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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/.
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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.
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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?
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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
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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
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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?
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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?
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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.”
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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
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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?
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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
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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
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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?
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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
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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?
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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.
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