed the Ground Segment Requirements Review (GSRR) in October, the System Design Review (SDR) in November and finally the Mission System Design Review (MSDR) in December. Except for a few issues that are presently settled in the normal course of work, the programme has been judged mature enough to enter Phase C/D. The Principal Investigators were given an opportunity to present the status of the payload during the MSDR and all teams were commended for their good work.

The Independent Review of the Lander was concluded on 30 October. The Review Team, chaired by Prof. Kottler, MIT Lincoln Laboratory (US), was satisfied with the overall design of the Lander. It expressed some concern with respect to the rather limited manpower available for the Lander consortium in the participating institutes to design and build such a complex system.

Specific recommendations were given to clarify certain parameters in the comet nucleus model, used as baseline for the mission. During two dedicated working sessions of the Mission Analysis Working Group the parameter list, provided by the Rosetta Nucleus Modelling Group (RNMG), was reviewed in detail. D. Möhlmann, co-chairman of the Modelling Group, presented the model to the Rosetta Science Working Team (SWT) during its 3rd meeting on 14-15 January for approval. The set of parameters will be described in detail in the report of the RNMG to be published by ESA in the near future.

The 3rd SWT meeting was well attended. Highlights were a detailed discussion of the Near Nucleus Observation Orbits (J. Fertig, ESOC) and the "science talk" on Comet Dust Analogues, by A. Rotundi, Ist. Univ. Navale, Naples. The Rosetta Science Journalist, Peter Bond, was officially introduced to the teams.

The Rosetta Science Operations Working Group met on 13 January, to define in more detail potential operational scenarii. As constraints with respect to thermal environment, power resources and data rate requirements consolidate, the design of the operations progresses.

Currently the investigator teams are busy to prepare the Structural Thermal Models of their instruments that will have to be delivered in course of the summer. Finally we move from paper work to actual hardware.

The 4th SWT meeting will take place at the Royal Society London. On 1 July the SWT will "meet" the Rosetta Stone, and on the same day the Giotto spacecraft will pass close to Earth again: an excellent opportunity to celebrate cometary science in Europe. Should you have the opportunity to visit London this summer, don't miss the special exhibition at the British Museum on the 200th anniversary of the discovery of the Rosetta Stone.

The 3rd in-flight Huygens Probe checkout was successfully executed on 22 December in the nominal cruise spacecraft attitude, i.e. Cassini High Gain Antenna (HGA) pointed to the Sun. On 28 December, the HGA was pointed to Earth for a period of 4 weeks. The first downlink window available was used to send the Probe checkout data to Earth. All six payload instrument reported excellent results, as did all Probe electrical subsystems that were tested. The low frequency (0.136 Hz) Doppler Wind Experiment (DWE) signal oscillation, which had been observed during the first checkout (DWE was not switched on during the 2nd checkout), was observed again. Although this threatens neither the DWE investigation nor the functionality of the radio link chain driven by the two DWE Ultrastable Oscillators, a special test programme using a spare unit will be undertaken to fully understand the effect and to assess its impact for the Huygens mission phase proper. The 4th in-flight checkout is planned for ~ 15 September.

The alignment of the Sun, the Earth and the Cassini spacecraft during the 4-week period allowed to use the HGA both as a spacecraft Sun-shade and for high data rate communication for the first time since launch. An extensive in-flight checkout of all 12 Orbiter instruments was conducted. All test objectives were met.

The spacecraft is now on its way for the Venus-2 encounter (24 June) and the Earth flyby (18 August). Limited observations of Venus and of the Earth/Moon system will be performed within the restricted operational capabilities of the spacecraft in the inner Solar System.

At its meeting at JPL, Pasadena on 1-5 March, the Cassini/Huygens Project Science Group (PSG) adopted a specific orbital tour plan that defines the trajectory of the spacecraft within the Saturn system for the nominal 4-year duration of the mission (1 July 2004 to 1 July 2008). The Tour, known as T18-5, allows 44 close flybys of Saturn's largest moon Titan, a prime target for the entire Cassini/Huygens mission. The PSG also discussed plans for Jupiter observations during the Jupiter encounter phase (~6 months centred around Jupiter closest approach on 30 December 2000).

The Huygens SWT met at LPL, Univ. of Arizona, Tucson on 11-12 March. The meeting was very well hosted by the imaging (DISR) team. A special activity was initiated that will investigate possibilities to use either ground-based observatories or Orbiter observations a few months before the Probe release, to validate the major Titan engineering models that were used for the design of the Huygens mission. Confirmation of the prograde character of the zonal wind flow with a high confidence level could be used to design the HGA pointing strategy and to provide a few dB's of additional link margin during the Probe mission.

Regular mission updates are available at http://sci.esa.int/huygens and http://www.jpl.nasa.gov/cassini

The Leonids in 1998 showed a slightly different behaviour than predicted. In particular, the storm did not take place. However, some increased activity (factor 2 higher than the "normal" activity at the peak) was visible on 17 November, 20:30 UT, which is consistent the predicted time of the storm. This activity was mainly due to faint meteors that were only observable with intensified video cameras and radar systems, leading to the disappointment in the public.

The night before, a broad (~20h long) maximum of large fireballs (meteors brighter than Venus) was observed. This was not predicted! Aggravated by a misleading report from one observing group, this led to the statement of the press that the scientists were off with their prediction by 16 h - this clearly is a misinterpretation of the facts! The conclusion is that indeed there was a sheet of freshly ejected material from the comet. The models were not wrong, but only overestimated the numbers.

If one converts the observed meteor numbers to fluxes, i.e. number of particles per volume in space, one can see that the increase in activity at the predicted storm time is very significant.

Currently, the meteor community compares this activity profile with the observations from 1965, one year before the Leonid storm in 1966. 1965 also showed the behaviour described above. Some people therefore expect in 1999 an activity similar in shape with 1966 - however, the actual numbers are hardly predictable.

Meteor scientists will discuss their findings in April, both at a Leonid MAC workshop organised by NASA AMES, and the EGS assembly in Den Haag. It can be expected that the modellers will update their predictions, taking into account last year's observations.

Members of the Division logged a few hours of video observations from a location in the Netherlands, unfortunately only at the night of the predicted maximum. During the previous night of the fireball activity we were clouded out. We discovered a high activity of meteors seemingly coming from a so far unknown radiant in the constellation Auriga. We are also analysing observations from other observing groups to find more evidence for this previously unknown radiant.

The polar regions on the Moon are of great scientific interest for a number of reasons. The unique illumination conditions that occur at the poles allow for the existence of permanently shadowed regions as well as areas that may receive near constant illumination. The discovery of ice in the polar regions makes mapping the extent of the permanently shadowed regions important as it is here that the ice deposits will be located. Similarly, knowing the position of highly illuminated areas is of particular interest as they represent future landing sites where ample amounts of solar energy would be available. Clementine has provided, for the first time, a digital data set to investigate these lighting conditions by showing how the illumination at the lunar poles varies over the course of a lunar day. The data was collected during winter time at the lunar South Pole thus showing the maximum extent of darkness there. Figure 3 is a medium resolution mosaic of the south polar region. It extends from 80° to the pole at a resolution of 500 m/pixel.

Clementine imaged the South Pole approximately every 10 hours. This means that the illumination direction between consecutive images changes by ~5°. Combining all images of the South Pole, taken during a month in orbit, into a movie reveals how the illumination conditions change during the course of a lunar day. It is a simple step to go from this to the production of an illumination map that shows the percentage of the time that a point on the surface is in daylight. This map indicates the existence of regions that receive high amounts of illumination (one point on the rim of Shackleton crater appears to be illuminated for ~85% of the time) as well as areas that receive no illumination. Further analysis will put a maximum value on the size of the permanently shadowed areas as well as allow us to study in detail the exact illumination conditions during a lunar day at some of these sites of interest.

Work has begun on analysing the data from Clementine's high-resolution camera. This instrument sent back imagery of the south polar region at a resolution of 15 m/pixel. The area imaged includes the part of the rim of Shackleton that receives the greatest illumination and therefore allows for the investigation of this possible landing site.

Helioseismology - the study of the acoustic resonant modes of oscillation of the Sun - is currently entering a new and exciting era. The quality of the observational data are now such that expectations regarding what can be learned from their study have increased; further, fresh challenges are being posed by the appearance of subtle, previously unseen effects in the data.

In our Division, much effort is being devoted toward the development and testing of new techniques of analysis. The motivational reasons for doing this are clear. Methods designed to cope with the added complexity of the data provide more-reliable estimates of the parameters of the modes (e.g., frequencies and rotational splittings), which are then used to infer the hydrostatic and dynamic structure of the solar interior. Further, they allow us to take advantage of the extra information afforded by the measurement and categorization of these new effects.

 Recent work - undertaken with data collected by our VIRGO instrument on SOHO, and the ground-based Birmingham Solar-Oscillations Network (BiSON) - has revealed the presence of significant skewness in the resonant profiles of those modes of oscillation that penetrate into the deep solar interior. A new technique has been developed for fitting these modes that allows for the asymmetry. This method returns direct information concerning the location of the excitation source of the oscillations, and the dimensions of the resonant cavity in which they are formed. Our analysis has established tight constraints on the source location, placing it just 300 km below the outer surface of the convection zone (Fig. 4).

We have moved this analysis a stage further by taking advantage of the fact that observations of the oscillations made by measuring Doppler-velocity or intensity variations over the solar disc provide complementary information regarding the interaction of the modes with their environment. Through the use of data collected, in intensity by the VIRGO instrument, and in velocity by BiSON, we have added to our understanding of one of the key puzzles of modern Helioseismology - the fact that resonant profiles observed in intensity and velocity display opposite signs of skewness.

The reversal is now thought to result from a component of the convective granulation imprinting itself upon observations of the acoustic resonances. We have measured the strength of this component as a function of frequency in the VIRGO data (Fig. 5). Our analyses indicate that a component with a fractional amplitude of the order of a few per cent of the oscillation signal is sufficient to cause the sign reversal. This result is consistent with theoretical expectations.

ESA's Science Directorate is investigating the feasibility of various ambitious and innovative space missions for the new millennium. Using a team of in-house experts, covering a range of technical and scientific disciplines, supported by several external scientists, two particular planetary exploration missions have been studied.

With the planning of the International Mars Sample Return Mission under way as a NASA/CNES-led programme, it can be anticipated that the international science community will be interested to also consider, at some stage, sample return missions from the other two terrestrial planets, Venus and Mercury. ESA has recently performed a study related to a Venus Sample Return mission and is carrying out a similar study related to a Mercury Sample Return mission. The results of those studies are intended to help the science community to shape Europe's short and long-term planetary exploration programmes and to provide a reference for planning purposes.

The Venus Sample Return (VSR) study

Venus poses many technical challenges. For example, the Soviet Venera Probes measured a temperature as high as 470°C and a pressure as high as 95 times the Earth's surface pressure. This presented many difficulties to the design engineers. The reference baseline scenario retained in the study involved the following key elements:

• Two Ariane-5 launchers, the first to position a composite spacecraft consisting of an orbiter and a return capsule into Venus orbit; the second to deliver a lander composite comprising entry, sampling and ascent modules
• The lander composite, which includes a small launcher, would descend to the Venus surface with partially inflated balloon and parachute
• Several hours operation on the surface involving measurements and collection of samples
• Balloon ascent and rocket launch of the sample container to rendezvous with the Venus orbiter
• Return of sample capsule to Earth on the Earth Return Vehicle

The ESA study report was published in June 1998 (SCI(98)3) and will be available shortly on the Web.

The Space Science Department (SSD) of ESA provides scientific support to ESA's space science projects in their planning, development and operational phases, acts as an interlocutor between ESA and the scientific community, and undertakes research programmes covering instrument development and data analysis using space-borne and ground based facilities. The research activities in SSD are undertaken by scientific staff and ESA research fellows with the appropriate engineering, technical and administrative support.

Research within the Solar System Division of SSD deals with plasma, charged particle and field measurements in various plasma environments of the heliosphere; planetary/cometary surface and environment investigations, and specific areas of solar physics.

Besides at ESTEC, Noordwijk, The Netherlands, Solar System Division staff are also located currently at the SOHO Experiment Operations Facility (EOF) at Goddard Space Flight Center, Greenbelt, MD, USA.

Principal Electronics Technician to assembly flight electronic circuits and support the development of scientific instrumentation. Ref: ESA/VN-ESTEC(98)38. Applications for this Staff Position should be sent to the Head of Personnel, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands.

Research fellows are usually under contract for two years. In principle, Fellowships will be awarded only to nationals from ESA member states. For more details see Solar System News 20, p. 8, September 1997, http://helio.estec.esa.nl/ssd/public/ssn/20/newsletter.html.

Applications for up to FIVE INTERNAL FELLOWSHIPS are solicited (applications due 15 June) for appointment in the autumn of 1999. Applications or CV should be sent to our Division at the address given below. Priority will be given for candidates in the following areas:

Heliospheric Physicists to work on Energetic Particle characteristics of CIRs, CMEs, Anomalous Cosmic Rays, shock acceleration, upstream particles or related topics. Data sets are available from the Low-Energy Telescope of the COSPIN instrument on Ulysses, from the 3-Dimensional Plasma and Energetic Particle Instrument on the WIND spacecraft and from the Energetic Particle Instrument on SOHO, as well as supporting plasma and field data. Contact: Trevor Sanderson, tsanders@estec.esa.nl.

Magnetospheric Physicists to work on research topics of interest in preparation of the Cluster II mission to be launched in mid-2000. Candidates with experience in handling large data sets and analysis of quasi-static electric fields are preferred. Data from current missions (e.g. POLAR, WIND, Equator-S) are available. Contact: Réjean Grard, rgrard@estec.esa.nl.

Planetary Scientists or engineers with interest in the development of hardware for future planetary missions, laboratory and field studies related to space experiments on Cassini/Huygens and instruments currently being developed for the Rosetta mission. Other topics include research related to the preparation of Mars Express and lunar science missions, ground-based observations and modelling of planetary atmospheres. Contact: Gerhard Schwehm, gschwehm@estec.esa.nl.

Solar Physicists to work in one or several of the following research areas: Helio- and asteroseismology, Solar/stellar coronal activity, SOHO data analysis. In the latter case, this may include extended working periods at the SOHO Experiment Operations Facility at Goddard Space Flight Center. Contact: Bernard H. Foing, bfoing@estec.esa.nl

For further information on all vacancies contact the person listed or the Head of the Division, K.-P. Wenzel, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands, telephone +31 71 565 3573, fax +31 71 565 4697, email: kwenzel@estec.esa.nl.

Solar System News is published twice a yearly the Solar System Division of the Space Science Department of ESA. You can contact us:

ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands,

tel.: +31-71-5653573,

fax: +31-71-5654697,

email: kwenzel@estec.esa.nl

Two other newsletters are produced in the ESA Science Directorate:

Astronews, a companion to Solar System News, is available from the Astrophysics Division in SSD and the Space Science Newsletter, concerned mainly with policy matters, is available from Head Office, Paris.