NASA's Asteroid Initiative consists of two separate but related activities: the Asteroid Redirect Mission (ARM), and the Asteroid Grand Challenge (AGC). NASA is developing concepts for the ARM, which would use a robotic spacecraft to capture a small near-Earth asteroid (7 to 10 meters), or remove a boulder (1 to 10 meters) from the surface of a larger asteroid, and redirect it into a stable orbit around the moon. Astronauts launched aboard the Orion spacecraft would rendezvous with the captured asteroid material in lunar orbit, and collect samples for return to Earth. The AGC is seeking the best ideas to find all asteroid threats to human populations, and to accelerate the work that NASA is already doing for planetary defense. The Asteroid Initiative will leverage and integrate NASA's activities in human exploration, space technology, and space science to advance the technologies and capabilities needed for future human and robotic exploration, to enable the first human mission to interact with asteroid material, and to accelerate efforts to detect, track, characterize, and mitigate the threat of potentially hazardous asteroids. On June 18, 2013, NASA issued a Request for Information (RFI) to gather innovative ideas that NASA will use to plan the Asteroid Initiative (Ref. 1). The RFI was open to individuals, companies, universities, government agencies, and international organizations. The RFI closed on July 18, 2013, and 402 responses were received from 16 countries. Approximately 40% of the responses were from the general public. All responses were evaluated for relevance, impact, maturity, and affordability, and 96 of the most promising ideas were selected for presentation at the Asteroid Initiative Ideas Synthesis Workshop. The purpose of the workshop was to further examine and foster a broad discussion of the most promising ideas gathered via the RFI, and to identify and synthesize ideas that could help inform NASA's planning of the Asteroid Redirect Mission and Asteroid Grand Challenge. The workshop participants also made recommendations for further studies and next steps. The workshop was held in two parts at the Lunar and Planetary Institute. The first part took place on September 30 before the government shutdown, and about 150 people attended. The workshop resumed on November 20-22, and about 120 people attended the second part. Over 2,000 people were able to participate virtually. The workshop sessions included presentations and discussion in the following areas: Asteroid Observation Asteroid Redirection Systems Asteroid Deflection Demonstrations Asteroid Capture Systems Crew Systems for Asteroid Exploration Partnerships and Participatory Engagement Crowdsourcing and Citizen Science (Grand Challenge) Next Generation Engagement (Grand Challenge) The Asteroid Observation area discussed concepts for augmenting and accelerating ground and space-based capabilities for detecting all near-Earth asteroids, determining their orbits, and characterizing their shape, rotation rate, mass, and composition as accurately as possible. This information is needed to identify candidate targets for the Asteroid Redirect Mission, as well as to expand our knowledge of the population of potentially hazardous asteroids for planetary defense. The main recommendations from the workshop were to encourage international participation by working through the United Nations, assist amateur astronomers in contributing to asteroid detection and characterization efforts, use surplus observational time on U. S. space surveillance systems, encourage commercial partnerships for asteroid precursor missions using small spacecraft, and include grants to detect and characterize small asteroids in NASA's annual space science solicitations.