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1 Table of content 1. EXECUTIVE SUMMARY INTRODUCTION SCIENTIFIC OBJECTIVES Cosmic Vision themes addressed by Millimetron Science with a 12m single-dish Space-ground VLBI science MILLIMETRON MISSION PROFILE Launcher Millimetron orbit Millimetron observing modes Ground segment requirements Special requirements Critical issues MILLIMETRON PAYLOAD Overview The 12m space telescope Scientific instrumentation Single-dish instrumentation Space segment VLBI instrumentation Special requirements BASIC SPACECRAFT KEY FACTORS SCIENCE OPERATIONS AND ARCHIVING KEY TECHNOLOGY AREAS PRELIMINARY PROGRAMMATICS/COSTS International collaboration Proposed management structure Schedule Preliminary costing COMMUNICATIONS AND OUTREACH INSTITUTIONS CONTRIBUTING TO THE MILLIMETRON PROPOSAL REFERENCES /35

2 1 Executive Summary The InfraRed (IR) and submillimeter wavelength regime was recognized by ESA s astronomy working group (AWG) as one of the few areas were great progress could be expected in astrophysics as soon as high angular resolution and good sensitivity could be achieved. A passively cooled 12m dish optimized for the far-ir/submillimeter range, with an instrument suite building on Herschel heritage, provides just this capability. We propose European participation in the Russian mission Millimetron whose goal is the exploration of the cool universe seen in submillimeter and far-infrared wavelengths as well as the study of very energetic phenomena associated with compact radio sources in the millimeter and submillimeter regime with extremely high spatial resolution. The spectral range with wavelengths between 60μm and 600μm is of crucial importance for understanding how stars, planets and galaxies form and evolve. Furthermore, Very Long Baseline Interferometry (VLBI) in (sub-)millimeter waves will give micro-arcsecond access to compact sources such as black holes, neutron stars, and gamma-ray afterglows. Millimetron will be the only mission able to make unique contributions to all four themes of the Cosmic Vision program by combining high spatial and high spectral resolution as well as photometric and spectroscopic capabilities in the submillimeter/fir regions. Millimetron will explore of the life cycle of gas and dust that leads to stars and planets (theme 1), measure the deuterium content in the giant planets of solar system (theme 2) investigate the physical parameters and processes near the event horizons of black holes and near the surfaces of neutron stars with sub-micro-arcsecond resolution (theme 3) trace the formation and evolution of black holes, trace the life cycles of matter in the Universe along its history, and resolve the far-infrared background (theme 4). Millimetron will have two distinct scientific operational modes: (1) as a single-dish 12m diameter submillimeter space observatory, and (2) as space antenna of a sub-/millimeter space-ground VLBI interferometer. This will provide unreached angular resolutions in the millimeter to far-infrared regime of a few arcseconds in single-dish mode and micro-arcsconds in VLBI mode. A suite of heterodyne instruments covering the astrophysically important bands around 557, 1100, 1900, 2700 and 4700 GHz as well as a FIR photometer/spectrometer will be part of the instrument complement. In addition, receivers at four ALMA bands and K-band will provide VLBI capability. The instruments will be based on technology and designs as developed for Herschel and ALMA thus decreasing risk and cost. The Russian Space Agency has included Millimetron in its Federal Space Plan with the commitment to provide the 12m space telescope, the spacecraft, launch, operations and ground segment. In this Cosmic Vision proposal, we ask ESA to contribute the following payload elements: telescope heat shields, instrument cryo-cooler, participation in the ground segment, communication link, and on-board mass storage memory for VLBI. The total cost for the ESA contributions is estimated as 66 M. The scientific instrument would be built by a European instrument consortium comprising leading science and technology institutes with relevant experience in Herschel and ALMA instruments. The Millimetron mission will give European astrophysicists the possibility to join a unique space observatory and reap the exciting, scientific results emerging from it. With a small ESA investment the wish of the AWG to have a FIR observatory can become true, early in the Cosmic Vision plan. 2/35

3 2 Introduction This proposal is for ESA participation in the Russian-led space mission Spectrum-M (Millimetron). This mission will enable astronomers to observe the universe with unprecedented sensitivity and angular resolution in the far-infrared and submillimeter spectral bands. These bands are crucial regimes for the study of the formation and evolution of stars, planets, and galaxies. In addition, extremely high-angular resolution imaging by VLBI allows exploration of ultra-compact radio sources including black holes. Millimetron is a large (12m diameter) space observatory for millimeter, submillimeter and farinfrared observations. It has two scientific observing modes each of which is unique and represents a major step forward in the investigation of the universe we are living in. Firstly, Millimetron will be used as a 12m diameter single-dish space observatory for high-sensitivity and high angular resolution observations of the submillimeter universe. Secondly, Millimetron will be used as a VLBI (Very Long Baseline Interferometry) antenna in millimeter and submillimeter wavelength bands providing extreme angular resolution of better than one micro-arcsecond. Observations in both observing modes will substantially contribute to solving questions as outlined in the Cosmic Vision themes. Spectrum-M (Millimetron) is part of the Space Plan of the Russian Federation. The Russian Space Agency (RSA) has approved the mission and has allocated funds for the development and implementation of Spectrum-M (Millimetron). At present, the Astro Space Center (ASC) in Moscow is carrying out studies for Millimetron which are funded by the RSA. Concerning Millimetron, ASC has established contacts with ESA, ESO, and lately with SRON Netherlands Institute for Space Research with the aim to explore possibilities for European participation in the mission. A number of technologies required for Millimetron, including the 12m diameter space antenna, are based on the Russian RadioAstron mission which is currently undergoing flight hardware integration and will fly a 10m deployable antenna in 2008/09 for ground-space VLBI. The higher frequency range of Millimetron as compared to RadioAstron means more demanding specifications in such areas as antenna surface precision, time reference system, phase stability etc. The instrumentation for Millimetron is based on the substantial investment into Herschel instruments and ALMA receivers and will build on developed (and largely space qualified) detector and instrument techniques. 3 Scientific objectives 3.1 Cosmic Vision themes addressed by Millimetron Millimetron will be operated as a single-dish and as space VLBI system. The Cosmic Vision themes 1 and 2 will be addressed in single-dish mode, and the themes 3 and 4 in both single-dish and VLBI mode. Theme 1 - What are the conditions for planet formation and the emergence of life? Millimetron will investigate the processes that lead from gas and dust to stars and planets with high angular and high spectral resolution. With its high sensitivity as a 12m diameter single-dish space observatory it will be able to map the birth of stars and planets by peering into the highly obscured cocoons where they form. The ability to probe far-infrared lines of water, C+, O and HD with high spatial and spectral resolution is a big step beyond Herschel and crucial to our understanding of the processes leading to stars and planets. 3/35

4 Theme 2 How does the Solar System work? Millimetron will make a unique contribution to Solar System science by measuring the deuterium content of the giant planets through the HD emission line at 2.7 THz. This measurement provides a crucial piece of information for our understanding of the origin of the Solar System. Theme 3 What are the fundamental physical laws of the Universe? Millimetron in space-ground VLBI mode will have the ability to explore matter under extreme conditions by investigating the physical parameters and processes near the event horizons of black holes and near the surfaces of neutron stars with sub-micro-arcsecond resolution. Theme 4 - How did the Universe originate and what is it made of? The combination of sensitivity, sub-micro-arcsecond angular resolution (in VLBI mode) and highresolution spectroscopy on Millimetron allows to trace the formation and evolution of the supermassive black holes at galaxy centers in relation to galaxy and star formation and trace the life cycles of matter in the Universe along its history. It can resolve the far-infrared background into discrete sources, and the star-formation activity hidden by dust absorption. 3.2 Science with a 12m single-dish Introduction: Zooming in on the formation of stars and galaxies Two prime foci of 21 st century astrophysics are the studies of the obscured universe and the molecular universe, at far-infrared and submillimeter wavelengths. The reason is that only through such studies, which target cool dust and gas, we can obtain crucial information about the formation processes of stars and galaxies, the central issues in astrophysics. Millimetron will permit to make the important next steps in spatial resolution as well as sensitivity. Following up on the IRAS mission, ISO and Spitzer have subsequently truly opened the dusty and molecular universe. These missions observed in great detail the processes involved in small- and large-scale star-formation, at mid- and far-infrared wavelengths. ISO revealed the presence of cold (15 K) dust in galaxies and established the unexpected fast decay of starburst episodes. Mid- and far-infrared luminosities, colors, and spectra of the [CII] and [OI] cooling provided insight in the physics of star formation. Imaging of the warm dust in nearby galaxies proved to be a fine tool: ISO revealed fascinating cases of obscured star-formation such as in the Antennae galaxies NGC4038/39 (Fig.1). The spectroscopic capabilities of ISO and Spitzer permitted great advance in our understanding of the gas properties of nearby dusty and gas-rich objects, including the important class of ULIRGs. The magnificent spectra obtained with the Spitzer IRS provide conclusive evidence for the starburst-agn symbiosis (as suggested from ISO observations) in a variety of extragalactic objects. Fig. 1 Antennae galaxies NCG4038/39 (Spitzer Space Telescope) 4/35

5 The Herschel Space Observatory, ESA s fourth cornerstone mission, will continue where its predecessors ISO and Spitzer stopped. Herschel will extend the wavelength range into the submillimeter, at much greater sensitivity, considerably higher spatial resolution, and much higher spectral resolution. These qualifications will permit studying the mid- and far-ir out to high redshift for the first time. Simultaneously, from the ground, ALMA will bring sub-arcsecond resolution to the submillimeter window. In space, a far-infrared interferometer is still far beyond the horizon, and larger antennas must make the necessary next step. If such a telescope delivers improved detector sensitivity at the same time, its advantages are even greater. The Millimetron mission will be able to deliver all this. Its sensitive receivers and its large collecting area will allow at least one order of magnitude improvement with respect to Herschel. Whereas Herschel will study the formation of stars and galaxies in a global fashion, Millimetron will zoom in on the processes, and observe fainter, more distant objects. The development of Millimetron would therefore be a wonderful far-infrared parallel to the submillimeter developments on the Chajnantor plateau! Diagnostic features in the far-infrared regime The infrared (IR) and submillimeter (submm) regions are crucial regimes because they reveal the radiative response of gas and dust in galaxies to the input of energy from stars (photon absorption) or by the dissipation of mechanical energy (shocks). The resulting spectrum contains the fingerprints of the astrophysical processes governing the formation of stellar populations and of supermassive black holes. Unfortunately, the Earth's atmosphere is opaque in essential regions of the far-ir/submm regime, such as the region from 50 to 200 micron which contains the fundamental interstellar gas cooling lines: [CII] 158 micron (1900 GHz) and [OI] 63 micron (4700 GHz). By providing observing capability in this region at unprecedented resolution (3-4") and sensitivity, Millimetron will revolutionize this field. Table 1: Main spectral features targeted by Millimetron Line Frequency (GHz) Goal H2O 1(10)-1(01) & & Tracers of star formation 1(11)-0(00) Dust continuum Mass and temperature diagnostic p-h2d+ 1(01) Unique tracer of protostellar 0(00) condensations [CII] 2P(3/2) Main coolant of interstellar 2P(1/2) gas HD J= Origin of molecular clouds and giant planets [OI] 3P(1)-3P(2) Tracer of heating by shocks and UV Competitive Edge Superior sensitivity and resolution wrt Herschel Superior sensitivity and resolution wrt Herschel Superior sensitivity and resolution wrt Sofia Superior sensitivity and resolution wrt Herschel Velocity information unique to Millimetron Velocity information unique to Millimetron Emission lines in the far-ir are excellent diagnostics of the physical conditions in interstellar gas, which are not affected by dust extinction. In relatively cold regions, the dominating line is the finestructure transition in the ground state of ionized carbon. In warmer conditions, the corresponding transition of neutral atomic oxygen makes a significant contribution or even outshines the carbon line. In addition, the dust emits thermal emission which is a sensitive probe of mass and temperature, especially since the emission peak falls in the far-ir for the relevant temperature range. In denser regions of the ISM, molecular lines take over the role of tracers from the atomic fine-structure lines. In particular, the far-ir hosts key molecular lines which trace all stages of the star formation process: the HD 1-0 line traces the transition from atomic to molecular clouds, the H2D+ line at 1370 GHz traces the formation of dense cores in these clouds, and the ground state 5/35

6 transitions of H2O are excellent tracers of gas warmed up by young stars. Table 1 lists the major spectral targets for Millimetron. Spatially resolving the Cosmic IR Background The Cosmic Infrared Background (CIRB) is a fundamental component of the present radiation content of the Universe and is made essentially of the long wavelength output from all sources throughout the history of the Universe from the present time till the epoch of recombination, only 400 thousands years after the Big Bang. In contrast, the Cosmic Microwave Background, dominating the radiation spectrum for frequencies lower than 800 GHz, has been produced in the hot and dense phases of the universe before the recombination. Note that the very different spectra of the CIRB with respect to the CMB allow them to be relatively easily separated for wavelengths shorter than 1 mm, and in this wavelength regime the CIRB dominates the galactic emission by a factor 4 in the lowest cirrus regions. Our current understanding of the CIRB considers it to be the integral of the reprocessed light by dust during phases on enhanced activity in galaxies and active nuclei. Dust, which is observed to be ubiquitous in galactic star-forming regions and star-forming galaxies in general, is likely to have been present also during the major past events of the formation of stellar populations. According to this interpretation, the long-sought primeval galaxies would be undetectable in the optical, and would have left an important trace in the CIRB. This is supported by recent observations with SCUBA/JCMT, ISO and Spitzer, able to resolve a few percent of the CIRB into sources, some of which appear indeed as very luminous IR sources. This indicates that the most important phases of the formation of galaxies and their nuclear supermassive black holes (responsible for the nuclear activity) might only be investigated in the far-infrared and in the submm, where the CIRB peaks. A crucial theme of observational cosmology for the next several years will then be this exploration of the far-ir & sub-mm sky in the attempt to identify and characterize the enigmatic sources of the CIRB. Figure 2 is a model representation illustrating the capabilities of future long-wavelength space missions (nothing can be done unfortunately from ground in this spectral domain) to resolve this background, in a similar fashion as it was done for example for other extragalactic relics like the X-ray or radio backgrounds. Limited sensitivity and resolution make it impossible to resolve the CIRB with the forthcoming Herschel mission or future space observatories like SPICA: all these will produce confusionlimited images able to resolve the CIRB only at its short wavelength boundary (see Figure 3). Similar considerations apply to its long wavelength (λ>500 μm) boundary accessible by ground based millimetric observatories. A solution to the problem of the formation of galaxies and cosmic structures will only be achieved after the enigmatic sources of the CIRB will be properly resolved into sources, which is only possible by a large far-ir/sub-mm telescope in space with adequate suite of imagers and spectrographs. The spectral capabilities of Millimetron will allow a spectral characterization of these sources through redshifted fine-structure emission lines characteristic of either stellar photoionization ([NeII], [SIII] lines) or photoionization by the hard continuum of an active galactic nucleus ([OIV], [NeV]). It will thus be able to trace directly the coeval buildup of stellar population and black hole with redshift in galaxies of a range of luminosities. Millimetron will thus provide the currently missing window on the region of photoionized gas, and provide direct complementarity to ALMA, which will probe principally the neutral molecular gas in the same objects. 6/35

7 Fig. 2 - The CIRB spectrum and fractions of it that will potentially be resolved by future missions (HSO, SPICA). Only a large (10-12m) diffraction-limited space observatory, like Millimetron, would completely resolve the CIRB into sources. Star-forming galaxies at low redshift Low-redshift galaxies form crucial laboratories for studying the physical processes occurring at higher redshifts in detail. By probing the neutral star-forming medium, we probe both the conditions in the prestellar gas phase and the feedback of the star formation (or black hole accretion) process on the ambient medium. Here Millimetron provides unique insight: the H2O ground-state transition forms a probe of warm, dense, cooling molecular gas that is not available from the ground. Simultaneously, the [CII] and [OI] lines probe the more extended lower density medium. The change in cooling balance from quiescent to actively star-forming galaxies such as ULIRGs is shown by the decreasing importance of [CII] cooling with increasing luminosity. For instance, in ultraluminous infrared galaxies (ULIRGs) the cooling by the CO rotational lines approximately equals that in [CII], indicating a totally different thermal balance than in lower luminosity objects (Papadopoulos et al. 2007). While Herschel will be able to skim the surface of this subject, what is really required is a study of fainter galaxies, both locally and at higher redshift, in order to establish the cooling properties as a function of physical parameters such as galaxy luminosity, type, environment, metallicity, presence (or not) of an active nucleus, etc, etc. Such as systematic study will form an indispensable benchmark for the study of higher redshift galaxies, both with Millimetron and other facilities such as ALMA. As a case in point, we note that in crucial aspects, the interstellar medium of low-metallicity galaxies resembles that of primeval galaxies. In metal-poor environments, heating and cooling of the gas operates in different ways from those in the Milky Way. Low dust-to-gas ratios allow UV radiation to penetrate deep into molecular clouds. The primary molecular cloud coolant CO is much reduced in abundance, but H2 itself is largely unaffected. CO is no longer a useful tracer of molecular gas column densities. Dissociation of CO increases the C and C+ abundances and thus the cooling luminosity of the [CII] line. Far-infrared spectroscopy of star-forming galaxies With a resolution of 3 4 arcsec at the wavelengths of the important [OI] and [CII] cooling lines, the medium-resolution (imaging) spectrograph on Millimetron will be able to trace accurately the location of the main cooling radiation and therefore characterize the thermal balance of the ISM of galaxies at a resolution comparable to seeing-limited observations in the visual regime. At the distance of the nearest ULIRG (Arp220, D=74 Mpc) the Millimetron resolution at 60 microns corresponds to ~1000 pc, sufficient to resolve the central concentration and gas and dust where 7/35

8 most of the luminosity originates. Given the linewidths of galactic nuclei, a spectral resolution R=3000 is sufficient for revealing the kinematic structure of the emitting gas. Finally, an attractive application of Millimetron is the search for primeval (metal-free) galaxies. In the absence of metals a cloud of molecular gas must cool through H 2 line emission and the rotational H 2 lines will be redshifted into the Millimetron regime. This process has been modeled in detail by Mizusawa et al. (2005) who demonstrate that for a cloud contracting at a rate (expressed as a star formation rate) of 100 M sun /yr a flux of W/m 2 is expected in the brightest H 2 line for a source at z=6 (presumable the end of reionization). If such sensitivities can be reached, Millimetron could for the first time detect population III (metal-free) galaxies, in the era just before or during cosmic reionization. While a blind search for such galaxies could be prohibitively time-consuming, targets may be preselected from Ly-alpha narrow-band imaging (since such galaxies are expected to be significant Ly-alpha emitters) or from high-z Gamma-Ray- Burst surveys. Physical conditions in Galactic regions of star formation The heating of interstellar gas reflects the action of powerful shocks driven by jets and outflows from young stellar objects. Alternatively, UV photons from nearby young massive stars photodissociate and heat the surrounding gas, forming a photon dominated region (PDR). Both of these types of environments are cooled by infrared atomic fine structure line emission. Calculations for shocks in the dense ISM have been presented by Hollenbach & McKee (1989) and for PDRs by, e.g., Tielens & Hollenbach (1985a+b), Liseau et al. (1999) and Kaufman et al. (1999). The latter paper, in particular, contains the results of an extensive parameter study, viz. for n(h) = cm -3 and G o = in units of the average UV field of the solar neighbourhood 1. Fig. 3 - (left) Line ratio plot for the fine structure lines of OI and CII, where error bars have been omitted to avoid crowding. The horizontal dashed line indicates the optically thin regime for the [OI]63μm/[OI]145μm line ratio above about ten. The two open symbols with vertical error bars refer to the average values of data lying above and below the dividing line, respectively. Fig. 3 - (right) Numerical results for oxygen line ratios at characteristic interstellar cloud temperatures. Displayed are the column densities of atomic oxygen N(O), for Δv =1 km s -1, needed to produce the line ratios for an H 2 density of cm -3. For these parameters and at 20 K, line center optical depths in this plot range from min τ 0 = 0.05 to max τ 0 = in the 145μm and in the 63μm lines, respectively. At 100 K, these values are 26 and in excess of (adapted from Liseau et al. 2006). 1 G o = 1 equals erg cm -2 s -1 for photon energies E = ev. 8/35

9 Comparing theoretical predictions of the line intensity ratios of the [OI]63μm (4.7THz) and [OI]145μm (2.1THz) lines (unaffected by abundance uncertainties) to the observation of more than 100 galactic star forming regions (relatively nearby), Liseau et al. (2006) found that more than two thirds of the observed values were not consistent with the theoretical models. In addition, Abel et al. (2007) found evidence for optical depth effects in the [OI] and [CII] lines. These unexpected results implied considerable lack of understanding of the physics of the line emitting regions, the line excitation mechanisms and/or the line radiation transport. Optical depth effects in the [OI] lines cannot explain this mismatch between theory and observation for most cases of interest. Maser action in the [OI] 145μm line is a viable option for dense and warm regions, such as the Orion-Bar, whereas self-absorption in the 63μm line may play a role in dense cold clouds (e.g., the ρ Oph cloud). High spectral resolution observations are needed to settle this issue, which Millimetron will provide. For protostellar jets & outflows, Hollenbach & McKee (1989) proposed that the luminosity of the [O I] 63μm line can be used to derive the rate at which the central object looses mass. In the momentum conserving case, this rate can also be estimated from the observed molecular outflows, generally mapped in rotational lines of CO. The large scatter in the observed relation clearly calls for a re-examination of the shock models. Heterodyne observations of the [OI] lines with Millimetron are clearly needed. In summary, our understanding of the physics of interstellar clouds is clearly incomplete as shown by our inability to model the excitation conditions in the cold [C II] and warm [O I] media. Local emission regions and intrinsic line widths, whether galactic or extragalactic, are expected to be small. Progress on the observational side therefore clearly requires significantly increased spectral and spatial resolution compared to what will be offered in the foreseeable future by, e.g., Herschel and/or SOFIA. A large telescope as that proposed for Millimetron and equipped with heterodyne receivers would be able to fulfill these requirements. For external ultra-luminous galaxies, the sensitivity provided by a large collecting area in combination with an intermediate-resolution spectrometer for far infrared wavelengths would be well adapted to study the [O I] 63μm emission for large redshifts, z > 3, and hence match the upcoming (lower spatial resolution) observations of the [C II] 157μm line with Herschel. Formation of molecular clouds and stars A large single dish far-infrared telescope equipped with array receivers such as Millimetron is also the ideal tool for studying the formation of molecular clouds and stars. Stars are born in dense cold cores inside molecular clouds, but the life time of these cores and their formation within molecular clouds, as well as the formation of molecular clouds themselves, are far from understood. Numerical simulations by Hennebelle et al. (2007) and Glover et al. (2007) have shown that molecular clouds can be formed out of diffuse atomic interstellar gas, and that the structure of the clouds is both a consequence of the early structure of the atomic gas as well as the condensation process. Furthermore, while the formation of molecular hydrogen itself can be accelerated by the shocks driven by turbulence, the formation of CO and other stable molecules requires longer times, as these molecules are easily photodissociated. Therefore, significant abundances are only achieved in regions shielded from UV radiation. Hily-Blant and Falgarone (2007) propose that dense molecular cores are indeed related to more diffuse atomic and molecular gas, from which the cores accrete material and gain mass. As the main coolants of diffuse matter, the [CII] and [OI] lines are the best probes to study the process of core formation in the interstellar medium and test the above theories. Disentangling the respective roles of turbulence, gravity and magnetic fields requires large scale maps at high spectral and spatial resolution, as small scale structures are known to exist down to arcsec scale in the diffuse interstellar medium. The role of the magnetic field will be revealed by the shape of the 9/35

10 structures, but it is also expected that the line profiles will bear an imprint of the magnetic field, because the velocity field of the molecular gas will be affected. Prior to star formation, the molecular gas becomes very cold in the interior of dense molecular cores, and most of the heavy molecular species get frozen on grains. Since the substitution of an hydrogen atom by a deuterium atom is favored at low temperatures, deuterated molecules become very abundant, and are the best tools to study the physical conditions, gas dynamics and chemistry in these environments. The recently detected molecular ions H2D+ and D2H+ are key actors in the deuterium fractionation process. While a single transition of either ion is accessible from the ground with great difficulty, Millimetron will routinely map both ions, offering unique diagnostic capabilities of the initial conditions and first steps of star formation. Measurements of the HD rotational lines at 112 and 56 micron would provide an ideal complement, as HD is the main deuterium reservoir. While the first detection of the rotational lines have been obtained by ISO, the diagnostic capabilities of HD have been demonstrated by Spitzer. Neufeld et al. (2006) have mapped the HD emission from supernova shocks, and show that the R(3)/R(4) ratio is a probe of gas pressure. HD lines probe the deuterium reservoir, and trace the presence of molecular gas accurately. The onset of actual star formation in the molecular condensations is best traced by the water molecule. Emission in its ground state lines at 557 and 1113 GHz is a clear sign of dense gas that has been heated up by nearby young stars. While Herschel will excel in the study of water in advanced stages of star formation, the weakness of the emission and small size of the emitting region in the very first phases of stellar activity call for the sensitivity and resolution of Millimetron. Protoplanetary disks The past decade has witnessed the discovery of a multitude of planetary systems, exhibiting a wide variety of properties. This shows that our Solar System is neither unique nor typical. Understanding how this richness arises from the formation process of planets will occupy astronomers for the next decades. It will require observations of sufficient spatial resolution that can penetrate the dense layers of dust present in circumstellar disks, the birth sites of planets. Millimetron offers two avenues to provide unique insight into the planet formation process: through ultra-high resolution VLBI observations in the ALMA bands, and through medium resolution single-dish observations of water lines in particular. VLBI: ALMA will image the cold gas and dust in proto-planetary disks at resolutions of a few AU and up at the typical distance of these systems. While these observations will probe the global planet formation environment, the actual planet formation takes place on much smaller scales corresponding to a few stellar radii for gas giants, and perhaps the Earth-Moon system for terrestrial planets. VLBI at ALMA wavelengths with Millimetron provides resolutions of a few hundred-thousand km at the typical distance of many young stars (140 pc), and should therefore be capable of directly detecting proto-planets, as well as the gaps they open in disks. We should also be capable of detecting substructure in the disk induced by the planets, such as spiral waves and accretion signatures onto the planet. A key question, which with current models cannot yet be fully addressed, is if the brightness temperatures of these features are sufficiently high to be detectable. Especially shocks and accretion flows may provide the required heating to generate emission with brightness temperatures of a hundred K or more. Single-dish: The water molecule is a key player in protoplanetary disks. Expected to be frozen out onto dust grains in cold regions (<100 K), it should be present in the gas phase in the disk atmosphere and the inner few AU of the disk. In these latter regions it is a key player in the cooling balance of the gas, and its presence in the terrestrial planet formation zone is crucial for the formation of life. While Herschel will bring the first opportunity to detect the ground-state water lines from protoplanetary disks, the limited sensitivity and resolution will at best permit detections in a few exceptional cases. The much larger Millimetron dish will enable systematic 10/35

11 studies of the water content of protoplanetary disks in nearby star-forming regions, and thus put the study of habitable planet formation on a solid footing. Debris disks: After planet formation, the remnant dust particles settle in so-called debris disks. The classical example is the tenuous disk around Vega, discovered by IRAS. The properties of such disks are important constraints on theories of planet formation, but are not well known from observations. The superior sensitivity and resolution of Millimetron relative to Herschel allow us to detect the dust and [CII] emission from debris disks out to large distances, and permit to study their physical properties in a statistically significant sample. Solar system science A large submillimeter antenna in space like Millimetron would be an important tool to study the water meteorology in planetary atmospheres and the water activity in comets. The small antenna beam at submillimeter wavelengths allows mapping the water lines on planets and comets, and by repeating these observations regularly, we may establish the meteorological system and probably even start with climate measurement. The atmospheres of planets and moons in our Solar System, as well as comets are the prime targets for spectroscopic observations. Kuiper Belt Objects are more easily studied in the continuum. This section addresses all these objects and highlights the main characteristics. While Millimetron will not be used for in-situ measurements, the power of remote sensing with a large single dish is such that Millimetron will be able to make a large contribution to Cosmic Vision Theme 2. Mars: The current martian climate is governed by 3 cycles: CO 2, H 2 O, and dust. While the dust and CO 2 cycles can be studied by other methods, H 2 O is best studied through its far-ir rotational lines. Since these lines are inaccessible from the ground, there are still many unknown sources and sinks of water, which are crucial to understand the present climate of Mars. The temporal and spatial column-integrated amount of water has been characterized in the Viking mission. However, extremely limited information is available on the vertical profile of water, which cannot be derived from near-ir or UV measurements. Only weak 22 GHz H 2 O lines and millimeter HDO lines have provided some results on the water vertical distribution. Herschel will provide the diskaverage abundance and vertical profile of water and its isotopes for different seasons, but only high angular resolution heterodyne submillimeter and far-ir observations could provide both spatial and vertical water distributions on Mars. Having this in hand, dedicated O2 observations could be used to relate its spatial variation with that of water, which is essential to understand their photochemical interaction. Other expected minor species (OH, NH 3, HCl) would constrain the coupling between photochemical and general circulation models. Giant Planets: ISO observations of stratospheric water in the giant planets have demonstrated the external origin of water. Various external sources has been proposed: interplanetary dust particles (IDPs), local sources (rings, surfaces), and cometary collisions (e.g., SL9). While Herschel will improve the current measurement of the vertical profile of water and will provide better constraints on its origin, high angular resolution observations will be essential to disentangle the different external origins of water. In particular, cometary impacts will have a different spatial distribution signature than homogeneous sources (e.g., IDPs), while magnetospheric effects influence the water distribution at polar latitudes. A key contribution of Millimetron will be the measurement of the HD ground state line in the atmospheres of the giant planets. This line probes the deuterium abundance, a very important measurement for understanding the formation of planets and the origin of the solar system. The HD abundance in the atmospheres of Saturn and Jupiter constrains the place in the Galaxy where our Sun has formed. While SOFIA and Herschel will assess this topic for the first time, Millimetron will map the HD abundance over the planetary disks, and directly test the origin assumption. One expects that on Uranus and Neptune, the D/H ratio is enhanced by mixing of their hydrogen envelopes with D-enriched grains and this process could also be at play on Saturn and 11/35

12 Jupiter. Maps of the four giant planets in HD will thus permit the determination of the composition and origin of the grains in the primitive Solar nebula. Comets: High-resolution microwave observations of comets allow to study the distribution of the outgassing at the surface of the nucleus, and the jets spiraling with the rotation of the nucleus. ALMA will allow to obtain dynamic, 3-D like, maps of several species, but the major species H 2 O, which drives both the nuclear activity and the hydrodynamics of the coma, will not be covered. High angular resolution observations of water with a large antenna in space are urgently needed. 3.3 Space-ground VLBI science Millimetron will also operate as a space-ground Very Large Baseline Interferometer providing unprecedented angular resolution. Here we address the important and unique science that can be done and give its relation to themes 3 and 4 of the Cosmic Vision plan. The main scientific goal of the Millimetron mission in Space VLBI (SVLBI) mode operation will be the exploration, with extreme high angular resolution (better than 1 micro arcsecond) of extremely compact radio sources. The list of the expected results includes: (1) first direct imaging of the event horizon of super-massive black holes in galaxies at different redshifts, particularly for the black hole at the center of our Galaxy; for these super-massive black holes and for stellar-mass black holes (microquasars) in our Galaxy and other galaxies in the local group, Millimetron will further study the physical parameters and processes near the black-hole horizon in direct accordance with theme 3; (2) determine the cosmological evolution (by measuring black holes at different redshift) of black holes parameters at the center of galaxies (themes 4 and 3); (3) first direct study of particle acceleration regions very close to a black hole (theme 3); (4) first measurements of proper motion and cosmological proper motion and parallaxes of such objects (theme 3); (5) first measurements of the dynamics of close binary quasars (theme 3); (6) first direct imaging of structures, physical parameters and process near the surface of neutron stars by observation of pulsars and magnetars with inverted radio spectrum (theme 3); (7) the first detection of structure, and study of the evolution of this structure, of gamma-ray bursts radio afterglows (themes 3 and 4). Fig. 4 - Spectrum of the cosmic background radiation for high galactic latitudes (Henry, 1999). The submillimeter regime shows a minimum. All these topics have in common that they require sources that are strong synchrotron emitters. As it was found using ground VLBI observations, the most compact radio sources have a flat or inverted spectrum (the spectral flux increase with frequency), which is the result of self-absorption by relativistic electrons, or absorption by plasma surrounding the compact source. This, together with interstellar scattering, blurs the image of an object and sets the minimum resolution that can be obtained at a given wavelength. This effect is very strong towards the black hole at the center of our Galaxy, the source Sgr A*. However, the importance of these effects decreases significantly with 12/35

13 B is frequency, and these effects are negligible in the sub-millimeter band. An additional advantage of the sub-millimeter band is that in that band there is an absolute minimum of the brightness temperature of the background radiation (e.g., Henry, 1999), Figure 4, and therefore there one can obtain the best signal-to-noise ratio. At a wavelength of μm (frequency GHz) there is a deep minimum of the spectral intensity I ν. Due to the gravitational lensing, black holes would cast a shadow larger than their horizon size over the background; the shape and size of that shadow can be calculated (item 1, from the list above). A simple estimate of the angular diameter of a Schwarzschild black hole for Sgr A* ( solar masse at 8 kpc) is 60 microarcsecs, which is under the resolution attainable with current astronomical instruments. Considering the image blurring by the interstellar medium, such a shadow image of Sgr A* would only be observable at wavelengths of 1 mm or less (Huang et al., 2007). Sub-milliarcsecond, and even sub-microarcsecond, astrometry and imaging of Sgr A* and many extragalactic sources only become possible at submillimeter wavelengths. For the black hole at the center of M87 ( solar masses at 14 Mpc), the shadow subtends 25 microarcsec. For a black hole with the mass of that in M87 at a redshift z~1, the size of the shadow would be 30 nanoarcsecs; at larger redshifts the angular size increases as (1+z) (items 1 and 2). A very exciting prospect is the possibility of observing hot spots in the accretion flow. Measurements of those spots could be used to determine the validity of the Kerr metric and measure all the black-hole parameters (Broderick & Loeb, 2006). Figure 1 Sgr A* - A strong and variable source in the center of our Galaxy with a solar masses black hole, with an expected Schwarzschild angular diameter of 50 micro arcsec, and a flux of ~3 Jy in the 1 mm and 0.3 mm bands. (Figure taken from: Marrone et al. 2006). Sensitivity estimates and maximum angular resolution are strongly connected. The flux of a n-α 2 circular Gaussian source with half with diameter φ=λ/b is F ν =πkt δ B /(2ln2(1+z)B ). Here λ is 3 wavelength, B is the base line projection on the plane of view ( km), T the brightness temperature of the source (10 12 K at saturation), δ n-α is the Doppler amplification factor, with n=3 for ballistic motion and n=2 for continuous jet, where α is the spectral index. Without taking into account the amplification factor, and for previously mentioned baselines, the expected fluxes are in the range of 30 mjy to 30 Jy, and angular resolutions are in the range of 6 microarcsec to 200 nanoarcsec for λ=0.3 mm. At the Lagrangian point L2 (1.5 billion km baseline), the resolution would be 40 nanoarcsec. 13/35

14 Polarization and Faraday rotation in the millimeter and submillimeter bands contain unique information on the central engine of such objects, e.g. on the strength of the magnetic field in the particle acceleration regions. Determination of brightness temperature and Doppler factors would allow discriminating between electron-synchrotron and proton-synchrotron sources (item 3). The science item 4 is limited by the astrometric measurements. For a redshift range of z = 0.01 to 1, the main estimates of cosmological proper motion in reference to the systematic motion of 380 km/s with respect to the CMB are (Kardashev, 1986) 1.4 microarcsec/year to 36 nanoarcsec/year and 34 to 0.9 nanoarcsec/year, respectively. Item 5 in the list relates to many narrow double nuclei extragalactic sources. The orbits of most narrow pairs can be measured by accurate astrometric observations. There is a class of neutron stars for which the inferred magnetic field is in excess to Gauss, the so-called Magnetars. Among these objects, XTE J , with a spin period of 5.54 s, is the only one so far that has also been detected in the radio regime (Camilo et al., 2006). The radio spectrum of this object is inverted, strongly polarized, and has high flux in the cm and mm bands. This means that it is possible to observe this object at shorter wavelengths reaching the limiting angular resolution (item 6). Item 7: Recent observations of gamma-ray bursts afterglows reveal extremely fine structure, an inverted spectrum and, as a result, there appears to be a very weak dependence of observed flux with redshift (Kuno et al., 2004; Frail et al., 2006). Observations open up the unique possibility to observe these objects and verify the existing coalescence models. Observations of the radio afterglow of GRB at z= (Kuno et al. 2005), shows that the expected flux 3 days after the explosion is ~70 mjy in the 1 mm and 0.3 mm bands. The RMS sensitivity limit of the Millimetron-ALMA interferometer, for each polarization, for a bandwidth of 8 GHz and an integration time of 10 s is 0.9 mjy in the 1 mm band and 5 mjy in the 0.3 mm band. Amongst the targets for SVLBI observations are: Sgr A*, M87, BL Lac, 3C 273, , OJ287, , CTA102, , , and use of already published data like for the gamma ray bursts GRB U-V coverage and multi-frequency synthesis In order to improve the u-v coverage the technique of multi-frequency synthesis (MFS) can be used for continuum sources. Rapid frequency changes in the receiver and create more points in the u-v plane for the same geometrical baseline. As an example, Figure 5 shows the u-v coverage for simultaneous observations between Millimetron and ALMA using frequency switching (MFS) within band 6 of ALMA (source , GHz, 4 channels, two days of observations). The Millimetron orbit is perturbed by interactions with the Moon which allows to further improve the u-v coverage if the same astronomical source is revisited after several months. 14/35

15 Fig. 5 u-v coverage of the Millimetron-ALMA interferometer for the source using ALMA band 6 and multi-frequency synthesis (MFS). 4 Millimetron mission profile Millimetron is designed to provide high sensitivity, high to extremely high angular resolution and high spectral resolution as well as far-infrared imaging and spectroscopic capabilities. All these characteristics are essential in achieving the science goals outlined in the previous sections. High sensitivity and (extremely) high angular resolutions are achieved by using a 12m diameter space antenna, either in single-dish mode or as element of a space-ground VLBI system. High spectral resolution is obtained by using heterodyne receivers, and the far-infrared imaging/spectroscopy will be done by an imaging photometer/spectrometer. In order to achieve good u-v coverage in VLBI mode, an elliptical orbit is chosen. 4.1 Launcher Launch services will be provided by Russia as the Millimetron mission is included in the Russian Federal Space Program. The main requirements are: mission payload mass (including space platform) 5000 kg into an elliptical orbit; fairing envelope diameter 4100 mm, length m. The Russian Proton type launcher in combination with a booster fully satisfies the Millimetron launcher requirements and is going to be used. The upgraded Proton heavy class launch vehicle is characterized by high power capacity. This type of launcher has been used for more than 30 years with very high reliability. The Proton payload fairing has been recently enlarged in order to double the space available for payloads. The Russian Navigator space platform is planned to be used as basis of the spacecraft (see section 6). For the Proton launcher see 15/35

16 4.2 Millimetron orbit Driven by the requirement of good u-v coverage in VLBI mode, an elliptical orbit with high apogee and an orbital period around the Earth of about 9.5 days is chosen. This orbit evolves as a result of weak gravitational perturbations from the Moon and the Sun. The perigee radius varies from to km, and the apogee radius from to km. Table 2 lists the main orbital parameters. Because of the orbit evolution, about 80% of the VLBI radio sources will be located on the sky close to the orbit plane projection at some time intervals, i.e. for such radio Table 2 - Millimetron orbit parameters. Period T = 9.5 days (7-10 days) Semi-major axis a = km Inclination o or o (depends on scientific program) Orbit evolution perigee 30,000 to 75,000 km; apogee 300,000 to 370,000 km; Possible transit to L2 (under study) sources both very large and small baseline projections will provide the possibility to make good images with high and moderate angular resolution. The remaining 20% of the sources can be observed only with high angular resolution. The possibility of transit to a L2 orbit is being investigated. 4.3 Millimetron observing modes Millimetron has two scientific observing modes: (1) Single-dish submillimeter/far-infrared observations, and (2) Space-ground VLBI observations (SVLBI) at (sub-) millimeter wavelengths. Single-dish observing mode Millimetron observations in single-dish mode do not differ fundamentally from observations with other space observatories like e.g. ISO or Herschel. The main difference is that space VLBI observations will take some of the available observing time, however, this amount is limited by the on-board data storage capacity and the required time for the down-link of the VLBI data (see Section 7). A demanding requirement is the pointing accuracy which for a 12m antenna operating at submillimeter and far-infrared wavelengths needs to be better than 1 arcsecond. Space VLBI observing mode The space-ground interferometer Millimetron allows having baselines more than twenty times the Earth diameter. SVLBI observing must be done simultaneously by the space radio telescope and ground-based radio telescopes. At both locations the received intermediate frequency signal is digitized and then recorded to a large memory (10TB). The transfer of (scientific and service) data to the ground tracking station is done by means of synchronization and communication radio links (1MBps). The scientific data is further processed at the correlation center. Due to the observing bandwidth (2x8 GHz), limitations in the on-board memory size (10Tbit foreseen) and the data transfer speed (1 Mbps), a VLBI observing session can last about 5 minutes before the data have to be down-linked for about 2.8 hours. Thus a total of 40 min VLBI observations per day are possible. During the data transfer single dish mode observations can be performed. It is envisaged that Millimetron will be working together with the following groundbased telescopes: 16/35

17 Atacama Large Millimeter Array (ALMA). Millimetron will carry receivers for four bands fully compatible with ALMA. In first contacts between the Astro Space Center and ESO (the ALMA Executive in Europe), ESO has expressed interest in this possibility. Suffa radio telescope, a millimeter wave telescope of 70 m diameter which is being built on the Suffa plateau in Uzbekistan. It is planned that a dedicated part of telescope time will be used for SVLBI with Millimetron. Other telescopes include e.g. Pico Veleta (Spain), Plateau de Bure interferometer (France), HHT telescope in the US (Arizona), radio telescopes on Hawaii (USA) as well as the Green Bank and Effelsberg 100m diameter telescopes. 4.4 Ground segment requirements Here we distinguish between the Mission Ground Segment needed for mission operations and single-dish data transfer, and the VLBI Ground Segment for the VLBI data transfer. The Mission ground segment needs to provide daily contact with the satellite to exchange telemetry information, single dish observation data and the observing program. Due to the long orbital period global coverage will be required. The SVLBI ground segment will be responsible for SVLBI operations support. The main tasks are: Provide time synchronization signals during SVLBI observations. Receive and record the SVLBI digital data from the satellite. Global coverage is required. Data transfer to the correlation center at the Astro Space Center. Data recording and synchronization at ground telescope locations. The necessary equipment will be provided by the Astro Space Center / Russian Space Agency. With three SVLBI tracking stations in the North (Pushchino near Moscow, provided by ASC), South (Tidbinbilla in Australia) and West (Green Bank, NRAO,USA) large part of the sky can be covered. It is proposed that ESA contribute with time on its global tracking stations network to support SVLBI as well as single dish operations, contributing to the global coverage. 4.5 Special requirements Special requirements for the Millimetron space mission arise mostly from the VLBI observing mode. In this mode Millimetron will record data in a large on-board memory and then down-link the data. Due to the amount of VLBI data a high-speed radio link is required. Preliminary specifications for this link are: two channels at a data rate of 512 Mbit/s per channel, operation 24h/day. Several ground tracking stations need to be available to cover the spacecraft at any one time. Another requirement is the need for cryogenic cooling of the scientific instruments onboard Millimetron to obtain the best sensitivity (analogous to Herschel). The cooling power of the cryogenic system is most likely among the most important limiting factors (maybe the most limiting factor) with respect to the number of scientific instruments on Millimetron. 4.6 Critical issues A critical issue for a scientifically successful mission is achieving the 10 μm rms accuracy of the primary dish surface after the deployment of the 12m antenna in space. The deployment itself will be demonstrated with the 10 m diameter RadioAstron antenna (launch planned for 2008/09) and is not seen as a high-risk item. However, in order to achieve the required surface accuracy for Millimetron, an active control system to adjust the (high-precision) petals is needed. Such a system requires development. We note that JWST will to use deployable, actively controlled mirror 17/35

18 segments employing wavefront sensing techniques. For the Millimetron mirror operating in submillimeter wavelength bands, direct position measurement and control of the petals may be more attractive. Another important item is the pointing accuracy which needs to be much better than 1 arcsec because of the small beams of Millimetron. This could be based on the Spitzer Space Telescope (better than 0.45 arcsec with a stability of ~0.03 arcsec over 600 sec), or an improved Herschel system. For the space-ground VLBI mode, phase distortions of the signal traveling through the Earth atmosphere need to be corrected for. This can be done through monitoring the atmospheric emission around 183 GHz (an atmospheric water line). The method is used very successfully at ground-based (sub-) millimeter interferometers and will be used at ALMA as well. The behavior of the 12m antenna under real operating conditions, i.e. at a physical temperature of 50 K, will have to be investigated. Any approach should include at least three activities: (1) Accurate thermal and mechanical modeling of the whole telescope assembly, (2) testing of individual telescope petals (length ~4.5m), and (3) testing of a scaled telescope model in an environmental chamber. The location of such testing could be part of the ESA-RSA negotiations. 5 Millimetron payload 5.1 Overview Table 3 gives an overview of all payload elements (with the responsible or proposed partner). Table 3 - Payload elements for Millimetron. Payload element Main characteristics TRL (as of Jun 07) Provided by Telescope 12m diameter, deployable, passively cooled to ~50K, TRL = 6 for deployment Russian Space Agency 10µm overall accuracy, 2µm central 3.5m mechanism based on RadioAstron mission Heat shields Multi-layer membrane, TRL = 4 for JWST ESA (this VLBI instr.: GHz receiver VLBI instr.: ALMA bands Single-dish instr.: Submm heterodyne receivers Single-dish instr.: Far-IR spectrometer Closed-cycle coolers to 4K VLBI Mass memory deployable Heterodyne front-end Receivers at ALMA bands 1, 3, 6, and 9; with ALMA compatible characteristics Dual polarization receivers in bands around 557 GHz, 1900 GHz, and 4700 GHz Imaging photometer/ spectrometer covering λ µm Capable to cool instrument sunshield RadioAstron receiver has TRL = 6 Based on ALMA development with TRL = and 1900 GHz based on Herschel- HIFI with TRL=6 Based on Herschel- PACS with TRL = 6 proposal) European Instrument consortium European Instrument consortium European Instrument consortium European Instrument consortium ESA (this suite, 5yr lifetime TRL = 6 for 20 mw cooling (Planck) proposal) 10 Tbit TRL = 8 for 3 Tbit ESA (this proposal) 18/35

19 Based on the experience with instruments for Herschel, RadioAstron and ALMA, a first estimate of the instrument suite requirements (single-dish and SVLBI) on spacecraft resources in given in Table 4. These first estimates will have to be refined as part of an assessment study. In particular, the available power for active cooling to 4 K will most likely be the primary limitation for the number of receiving channels of the instrument suite (with mass, volume and electrical power being secondary limitations). Table 4 - Millimetron instrument interface and resource summary. Parameter Baseline requirement / Comments specification Instrument suite mass < 500 kg total, distributed over focal plane and service module Overall mass of single-dish and VLBI instrumentation including warm electronics Instrument suite power < 1400 W Total available power for instrument suite on Navigator spacecraft incl. cooler Instrument suite volume 2.7 m 3 Instrument suite cooling 50 mw at 4 K, 200 mw at 20 K 2 W at K Closed-cycle cryo-cooler to provide instrument cooling, first rough estimate (requirements to be refined during assessment phase) Telemetry 80 Tbit daily TM Requires 1 Mbps link Pointing < 1 required Navigator spacecraft to be modified 5.2 The 12m space telescope Optical and mechanical/thermal parameters, design The optical design of the telescope is a classical two-mirror Cassegrain type. The main parameters and a design outline are given in Figure 6 and Table 5. The need for a low physical temperature telescope requires minimization of the exterior thermal radiation loading driving the telescope design to a two-mirror system with the secondary mirror shielded by the deep main mirror. The reflective surface of the main mirror is formed by a central solid mirror (3.5m diameter with high surface accuracy) and outer petals unfolded after launch. It will be made out of C-C or Si-C (possibly in combination) with metallic (Gold) reflective coating. Special measures have to be taken to achieve the required telescope surface accuracy. An active surface control system will be employed including either actuators in the petals support structure or active surface elements in the main optical path and main surface shape measurement system. The active control system will mainly compensate for inaccuracies in the deployed petals positions and variations of the overall surface due to temperature changes. This system will ensure that the requirement for the overall surface accuracy of 10 micron (RMS) will be met for the whole dish surface. Actuators in the secondary mirror support structure will allow refocusing of the telescope by mirror displacement. Passive radiation cooling will be used to achieve a telescope physical temperature of ~50 K. 19/35

20 a) b) Fig. 6 - Millimetron 12m telescope. a) Main distances b) Layout. Table 5 - Main telescope parameters. Parameter Value Main dish diameter mm Main dish focal length 2800 mm Main dish total surface accuracy (with active control system) 10 micron (RMS) Main dish central solid part diameter 3500 mm Main dish central solid part surface accuracy 3 micron (RMS) Petals individual surface accuracy 5 micron (RMS) (TBC) Hole diameter in main dish 600 mm Secondary mirror diameter 600 mm Secondary mirror accuracy 3 micron (RMS) Nominal distance from primary focus to secondary focus 4000 mm Total focal length mm Primary and secondary mirror physical temperature 50 K Deployment strategy The main mirror design and deployment strategy is based on the RadioAstron project experience. RadioAstron has a 10 meter diameter deployable mirror (Figure 7) which is now under vibration flight qualification tests and is being readied for launch in Deployment of the telescope is made by one drive and is based on a rocker-lever mechanism. Different stages of the telescope deployment are shown in Figure 8. The launch packaging is shown at the left and the fully open telescope is shown at the right. The petals will be mechanically joined at the outer edge of the telescope providing higher accuracy of deployment. The length of the Millimetron petals is 4.3 m and determines the height of the telescope package in the fairing. An active surface control system will be responsible for the correction of residual errors of the panel positions. Fig. 7 - Different stages of the RadioAstron 10m antenna deployment. 20/35

21 Fig. 8 - Stages of the Millimetron telescope deployment. Left: launch packaging, right: operational telescope. Heat shielding concept The telescope surface will be passively cooled to a temperature of ~50K.The basic thermal concept of the Millimetron telescope is shown in Figure 9. In order to protect the surfaces of the primary and secondary mirrors from the thermal loading by the Sun, Earth, Moon and spacecraft itself, deployable multi layer heat screens in the form of cones can be used. The first screen diameter is 30-35m, the second m, the third (auxiliary) 13-15m. The screens could be made of metallized film similar to Kapton. The first screen has two layers. All film layers have doublesided metallization. Preliminary thermal modeling indicates the following average temperatures of the screens: First screen 1 layer less then 350 K, 2 layer less than 250 K; Second screen less then 150 K; Third screen less than 50 K. As part of this Cosmic Vision proposal, we propose that ESA contribute the thermal shields to the Millimetron mission. Fig. 9 - Preliminary scheme of thermal screens of the Millimetron observatory. 5.3 Scientific instrumentation Here we describe a baseline instrumentation plan for the two basic scientific modes of operation (single-dish and SVLBI). The final instrument suite will depend to a large degree on the available spacecraft resources with 4K cooling power probably being the most uncertain parameter. An assessment study needs to refine the instrument technical requirements and evaluate various tradeoff options. The instrumentation would be built by a European consortium of scientific and technical institutes similar to the Herschel and ALMA schemes. All the required expertise and experience is readily available, and many institutions of the present Herschel and ALMA consortia have already expressed interest to participate Single-dish instrumentation The baseline instrumentation for the single-dish observing mode consists of the two heterodyne instruments HET-1 and HET-2 and the far-infrared imaging photometer and spectrometer M- PACS. HET-1, a dual-frequency SIS array, will operate around the astrophysically important frequencies 557 and 1100 GHz, and HET-2, a three-channel HEB receiver, will cover 1.9, 2.7 and 21/35

22 4.7 THz (the latter using the central 3.5 m high-precision part of the antenna). M-PACS will be an adapted copy of Herschel-PACS with improved detectors covering the wavelength regime 60 to 210 µm. The instrument and detector technologies as well as operational modes and calibration schemes can build heavily on the developments done for Herschel. The technical risk is accordingly low. Table 6 lists the key characteristics of the Millimetron science instrumentation for single-dish observations. SIS 2x2 mixer Table 6 - Single-dish instrumentation key characteristics. Millimetron Single-dish instrumentation Instrument Frequency (GHz) or wavelength Ang. res. ( ) Spectral res. Detector technology Sensitivity TRL Heterodyne receivers HET T sys < 100 K array with multiplier LO T sys < 200 K 6 HET ~ HEB mixers T sys < 500 K ~ with multiplier T sys < 700 K (1) 10 6 or QCL LO T sys < 1000 K 4 Far-Infrared imaging photometer/spectrometer M-PACS μm 4 few 10 3 spectrom. Note: (1) Using the central 3.5m dish Photoconductor arrays 2 x Wm -2 6 HET-1 and HET-2 are heterodyne receivers providing very high spectral resolution ( 10 6 ) in combination with a Fast-Fourier-Transform spectrometer (FFTS). The channels up to 2000 GHz can directly build on the successful developments for Herschel-HIFI, whereas the higher frequency channels of HET-2 around 2.7 and 4.7 THz, unique to Millimetron, have been demonstrated in the lab. For HET-1 it is planned to use 2x2 SIS waveguide mixer arrays (Fig. 10) with multiplier chain local oscillators (LO). This type of technology has been developed for many ground-based telescopes and Herschel-HIFI. It is interesting to note that multiplier LOs up to 2000 GHz are now becoming available commercially and at much lower cost than for HIFI. HET-1 will make use of demonstrated SIS technology using Nb-AlN-Nb tunnel junctions in combination with Nb-SiO2-Nb on-chip tuning elements as used at all major submillimeter observatories and in Herschel-HIFI. HET-2 will in principle employ hot electron bolometer mixers (HEBM) as used in HIFI. However, due to sensitivity and IF bandwidth limitations of HEBM, it is attractive to develop SIS junction technology up to 2000 GHz by utilizing high energy gap superconducting materials. If successful, this SIS technology will allow to achieve better sensitivity and IF frequency coverage. The best technology for the GHz channel of HET-2 can be selected depending on development result. The 2.7 and 4.7 THz channels will in any case use HEB mixers. Local oscillators for HET-2 will be multiplier chains and quantum-cascade-lasers (QCL). QCLs have been used in the lab as THz LO source. Some development is required for the QCL to stabilize its frequency and reduce the dissipated power at the K level. 22/35

23 Fig Typical 2x2 array heterodyne scheme Fig 11 4x4 pixel 2.5 THz HEB mixer array protoype Several developments of HEB mixers and mixer arrays are underway for frequencies beyond 2 THz. A heterodyne receiver at 2.8 THz using a quasi-optical HEB mixer and QCL local oscillator has been demonstrated with a noise temperature of 1400 K (DSB) (Gao et al. 2005). Another interesting development is work carried out under ESA contract nr at Chalmers University (Sweden), LERMA (Observatoire de Paris) and LAAS (Toulouse) to build a 4x4 pixel array at 2.5 THz (called SHAHIRA) using membrane-based HEB mixers. Figure 11 shows a first prototype of this 16-pixel array ready for device integration. Heterodyne back-end The heterodyne receivers will share a Fast Fourier Transform Spectrometer (FFTS) backend which is a digital spectrometer providing wide instantaneous bandwidth with high spectral resolution. In the case of a 2x2 pixel receiver (dual polarization) with an IF bandwidth of 4 GHz each, a total spectrometer bandwidth of 32 GHz is required. Current FFT technology (TRL=6), field-proven in now almost 2 years of continuous operation at, e.g., the APEX submillimeter telescope, provides an instantaneous bandwidth of 1 GHz with 8-16 k channels. Under development at MPIfR (Germany) are single-board FFTs with 1.5 GHz bandwidth /16 k (readiness mid 2007) and, using the most recent ADC available, 2.5 GHz/8 k channels (spring 2008). With the latter implementation of a hybrid backend with 3 x 2.5 GHz to combine to a total of 7 GHz (allowing for some overlap) bandwidth is within reach. The enormous increase of ADC bandwidth during the last years makes it very likely that FFTS can be pushed to instantaneous bandwidths wider than 3 GHz in the near future, thereby further reducing the complexity of the backend. The spectral resolution (the number of channels) that can be achieved is basically constrained by the on-board resources (power dissipation) and the level of complexity that appears acceptable for a space mission. FPGAs have quite a long space heritage. In any case, digital FFT spectrometers can provide the back-end capacities required by the Millimetron mission concept. Some development work will be needed to increase bandwidth, to optimize operation to minimum power dissipation, to adapt to particular constraints of a space observatory, and to comply with space qualification requirements. The Far-infrared photometer and spectrometer M-PACS will be based on the successful development of the PACS instrument, as built for Herschel which offers photometric and spectroscopic capabilities in the wavelength band from 60μm 210μm: A) Imaging dual-band photometry (60 85μm or μm and μm) over a field of view of , with full sampling of the telescope point spread function. B) Integral-field line spectroscopy between 57 and 210 μm with a resolution of 175 km/s and an instantaneous coverage of 1500 km/s, over a field of view of Both modes will allow spatially chopped observations by means of an instrument-internal chopper mirror with variable throw. 23/35

24 Fig. 12. Left: Focal plane footprint of PACS. A fixed mirror is used to split the focal plane into the photometry and spectroscopy channels of the instrument. In the photometry section, the two wavelength bands are simultaneously imaged with different magnification to reach full beam sampling in both bands. In the spectroscopy section (right), an optical image slicer re-arranges the 2-dimensional field along the entrance slit of the grating spectrograph such that, for all spatial elements in the field, spectra are observed simultaneously. Chopping is along the y axis (left-right in this view) and also allows observation of the internal calibrators on both sides of the used area in the telescope focal plane. The focal plane sharing of the PACS instrument modes is shown in Figure 12. The focal plane unit provides these capabilities through five functional units: 1. Common input optics with the chopper, calibration sources and a focal plane splitter. 2. The photometer optical train with a di-chroic beam splitter and separate re-imaging optics for the two short wavelength bands (60 85μm / μm) and the long-wavelength band ( μm), respectively; band-defining filters on a wheel select one of the two shortwavelength bands at a time. 3. The spectrometer optical train with an image slicer unit for integral field spectroscopy, an anamorphic collimator, a diffraction grating in Littrow mount with associated actuator and position readout, anamorphic re-imaging optics, and a di-chroic beam splitter for separation of diffraction orders. 4. Two filled silicon bolometer arrays with and pixels, with cryogenic buffers/multiplexers and a common 0.3 K sorption cooler, for simultaneously imaging in two bands, 60 85μm or μm and μm over a field of view of Two Ge:Ga photoconductor arrays (stressed and unstressed) with pixels each, that allow to perform imaging line spectroscopy over a field of 50 50, resolved into 5 5 pixels, with an instantaneous spectral coverage of 1500 km/s and a spectral resolution of 175 km/s, with sensitivities (5σ in 1h) of 4 mjy or W/m 2. Both the heterodyne instruments HET-1/HET-2 and M-PACS need cooling to ~ 4 K from the spacecraft instrument cooling system (analogue to Herschel). M-PACS will have its own internal cooler to 0.3 K. For more detailed requirements on cooling see Section Special requirements Space segment VLBI instrumentation Overview Figure 13 describes in general terms what is needed for performing Space VLBI (SVLBI). The signal from the telescope is received by one of the SVLBI front ends and down converted to an intermediate frequency (IF) which is filtered and conditioned in the IF processor unit and then digitized. Currently quantization of two bits over a 4-8 GHz band with dual polarization is considered which would result in a data rate of 16 Gbit/s. The digital signals are recorded in a data 24/35

25 storage unit which should have sufficient capacity to hold approx 40 min of SVLBI data (10 TB capacity). A high-speed down-link transfers the data to the ground. SVLBI front-ends The front end instrumentation for the VLBI observing mode will consist of a low frequency (18-26 GHz) front-end very similar to the one which will be flown on the Russian RadioAstron mission in 2008/09. This receiver on Millimetron will greatly improve the u-v plane coverage achieved by RadioAstron and is required to ensure proper cross calibration. Unique to Millimetron will be the VLBI receivers at the ALMA frequency bands 1 ( GHz), 3 ( GHz), 6 ( GHz) and 9 ( GHz). Table 7 summarizes the key characteristics of the Millimetron VLBI instrumentation. Fig. 13 Layout of SVLBI instrumentation package Table 7 - VLBI instrumentation key characteristics. Instrument type VLBI receiver Heterodyne receivers covering ALMA bands Receiver VLBI-1 ALMA-1 ALMA-3 ALMA-6 ALMA-9 Frequency GHz GHz GHz GHz range GHz Detector technology HEMT amplifier SIS mixers, multiplier chain LO, dual pol. SIS mixers, multiplier chain LO, dual pol. SIS mixers, multiplier chain LO, dual pol. SIS mixers, multiplier chain LO, dual pol. Sensitivity T sys < 40 K < 17 K SSB < 37 SSB < 90 K SSB < 150 K DSB TRL The VLBI-1 receiver will be based on previous developments as carried out for many radio telescopes and the RadioAstron or VSOP missions. The ALMA bands will follow technology developed within the ALMA project both for sideband separating SIS mixers, IF amplifiers and LOs. Adaptation of the ALMA technology for space use should not pose much difficulty as it is conceptually similar to the one used for Herschel (in fact ALMA uses some components that were developed for HIFI). Special attention will be paid to the polarization response of these instruments as observing polarization is one of the scientific goals. All ALMA band mixers require cooling to 4K like the HET-1 and HET-2 instruments. On board time, frequency standard There are two possibilities for onboard time synchronization. The first one is a hydrogen frequency standard developed in Russia which will be flown on the RadioAstron mission. The second one is an optical frequency standard with a stability of in 5 minutes. This optical standard is under construction at the Lebedev Physical Institute. The package will be delivered by the Russian Space Agency. 25/35

26 A/D converter and data storage The A/D converter technology will be the same as used for the FFTS backends. Adequate IF bandwidth can be covered by current technology already (ALMA). More weight/energy efficient solutions are expected to appear in the near future. On board data storage modules of up to several TBit are available commercially and space qualified from e.g. EADS-Astrium. It is anticipated that the maximum available capacity will only grow over the years. 10 TBytes would be sufficient for the mission but expanding on the capacity up to TB will benefit the mission. The mass storage memory is part of the requested contribution from ESA. Down link The high speed down link is a crucial part of the SVLBI system. Its speed will define the ground tracking station load for data transfer. The currently demonstrated radiolink data rate is two channels of 512 Mbit/s. It will take 22 hours to transmit 10 TBytes to Earth. A development towards improving data rates by using optical and other means would be of a great benefit for the Millimetron mission. The high speed data link is part of the requested contribution from ESA. Telemetry and time synchronization data links can be common for the single dish and the SVLBI mode as they do not have high requirements concerning the data rate. Current state-of-the-art satellite communication equipment cold be used (similar to Herschel) Special requirements Special requirements for the scientific instruments are: Instrument cooling to 4 K The planned minimum mission life time of 5 years calls for a closed-cycle cryo-cooler to 4 K, also providing cooling to 20 K and K levels. The temperatures below 1 K required for the M- PACS detectors will be generated within the M-PACS instrument (similar to the Herschel PACS scheme). A preliminary estimate of the required cooling powers for the scientific instrumentation gives: mw at 4 K, 200 mw at 20 K, and 2 W at K, with a temperature stability of 5 mk at 4 K, 10 mk at 20 K, and 0.2 K at K. These values are first estimates based on the specifications and experience with Herschel and ALMA instruments and will have to be refined during the assessment phase. We propose that ESA develop and contribute the cryo-cooler to the Millimetron mission. Mass storage memory The SVLBI observing mode generates large amounts of data which will have to be stored on-board before down-link. The duration of SVLBI observations depends on the available mass storage memory and the IF bandwidth of the recorded data. For an IF bandwidth of 2 x 8 GHz (dual polarization) of an ALMA band and 300 seconds of observations, about 10 Tbit of memory are needed. ESA s Sentinel-2 mission will fly 2 Tbit of memory (provided by EADS-Astrium), and presently modules of 3 Tbit are commercially available. It is anticipated that the rapid development of memory technology and density will continue, and that within the coming years (mostly driven by commercial applications) larger amounts of memory for space applications will become available. We propose that ESA provide the mass storage memory to the Millimetron mission. 6. Basic spacecraft key factors The spacecraft platform for the Millimetron mission will be supplied by the Russian Space Agency. It will largely be based on the general purpose space platform Navigator which is built by the Lavochkin Association. The basic layout of the Navigator spacecraft is shown in Figure 14. It will provide attitude control, power and control/telemetry communications to the ground 26/35

27 segment. The scientific payload instruments, telescope and high speed communication link will be mounted on a mechanical interface provided by the platform. The Navigator platform (current TRL 4) will be used for the upcoming space missions Electro (launch in 2008), RadioAstron (launch in 2008) and other scientific missions. Some of the underlying systems of this platform have already been flown successfully. On-board Service system Radiator Octahedron- SC structure Solar batteries Solar panels drive Correction and stabilization drives Tank Flywheel Fig Layout of the space platform Navigator (left) and the instrument complex of RadioAstron mounted on the Navigator platform in the Proton launcher fairing (right). The key requirements of the Millimetron mission to the space platform are shown in Table 8 with an indication where the current Navigator platform will be adapted to the Millimetron needs. There are several parameters which require modification: the available power, payload mass and pointing/stabilization accuracy need to be increased. The Russian partner is working on these elements and takes full responsibility for achieving the mentioned improvements. Table 8 - Spacecraft key requirements for Millimetron. Parameter Provided by Mission Status Navigator Requirement Domain of possible Sun, Moon, Earth Any point orientations avoidance pointing OK Speed of re-orientation deg/s OK Stabilization amplitude 2.5 arc second Better than 1 Modification needed Stabilization speed deg/s --- OK Solar batteries area m Modification needed Correction pulse accuracy 0.5 deg --- OK Platform mass (dry) kg --- Modification needed Maximal fuel mass (hydrazine) 700 kg --- Modification needed (TBC) Maximal payload mass 2600 kg 3000 kg Modification needed Maximal payload consumption 1500 W 2000 W Modification needed Diameter 3717 mm Min 3700 mm OK Height 700 mm --- OK 27/35

28 7. Science Operations and Archiving Science Operations The science operations group, responsible for the scientific output of the mission, determines a schedule of scientific observations in general this is a mix of SVLBI and single dish operations to be carried out in the next orbit. The scientific priority combined with the sky visibility constraints give the main guidelines for observations to be carried out. Clearly for SVLBI observations the availability of the VLBI ground segment is a main driver as well. After the observations have been carried out and the first level processing is done the observer is updated on the status of his program. When needed dedicated calibration and engineering observations are interspersed between science observations. These extra observations are used to support instrument health monitoring and calibration studies by instrument specialists. Satellite Operations The observatory will have two distinctly different operations modes for SVLBI and single dish operations. Before observations are carried out all relevant satellite and instrument commands will be uplinked for execution on board. During the observations data from the instruments as well as house keeping data will be stored in the on board solid state memory. After the observations the data in the SSM will be transmitted to ground. Satellite health and safety The onboard control computers continuously monitor satellite parameters and autonomously take pre-determined corrective action for non-nominal conditions. A second level safety is provided through house keeping telemetry containing measured voltages, temperatures etc. of the onboard systems that is continuously generated. This telemetry is received at the ground station and analyzed by the real time monitoring system. Satellite controllers in the satellite operations centre can adjust the future operations based on this analysis. VLBI operations In VLBI mode the satellite and the earth based VLBI stations will be configured and take data at high speed (up to 16Gbit/sec) for about 5 minutes generating a total of 10Tb of data. After a 5 minute VLBI observation, the satellite data are down linked which will take about 2.8 hours at full dual channel downlink rate (2 x 512Mbps). During this time the satellite is available for single dish observations. The downlinked raw telemetry data are stored in a temporary archive until they have been correlated with the ground stations. Single dish operation When not in SVLBI mode, the observatory will take data as single dish observatory. In single dish mode data taking is carried out following a predefined schedule containing several days worth of observations (interspersed with VLBI observations). Each observation will be self-contained in that appropriate calibration measurements (internal as well as external) are taken in the context of the observation. With the available high downlink bandwith the required downlink time is a very small fraction of the observing time. Thus after a few days of single dish observations a few hours ground contact is needed to downlink the acquired data and uplink a schedule for the next few days. Archiving and data processing After down linking all data are stored in the central long term Millimetron Science archive. This archive will be maintained such that data products can be retrieved during the mission and for a period of at least 10 years after mission end. 28/35

29 All single dish mode observations are processed using a standard pipeline applying the default observatory calibration to generate a set of calibrated spectra, ready for further data analysis by the observers. In this process also quality analysis procedures are used to assess the data and observation quality. Based on this quality analysis observations may be rejected and scheduled for re-observation. The pipeline will also generate trend data (e.g. T sys values) to allow investigation of the long term behavior of the instruments. These trend data are further analyzed by instrument specialists to asses the instrument health. The calibrated spectra, quality data and trend data are also stored in the science archive for later reference. In VLBI mode the satellite data are correlated with the ground telescope data stream to generate visibilities. These visibilities are subsequently stored in the long term science archive for retrieval by astronomers. Based on the calibrated visibilities a set of standard image products will be generated as well as quality and trend products. Data access and data rights Astronomers will have access to the science archive through standard internet web techniques, allowing them to select observations and download raw data as well as the observatory generated products for these observations. For all observation data that are part of an observing program there is a proprietary period of 1 year after the last data in the program have been taken. During this period only the owner of the proposal is allowed access to the data. After this period the data are accessible to all registered users of the Millimetron Science Archive. 8. Key technology areas Table 9 lists the key technology areas. The most critical item appears to be the control of the 12m dish surface after launch and deployment to achieve the 10 micron surface accuracy. All other key items are demonstrated at different levels (lab, ground, space, or flight proven). Table 9 Key technology areas for Millimetron. Payload element Technology area TRL Comment Telescope Telescope petals 3-4 Russian Space Agency Deployment strategy 6 Based on Russian RadioAstron telescope Active surface control 2-4 Development by Astro Space Center Heat shields 4-6 Developed for JWST Spacecraft all 5-6 By Lavochkin Association Scientific instrumentation Heterodyne and bolometer instrument for single-dish operation 4-6 Spin-off from Herschel Heterodyne receivers for VLBI 6 Spin-off from ALMA Cryo-cooler 4-6 Proposed ESA development (TRL 6 for Planck compatible cooling power) VLBI mass storage memory 6-7 Available from EADS-Astrium 29/35

30 9. Preliminary programmatics/costs 9.1 International collaboration Millimetron (called Spectrum-M when the spacecraft and ground segment are included) is proposed as a joint mission between the Russian Space Agency and ESA. The scientific instruments would be provided by a European consortium of institutes with leading expertise and experience in Herschel instruments as well as ALMA receivers. The instruments would be funded through national contributions as for Herschel. The proposed management structure and cost estimate reflects the current situation which is rapidly evolving. In a recent meeting (27 June 2007) in Moscow, an intergovernmental commission with representatives of the Russian Space Agency, Astro Space Center, and the China National Space Administration CNSA have agreed to start negotiations in July 2007 about the collaboration on scientific space missions including Millimetron. Depending on the outcome of these negotiations, the proposed mission management structure and cost distribution may change. 9.2 Proposed management structure The proposed distribution of responsibilities between the Russian Space Agency (RSA), the Russian Astro Space Center (ASC), the European instrument consortium (coordinated by SRON), and the proposed contributions from ESA are shown in Figure 15. RSA has the overall responsibility of the mission including provision of the spacecraft Navigator and launch vehicle and services. ASC is responsible for the 12m space antenna, the scientific payload elements (which together are called Millimetron ) and the ground segment. A European instrument consortium with participation from institutes in ESA countries and Russia is responsible for the instrumentation payload as described in Section 5. Proposed contributions from ESA are the provision of the antenna heat shields, the instrument cryo-cooler, the VLBI memory, the scientific radio link, and participation in the mission ground segment. Table 10 lists the roles of the Russian Space Agency, the Astro Space Center, ESA (proposed), and SRON. Fig. 15 Spectrum-M (Millimetron) mission product tree with an indication of responsibilities and proposed ESA contributions. 30/35

31 Table 10 Roles of parties in the Millimetron collaboration. Party Role Russian Space Agency - Lead space agency - Financial State representative - Overall budget control in Russia - Satellite platform Navigator - Launch vehicle and services - Funding of Astro Space Center Millimetron payload activities Astro Space Center - Russian mission PI - Responsibility and project management for Russian payload contributions - System integration and system project management - Mission ground segment responsibility - VLBI ground segment responsibility ESA (proposed) - Partner Agency and European mission coordinator - Contribution to ground segment and communication link - Contributions to payload - Coordinator of European scientific community SRON - Coordinate the European scientific instrumentation consortium - Provide European scientific instruments The proposed management structure foresees three bodies covering the daily management, project oversight and science. The structure is designed to ensure maximum efficiency by keeping the Executive Committee (responsible for the daily management) small, provide a forum for all involved parties to track and steer the project with the Oversight Committee and provide a link to the science community via the Scientific Committee. In addition to these three committees, there will be consortium structures in Russia and Europe for their specific contributions. Millimetron Executive Committee (MEC): consists of the Russian project PI, Russian Project Manager, European Co-PI, and European Project Manager. Responsible for the management of the Millimetron project. Millimetron Oversight Committee (MOC): to provide oversight to the project, both technically and management-wise. Consists of the MEC (Millimetron PIs and Project Managers) plus representatives from the Russian Space Agency, ESA, Lavochkin Association, and SRON. Millimetron Scientific Committee (MSC): to discuss science questions with distinguished members from Russia and participating institutes in Europe. Chair and Co-chair are determined by committee election and rotating between Russia and Europe. 9.2 Schedule Figure 16 shows the overall mission schedule for ESA (corresponding to the Cosmic Vision schedule for a M class mission), the Russian Millimetron project, and the European Instrument consortium. The mission schedule is mainly driven by the planning of the Russian Space Agency with a planned launch in 2016 and the ESA Cosmic Vision timetable. Critical technology development items include the active optics system to achieve the surface accuracy for the 12m deployable antenna (the deployment mechanism itself is already developed and used in the 10m RadioAstron antenna), and the cryo-cooler for instrument cooling. 31/35

32 Fig. 16 Overall Millimetron mission schedule 9.3 Preliminary costing A rough order of magnitude cost estimate is given in Table 11. The cost of the Russian contributions cannot be given at this stage due different employed costing systematics and standards in Russia. Instead, the mission elements provided by the Russian Space Agency and Astro Space Center are commitments. Cost to ESA is 66 M, and for the scientific instruments 171 M of European national funding are required. As pointed out in Section 9.1, the outcome of talks between the Russian and Chinese Space Agencies about collaborations on scientific space mission including Millimetron may impact the financial and organizational plan. Table 11 Rough order of magnitude estimate of costs. Russian contributions are given as commitments and not cost (due to different costing systematics and Russian internal rules). 32/35

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