3

Earth Venture—Challenges and Opportunities for the Notional Platform

Earth Venture is a program element within the Earth System Science Pathfinder Program (ESSP) consisting of a series of science-driven, competitively selected, low-cost missions intended to provide opportunity for investment in innovative Earth science to better understand the current state of the Earth system and to enable continual improvement in the prediction of future changes.¹

By design, Earth Venture targets science investigations that complement NASA’s satellite and research program. With their relatively high risk, EVs are selected with the understanding that failure of a particular “mission”² should not compromise the overall objectives of the NASA Earth Science program. Thus, while aligned with ESD objectives, which are guided in part by the recommendations of National Academies’ Earth science and applications from space decadal surveys, EV missions were not intended to be—and to date have not been—critical to ESD plans for decadal survey implementation.

Like the proposed platform, the ISS can also serve as a host for multiple-instrument payload; indeed, the ISS has been utilized for several EV space missions (see Figure 3-1). However, while the synergy between Earth Venture instruments on the ISS and other ISS sensors has provided enhanced science capabilities, this committee believes it is unlikely that the ISS would have been the platform of choice if not for the substantial cost benefits to Earth Venture proposing teams and to NASA ESD related to launch and accommodation costs.

The Earth Venture Continuity (EV-C) strand was recommended in the ESAS 2017 decadal survey to promote “innovative, capable approaches to acquiring existing measurements at lower cost.” EV-C is directed toward long-term acquisition of key continuity observations through innovative technology infusion. While EV-C concepts must demonstrate these innovative approaches for making long-term measurements, they are not expected to address continuity beyond their short mission duration.³ Without cost savings like those provided by the ISS, it is unclear what benefits the notional large platform would provide for EV-C.

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¹ NASA, 2013, “Missions: Earth Venture Class: NASA’s Earth Observing System,” https://eospso.nasa.gov/mission-category/13.

² In this report, the committee adopts the common use of “mission” to refer to elements in Earth Venture-Instrument and Earth Venture-Continuity, both of which develop instruments that are hosted on missions of opportunity, and Earth Venture-Mission, which is designated as a mission because it includes the requisite launch vehicle and spacecraft.

³ The minimum demonstration period is one year beyond on-orbit commissioning. Libera, the first EV-C mission directed to Earth’s radiation budget (ERB) continuity with CERES, is an exception; it has a 5-year goal of continuity of the ERB record.

OPPORTUNITY FOR MAINTAINING DATA RECORD CONTINUITY

Many Earth system variables require continuous measurement, including some associated with the Targeted Observables shown in Table 3.5 of the ESAS 2017 decadal survey.⁴ Several of the observations listed in Table 3.5 were part of the program of record for the present decade, for example, the Total Spectral Solar Irradiance Sensor (TSIS-1) and TSIS-2 for solar irradiance and the Clouds and the Earth’s Radiant Energy System (CERES) Flight Model-6 instrument, launched in November 2017 on the first Joint Polar Satellite System satellite, for measurements of Earth’s radiation budget (ERB). While EVC-1 was directed to ERB continuity, there is no long-term plan for either solar irradiance or ERB beyond the early part of the next decade, though they provide critical climate data records.⁵

NASA continually faces the challenge of balancing a portfolio between new measurements and data continuity.⁶ Leaving aside cost, engineering, and other challenges beyond the scope of this short study, the notional large-instrument platform could play a role in mitigating gap risks for solar irradiance, Earth’s radiation budget, and many other continuity observations, just as the ISS did in maintaining solar irradiance continuity by hosting TSIS-1. Meanwhile, the committee affirms the approach for continuity recommended by ESAS 2017, which asked NASA ESD to “lead the development of a more formal continuity decision process (as in NASEM, 2015⁷) to determine which satellite measurements have the highest priority for continuation, then work with U.S. and international partners to develop an international strategy for obtaining and sharing those measurements.”⁸

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⁴ NASEM, 2018, Thriving on Our Changing Planet.

⁵ NASA, 2018, “Recommended Measurement and Instrument Characteristics for an Earth Venture Continuity Earth Radiation Budget Instrument: Report of the Earth Venture Continuity Radiation Budget Science Working Group,” Updated November 20, https://essp.larc.nasa.gov/EVC-1/pdf_files/ERB_SWG_Rept_FINAL.pdf.

⁶ NASEM, 2015, Continuity of NASA Earth Observations from Space: A Value Framework, Washington, DC: The National Academies Press, https://doi.org/10.17226/21789.

⁷ Ibid.

⁸ NASEM, 2018, Thriving on Our Changing Planet, p. 195.