A 1.5-meter wide-field-of-view near-infrared-imaging and low-resolution-spectroscopy telescope, WFIRST will settle fundamental questions about the nature of dark energy, the discovery of which was one of the greatest achievements of U.S. telescopes in recent years. It will employ three distinct techniques—measurements of weak gravitational lensing, supernova distances, and baryon acoustic oscillations—to determine the effect of dark energy on the evolution of the universe. An equally important outcome will be to open up a new frontier of exoplanet studies by monitoring a large sample of stars in the central bulge of the Milky Way for changes in brightness due to microlensing by intervening solar systems. This census, combined with that made by the Kepler mission, will determine how common Earth-like planets are over a wide range of orbital parameters. It will also, in guest investigator mode, survey our galaxy and other nearby galaxies to answer key questions about their formation and structure, and the data it obtains will provide fundamental constraints on how galaxies grow. The telescope exploits the important work done by the joint [Department of Energy] DOE/NASA design team on the Joint Dark Energy Mission—specifically the JDEM-Omega concept—and expands its scientific reach. WFIRST is based on mature technologies with technical risk that is medium low and has medium cost and schedule risk. The independent cost appraisal is $1.6 billion, not including the guest investigator program. As a telescope capable of imaging a large area of the sky, WFIRST will complement the targeted infrared observations of the James Webb Space Telescope. The small field of view of JWST would render it incapable of carrying out the prime WFIRST program of dark energy and exoplanet studies, even if it were used exclusively for this task. The recommended schedule has a launch date of 2020 with a 5-year baseline mission. An extended 10-year mission could improve the statistical results and further broaden the science program. The European Space Agency (ESA) is considering an M-class proposal, called Euclid, with related goals. Collaboration on a combined mission with the United States playing a leading role should be considered so long as the committee’s recommended science program is preserved and overall cost savings result.

NASA holds regular senior reviews to decide which missions to terminate, and it is anticipated that every one of its currently orbiting space telescopes, including Hubble (which needs an expensive de-orbiting mission), will cease operations before the end of the decade. SOFIA [Stratospheric Observatory for Infrared Astronomy], which has operations costs of $70 million per year, will be subject to a senior review after 5 years of operations. Thus, with the possible exception of JWST and SOFIA, none of the missions operating or started today are expected to be operational at the end of the decade.

In the course of formulating recommendations that include large, medium, and small missions, as well as targeted augmentations to some of the core supporting activities, the committee considered broader issues of balance between a range of elements across the NASA program: between larger and smaller missions; between NASA-led and international-partner-led missions; between university-led and NASA-center-led missions; between mission-enabling and mission-supporting activities (technology development, suborbital program, theory, ground-based observing) and the missions themselves; between mission construction/operation and data archiving and analysis; and between extended mission support for operating missions versus funding of new missions. During its deliberations the committee attended to the general principle of balance in developing its recommended prioritization of projects within the NASA Astrophysics Division program during the coming decade.

In a 5-year baseline mission, its observations would emphasize the planet census and dark energy measurements, while accommodating a competed general investigator program for additional surveys that would exploit WFIRST’s unique capabilities using the same observation modes. The powerful astronomical survey data collected during all of the large-area surveys would be utilized to address a broader range of science through a funded investigator program. An extended mission, subject to the usual senior review process, could both improve the statistical results for the main science drivers and broaden the general investigator program.

The technical risk of LSST as determined by the survey’s cost appraisal and technical evaluation (CATE) process was rated as medium low. The committee did identify additional risk with establishing data management and archiving software environments adequate to achieving the science goals and engaging the astronomical community. The appraised construction cost is $465 million with a time to completion of 112 months. The committee recommends that LSST be started as soon as possible, with, as proposed by the project, two-thirds of the construction costs borne by NSF [National Science Foundation] through its MREFC [Major Research Equipment and Facilities Construction] line and a quarter by DOE using Major Item of Equipment (MIE) funds. The estimated operations cost is $42 million per year over its 10-year lifetime, of which roughly $28 million is proposed to be borne by the U.S. agencies—the committee recommends two-thirds of the federal share of operations costs be borne by NSF and one-third by DOE. It is recommended that any extended mission should only happen following a successful senior review. By its very nature LSST will stimulate a large number of follow-up studies, especially of a spectroscopic character. The planning and administration of an optimized plan for follow-up studies within the public-private optical-infrared system could be carried out by the National Optical Astronomy Observatory.

Continue missions currently in flight, subject to approval obtained through the appropriate senior review process. Ensure a level of funding that is adequate for successful operation, analysis of data, and publication of the results of these missions, and for extended missions that afford rich new science return.

Within the category of small missions are three elements of particular interest: the Discovery program, extended missions for ongoing projects, and Missions of Opportunity.

Mission extensions can be significant and highly productive, and may also enhance missions that undergo changes in scope because of unpredictable events. In some cases, particularly the “re-purposing” of operating spacecraft, fundamentally new science can be enabled. These mission extensions, which require their own funding arrangements, can be treated as independent, small-class missions. The committee supports NASA’s current senior review process for deciding the scientific merits of a proposed mission extension. The committee recommends that early planning be done to provide adequate funding of mission extensions, particularly for flagship missions and missions with international partners.

The 2003 decadal survey identified two small-class initiatives. They were, in priority order:

Given the growing number of known Centaurs and KBOs, the committee concluded that it is scientifically desirable that missions directed to the outer solar system take advantage of opportunities to fly by such objects (at ranges less than 10,000 km) en route to their ultimate targets. During the next decade there will be a growing desire to investigate some large trans-Neptune objects beyond the orbit of Pluto. The New Horizons mission already en route to Pluto (Figure 4.4) has the potential to fly by a small KBO. This extended mission opportunity will be a first chance for a close-up view of this class of object and should not be missed if a suitable target is available.

Data from the ASPERA [Analyzer of Space Plasmas and Energetic Atoms] instrument on Venus Express suggest provisionally that hydrogen escape rates are an order of magnitude slower than previously assumed, implying that the hydrogen in Venus’s atmosphere has an average residence time of some 1 billion years. This result, if confirmed by further observations during an extended Venus Express mission, has important implications for the history of water and the current rate of outgassing on Venus. Another significant discovery is that Venus’s atmosphere is losing unexpectedly large quantities of oxygen to deep space by way of nonthermal processes. This finding calls into question the long-standing assumption that a massive escape of hydrogen from Venus’s atmosphere must have left the atmosphere and surface highly oxidized.

The individual flight projects for the coming decade must be considered within the context of the broader program of planetary exploration. The goal is to develop a fully integrated strategy of flight projects, technology development, and supporting research that maximizes the value of scientific knowledge gained over the decade. All of the recommendations in this chapter are made under the assumption that the following basic programmatic requirements are fully funded:

Mission extensions can be significant and highly productive, and may also enhance missions that undergo changes in scope because of unpredictable events or opportunities. The Cassini and Mars Exploration Rover extensions are examples of the former, and the “re-purposing” of missions such as Stardust (NExT) and Deep Impact (EPOXI) are examples of the latter. In some cases, particularly the re-purposing of operating spacecraft, fundamentally new science can be enabled. These mission extensions, which require their own funding arrangements, can be treated as independent, small-class missions. The committee supports NASA’s current senior review process for deciding the scientific merits of a proposed mission extension. The committee recommends that early planning be done to provide adequate funding of mission extensions, particularly for flagship missions and missions with international partners.

A related issue concerns the process for extension of a NASA-developed Earth science mission that has accomplished its initial objectives or exceeded its design life. NASA decisions on extension of operations for astronomy, space science, and planetary exploration are based on an analysis of the incremental cost versus anticipated science benefits. Historically, NASA has viewed extended-phase operations for Earth science missions as operational and therefore the purview of NOAA [National Oceanic and Atmospheric Administration]. However, the compelling need for measurements in support of human health and safety and for documenting, forecasting, and mitigating changes on Earth creates a continuum between science and applications—illustrating again the need for multiple agencies to be intimately involved in the development of Earth science and applications from space.

The elimination from NPOESS [National Polar-orbiting Operational Environmental Satellite System] of requirements for climate research-related measurements is only the most recent example of the nation’s failure to sustain critical measurements. The committee notes that despite NASA’s involvement in climate research and its extensive development of measurement technology to make climate-quality measurements, the agency has no requirement for extended measurement missions, except for ozone measurements, which are explicitly mandated by Congress. The committee endorses the recommendation of a 2006 National Research Council report that stated, “NASA/SMD [Science Mission Directorate] should develop a science strategy for obtaining long-term, continuous, stable observations of the Earth system that are distinct from observations to meet requirements by NOAA in support of numerical weather prediction.”

In the area of comparative magnetospheres, Juno will enter its prime mission phase when it arrives at Jupiter in 2016, while Cassini at Saturn is approved for a final mission extension to 2017, and MESSENGER [Mercury Surface, Space Environment, Geochemistry, and Ranging] will complete its prime mission early in the decade. Past and current missions continue to provide deep insights into general solar wind magnetosphere interactions. For example, Ganymede’s Alfvén wings have led to modern theories of Earth’s own polar cap potential saturation mechanism; Saturn’s explosive energy releases have much in common with substorm injections at Earth; and Jupiter’s interchange motions enabling convection under Io’s mass loading have led to similar theories pertaining to inward penetration of fast reconnection flows. As is the case for Earth-orbiting satellites, extended missions for planetary missions that continue to return valuable science data are strongly encouraged.

Two science phases are envisioned: drift to L5 at about 38° per year with continuous collection of science data and orbit around L5, 45°-90° from the Sun-Earth line. A long extended mission is possible.

Resource allocation among extended HSO missions is determined through the senior-review process, which evaluates future scientific priorities for each mission. The present 5-year budget requests show flat or declining HSO funding. In addition to supporting existing HSO missions, the budget must accommodate new missions, such as RBSP [Radiation Belt Storm Probes] (renamed the Van Allen Probes) and SDO [Solar Dynamics Observatory], that finish their prime mission in or before [fiscal year] FY 2015; this will inevitably lead to forced termination of or severe cuts in current HSO missions. As a consequence, key systems-science objectives are endangered, and essential legacy data sets may be foreshortened at a time when solar activity is apparently evolving in unexpected ways. Multipoint observations throughout the heliosphere and from the Sun to geospace regions need to be maintained to enable systems science. The SHP [Solar and Heliospheric Physics] panel assigns high priority to augmenting MO&DA support by annual inflationary increases plus $5 million to $10 million per year to accommodate new missions so that seniorreview decisions can be prudently based on strategic evaluations of existing and emerging assets.