NEO Surveys and Ground-Based Follow-up

The white paper "The Future of Planetary Defense in the Era of Advanced Surveys" (Mainzer, et.al. 2020) discusses motivations and details of next-generation surveys for Near Earth Objects (NEOs).This companion paper's goal is to discuss how NEO surveys and follow-up telescopes work together and how they will build on successful community collaborations into the future.1.More and larger telescopes investing time on solar system observations are required to respond to the accelerating NEO discovery rate.The Vera Rubin Observatory (Legacy Survey of Space and Time, LSST) and the NEO Surveyor Mission (NEOSM) are in advanced planning and construction.Other telescopes will need to increase NEO observations or be constructed to fully capitalize on the new discoveries and data.2. Current and future surveys complement each other in survey strategy, field of regard, and other figures of merit.Current facilities are sensitive to rapid close approachers to Earth while future surveys will search for more distant NEOs, moving more slowly.3. Infrared and optical observations are complementary.Thermal IR data provide a measure of diameter, and of albedo when combined with optical data.4. A robust NEO community exists (surveys, follow-up telescopes, archive and orbit computation centers) in the United States and internationally.However, the community must identify a sustainable path to grow and evolve to prepare for more extensive and larger aperture telescope support for next decade's surveys. 5. NEO follow-up time is sparsely distributed, and many telescopes used by the NEO community are overcommitted, especially during dark and gray times of the lunar month.NEO discoveries have been accelerating for more than two decades 1 , challenging followup facilities to keep up with NEO confirmations, arc extensions, and characterization.Discoveries from NEO surveys can be lost to insufficient follow-up (Vereš 2018).NEOSM and LSST will increase by orders of magnitude the number of NEOs that can be targeted with small and medium aperture telescopes, thus increasing the observing load on current follow-up facilities.Current facilities can prioritize brighter targets but new dedicated largeaperture follow-up facilities and/or significant access to existing large-aperture telescopes will be required to complement the surveys' self-follow-up plans.The NASA Authorization Act of 2005, also known as the George E. Brown, Jr. Near-Earth Object Survey Act 2 , established a Congressional mandate for NASA to "detect, track, catalogue, and characterize" 90% of NEOs ≥ 140-m by 2020.Since 2014, surveys have discovered on average 500 discoveries per year in this size range.The estimated population of ≥ 140-m NEOs is ~25,000, 63% of which remain undiscovered as of June 2020.To be confirmed, each discovery requires a sequence of observations, usually contributed by multiple telescopes.While NEOSM and LSST plan on self follow-up, there will always be a need for coordinated community astrometric followup of priority targets and corresponding characterization.NEOSM and LSST, working together with current NEO surveys, should be able to reach the 90% discovery completion of ≥ 140-m NEOs within in a decade after the new surveys begin.This will require an average ~1,300 discoveries per year in that size range.Efficient strategies will be required to find edge case NEOs (e.g., asteroids that approach Earth from the direction of the Sun or quadrature) instead of solely emphasizing those from opposition.A large network of interdependent telescopes and data centers will be needed to accomplish the 90% goal.