The Committee on the Assessment of a Plan for U.S. Participation in Euclid held a meeting on January 18-20, 2012, at which a number of presentations were made as described in Appendix B. Below is a brief overview of the presentations made at the committee’s meeting. In order to help focus the presentations and in the interest of efficient data gathering, the committee prepared guiding questions that were delivered to the speakers prior to the meeting. These questions are reproduced below, alongside a short summary of each speaker’s presentation. Additional questions not listed below were asked during the actual meeting. Speakers’ viewgraphs are available, as provided, on request through the National Research Council’s (NRC’s) Public Access Records Office.1
DAY 1—JANUARY 18, 2012
NASA Discussion of a Plan for U.S. Participation in Euclid
Speaker: Waleed Abdalati, NASA Chief Scientist
1. What does NASA propose to provide to ESA?
2. Would this commitment likely to grow over the mission?
3. What data access will the U.S. community acquire?
4. What would be the potential U.S. role on the Euclid science team? How would U.S. participants be selected?
5. What are possible connections between Euclid and WFIRST enabled by a NASA commitment?
6. What are the current plans for implementing the NWNH recommendation on WFIRST? If they do plan to implement, what schedule, cost, scope do they currently envision, given the current budget situation, JWST, etc.? How might NASA investment in Euclid impact the WFIRST mission with respect to science goals, instrumentation, cost, and schedule?
7. How would a NASA investment in Euclid be coordinated with potential sharing of data from U.S. ground based DE projects, in particular, DES, PanSTARRS, and LSST?
8. Would a NASA investment in Euclid be likely to lead to an ESA investment in WFIRST?
9. What is the impact of NASA participation in Euclid on the Explorer program?
10. How would Euclid instrumentation be altered if United States did not participate?
11. How is U.S. data access affected by U.S. participation or non-participation?
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C Meeting Presentations and Open Session Summaries The Committee on the Assessment of a Plan for U.S. Participation in Euclid held a meeting on January 18-20, 2012, at which a number of presentations were made as described in Appendix B. Below is a brief overview of the presentations made at the committee’s meeting. In order to help focus the presentations and in the interest of efficient data gathering, the committee prepared guiding questions that were delivered to the speakers prior to the meeting. These questions are reproduced below, alongside a short summary of each speaker’s presentation. Additional questions not listed below were asked during the actual meeting. Speakers’ viewgraphs are available, as provided, on request through the National Research Council’s (NRC’s) Public Access Records Office.1 DAY 1—JANUARY 18, 2012 NASA Discussion of a Plan for U.S. Participation in Euclid Speaker: Waleed Abdalati, NASA Chief Scientist Guiding Questions 1. What does NASA propose to provide to ESA? 2. Would this commitment likely to grow over the mission? 3. What data access will the U.S. community acquire? 4. What would be the potential U.S. role on the Euclid science team? How would U.S. participants be selected? 5. What are possible connections between Euclid and WFIRST enabled by a NASA commitment? 6. What are the current plans for implementing the NWNH recommendation on WFIRST? If they do plan to implement, what schedule, cost, scope do they currently envision, given the current budget situation, JWST, etc.? How might NASA investment in Euclid impact the WFIRST mission with respect to science goals, instrumentation, cost, and schedule? 7. How would a NASA investment in Euclid be coordinated with potential sharing of data from U.S. ground based DE projects, in particular, DES, PanSTARRS, and LSST? 8. Would a NASA investment in Euclid be likely to lead to an ESA investment in WFIRST? 9. What is the impact of NASA participation in Euclid on the Explorer program? 10. How would Euclid instrumentation be altered if United States did not participate? 11. How is U.S. data access affected by U.S. participation or non-participation? 1 The Public Access Records Office provides access to project materials available to the public, and can be accessed via the Current Projects System at http://www8.nationalacademies.org/cp/. 23
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12. What will not get done at NASA if this money is spent on Euclid? 13. What chance is there that WFIRST will not be done at all, with or without Euclid? Session Summary Waleed Abdalati delivered an overview for the study to Assess U.S. Participation in Euclid. He began with the current status of the WFIRST mission. JWST has been designated as the first funding priority for NASA Astrophysics with a launch date for WFIRST no earlier than 2022. Abdalati cautioned that this was a highly ambitious launch date due to the current budget situation. He continued on to discuss previous NASA contributions to foreign missions and the current opportunity for U.S. participation in the ESA Euclid mission, which is scheduled to launch in 2019. The contribution being discussed was a hardware contribution, possibly in the form of one of the following: near-infrared (NIR) detectors, a filter wheel for the NISP instrument, or reaction wheels. In return, NASA would receive one position on the Euclid Science Team (EST) with accompanying co-collaborators becoming members of the Euclid Consortium (EC). NASA would also receive immediate access to the Euclid data, as opposed to waiting until the end of the proprietary period. In addition, this would set the stage for discussions of future collaborations on software development for Euclid as well as European collaborations on WFIRST—although neither of these are under discussion at this time. Abdalati stated that a formal commitment from NASA to ESA would be necessary by Spring 2012. Abdalati stated that the $20 million to $25 million cost of the hardware contribution to Euclid would have no impact on WFIRST since the project is not likely to begin within the next few years. When asked about possible coordination with other U.S. agencies, such as the Department of Energy, he stated that there are no collaborations in the works at the moment, but this could be a possibility in the future. Panel Discussion with NASA Summary Panelists: Paul Hertz (Acting Director, Astrophysics Division), Richard Griffiths (Euclid Program Scientist), Rita Sambruna (WFIRST Program Scientist), Lia LaPiana (Euclid and WFIRST Program Executive) Representatives from NASA participated in a panel discussion with the committee to offer insight into the proposed agreement with ESA concerning a hardware contribution to the Euclid program. Building on Waleed Abdalati’s earlier presentation and answering questions from the committee, the NASA panel outlined more details of the expected terms of an agreement with NASA—that is, a hardware contribution in exchange for a seat on the EST and immediate access to the data. They stressed that the deal would be neither a quid pro quo nor a package deal with a potential future NASA-ESA collaboration on WFIRST. A separate discussion of ESA’s potential participation in WFIRST would come at a later time. Hertz discussed the potential effects on WFIRST, financial and otherwise, assuring the committee that although there would be some cost constraints associated with participation in Euclid, this would not hinder the WFIRST schedule. He confirmed that there would also be costs in the out years to support a science team, but these would most likely be traded with other opportunities in the astrophysics budget. Owing to the costs of completing JWST, the current expectation for the budget does not have an opening for WFIRST until 2018, with a launch date of 2022 or later. The committee questioned whether the proposed $20 million for Euclid could instead be used to accelerate WFIRST. The NASA panel responded that while $20 million is a significant amount of money, Phase B of WFIRST is easily $100 million per year, so this current Euclid plan would not considerably impact the ramp-up phase of WFIRST when it occurs. 24
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ESA Perspective on a Plan for U.S. Participation in Euclid Speaker: Fabio Favata, Head of ESA’s Science Planning and Community Coordination Office Guiding Questions 1. What is the U.S. contribution to Euclid discussed with NASA? Is it likely to grow? What are the consequences of the United States not joining Euclid? 2. What would be the U.S. role on the Science Team? What is the Management structure of Euclid? How would the United States fit into this structure? 3. What is the potential ESA role in a WFIRST mission? 4. What is the current Euclid schedule? 5. What are the major technical, cost and schedule risks in the Euclid mission? Does NASA participation reduce these risks? Session Summary Fabio Favata delivered a presentation to the committee concerning U.S. participation in the ESA Euclid program. Favata began by explaining the organization and budget of ESA. He continued on to the role of the United States, which would consist of a hardware contribution in the form of NIR detectors, a filter wheel for NIR instruments, reaction wheels, or a contribution to the science ground segment. In exchange, the United States would receive one seat on the Euclid Science Team (EST) and a guaranteed “10 percent” science return which would be measured by the number of first authorships or by other alternative metrics as agreed upon by the EST. The Euclid management structure includes the Euclid Consortium (EC), which is responsible for scientific exploitation of the data, and the EST, which manages the program and proposes program elements. Favata elaborated on the current schedule for Euclid, stating that a 7-year development period is foreseen with no major risks compared to other Soyuz- class ESA astronomical missions. The mission is currently approved as a “European-only” mission; however, U.S. participation would be welcome. As far as WFIRST and Euclid are concerned, Favata noted that the two missions are decoupled and in very different stages. ESA would be happy to discuss possible collaborations on WFIRST once the mission is defined and approved. The Euclid Mission Speaker: Yannick Mellier, Institut d’Astrophysique de Paris; Spokesperson for the Euclid Consortium Guiding Questions 1. What are Euclid capabilities for measuring dark energy? 2. Describe Euclid’s capabilities in the following four areas: a. Gravitational Lensing b. BAO c. Microlensing d. Infrared Surveys 3. Would the Euclid team be open to making surveys and microlensing part of its core mission? 4. What is the role of ground-based missions in the Euclid analysis? Please discuss the likely role of DES, panSTARRS and LSST? How accurately will Euclid need to characterize the color gradients? 5. What are the Euclid plans for data release? 25
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6. What would be the U.S. role on the Science Team? What is the scientific Management structure of Euclid? How would U.S. scientists fit into this structure? 7. What do you see as the scientific relationship between Euclid and WFIRST? Session Summary Yannick Mellier gave a follow-up presentation complementing information discussed by Fabio Favata. Mellier began with Euclid’s capabilities for measuring dark energy, distinguished by using two independent techniques—the geometry of the universe and the history of structure formation. Weak lensing (WL) and galaxy clustering would be used to study the geometry of the universe while WL, redshift-space distortion (RSD), and clusters of galaxies would be used for information on the cosmic history of structure formation. Minimizing and controlling systematics will be done with an unprecedented level of accuracy. Euclid will include an instrument for VIS (one wavelength wide field, high image quality) and two for NISP (one wide field NIR with Y, J, and H filters for photo-z, and one wide-field NIR slitless spectrograph for spectroscopic redshifts). Dark energy probes include cosmic shear weak lensing tomography, baryon acoustic oscillation (BAO), clusters of galaxies, RSD, and ISW. Mellier also discussed the role of ground-based missions. He noted a need for photometric redshifts for all sources used for WL as well as a need for spectra to calibrate photometric redshifts. Mellier noted that there has been some interest in using results from Pan-STARRS to assist in northern sky coverage; however, there is some uncertainty pertaining to the Pan-STARRS2 project at the moment. He envisioned the cost for coordinating with Pan-STARRS being between $15 million to $19 million. Mellier then described Euclid’s capabilities for microlensing and infrared surveys and the willingness to include this as part of their core mission. The NISP instrument is capable of 0.54°2, Y, J, and H photometry for microlensing and infrared surveys, and there is also possible low-resolution slitless spectroscopy specifically for infrared surveys. He stated that the instrument is capable of keeping the same target for 1 month and can cover very wide fields. The Euclid Consortium (EC) is interested in expanding the program to include microlensing and NIR as well as supernovae, but not at the expense of the core cosmology program. He did suggest that this could later become a possibility if the mission were to be extended. An outline of the Euclid management structure and U.S. contribution was discussed next. Mellier stated that there are currently more than 900 registered members of the EC. The EC is responsible for the science requirements and goals, instrument maintenance and operation, data exploitation and processing, and any external ancillary data to achieve the mission’s scientific goals. The EC Board (ECB) acts as the governing body of the EC and contains 18 full members from Europe and would have 2 at-large members without voting privileges from the United States. The EST is the only Euclid scientific advisory body and currently has 9 members. Mellier noted that possible U.S. contributions include hardware, ground observations, and science. In return, the United States would hold a seat on the EST with possible expertise in weak lensing or NIR plus a possibility of 1-2 members of the ECB and guaranteed science return. The terms of the science return would be further determined by the EST. When questioned about the need for a representative on the ECB, Mellier said it was the best way to interact with the consortium, but not absolutely necessary. With respect to plans for data release, he said that the data would be immediately available to the United States as it would any other EST member. For the outside community, level Q (quick-release) data would be released 14 months after the start of the survey, and products from all levels would be released 26 months after the start of the survey. Mellier discussed the current Euclid timeline, scheduled to begin the Implementation phase in the fourth quarter of 2012. PDR would follow in the third and fourth quarters of 2013 with structural and thermal delivery in the first quarter of 2014, electrical model delivery in the third quarter of 2014, flight model delivery in the third and fourth quarter of 2017, and finally the launch in the fourth quarter of 2019. Concerning the relationship between WFIRST and Euclid, he remarked that they are complementary— Euclid is designed for wide sky coverage and deep surveys of extragalactic sky while WFIRST is 26
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optimized for microlensing surveys, Type 1a supernovae surveys, and ultra-deep surveys of extragalactic sky and, possibly, of the galactic plane. The committee questioned if LSST data would be used. Mellier responded saying that from the Euclid side, the data would be useful for photometric redshift, but was not positive it was necessary for the Southern sky. There was some discussion on the importance of color gradients in WL studies to which Mellier noted that this is not a problem on Euclid because the VIS instrument is equipped by two identical narrow band filters and just one filter is sufficient to observe many more galaxies than needed to correct color gradient effects. He also noted that a working group has been established to study color gradient effects and this working group has demonstrated that there is no need for another (third) filter different from the narrow band filters already put on VIS instrument. U.S. Perspective on a U.S. Contribution to Euclid Speaker: Jason Rhodes, Jet Propulsion Laboratory; member of the Euclid Consortium (EC), non-voting member of the EC Board, member of the WFIRST science definition team Guiding Questions 1. What do you see as the U.S. contribution to Euclid? Is it likely to grow? 2. What would be the U.S. role on the Science Team? 3. What are the Euclid plans for data release? 4. What do you see as the relationship between Euclid and WFIRST? 5. What do you see as the relationship between Euclid and various U.S.-led ground-based surveys? 6. What do you see as the relationship between Euclid, WFIRST, and the goals of the decadal survey? Session Summary Jason Rhodes gave a presentation to the committee on the potential U.S. contribution to Euclid from a U.S. perspective. Rhodes began by stating that the U.S. contribution would likely be in the form of hardware such as reaction wheels, NIR detectors, or detector performance validation for weak lensing. There is also the possibility of a contribution to the processing/ground segment as well as the science. In return, the United States could expect to receive one seat on the EST and a 10 percent science return. Rhodes remarked that the presence of a U.S. member on the EST would be important to safeguard U.S. interests and also to facilitate Euclid’s tapping into U.S. expertise and resources. The member would participate in all EST activities, with possible additional duties depending on their expertise. He noted that this member should, but is not required to, integrate personnel and U.S. science efforts with the EC and become fully engaged in the science exploitation of the data. In terms of data release, Rhodes said the members of the U.S. community that are involved in the Euclid Consortium (via joining the science team NASA would support) are the only members of the U.S. community that would have immediate access to data. This is the same as in Europe—EC members have immediate access. All outside parties would have to wait the duration of the proprietary period, which would be 14 months for quick data and 26 months for full data, with subsequent yearly releases. Rhodes also discussed the relationship between Euclid and WFIRST, noting that they should be largely complementary. Independent, complementary approaches would not only be desirable but necessary in order to accomplish the goals outlined in the NWNH decadal survey. He stated that a phased approach to implementing Euclid and WFIRST could prove beneficial, with WFIRST benefitting from 27
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early Euclid observations. With regard to Euclid and U.S.-led ground-based surveys, Rhodes stressed that ground-based data would be required over the entire survey area for photo-z’s as well as ground-based spectra for calibration. Finally, he commented that the United States is capable of leadership in all aspects of Euclid science, but competition is not beneficial. He believed that shared leadership should be sought and coordination with the EC would be ideal. When questioned how amenable ESA would be to a U.S. influx into the working groups, Rhodes suggested it might take a little bit of work and patience, but no more so than when the groups were originally formed. Discussion of WFIRST and Euclid Speaker: Paul Schechter, Massachusetts Institute of Technology; Co-Chair of NASA’s WFIRST Science Definition Team Guiding Questions 1. What is your assessment of Euclid ability to address the scientific goals of the decadal survey? Will the U.S. contribution affect its capabilities? 2. Can you compare and contrast Euclid and WFIRST? 3. What is the current status of WFIRST planning? 4. How does the planned launch of Euclid affect plans for WFIRST? Does the infrared contribution alter this relation? Session Summary Paul Schechter discussed the Euclid and WFIRST missions. Schechter began with the current status of WFIRST, remarking that if the mission got a “new start” in 2013, it would be possible to launch by 2020 and that any slippage will be the result of budgetary rather than technical considerations. When comparing the two programs, he noted that Euclid’s science program does not include exoplanet microlensing, a guest observer program, and supernovae dark energy measurements. By contrast, the current design reference mission for WFIRST includes all of the science objectives mandated by the NWNH decadal survey. Euclid devotes 6.25 years to BAO plus weak lensing as opposed to 2 years for WFIRST. Schechter noted that Euclid uses an obstructed telescope, while WFIRST will use an unobstructed telescope. He also remarked that WFIRST is preferred for weak lensing, which will be the riskiest program. Schechter argued that that the BAO programs of both missions are comparable. He also said that if WFIRST did not get a new start in 2013, the added year might be productively used to bring the next generation of infrared detector, called “Hawaii-4RG” up to the required technical readiness level, enhancing the capabilities of WFIRST by somewhere between 50 and 100 percent. Discussion of LSST, WFIRST, and Euclid Spaker: Steve Kahn, Stanford University; Deputy Project Director and Camera Lead Scientist for the LSST project Guiding Questions 1. Do you see the Euclid data as useful for LSST analysis? 2. Do you see the LSST data as useful for Euclid analysis? 3. What are the plans for LSST data release? 28
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4. What is the current LSST schedule? 5. What do you see as the scientific synergies between LSST and WFIRST? 6. What do you see as the relationship between Euclid, WFIRST, and the goals of the decadal survey? Session Summary Steve Kahn delivered a discussion of the LSST, WFIRST, and Euclid missions and the potential relationships among the three. He began by stating that the Euclid data would benefit LSST in a number of ways. The Y, J, and H color information would produce a modest improvement in the photo-z determination, the spectroscopic survey would help calibrate and understand photo-z systematics, and a comparison of the shear determinations will assist in constraining and understanding shape measurement systematics. Kahn also believed LSST is crucial to Euclid, since Euclid requires multicolor visible band photometry in the Southern Hemisphere, and LSST will be the premier facility to deliver such data. LSST will go deeper than Euclid, while covering a comparable fraction of the sky. He continued on to discuss the plans for LSST data release that will be processed annually to produce calibrated images and a catalog of detected sources and their measured properties. Processed data will be released publicly to the U.S. and Chilean communities as well as select foreign partners. With respect to Euclid, Kahn recommended that the United States and ESA should negotiate over the use of LSST data for Euclid analyses. He then provided a complete schedule for LSST, including milestones for the National Science Foundation, the Department of Energy, and private-sponsored endeavors. Moving on to LSST and WFIRST, Kahn emphasized several areas in which the two missions are complementary. LSST will be a synoptic, time-dependent survey of half the sky in the visible band. WFIRST will be a more detail-targeted survey for distinct scientific missions in the NIR. LSST will is purely an imaging facility, while WFIRST will incorporate imaging and spectroscopic survey capabilities. He stressed that both will contribute significantly to dark energy science. When addressing Euclid, WFIRST, and the NWNH decadal survey, Kahn felt that the two missions offer complementary capabilities that will further the goals set forth in the survey. To conclude, he noted that a tight collaboration between Euclid and LSST will be necessary to ensure a common strategy in the derivation of the photometry in the visible and NIR bands. Since the LSST data will require a reanalysis to facilitate any collaboration, Kahn suggested that the provision of LSST data be a key component of any proposed U.S. contribution to Euclid. Discussion of Ground- and Space-Based Dark Energy Speaker: David Weinberg, Ohio State University; Former Vice-Chair of the Astro2010 Science Frontiers Panel on Cosmology and Fundamental Physics; member of BOSS (SDSS-III Project Scientist); member of the Dark Energy Survey collaboration; member of the BigBOSS collaboration Guiding Questions 1. Please discuss the likely capabilities of ground-based projects (BigBOSS, point spread function, eBOSS, etc.), compare to the likely capabilities of Euclid and WFIRST? 2. Do you see the Euclid observations as complementary to the WFIRST measurements or likely to eliminate the need for space-based BAO observations? How is this affected by a U.S. contribution? 29
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Session Summary David Weinberg gave a discussion on ground- and space-based dark energy facilities and began with an overview of a fiducial stage IV program,2 including supernovae, baryon acoustic oscillations (BAO), weak lensing (WL), and cosmic microwave background. Weinberg stated that ground-based galaxy BAO surveys will do well out to z ≈ 1.0 to 1.2 and for z = 2 to 3 from the Lyα forest. However, he noted that the low-infrared background from space is an immense advantage for observing over z = 1 to 2. He felt that the ground would make a start in this z-range but would be unlikely to compete with space, unless radio intensity mapping proved to be a feasible possibility. As a result, Euclid and WFIRST would offer access to precision BAO and redshift space distortion in a range inaccessible from the ground. Weinberg then discussed the planned observations of Euclid as compared to WFIRST. The baseline plans currently show that WFIRST would perform a factor of two better than Euclid in wide survey mode and would be much better in deep mode. He believed that observations from the two missions could easily be arranged to be complementary. In conclusion, he stated that the United States has a strong interest in the scientific success of Euclid and in ensuring timely and effective dissemination of Euclid data. He also noted that giving top U.S. WL experts a role in Euclid would help Euclid and WFIRST and LSST. When questioned how he felt about giving up BAO on WFIRST, Weinberg said that if the impact on the other WFIRST observing programs were equal, then he thought there would be as good an argument for giving up weak lensing as for giving up BAO. Discussion of the Current Study in the Context of New Worlds, New Horizons Speaker: Roger Blandford, Stanford University; Chair of the NRC’s 2010 Astronomy and Astrophysics Decadal Survey (Astro2010) that produced New Worlds, New Horizons in Astronomy and Astrophysics Guiding Questions 1. Based on the decadal survey and the implementation report, what are your recommendations for the committee’s charge? 2. How would U.S. participation in Euclid as a minor partner address the goals and priorities of NWNH? Session Summary Roger Blandford reviewed the task of the Astro2010 decadal survey and the recommendations of the NWNH report. He reminded the committee that NWNH made recommendations for two budget scenarios, and he noted that the reality of the budget climate now is worse than the pessimistic NWNH scenario. He said that the WFIRST program as currently envisioned remains true to the scientific program laid out in NWNH, and he reminded the committee that WFIRST is the top large space-based priority, while noting it was not ranked against the medium and small recommendations. He said the NWNH statement that the United States play a leading role was carefully chosen, in that the committee did not intend that the United States lead any joint ESA-NASA collaboration alone (the leading role, versus a leading role). Blandford gave a brief update of the status of the NWNH recommendations and agency actions since the report release in August 2010. He noted that NASA has created a science definition team for WFIRST, the Explorer Program funding is being increased, and the U.S. teams for IXO and LISA were 2 Stage IV program is defined on page 2 of the AAAC Dark Energy Task Force Report as “major, long-term projects.” 30
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disbanded. Since then, ESA has decided to pursue x-ray and gravitational-wave missions without U.S. support. He said that NASA’s astrophysics discoveries have been remarkable, and he noted several upcoming Explorer program missions. In response to the first questions asked, Blandford said that the kind of U.S. participation in Euclid, with the United States as a minor partner as described by NASA and ESA at this meeting, would give quick access to the data for the U.S. science team. He noted that that it was implicit in NWNH that the United States would be a leader in executing the science of WFIRST. He also said that the United States could significantly impact the Euclid mission by means of scientific and hardware contributions. He noted that a micro-lensing survey is proposed with the Euclid satellite was possible after about 6 years when the cosmology survey is finished. Responding to further questions, Blandford said that while he could not speak for the Astro2010 survey committee since the current scenario was not discussed in the preparation of the survey report, his personal view is that, given the financial situation, the United States should engage in Euclid as proposed, along with continuing to develop WFIRST. Going forward, he said it will be vital to ask the NRC’s Committee on Astronomy and Astrophysics to review any future escalation of the commitment and to advise on the balance against WFIRST development, the Explorer program, NASA’s program of smaller activities, technology development, and the other NWNH recommendations. Discussion of the Current Study in the Context of the “Implementation” Panel Report Speaker: Adam Burrows, Princeton University; Former Co-Chair, with Charles Kennel, of the NRC’s Panel on Implementing Recommendations from New Worlds, New Horizons Decadal Survey Guiding Questions 1. Based on the decadal survey and the implementation report, what are your recommendations for the committee’s charge? 2. How would U.S. participation in Euclid as a minor partner address the goals and priorities of NWNH? Session Summary Adam Burrows opened his discussion reviewing the history that brought about the NRC Panel on Implementing Recommendations from the New Worlds, New Horizons Decadal Survey (the Implementation Panel)—which was convened in November 2010 to consider an earlier proposal for U.S. participation in Euclid. Burrows noted that in September 2010, following the prepublication release NWNH in August 2010, the White House’s Office of Science and Technology Policy requested a short study on whether a proposed NASA 20-percent share in Euclid was consistent with NWNH recommendations. He said that the task of the panel he co-chaired was not to review or revise the Astro2010 survey, but instead it was tasked to focus on the question of whether the proposed 20-percent investment in Euclid was consistent with accomplishing the recommendations of NWNH. The panel concluded that the proposed contribution was not consistent with the recommendations of NWNH. The panel also considered three other options for U.S. participation in Euclid. Burrows described the four options the panel report laid out: the launch of WFIRST in the decade 2012-2021, a joint WFIRST/Euclid mission, commitment by NASA of 20-percent investment in Euclid prior to the M-class decision, or no U.S. financing of an infrared survey mission this decade. Burrows said that the panel was cognizant of the wording in NWNH about the United States having a leading role in fulfilling the WFIRST science capabilities. He said that the Implementation Panel concluded that the Euclid mission would only address one of the WFIRST science goals and that an 31
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investment in Euclid might cause an imbalance in the survey’s recommended strategy. He noted that NWNH did not rank specific science goals or prioritize between large-, medium-, and small-scale activities and that the survey emphasized the need for balance across all scales of activities. In response to the questions asked by the committee, Burrows said that it seems the current proposal from NASA is similar to the Implementation Panel’s second option—a joint Euclid-WFIRST mission—with the difference that instead of a joint mission there could be an overall joint science effort toward achieving the WFIRST science goals by pursuing both missions. He said that having a Decadal Survey Implementation Advisory Committee (DSIAC), as recommended by NWNH to monitor the survey’s recommendations, is all the more important in the current budget situation. When asked about the language about the United States being a leader in any joint mission, Burrows elaborated that the Implementation Panel felt that U.S. scientists should have full access to data—that the United States would need to archive—and that the United States should be involved in planning, but that the contribution does not necessarily need to be dominant. Final Discussion Summary The final discussions from the first day centered on possible hidden costs in the current proposal for a $20 million hardware contribution. Paul Hertz from NASA was asked about clarifying the cost of the hardware contributions under consideration and for information on what the cost for supporting a U.S. Euclid Science Team would be, and Hertz offered to prepare a response to be discussed during the discussion on the second day of the meeting. Hertz reminded the committee that these additional costs would not be included in the current proposal, and future involvement would be decided as those issues arose later. Additionally, Hertz said that a U.S. Euclid Science Team would not be a full-time group, which would limit the associated costs. Jason Rhodes, Jet Propulsion Laboratory, volunteered that, in his experience with a NASA- funded science team, the cost for a group of about 20 members over 11 or 12 years was about $30 million, including several senior principal investigators. Another issue raised was the need for funding for LSST to adapt to complement the Euclid surveys, but it was noted that NASA does not support LSST or the Dark Energy Survey (DES). It was noted in the discussion that funding would also be needed for Euclid data archiving. The discussion also touched on the issue of a commercial procurement for an infrared detector, and Hertz noted that ESA has only asked for the detectors directly from Teledyne with no other U.S. characterization or testing. Hertz continued noting that if the United States wanted to characterize or supply electronics that would cost more than the $20 million currently being considered, he would look into those costs and try to prepare an answer for the committee to discuss on the second day. Hertz also noted that NASA make its contribution in the form procuring the infrared detector. If NASA did not procure the detectors for the mission, the Euclid project would do so. DAY 2—JANUARY 19, 2012 WFIRST and Euclid and Their Impact on Dark Energy Research Speaker: Michael Turner, University of Chicago; expert in dark energy and U.S. science policy Guiding Questions 1. How do you see Euclid and WFIRST contributing to dark energy studies? 2. What do you see as the impact of U.S. participation in Euclid on U.S. dark energy efforts? 32
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Session Summary Reminding the committee that he is an advocate for dark energy and for U.S. astronomy, Michael Turner opened by remarking that the WFIRST mission is highly optimized to address science priorities of NWNH. In contrast, Euclid does not achieve as many of the science goals of WFIRST or the near- infrared survey science. He noted that the United States has the largest dark energy community, and yet only a small fraction of that group would benefit from Euclid. He said he believes a small investment in Euclid will have a negative impact on WFIRST and cautioned that small investments can grow larger than anticipated. To illustrate these two points he made comparisons to the recent WMAP/Planck experience. In comparing the potential impact of Euclid and WFIRST, Turner said that Euclid’s lack of a supernovae survey capability is significant because that method is the only proven method of studying dark energy. He said, if weak lensing surveys do not realize the science results that are expected, then the figure of merit for WFIRST would be twice that of Euclid. Furthermore, BAO surveys are not proven to perform as well as the Fisher matrix estimates used to characterize their performance. He said the current WFIRST design is better than Euclid, and Euclid’s design will involve under-sampled infrared pixels, have an undersized aperture, and have an inferior point spread function (because of the obstructed field of view). Turner concluded his presentation by reminding the committee that Europe has its own financial issues right now, and limiting the U.S. financial exposure to reduce risk of cost growth is important while still trying to ensure mission success for Euclid. One possible scenario is having two complementary satellites. During the discussion, Turner clarified that there are many issues that threaten WFIRST and, although WFIRST is not a dark energy mission alone, joining Euclid would dramatically increase the threat to WFIRST because a mis-perception exists that WFIRST is primarily a dark energy mission and because to non-experts the Euclid hardware appears superior to that of WFIRST. Discussion of Euclid and WFIRST Gravitational Lensing Capabilities Speaker: Chris Hirata, California Institute of Technology; expert in dark energy and gravitational lensing Guiding Questions 1. What is your assessment of Euclid’s lensing capability? 2. How essential is ground-based data for Euclid lensing analysis? 3. What are the overlaps and synergies between Euclid and WFIRST planned lensing measurements? 4. What are the synergies between LSST and Euclid lensing analysis? Session Summary Chris Hirata started his presentation by noting what is needed by a weak lensing program for which obtaining statistics, shape measurement, and photometric redshifts are all goals, and he noted that there is no requirement to do all of these surveys from the same platform. He reviewed the imagining capabilities of LSST, WFIRST, and Euclid—noting that each has unique capabilities. He pointed out that LSST has six-band optical imaging and time domain capabilities; WFIRST is designed with deep, high- resolution NIR imaging (2 of the 3 bands are fully sampled); and Euclid will have high-resolution optical imaging. Hirata noted that among the advantages of LSST are that its many exposures will allow subsets of the data, it will cover the entire southern sky, it will provide a complete complement of optical filters, and it is the most advanced of the Stage IV projects. He said that the angular resolution of LSST, as well as the complications inherent in ground-based point spread function (PSF), are both disadvantages for 33
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LSST. He said that Euclid will have the highest resolution of the three and will have large sky coverage, including lots of galaxies and will have a stable PSF with few dyanmic degrees of freedom (DOFs). The disadvantages of Euclid, he said, are that it will construct only one galaxy-shear map, and will have the charge transfer inefficiency issues that are common to space-based CCD detectors. Hirata noted that he does not see how the Euclid data sets could be divided into subsets, which would be a concern. For WFIRST, the advantages he noted were the inclusion of two high-resolution shape filters (the only project with high-resolution multicolor imaging, he noted); an unobstructed telescope; and, as with Euclid, WFIRST will have a stable PSF with few dynamic DOFs. The disadvantages of WFIRST were a small area, only 2,700 square degrees, in baseline mission, and he noted that the HgCdTe detectors have unique systematics. If the United States is part of Euclid, he said, then the United States might reallocate extragalactic survey time on WFIRST to deep mode survey to limit duplication. Hirata said that ground- based optical imaging will be required for both Euclid and WFIRST and that LSST depth will be more than sufficient for both Euclid and WFIRST. BAO on WFIRST will include “deep” surveys (parallel to NIR imaging survey) and “wide” surveys (BAO only) parts, and, Hirata noted, the BAO survey Euclid will provide is similar to the “wide” BAO on WFIRST, so it might make sense to perform WFIRST BAO surveys all in the deep mode. In concluding his presentation, Hirata reminded the committee that Stage IV weak lensing is going to be hard from the ground or from space. Euclid provides a unique high- resolution imaging capability over a wide field, and he would advocate for overlapping (or nested) footprints of the WFIRST and Euclid missions. He said that exploiting these scientific opportunities, including running analysis and cross correlating, will be much easier if the United States has people intimately familiar with both projects. Discussion of WFIRST and Euclid Exoplanet Microlensing Speaker: David Bennett, University of Notre Dame; expert in exoplanets and gravitational microlensing; member of the WFIRST Science Definition Team Guiding Questions 1. What is your assessment of Euclid microlensing capabilities? 2. What are the likely microlensing capabilities of WFIRST? How will these evolve if the United States contributes infrared detectors to Euclid? 3. What are the synergies/overlaps between the two missions as currently conceived? 4. If U.S. scientists have access to Euclid data, what is most important for the exoplanet/microlensing community? Session Summary David Bennett delivered a presentation entitled “Exoplanet Microlensing Surveys with WFIRST and Euclid.” Bennett started with reviewing why space-based microlensing is important and what unique science a space-based microlensing survey could provide, including complements to Kepler surveys. He discussed space-based versus ground-based data sensitivity and remarked that some ground-based confusion can be resolved with space-based data. He briefly reviewed the science basis for measuring masses with regard to high magnification, lens systems, and microlensing parallax. In the second half of his presentation he responded to the questions asked in advance by the committee. He noted that the main drawback to Euclid is programmatic: the exoplanet program is not part of the core science program for Euclid. With regard to microlensing capabilities, Bennett reported that the photometric detection rate for the Euclid infrared channel and the WFIRST Interim Design Reference Mission are about the same and that the difference in photometry will be in the detection of inner planets (near the habitable zone) where 34
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low-amplitude signals occur at low magnification—which will be easier with WFIRST. For lens identification and mass measurements, he said that relative astrometry will benefit more from the higher WFIRST angular resolution in the infrared. However, the high angular resolution Euclid optical data is probably better than the Euclid infrared data for these astrometric measurements. He also noted that no detailed mass measurement simulations have been done for either mission. The optimal microlensing fields, he reported, are highly obscured and four times more photons are detected in the infrared and that HgCdTe detectors are much better than CCDs in this regard, but a 2 square degrees CCD field of view could compensate for this. Bennett remarked that orbital microlensing parallax measurements will be difficult with 1-month observing windows on Euclid. He said that if Euclid and WFIRST fly at the same time, then simultaneous observations of microlensing events would yield some L2-L2 microlensing parallax measurements if they are out of phase by π and this would be an interesting possibility. But the microlensing community cannot make realistic plans for this because it depends on the timing of missions run by different agencies. If available, Bennett stated that early microlensing data would provide a long- time baseline for relative proper motion measurements and, therefore, would help to improve mass measurements for a large fraction of all WFIRST and Euclid discoveries. Bennett concluded by remarking that if Euclid does not do a microlensing program, then Euclid data is of little interest to the U.S. microlensing community. During the discussion, Bennett clarified that although a microlensing program will not be a priority on Euclid before the 6.3-year dark energy program is complete, it is possible to get a few months of microlensing done early on, in part because the limited number of cosmology fields that can be observed at the same time as the microlensing fields. However, such a program would not be comparable with WFIRST. He commented again that he felt the two 1-month windows planned for Euclid’s mission are the biggest issue for microlensing but that the optical component from Euclid helps to compensate for Euclid’s poor angular resolution in the infrared. When asked about a baseline comparison between WFIRST and Euclid of the relative number of planets that could be found, he responded that the baseline is pretty similar per unit observing time, although WFIRST has a particular advantage in finding planets in the most difficult region (closest to the habitable zone), and WFIRST would be better in determining masses. The Euclid mission is not guaranteed to do any microlensing. He also reminded the committee that the main goal of exoplanet science is cataloging planets, but a big goal within that is identifying planets in habitable zones around nearby stars and how they may be similar or different to Earth. When asked about the benefit of having early access to Euclid data, Bennett replied that it would be useful to have data earlier than the 14-month data policy, but that it also depends on how much microlensing they do. Processing the data quickly depends somewhat on hardware, and it is possible to do orbital microlensing parallax, but this might be easier to with a dedicated ground telescope. Finally, when asked about quantifying the statement that mass measurement would be better with WFIRST, Bennett replied that people are currently working on this, but the answer is not available yet. Impact of Current and Future Developments in Microlensing on Euclid and WFIRST Speaker: Dimitar Sasselov, Harvard University; expert in exoplanets and gravitational microlensing Guiding Questions 1. Have the Kepler results changed the importance of the WFIRST microlensing program? 2. What are the likely ground-based developments that will compete/complement planned Euclid and WFIRST activities? 35
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Session Summary In response to the first question, Dimitar Sasselov answered, yes, Kepler results strengthen the case for a complementary survey. One reason why the case is strengthened is because the Kepler survey has already uncovered a very significant fraction of planets within an orbital radius of 2 to 3 astronomical units (AU) of their stars. Sasselov presented one viewgraph to accompany his discussion depicting expected results for an extended Kepler mission currently under review. This extended mission, he remarked, would provide completeness beyond 1 AU for planets with a radius larger than Earth. He said that going forward much work will be focused on the characterization of small planets—such as looking for bio-signatures in atmospheres—and this will require going beyond Kepler and the extended mission, and he noted that most of the overlap will be for small-mass stars. He said that smaller rocky planets are crucial to our understanding of planet formation. Answering a second question, Sasselov said that in the next few years he expects a lot of ground-based technologies will be focused on characterization, particularly with improvement in radial velocity measurements and imaging. The Kepler survey does not determine the mass of free-floating planets, but the high frequency of planets being discovered by Kepler makes an even stronger case for a microlensing survey. When asked why the exoplanet community was not very supportive of WFIRST microlensing, Sasselov reminded the committee that spectroscopy of planetary atmospheres turned out to be very successful and a lot of community effort was put into bringing this success down to the smaller planets as well. With the excitement around this area, the younger exoplanet community became more involved in spectroscopy and so they do not see direct benefits of WFIRST microlensing. He also noted that where the microlensing benefit will come, indirectly, from increasing the understanding of the physical properties characterization of the planets and formation scenarios. He closed by noting that the results of Kepler, and inability to match them to the models, are increasing interest in microlensing. Lessons Learned from Similar Past NASA-ESA Collaborations Speaker: George Helou, California Institute of Technology; Deputy Director of the Spitzer Science Center; Director of the NASA Herschel Science Center Guiding Questions 1. What are the successes and failures of previous missions where NASA astrophysics has contributed to an ESA mission (ISO, Herschel, Planck)? 2. What are your recommendations for the framework for U.S. role in Euclid? Session Summary George Helou presented some lessons learned from collaborations between NASA and ESA on the Infrared Space Observatory (ISO), Spitzer, Hershel, and Planck missions. He said that ISO began as an ESA-only mission, with some U.S. individual participation as co-investigators on instrument teams and on the ISO Science Team and several U.S. “scientific associates” also involved. He noted that a late agreement was made for guaranteed time and access to open time competitions in exchange for use of the Deep Space Network. He said that NASA competed its guaranteed time independently. The U.S. community participated in the competition for open time and was allocated approximately 30 percent of the open time, which resulted with the United States having responsibility for approximately 25 percent of the ISO time. Helou said there were data analysis issues because the United States did not become more 36
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involved until later in the project, but in the end the United States had about 25 percent of the first authors on papers published. With Spitzer, a NASA Great Observatory, Helou said that about 20 percent of the observing time was allocated to the European community through competition, but there was no ESA investment in Spitzer. For Hershel, Helou said that the NASA contributions were used primarily for enabling detectors and that was crucial to the mission. He said the U.S. Hershel Instrument Team members had access to guaranteed time, and in addition three U.S. scientists were independently selected from the Hershel Science Team in open competition, the net result being that U.S. scientists received nearly half of the open time and participated on another 35 percent of the open time. Planck has two U.S. members on the science team and about 80 U.S. scientists on their teams, all with full access to data and software. NASA will provide engineering support for delivered hardware and support for mission design and planning, around 20-25 percent of the data analysis on Planck, and there will be a U.S. version of the Planck archive. Looking at all of the activities, Helou said it is interesting to note that all the hardware contributions are through instrument-related activities, and none are to ESA directly. In concluding his presentation Helou said that both NASA and ESA can fund, build, and operate major missions. Euclid will happen, but Euclid by itself will not kill WFIRST, nor would NASA buying into Euclid. He said that the unique capabilities of the United States are in leading-edge technologies and more especially in human and institutional resources, and the United States do not want to lose this edge. He said that critical mass of participation is also important to think about, and he believes a single U.S. scientist on the science team could be risky. Helou suggested as a framework that NASA should make sure that data are available, and he noted that the United States needs to get science data system participation. Finally, Helou also believes that along with hardware, the hardware characterization and data reduction pipelines should be included as U.S. deliverables, keeping that expertise alive in the United States and ensuring we have appropriate data access later. Helou also said that NASA would need to fund selected science team members to set up teams capable of exploiting data in a timely fashion and that NASA would need to establish a U.S. science center to support all Euclid users as it has done for missions in the past. He said that most of that cost happens after launch, and the cost would depend on what tasks the United States is contributing to Euclid. In the discussion that followed, Helou clarified that the science data center operation would be much smaller than what would be hosted in Europe, but that this is important to help enable scientists inside the team and outside the team to have good access to the data. Discussion with NASA Speaker: Paul Hertz, Acting Director of the Astrophysics Division within NASA’s Science Mission Directorate Guiding Questions 1. What is the cost of the U.S. hardware contribution to Euclid? 2. In Mellier’s presentation, we heard that Euclid would be interested in NASA providing support for PanSTARRS or other ground-based efforts. Is this consistent with NASA’s plans? 3. Does NASA view a 10percent lead authorship as a necessary return? 4. Would a possible role for the U.S. scientists be taking the lead in the Legacy science role of combining Euclid photometry with ground-based (primarily U.S.) photometry and providing this data to the public? 37
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Session Summary Paul Hertz reviewed the president’s fiscal year (FY) 2012 budget request, and he presented a table from the president’s FY2012 budget request of specific budget allocations for the NASA recommendations from NWNH, projected through FY2016. Hertz stated that the $20 million to $30 million for the NIR detectors would constitute (and be reallocated from) about 20 percent of the augmentation of funds planned for FY2013-FY2014 within the run out of the president’s FY2012 budget request for allocation by the division for NWNH priorities in the same time frame. He concluded that the contribution would thus have a small, albeit non-negligible, impact on those programs. Hertz also stated that expenditure of these funds on Euclid hardware would not impact the launch schedule for WFIRST, since according to current NASA budget projections, significant expenditure on the WFIRST mission would only commence in the 2017-2018 time frame, when JWST construction spending rolls off. As part of its participation in Euclid, NASA would also support a science team at an annual level of $1.5 million to $3 million. He also noted that because the budget table he displayed to the committee was composed last year it included both the IXO and LISA missions; however, those projects were no longer being supported, and those budget lines would probably go to fund concepts being studied under current requests for information. Hertz also said that the WFIRST-development budget item was not included on the chart but is of the order of $4 million per year. Finally, he showed a slide with quickly assembled NASA-estimated costs for the specific possible Euclid-related contributions in which the committee expressed interest on the meeting’s first day—including NIR detectors, $20 million to $30 million; NIR detectors and characterization, $40 million to $50 million; reaction wheels, approximately $10 million; filter wheel, $20 million to $25 million; and supporting a U.S. science team, between $15 million to $30 million. He reminded the committee that a Guest Observer program and a U.S. science center to support involvement in Euclid are not being discussed with ESA as part of the current discussions. In the discussion that followed, Hertz clarified that NASA and ESA have discussed NASA’s providing either the detectors, the reaction wheels, or the filter wheels, but not multiple hardware contributions. He said that ESA would prefer that the United States contribute the NIR detectors, and NASA had specifically discussed with ESA a hardware contribution that is linked to the science. When asked, Hertz also noted that NASA has not been involved in discussions with the EC, nor with NSF or the DOE, on the need for cooperation with ground-based surveys such as LSST, Pan-STARRS, or the Dark Energy Survey. Final Discussion Summary In the final discussions, Paul Hertz (NASA) reminded the committee that the 17 current U.S. scientists involved in the EC do not have the right to share data outside the EC, and that part of what NASA would get from becoming a partner in Euclid in the manner described at this meeting would be data access for the entire U.S. science community. Hertz said that while a NASA-selected Euclid science team would be relatively small, it would be openly competed through peer review so that any U.S. scientist would have a chance to be on the team. Hertz also said that NASA has not discussed putting a U.S. scientist on the ECB. A question arose about how the ECB is appointed and Jason Rhodes (JPL) explained to the committee that the EC is self-organizing and created the ECB. The discussion transitioned back to the hardware contribution, and various attendees gave their opinions and impressions on the relative merits of each. As the open session came to a close, the discussion concluded with final remarks on the 10-percent science return for U.S. scientists, where Hertz said that the inclusion of that statement in the request from ESA was meant to clarify that NASA would have an appropriate role in the science, and he reminded the committee that the details of the science return will be discussed by the EST. 38