Feb 2007 The New Earths Facility (NEF) Project Goals & Plans 1. The HARPS-NEF spectrograph is a high-precision instrument, similar to HARPS on the 3.6-m ESO telescope in Chile. It will be located in the Northern hemisphere to allow for synergy with the NASA Kepler mission. The HARPS-NEF team is a collaboration between the New Earths Facility scientists of the Harvard Origins of Life Initiative and the HARPS team at the Geneva Observatory. The construction and operation of HARPS-NEF is funded by the Harvard Origins of Life Initiative which will own it. 2. Main scientific rationale for HARPS-NEF: To allow the characterization and discovery of terrestrial planets by achieving long-term sub-meter per second precision on V<12-mag stars. 2.1 General HARPS-NEF capabilities - use by the broader community: HARPS-NEF is a high-resolution (R=120,000) optical spectrograph with broad wavelength coverage (378-691 nm). In order to understand it capabilities, one could use the existing HARPS instrument (on the 3.6-m ESO telescope) as a baseline. However, HARPS-NEF will benefit from updates and improvements, as well as from larger telescope aperture. HARPS-NEF on WHT would be made available for use by the astronomers from the ING communities, following the approval of the Director of ING Observatories and the Principal Investigator of the HARPS-NEF project. Their responsibility will be to avoid duplication of observing programs which are in direct competition with the HARPS-NEF projects outlined in sect.3 & 4 below. The procedural details are described in a HARPS-NEF-WHT MoU. With its unsurpassed Doppler precision and throughput, HARPS-NEF will be available to ING astronomers for discovery and follow-up of extrasolar planets in a wide range of masses and orbits. It could be used for detailed study of orbital diynamics (Rossiter effect), atmospheric studies (reflected or transmitted spectroscopy), etc., of extrasolar planets. With its high resolution, HARPS-NEF will be available to ING astronomers for wide variety of stellar astrophysics projects - stellar abundances, stellar atmospheres, asteroseismology, binary stars, etc. The possibilities to use HARPS-NEF for astroseismology are particularly exciting, given the spectacular results by HARPS in Chile. The ING community has a major involvement in GAIA, and HARPS-NEF provides a perfect match (in radial velocities) to GAIA (in the astrometric domain). The following is a description of the projects the HARPS-NEF team plans to do during the first 5 years after the instrument commissioning. 3. Main project - synergy with Kepler: The NASA Kepler mission is scheduled for launch in Nov.2008. It will monitor a single field in Cygnus/Lyra (RA=19:23h,Dec=44.5d) and discover many hundreds of transiting planets orbiting preselected main sequence stars (F to M type) of V= 11-15 mag. Kepler is capable of detecting more than 50 Earth-sized planets in all orbits, with about a dozen in orbits approaching 1-year period; as well as several hundred Super-Earths (~1.3 Earth radii) in all orbits up to 1 year. The Kepler mission had no provisions for measuring their masses (in its follow-up effort), because the expected Doppler amplitudes are less than 1 meter per second. HARPS-NEF will make that possible, and to our knowledge is unique in that capability. 3.1 Main project goals: Our main project has three broad scientific goals that can be achieved by delivering planetary masses of certain precision: (a) confirming an Earth-twin planet in the habitable zone of a G5V star or later - 30% in mass; (b) characterizing Earth-like planets of 2-5 M_Earth ("Super-Earths") in different orbits: distinguishing between water-rich and dry planets - 10% in mass; (c) characterizing the transition between Super-Earths and Ice Giants (hot Neptunes, for example) near 10 M_Earth - 5% in mass, or better. For planet classes in goals (b) & (c), Kepler will determine planetary radii of 5% or better, for stars in the "sweet spot" around V=12 mag. For the Earth-like planets in goal (a), Kepler could provide 15% in radius precision. All these estimates improve considerably for M-stars, but the probability of discovery is assumed low. These values: 5% in radius, and (a),(b),& (c) in mass, allow achieving our goals, as shown by the theoretical models (Valencia,Sasselov,O'Connell 2006,2007; Fortney et al.2007). Note that achieving goal (b) is essential, in a boot-strapping sense, to achieving confidence in completing goal (a), and hence - of Kepler's legacy as whole. HARPS-NEF in the Doppler domain is a true match to Kepler in the photometric domain, thus providing vastly improved planetary mean densities for a meaningful comparison to interior models. 3.2 Main project observing time requirements: HARPS-NEF on a 4-m class telescope in the Northern hemisphere (e.g. WHT) can achieve the above tolerances in mass determination with certain number of Doppler measurements. That number of observations can be evaluated under the following set of conditions. First, the Kepler light curve constrains the period and phase of the planet's orbit. Second, we select targets of V=12 mag or brighter, for which HARPS-NEF should achieve 1.0 m/s in 1 hour. This has been demonstrated with the HARPS in Chile. We illustrate our estimate of required number of observations to achieve 10% in planet mass at a 0.10 AU orbit in the table below: Star/Planet 5 M_Earth 10 M_Earth --------------------------------------------------- F0 (1.60 M_s) 158 40 G0 (1.05 M_s) 104 26 K0 (0.79 M_s) 78 20 M0 (0.51 M_s) 50 13 --------------------------------------------------- With such estimates in hand, we have determined the number of effective clear observing nights (HARPS-NEF on WHT) required to accomplish the three goals of our Main Project: (a) for 2 planets (over 3 years) - 160 h = 16 nights per year; (b) for 20 planets in different orbits - 250 h = 25 nights per year; (c) for 20 planets in different orbits - 210 h = 20 nights per year. 3.3 Main project scheduling: The 60 clear nights per year estimated above fall within the season of about six months - April through October, when the Kepler field is accessible from WHT. They do not have to be consecutive or time critical; queue scheduling would work fine. We expect planets that orbit stars of different brightness and with different periods, we can fill efficiently observing nights regardless of seeing conditions. We anticipate having Kepler targets for goals (b) & (c) during year 1 and can begin work on them immediately - in summer 2009. For goal (a), we may have to wait until year 3, i.e. begin in 2011, and continue until 2014. The observing time estimates and scheduling make use of the expectation that Kepler will provide a very large number of good targets in each of the categories of planets. This will allow our team to select the best ones for follow-up, and avoid parent stars that show high activity or with other problems. For example, we estimate that about 50% of the initial targets will show intrinsic variations which are too high for efficient HARPS-NEF follow-up. 3.4 Main project - interface with Kepler: The synergy with Kepler is crucial to the success of our main project. David Latham and Dimitar Sasselov of the HARPS-NEF team are members of the Kepler team. Latham is a founding Co-I of Kepler and is responsible for two tasks: "Giant planets masses" and "Low-res RV to eliminate stellar companions"; Sasselov is responsible for tasks: "Terrestrial planets masses" and "Atmospheres". They will have early access to Kepler targets for follow-up with HARPS-NEF. The Kepler team was briefed on HARPS-NEF and the main project has become a part of Kepler's follow-up plans. 4. Secondary projects - Earth-like planets around nearby stars & synergy with TESS: These two projects will be performed mainly in the season not overlaping with the Kepler field, fill in partial nights, and after completion of the main project. 4.1 Secondary project - discovering Earth-like planets around nearby stars: HARPS-NEF will be capable of better than 20 cm/s precision and stability for very bright stars. The HARPS-NEF team plans to observe a sample of the brightest, least active, and least noisy northern stars. The goal is to discover Earth-like planets and multiple planet systems, and to push the envelope of the instrument. The value of such discoveries is that a number of exciting follow-up possibilities become possible for such nearby objects. While bright stars do not require very long exposure times, in order to achieve long-term precision below ~50 cm/s we have to devote additional observing time to characterize the stellar p-mode oscillations, granulation noise power, and rotation induced variations. Judging from our current experience, this project will require about 10 clear nights per year, in order to be scientifically viable. There are no scheduling constraints. We expect our sample to include very few stars that are going to be selected before the beginning of our program, and shall pose no constraints on other ING community requests for similar observations. 4.2 Secondary project - synergy with TESS: TESS (Transiting Exoplanet Survey Satellite) is a space mission to survey nearly the entire sky to discover hunderds of bright transiting exoplanets with periods up to 60 days. In that TESS is complementary to Kepler and CoRoT. TESS is an MIT-Harvard-Smithsonian project done in collaboration with NASA. If fully funded this year it will launch in 2009. HARPS-NEF will allow Doppler follow-up for the large number of Neptune-like and sub-Neptune planets TESS will discover. This is unique, because infrared and other follow-up on such planets might prove impossible for the Kepler targets. However, a few of the TESS Neptune-like planets could have their atmospheres detected and studied. The synergy between HARPS-NEF and TESS is again unique, and would allow breakthroughs in a different field. The HARPS-NEF team plans to observe the most interesting systems for such atmospheric and interiors characterization - e.g., high-e orbits, multiple systems, the 10-15 Earth mass range. With the table in 3.2 above as a guide, we estimate about 15 nights per year over 3 years, starting in 2011.