The Keck Institute for Space Studies (KISS) workshops on the Asteroid Return Mission concept explored and established the feasibility of capturing and returning an entire near-Earth asteroid (NEA) to lunar orbit by the middle of the next decade, and identified the benefits that such an endeavor would provide to NASA, the nation, and the world. This technical development has begun work on select technical issues identified in the study to significantly enhance the prospects of making an asteroid capture and return mission a reality. Selected issues include:
As part of the Keck program that initiated the NASA Asteroid Return Mission (ARM), technical development work was undertaken with KISS funds to develop new techniques for detecting small asteroids, down to 5-10 meters in size, appropriate as possible candidate targets for the ARM mission.
Work was initiated using the Palomar Schmidt Telescope using a CCD camera with 7.25 square degree field of view and making 60-second exposures. Small asteroids can only be detected close to the Earth because of the small amount of light they reflect and therefore they have large angular velocities across the sky, somewhat analogous to earth satellites. They therefore appear as linear features (“streaks”) in the images from the Schmidt telescope.
A sophisticated software pipeline was developed to identify asteroid streaks employing machine-learning techniques (see Waszczak et al., reference below). The initial trials of the pipeline in 2014-2015 yielded immediate results: a 7.5 meter diameter asteroid, less than 1/3 the distance to the Moon. See figure.
Future work enabled by the KISS program results. Caltech has built a new ½ Gigapixel CCD camera for the Palomar Schmidt Telescope that has a 47 square degree field of view, more that 6 times that of the earlier camera. In addition, the camera is more sensitive allowing 30 second exposures. For small asteroids, the improvement in detection rate should increase by about x20. Instead of a rate of about one small asteroid detection per month, the rate should now be about one per day. Although the possibility of an ARM mission is now less probable, the scientific interest in characterizing the population of near earth asteroids is even higher. Surveys using the new Palomar Schmidt CCD camera will be a major step forward in detecting small asteroids. This program would not have been possible without the earlier KISS funding.
Waszczak et al., PASP, https://doi.org/10.1088/1538-3873/129/973/034402
This continuing technical development project had two task areas:
(1) mission architectures, and (2) demonstration of techniques to detect small NEAs suitable for an Asteroid Retrieval Mission (ARM).
The Mission Architecture task was completed and documented with the publication of Synergies of Robotic Asteroid Redirection Technologies and Human Space Exploration1 at the 65th Conference of the International Astronautical Congress (2014). Whereas the first year of technical development for the Asteroid Retrieval study focused on the feasibility and mission design for capturing and moving a small asteroid from its natural orbit to cis-lunar space, the more recent technology development task examined how the various technologies required for such a mission can be used in other planetary exploration applications and might be incorporated in an architecture to extend human exploration to Mars. A workshop was held in April 2014 on Applications of Asteroid Redirection Technology, attended by 35 participants. A report of the workshop can be found on the KISS website:
This workshop and report formed the basis of the IAC publication mentioned above.The areas of research and technology included solar electric propulsion use on cargo missions to support human space flight, analysis of resonant heliocentric orbits that might enable intermediate flights between Earth and Mars, planetary defense applications of asteroid deflection, and applications to utilization of putative asteroid resources. A single architecture could, in principle, be derived from the options studied, but that would of course depend on program objectives outside the scope of a technology development study. Instead various pathways for applications were identified, as well as areas for further study. A summary chart of all the considerations follows:
During 2014, our team successfully developed a prototype pipeline for detection of small Near-Earth Asteroids (NEAs) as part of the Palomar Transient Facility (PTF), using the 1.2 meter (48-inch) Oschin Schmidt telescope on Mt. Palomar. This project was led by Caltech graduate student Adam Waszczak, working with Russ Laher and Frank Masci of IPAC for pipeline implementation and with Brian Bue and Umaa Rebbapragada of JPL for machine learning development.
The task was highly successful, leading to the detection of several small NEAs including an ~7 meter object (2014 JG55) only one third of the distance from the earth to the moon (for which there was some external media coverage, see http://www.ptf.caltech.edu/news/ptf_asteroid2014 for the text of the release), as well as an NEA (2014 ST223) whose characteristics were close to those desired for an ARM Mission candidate, but was somewhat too large and too fast to be an ARM candidate (15m diameter and 5 km/s velocity). The development of the NEA pipeline and the discovery results are discussed in an extensive paper being submitted to the Proceedings of the Astronomical Society of the Pacific (Waszczak et al., in preparation, PASP).
Many of the discovery results as well as the daily operation of the pipeline can be viewed at the website: http://ptf.caltech.edu/marshals/asteroids/
The NEA pipeline will be transferred to the recently funded Zwicky Transient Facility (ZTF), a 47 square degree imager on the 1.2 meter Schmidt telescope at Palomar that will start taking data in 2017. When it becomes operational, it will be the most capable instrument anywhere for small NEA discovery.
This task also led directly to a Caltech/JPL President’s and Director’s Fund project for discovery of small NEAs with ZTF having total funding of $597,540, thus significantly leveraging the W.M. Keck Institute investment in this science and technology area.
1 IAC-14.A5.3-B3.6.7, x26388: John R. Brophy, Jet Propulsion Laboratory, Caltech; Louis Friedman, Executive Director Emeritus, The Planetary Society; Nathan J. Strange, Jet Propulsion Laboratory, Caltech; Thomas A. Prince, Director, Keck Institute for Space Studies, Caltech; Damon Landau, Jet Propulsion Laboratory, Caltech; Thomas Jones, Florida Institute for Human and Machine Cognition; Russell Schweickart, B612 Foundation; Chris Lewicki, Planetary Resources, Inc.; Martin Elvis, Harvard-Smithsonian Center for Astrophysics; David Manzella, NASA Glenn Research Center, USA.