9th SSEWG Meeting 18-19 October 2011

Report

Solar System Missions Division (SRE-SM)

1. Missions in Orbit

1.1 SOHO (Project Scientist: Bernhard Fleck) Chen et al. (GRL 116, A04304, 2011) have studied the relationship between the EUV flux during the recent solar minimum as measured by CELIAS/SEM (Charge, Element, and Isotope Analysis System/Solar Extreme Ultraviolet Monitor) and the F10.7 index (solar 10.7 cm radio flux), which has been routinely recorded since 1947 and is widely used in ionospheric physics as a proxy for the solar EUV flux. They find that the EUV irradiance measured by SEM was significantly lower during the recent minimum than during the previous one for the same F10.7 level. The same was found for the critical frequency of the ionosphere F2 layer (f0F2) when compared to the F10.7 index. This suggests that during the recent minimum, at least, the F10.7 index was in fact not a good proxy for the solar EUV flux, although it was adequate during previous minima. Solar irradiance models and ionospheric models will need to take this into account for solar cycle investigations.

Combi et al. (ApJ 734, L6, 2011) have reported global water production rates of 103P/Hartley 2, observed with SWAN (Solar Anisotropy experiment) around the time of the November 4, 2010, by EPOXI (from September 14 to December 12, 2010). The water production was measured to be three times lower than during the 1997 apparition. On September 30, 2010, it increased by a factor of ~2.5 within one day, with a similar corresponding drop between November 24 and 30, 2010. The high total surface area of sublimating water suggests that a significant fraction of comet Hartley-2’s water production results from the extended halo of icy fragments that appear to be carried off the surface by CO2-driven activity, rather than from the nucleus itself.

Ilonidis et al. (Science 333, 993, 2011) have for the first time succeeded in detecting sunspot regions in the deep interior of the Sun, 1-2 days before they appear at the solar surface. Their results, based on data from MDI (Michelson Doppler Imager), suggest that sunspots are generated at least 60,000 km below the surface and emerge from this depth with an average speed of 0.3-0.6 km s-1. This paper received considerable media attention.

The 24th SOHO workshop “The Sun 360” was successfully held July 25-29, 2011 at the University of Kiel, Germany, together with the STEREO and SDO projects. It was attended by over 160 participants.

At the time of writing of this report, 4138 papers based on SOHO observations have been published in the refereed literature since launch. In 2011, 230 papers have appeared in the refereed literature so far.

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1.2 (Project Scientist: Bernhard Fleck) Martínez Pillet et al. (A&A 530, A111, 2011) have identified ubiquitous quiet-Sun jets in Hinode/SP spectropolarimeter data. They often appear in pairs (both red- and blue-shifted components), mostly in the outer boundaries of granules next to regions of transverse magnetic fields. The authors suggest that the high speed flows are driven by magnetic reconnection.

Verth et al. (ApJ 733, L15, 2011), using observations from Hinode/SOT optical telescope of a kink wave propagating along a spicule, have measured the variation of magnetic field strength and plasma density along the spicule using magneto-seismology. In addition, combining these results with electron density estimates from spectroscopy, they have determined the degree of hydrogen ionization along the spicule.

Harra et al. (ApJ 737, L4, 2011) have combined Hinode/EUV Imaging Spectrometer (EIS) and SDO/AIA (Atmospheric Imaging Assembly onboard Solar Dynamics Observatory) observations to determine, for the first time with a high time cadence, the spectroscopic signature of an EIT wave (large scale coronal wave, first detected by the SOHO EUV Imaging Telescope) as it propagates away from an active region. They have found that the main wave front travels at ~500 km s-1 and is strongly red-shifted, i.e. as the wave propagates it also pushes plasma downward toward the solar chromosphere with a speed of ~20 km s-1. After a low-velocity period they have observed a second red-shifted feature with velocities from 200 to 500 km s-1 and of comparable or somewhat lower Doppler velocity.

At the time of writing of this report, 520 papers based on Hinode observations have been published in the refereed literature since launch. In 2011, 110 papers have appeared in the refereed literature so far.

1.3 Cluster/Double (acting Project Scientist: Matt Taylor) Eastwood et al. (JGR 116, A08224, 2011) have combined Cluster and measurements during Rosetta’s flyby. They have used Cluster observations outside of the bow shock to suggest a relation between upstream waves to waves detected within the magnetosphere by Rosetta and also ground based magnetometers.

Amariutei et al. (Ann. Geophys. 29, 717, 2011) have examined the evolution of magnetic holes, depressions in the local magnetic field magnitude. Magnetic holes are found throughout the solar system, but whether they are created locally or at the Sun and transported with the solar wind is unclear. Using observations from VEX and Cluster the authors propose that the similarities in observations suggest convection of these structure in the solar wind. However, we cannot discount that, due to similar solar wind conditions at Venus (0.7 AU) and Earth (1 AU), the holes are not generated locally.

Khotyaintsev et al. (Phys. Rev. Lett. 106, 165001, 2011) have reported in-situ observations by Cluster of wave-particle interaction in a magnetic pile up region created by a magnetic reconnection outflow jet in the Earth’s magnetotail. How plasma gets heated and accelerated in the reconnection process is a very active area of research and is a key to understanding solar activity – Coronal Mass Ejections and flares, for example. The work details how plasma jets interact or brake with magnetic pile-up regions, experiencing betatron acceleration as the magnetic field strength increases, to produce significant particle acceleration after magnetic reconnection occurs. In a general 2 astrophysical context, the observations suggest that one can expect particle acceleration anywhere where plasma jets are interacting with the local environment and braking. The observations show that wave generation strongly affects the electron dynamics and plays a crucial role in the energy conversion chain during plasma jet braking, highlighting the role of electron physics which is at the heart of reconnection and the focus of the upcoming NASA’s Magnetospheric Multiscale (MMS) mission. The results presented must be of universal importance for solar and astrophysical environments.

As of end of September 2011, 1469 refereed papers have been published since 2001 and 58 PhDs have been obtained using Cluster and Double star data.

1.4 (Project Scientist: Olivier Witasse) August and September have been difficult for Mars Express: the science operations were suspended for about 5 weeks, due to two safe modes and problems related to the mass memory. The spacecraft and instruments work nominally again, on the redundant side (B-chain) of the Sold State Mass Memory controller. These problems have an impact on the science: first, one third of good data related to the radar sounding of the North polar cap (one of the main reasons to extend the mission) have been lost. Secondly, the change to the B-chain results in the loss of the super resolution channel of the High Resolution Stereo Camera (HRSC) camera.

Maltagliati et al. (Science 333, 1868, 2011) have reported observations made by the SPICAM dual UV/IR spectrometer that provide evidence, for the first time, of the existence of water vapour in excess of saturation, by an amount far surpassing that encountered in Earth’s atmosphere. This finding contradicts the assumption that atmospheric water on Mars cannot exist in a supersaturated state, directly affecting the long-term representation of water transport, accumulation, escape and chemistry on a global scale.

Rosenblatt (A&A Rev 19, 44, 2011) has summarised very well in a review paper the different hypotheses for the formation of Phobos and Deimos and has outlined the fact that the internal structure of the moons is a key observational constraint for their origin, while, until now, this question was mainly relying on observations of their surface and orbit. The paper has been triggered by the Mars Express Phobos flybys.

Reiss et al. (Icarus 215, 358, 2011) has reported on multi-temporal observations of identical active dust devils on Mars with the Mars Express - HRSC and the Mars Orbiter Camera aboard Mars Global Surveyor. One interesting result is that larger dust devils on Mars are active for much longer periods of time than smaller ones, as it is the case for terrestrial dust devils. Knowledge of dust devil lifetimes is an important parameter for the calculation of dust lifting rates into the atmosphere.

Mars Express will celebrate its 10,000 orbit on 4 November.

A joint Mars Express (PFS – Planetary Fourier Spectrometer) – Venus Express (SOIR – Solar Occultation Infrared Spectrometer) data workshop was successfully held in ESAC in June 2011. 18 participants and lecturers were present, including 6 from Japan.

The cumulative number of refereed publications related to Mars Express is now 543, of which 47 are from 2011.

11 web stories have been published on the ESA web sites in 2011.

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1.5 Venus Express (Project Scientist: Håkan Svedhem) Montmessin et al. (Icarus 216, 82, 2011) have reported the discovery of ozone in the upper atmosphere of Venus by the SpicaV imaging spectrometer, operating in stellar occultation mode in the UV. Before this discovery ozone had only been found in the atmospheres of Mars and the Earth. The total columnar content on Venus is only about one in a thousand of that of the Earth but the finding is important as it provides new information on the chemistry in the upper atmosphere. In addition, information on the dynamics in this region can be derived from these data. The source is likely oxygen atoms originating from dissociation of carbon dioxide by solar UV on the sun lit side of the and then migrating towards the anti solar point, where they descend down and combine, first into oxygen molecules and then into ozone. The loss mechanism is more uncertain but may be related to chlorine related catalytic reactions, like on the Earth. Therefore, as in many other cases, comparisons between the two are important to better understand both systems. An additional interesting aspect of ozone is in the field of characterising exo-planets, as astrobiologists consider ozone (in sufficient quantities, i.e. more than on Venus), if found in combination with carbon dioxide and oxygen, a strong evidence of life.

The innovative technique of using the spacecraft itself as a probe for measuring atmospheric density at low altitudes has been used during two campaigns, in May and September 2011. New data show a variable density at altitudes between 165 and 180 km, consistently varying with a periodicity of about two days. This peculiar behaviour is not yet understood but may be related to the polar vortex which is rotating below at about this rate but at a much lower altitude.

On June 5, 2011 suddenly the active star tracker lost track of all and the backup star tracker that was commanded on was also unable to find stars. The situation remained until the communication pass was ending and only the next day it could be confirmed that the star trackers operated again as normal. An analysis of the ASPERA (Analyser of Space Plasma and Energetic Atoms) background level and the high CDMU (Central Data Management Unit) error correction count led to the conclusion that a strong solar flare must have been the cause of this anomaly. This was later confirmed by other spacecraft. During the down time of the star trackers the spacecraft was kept in correct attitude by the on board gyros.

An aerobraking feasibility study by ASTRIUM was finished in June. Additional studies related to the spacecraft and science operations were performed by ESA Venus Express Mission and Science Operation Centres. Aerobraking to lower the orbit, as a science and technology experiment, remains in the future plans.

The cumulative number of refereed publications related to Venus Express is now 258, of which 72 are from 2011, of which 31 in press (available on-line).

1.6 Rosetta (Project Scientist: Rita Schulz) Now that the Rosetta spacecraft is in hibernation (since June 8, 2011), the Rosetta science team is busy in continuing the detailed preparation of the comet operations phase. The orbits around the comet nucleus that are possible to be achieved during various phases of comet activity have been calculated by flight dynamics and are being evaluated by the science team to make sure they fulfil the needs of the scientific measurements during the comet rendezvous phase. In this context a very successful PI workshop took place in late September where the skeleton plan for the Rosetta escort phase was discussed. The basic orbits provided by flight dynamics could be confirmed to be appropriate, in principle, for the scientific measurements and that the fine tuning and the calculation of additional options can start. 4

The most important results of the measurements of the Visible InfraRed Thermal Imaging Spectrometer (VIRTIS), the OSIRIS camera and the RSI (Radio Science Investigation) during the fly-by at (21) Lutetia were summarized in three papers for publication in Science Magazine. The manuscripts have been approved and the tentative date of publication has been set to October 28, 2011. An ESA Press Release is planned for this occasion. In addition, a special issue of Planetary and Space Science is currently being worked at, which will contain about 20 papers providing the latest results of the detailed analysis of the data collected during the fly-by.

The total number of Rosetta related refereed publications since launch is 206, of which 13 are from 2011.

1.7 Cassini‐Huygens (Project Scientist: Nicolas Altobelli) Cassini’s orbit remains close to the equatorial plane of Saturn, as planned for the so-called ‘Equatorial Phase 1’ lasting until May 2012 of the Solstice Mission. The primary science objectives of this phase are Saturn, its magnetosphere and its moons. Since May 2011, three additional Titan flybys have been performed between 1350 km and 5800 km altitude, aiming at constraining Titan’s interior properties and seasonal changes in the atmosphere. One close Enceladus flyby was performed (99 km) at the South pole, performing in-situ measurements at closest approach to obtain a new ‘taste’ of the plumes particles, as well as remote sensing measurements at high phase angle to detect any variability in the plume activity compared to previous flybys.

West et al. (GRL 38, L06204, 2011) have studied the evolution of Titan's detached haze layer near equinox in 2009. The thick haze layer surrounding Titan is made of droplets of organic compounds, which result in the typical opacity of the moon atmosphere at visible wavelengths. Following the evolution of this haze layer provides clues on atmospheric variations triggered by seasonal changes. On Titan, seasonal changes happen on the time scale of Saturn orbital period. In August 2009, the equinox was passed. A careful analysis of the haze layer altitude reveals a dramatic drop of 120 km, from 500 km down to 380 km, with a maximum change of altitude rate within a few months around equinox. This behaviour cannot be properly reproduced by current atmospheric models and casts new light on Titan’s dynamic atmosphere.

Fischer et al. (Nature 475, 75, 2011) have reported direct lightening evidences, recorded by the Radio and Plasma Wave instrument, during a giant storm that has been developing and raging in Saturn’s northern hemisphere since December, 2010. The lightening occurs at a rate 10 times higher than any storm previously observed on Saturn. The atmosphere has not shown such intense storms during the nominal mission, and the authors suggest that these storms are linked to seasonal changes, in regions not shadowed by the ring and receiving full solar illuminations (after equinox flip).

Simon et al. (GRL 38, L15102, 2011) have reported magnetic field measurements performed at Dione during two targeted encounters, when a perturbation in Saturn’s field lines was revealed close to the moon. In the absence of an intrinsic magnetic field, these observations can be explained with a tenuous atmosphere. It is remarkable that at the time these measurements were made, a newly discovered transient radiation belt (linked to solar storm activity and localized at Dione- Thethys orbital distance) had showed a dramatic increase in intensity, providing the required strength in plasma density for efficient sputtering.

A joint NASA/ESA review of the applications to the Cassini Participating Scientist Program was conducted in September. 3 European successful candidates (together with 8 from US) will be announced soon.

5 At the time of writing of this report, 2097 papers have been published in the refereed literature since launch. In 2011, 131 papers have appeared in the refereed literature so far.

1.8 PROBA ‐2 (Project Scientist: Joe Zender) PROBA2 will fly its 6000th orbit early on October 17, 2011.

The SWAP extreme-ultraviolet telescope and the Large Yield Radiometer have observed 5 solar eclipses since launch. The third solar eclipse in 2011 darkened the Sun on July 1, 2011 – only visible from a tiny spot in Antarctica and from space. This eclipse started the new Saros Cycle 156 and was observed by PROBA2 alone.

Habbal et al. (ApJ 734, 120, 2011) have published a paper discussing the thermodynamics of the solar corona and the evolution of the solar magnetic field as inferred from the total solar eclipse observations of July 11, 2010. Ground- and space-based measurements have been analysed. SWAP observations of the Fe X line at 17.4 nm have provided the first opportunity to compare this EUV line with the Fe X counterpart at 637.4 nm. The comparison demonstrates the unique diagnostic capabilities of the coronal forbidden lines for exploring the evolution of the coronal magnetic field and the thermodynamics of the coronal plasma, in comparison with their EUV counterparts in the distance range of 1–3 solar radii.

Pasachoff et al. (ApJ 734, 114, 2011) have studied the structure and dynamics of the white-light corona during the July 11, 2010 eclipse. The eclipse data from two on-ground observation stations at French Polynesia were compared to in-orbit data from SDO, STEREO, SOHO, and Proba-2. Several coronal structures were seen in the 10 second cadence images of the SWAP imager, improved by radial filtering and compared to the white-light on-ground images.

Van Doorsselaere et al. (ApJ 740, article id. 90, 2011) have described for the first time the deduction of flare plasma parameters from remote oscillation measurements (coronal seismology). As the LYRA radiometer provided several oscillations (short waves and long waves in one measurement and in one flare event), it was possible to constrain the plasma-ß and density contrast parameters of the flaring loop.

As part of the Guest Investigator Programme, 10 guest investigators were already visiting the Royal Observatory of Belgium, Brussels, for several weeks executing special instrument campaigns and contributing to or learning about the instruments calibration pipeline. Four of them have already submitted a publication for a PROBA-2 Topical Issue of the Solar Physics Journal.

At the time of writing of this report, the total number of refereed articles is 7.

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2. Missions under development

2.1 BepiColombo (Project Scientist: Johannes Benkhoff) The tests on the MPO-STM have been completed. First results indicate slightly higher temperatures at some of the spacecraft/instrument interfaces. The vibration tests of the BC components will be performed in January/February 2012.

The Science Ground Segment (SGS) team, together with the Project Scientist and the instrument teams of the BepiColombo mission are drafting a science activity plan for the nominal Mercury science operation phase. The goal of this activity is to prove that all individual science and measurement objectives of all teams combine and can be fulfilled with the spacecraft resources available.

The 8th Science Working Team (SWT) meeting was held on September 8-10, 2011 in Japan. After a presentation of the BC project status, there was an intense discussion on the updated higher worst case shock levels the instruments have to withstand. Tests to obtain a better understanding on this issue are still to come.

A BepiColombo-MESSENGER workshop was held in connection with the SWT meeting. New and unexpected results from MESSENGER (e.g., the centre of Mercury’s magnetic dipole seems to be shifted by 484 km, Mercury seems to contain much more volatile components than expected) were discussed. Seven papers about results from MESSENGER operations in orbit were published in the September 27, 2011 issue of the Science Magazine. These results have had quite an impact in the science community since they question commonly believed formation theories of Mercury. The good news is that BepiColombo mission features and instrument performances will provide unique observations to shed light on past and new arising questions.

In the frame of an overview about future ESA missions, dedicated invited talks were given on the and BepiColombo missions during the ESA plenary session at the JENAM conference (St. Petersburg, July 4-8, 2011).

In connection with the joint EPSC-DPS conference held from October 3 to 7, 2011 in Nantes, a science press conference was held, where the BepiColombo Project Scientist was one of six panel members: a presentation about BepiColombo was given.

2.2 (Project Scientist: Richard Marsden) Clearly, the major event since the previous report was the selection and adoption of Solar Orbiter as the first Cosmic Vision Medium-class mission (M1) by the SPC at its meeting on October 4, 2011. As in the case of the other two M-class candidates, this decision was preceded by the delivery in July of the Definition Study Report (so-called Red Book) prepared by the Study Scientists in collaboration with the Solar Orbiter Science Working Team (SWT), and the presentation of the key points of the mission to a joint meeting of the Working Groups and SSAC in September 2011 by Prof. T. Horbury, representing the Solar Orbiter SWT. The latter presentation also included the response of the Solar Orbiter SWT to questions drafted by members of the Advisory Structure. Another event of significance for the science of Solar Orbiter during the reporting period was the submission to ESA of two unsolicited proposals by European-led consortia for the provision of instruments to replace the SPICE EUV spectrometer and the SIS ion sensor that were to have been 7 provided by NASA as part of its contribution to Solar Orbiter. In both cases, the proposed replacement instruments rely heavily on the earlier SIS and SPICE development work, and retain the contributions from ESA Member States involved in those original instruments. Both proposals were subjected to an internal ESA review, and were found to be of sufficient quality to warrant the instruments being proposed to SPC as “facility instruments”, i.e. part of the ESA-funded Solar Orbiter mission package.

A Solar Orbiter Science Working Team meeting was held on July 26, 2011 in Kiel, during the STEREO-4/SDO-2/SOHO-25 Workshop “The Sun- 360”.

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3. Missions under study

3.1 JUICE (Study Scientist: Dmitri Titov) In May-October 2011 the former ESA-NASA EJSM-Laplace concept has been re-formulated in a European-led mission to the Jovian system, now called JUICE (JUpiter ICy moon Explorer). The Science Study Team (SST), re-appointed by ESA in April 2011, focused its work on elaboration of a new science case trying to preserve as much as possible the original science goals of EJSM- Laplace. In particular, as a result of withdrawal of the NASA participation and cancellation of the NASA-led Jupiter Europa Orbiter (JEO), SST faced the challenge to compensate for the loss of the science objectives related to the JEO investigations at Europa and synergistic studies of the Jupiter system, including the atmosphere and magnetosphere of the giant.

SST confirmed that the new mission should keep the main science themes of its predecessor: (1) habitability of the icy worlds and (2) Jupiter as archetype of gas giants, therefore keeping coherence with the major Cosmic Vision themes. The SST studied in detail the following three scenarios of the new mission: (1) Jupiter Ganymede Orbiter (JGO) like it was within EJSM-Laplace; (2) JGO extended by flybys of Europa and high inclination orbit at Jupiter; (3) a new mission concept aimed at the investigation of oceans on Europa and Ganymede. The SST selected the 2nd option since it allowed significant expansion of both Europa and Jupiter investigations while preserving the original JGO goals at Ganymede.

The SST efforts were supported by the ESA study team and three industrial contractors who addressed in as much detail as possible in such a short time various technical aspects of the selected scenario: mission analysis and trajectories, radiation and planetary protection issues, science operations and return at Europa and Ganymede. These studies concluded that the mission concept selected by SST is feasible and well within the current technical capabilities.

The baseline scenario and science milestones of the re-formulated JUICE mission resulted from the studies by SST, ESA study team and industrial contractors are summarized as follows: June 2022 – launch (with backup launch in August 2023); January 2030 – Jupiter orbit insertion; Jan-Dec 2030 – Jovian tour to study atmosphere and magnetosphere of the giant; January 2031 – two flybys of Europa with a primary goal of high resolution composition investigations (determination of non-ice materials and possible organic chemistry), sub-surface sounding (constraining minimal thickness of the ice shell in most active regions), high resolution geological mapping, and plasma investigations; Mar-Oct 2031 – Callisto phase (1) remote sensing, geophysical and plasma investigations of the moon during 12 flybys and (2) raising inclination of the orbit around Jupiter up to 30 degrees to enable enhanced Jupiter atmosphere and magnetosphere science due to observations of high latitudes; July 2032-Apr 2033 – Ganymede tour, consisting of high (5000 km), medium (500 km) and low (200 km) altitude phases and two intermediate elliptical phases. The tour would provide detailed investigation of Ganymede, with the main goal to characterise it as a planetary object with emphasis on habitability.

The SST supported by the ESA study team carried out a detailed analysis of the science return at Ganymede and concluded that the JUICE baseline scenario allows reaching all science goals stated in the JGO Science Requirement Matrix for Ganymede. It is important to note that it was possible to add two Europa flybys while keeping the original JGO science due to the launch in 2022 (2023) and longer interplanetary transfer that enabled greater dry mass of the spacecraft.

9 The new JUICE scenario was presented by SST, discussed in detail and endorsed by the science community at the Science Workshops on August 31-September 1 and October 2, 2011.

The DOI (Declaration of Interest) studies of potential JUICE instruments are in progress focusing on the impact of the harsher radiation environment at Europa on instrument design and performance. On November 9-11, 2011 a workshop is organized by ESA to inform instrument teams about the status of the mission, to present ESA technological development activities for JUICE and discuss their possible applications for designing and building payloads, and to present instruments’ concepts and status and discuss possible resources optimization.

In October-November 2011, SST and the ESA study team will complete writing Yellow Book. Technical aspects and costs of the JUICE mission will be reviewed by an ESA review board in November 2011. The Board Report and Yellow Book will be submitted for consideration by the ESA Advisory Structure in December 2011.

3.2 ‐R (Study Scientist: Detlef Koschny) The Science Study Team has met three times so far to produce a first issue of the Science Requirements Document (Sci-RD). The Sci-RD was released at the end of September 2011. It is used as input, together with other requirements documents, for the internal Concurrent Design Facility (CDF) study which has started on October 4, 2011. Discussions with the US on possible collaboration are ongoing.

3.3 EChO (Study Scientist: Kate Isaak) The principle science activity on EChO over the last 5 months has been the definition, specification and refinement of the science requirements for the EChO mission with the Science Study Team (SST). Work has been done during the course of two meetings of the science team at ESTEC (May 23 and September 5, 2011) and a number of telecons. The SciRD has been significantly updated since the first issue of the document that was used as input for the EChO CDF. The current Issue includes a preliminary mission reference sample of ~100 host star/ system targets. The feasibility, viability and accessibility of the proposed sample are under review by the science team and will be the subject of detailed study in coming months.

The baseline wavelength coverage of EChO is 0.4 – 11 m (simultaneously, and with a goal to extend to 16 m), and is driven by the need to cover a wide range of spectroscopic emission and absorption features that will be used to characterize the atmospheres of a selection of ranging from hot (>750 K) Jupiters to temperate (250 – 350 K) Super-. The principle molecules that will be used by EChO are H2O, CO, CO2, CH4 and NH3. Access to the visible waveband is required to monitor the variability of the host star, crucial for distinguishing between variations arising from the differences between in- and out-of- signals from the exoplanet and those from the star itself. The 1-5 m waveband is essential for the characterization of atmospheres of hot/warm ( >400 K) exoplanets, as both the peak of emission from bodies at such temperatures as well as key spectroscopic tracers fall into this band. Practically no photons are emitted shortward of 5 m by bodies at ~ 300 K, and so the 5-11 m waveband is essential for the characterization of temperate (250 – 350 K) exoplanetary atmospheres. All key molecules, in addition to CH3D, SO2, NO2 and the biomarker O3, have spectral features in this waveband which can be used in isolation, or in conjunction with those in the 1-5 m waveband to improve the retrieval of the thermal structure of the exoplanetary atmospheres. The 11-16 m waveband plays host to molecular species that can be used to recover the thermal profile of atmospheres: in the case of terrestrial planets

10 access to the CO2 band at 15 m is essential, as CO2 cannot be detected in the atmospheres of such planets at shorter wavelengths.

The most stringent requirement of the mission, with significant system-wide impact, is the need for high photometric stability: 10-4, 3 sigma (goal 10-5, 3 sigma) over a time period that includes either side of eclipse/transit as well as the transit itself and currently taken as 10 hrs.

The EChO CDF ran at ESTEC between June 6 and July 7, 2011 with sessions well-supported by members of the science team either in person and/or by videolink. A summary of the conclusions of the CDF study was presented to the science team by the EChO study manager (Ludovic Puig) at a meeting on September 5, 2011. The study identified a mission concept for EChO that complies with most of the technical requirements that have been derived from and driven by the science requirements. The study highlighted a number of technical challenges, notably (but unsurprisingly) in the area of detectors and on the AOCS. It is possible to meet the requirements on photon-noise limited performance and photometric stability across the EChO waveband, however this is at the expense of adopting US detectors that require cooling to sub-10K temperatures. (It should be noted that at this point there is insufficient data to determine whether European alternatives will provide sufficient performance). The complexity at system level introduced to the mission concept by the cryogenic requirements of the US detectors pushes the overall Cost at Completion for the EChO mission to above the allocation for the Cosmic Vision M3 slot. It will be necessary to carefully review all science requirements during the course of the assessment study and to possibly relax the wavelength coverage requirement in order for the mission concept to remain within budget.

A paper (Puig, Isaak, Escudero-Sanz, Martin, Crouzet, Rando) on EChO – essentially an overview of the results of the EChO CDF – was submitted by Ludovic Puig to the SPIE “Optics and Photonics” meeting in mid-August 2011 in San Diego.

3.4 Plato (Study Scientist: Malcolm Fridlund) The PLATO Preliminary Requirements Review (PRR) took place between May 16 and June 15, 2011. The main objective of the review was to demonstrate that the mission space segment definition had reached a maturity level that was compatible with the start of the Implementation Phase preparation.

Two panels were appointed at ESA, for payload and spacecraft respectively. The Payload Panel concluded that the maturity of the requirements is good considering the status of the program and there are no show stoppers in the payload design. The critical aspects are all in reach of the available technology and areas requiring development attention have been identified. Previous issues on the Consortium organization have been answered and the overall leadership of CNES with support of the two French laboratories LESIA and LAM is in place. A survey of potential contractors for the implementation phases has been given. The schedule is consistent: CCDs to be furnished by ESA have their deliveries integrated in the overall planning. This schedule is challenging and depends on the development of some items. A launch by the end of 2018 is, however, feasible if the planned consortium related industrial activities can start in the beginning of 2012 as assumed. The Spacecraft panel reported no issues for resolution by the PLATO PRR Board. Industrial designs are well defined, and to a higher level than a normal Phase A. The payload interface and performance requirements as specified by ESA are satisfied; no new technology outside the payload is required for the support of this mission. Necessary equipment exists and/or can be modified from other missions.

11 The mission was not selected for M1/M2 at the SPC meeting on October 3, 2011. SPC recommended that an attempt be made to introduce PLATO into the M3 selection. The situation w.r.t. such a M3 participation remain currently unclear.

Prepared by: L. Colangeli (Head SME-SM) with inputs from SM members, Project Scientists and Study Scientists

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