Table mountain observatory support to other programs

The Table Mountain Observatory (TMO) facilities include well equipped 24 inch and 16 inch telescopes with a 40 inch telescope (owned by Pomona College) due for completion during FY 89. This proposal is to provide operational support (equipment maintenance, setup, and observing assistnce) at TMO to other programs. The program currently most heavily supported by this grant is the asteroid photometry program directed by A. W. Harris. During 1987, about 20 asteroids were observed, including a near-earth asteroid, 1951 Midas. The photometric observations are used to derive rotation periods, estimate shapes and pole orientations, and to define the phase relations of asteroids. The E class asteroid 64 Angelina was observed, and showed the same opposition spike observed of 44 Jysa, last year. Comet observations are made with the narrow band camera system of David Rees, University College London. Observational support and training was provided to students and faculty from Claremont Colleges for variable star observing programs. Researchers propose to continue the asteroid program, with emphasis on measuring phase relations of low and high albedo asteroids at very low phase angles, and supporting collaborative studies of asteroid shapes

Near Earth asteroid orbit perturbation and fragmentation

Collisions by near earth asteroids or the nuclei of comets pose varying levels of threat to man. A relatively small object, approximately 100 meter diameter, which might be found on an impact trajectory with a populated region of the Earth, could potentially be diverted from an Earth impacting trajectory by mass driver rocket systems. For larger bodies, such systems would appear to be beyond current technology. For any size object, nuclear explosions appear to be more efficient, using either the prompt blow-off from neutron radiation, the impulse from ejecta of near-surface explosion for deflection, or as a fragmenting charge. Practical deflections of bodies with diameters of 0.1, 1, and 10 km require interception, years to decades prior to earth encounter, with explosions a few kilotons, megatons, or gigatons, respectively, of equivalent TNT energy to achieve orbital velocity changes or destruction to a level where fragments are dispersed to harmless spatial densities

The 2060 Chiron: CCD photometry

R-band CCD photometry of 2060 was carried out on nine nights in Nov. and Dec. 1986. The rotation period is 5.9181 + or - 0.0003 hr and the peak to peak lightcurve amplitude is 0.088 + or - 0.0003 mag. Photometric parameters are H sub R = 6.24 + or - 0.02 mag and G sub R = + or - 0.15, though formal errors may not be realistic. The lightcurve has two pairs of extrema, but its asymmetry, as evidenced by the presence of significant odd Fourier harmonics, suggests macroscopic surface irregularities and/or the presence of some large scale albedo variegation. The observational rms residual is + or - 0.015 mag. On time scales from minutes to days there is no evidence for nonperiodic (cometary) brightness changes at the level of a few millimagnitudes

Asteroid photometry

Photoelectric light curves provide fundamental information about asteroids: rotation periods, pole orientations, shapes, and phase relations, which yield some information about the surface physical properties. This task is to carry on a program of such observations to increase the overall data base, obtain data on newly discovered asteroids, and to observe asteroids which are the subject of other complementary observations, such as occultations, radar, and infrared

Metallic Asteroids in the IRAS Minor Planet Survey - a NEOShield Study

Studies of the compositions of asteroids, especially their metal content, are relevant not only to investigations of their nature, but also to estimations of their potential to wreak devastation on impacting the Earth. In this respect it is informative to compare the airburst of a stony object, such as the Tunguska event, which destroyed a forest but left no crater, with the impact of a similarly sized metallic object, which produced the 1.2 km diameter Barringer Crater in Arizona. In view of the evident link between metal content and the near-Earth asteroid thermal model (NEATM; Harris 1998) fitting parameter, eta, which carries information on thermal inertia (Harris and Drube, 2014; see abstract submitted to this conference), we are carrying out a re-analysis of Infrared Astronomical Satellite (IRAS) data (Tedesco et al., 2002) with NEATM to further explore the dependence of eta and thermal inertia on metal content. In addition to calculating best-fit values of eta, we are calculating the angle between the spin vector and the solar direction, theta, for all IRAS sightings of each asteroid for which a spin vector is available. The eta values of objects with high thermal inertia and moderate to high spin rates should depend strongly on theta, whereas those with low thermal inertia and/or low spin rates should not. By studying the relationships between theta and eta, we aim to further explore the potential of the results of Harris and Drube (2014) and provide insight into relationships between asteroid thermal properties, taxonomic type, albedo, spin rate, etc. We will present the first results of our work and provide a demonstration of its potential. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 282703 (NEOShield Project). Harris, A. W., 1998, Icarus, 131, 291. Harris, A. W. and Drube, L, 2014, Ap. J. Letters, 785, L4 Tedesco, E. F. et al, 2002, Astron. J., 123, 1056

The Neoshield project for Near-Earth object impact threat mitigation

Every day Earth is hit by around 100 tonnes of cosmic material, most of it comes in the form of dust or small rocks, which burn up as meteors in the atmosphere. Sometimes, however, larger objects, asteroids or comets, enter the Earth’s atmosphere and then even relatively small objects can cause considerable damage. The object that exploded over the Russian city of Chelyabinsk in February 2013 had a diameter of only 17–20 m, yet it produced a blast wave that damaged buildings and injured some 1500 people. It entered the Earth’s atmosphere with a velocity of 65 000 km/h and, due to the frictional heating and stresses caused by compression of the air, it exploded at an altitude of some 25 km releasing an energy 30 times that of the Hiroshima bomb. The potentially devastating effects on Earth of a collision with a large asteroid or comet are now well recognized by scientists and policy makers. So the question is now, can we protect our civilization from the next major impact? NEOShield, a project funded by the European Commission’ Seventh Framework Programme, brought together an international team of 13 partner organizations from 6 countries to address the global issue of near-­‐Earth object (NEO) impact prevention. The project ran from 2012 to mid 2015, after which the NEOShield-­‐2 project funded by the European Commission’ H2020 Programme is continuing the research until fall 2017. The purpose of the projects is to carry out detailed analysis of realistic options for preventing a potentially catastrophic impact of a NEO on Earth. While a mitigation test mission is beyond the financial scope of the current project, the NEOShield technical partners, with the support of the science team, aim to provide detailed designs of appropriate test-­‐missions for the 3 most feasible mitigation concepts: kinetic impactor, gravity tractor, and blast deflection, so that it will be possible to quickly develop an actual test mission at a later stage. Project partners are also carrying out research into the mitigation-­‐relevant physical properties of NEOs, including observations of near-­‐Earth asteroids, analysis of available observational data, laboratory experiments on asteroid analogue materials, and modelling and computer simulations. The aim of the scientific work is to facilitate predictions of the outcome of deflection attempts using different techniques on a variety of NEO types

Asteroid Thermal Inertia Estimates from Remote Infrared Observations: The Effects of Surface Roughness and Rotation Rate

The thermal inertia of an asteroid's surface can provide insight into regolith properties, such as the presence of a layer of fine dust, the density and thermal conductivity of a rocky surface, and, together with other observational data, mineralogy. Knowledge of the surface characteristics of asteroids is important for planetary defense initiatives and the extraction of resources ("asteroid mining"). A simple means of estimating asteroid thermal inertia has been proposed by Harris & Drube, which is suitable for application to large sets of thermal-infrared observational data, such as those obtained by infrared space telescopes. We compare results from the Harris-Drube estimator with recently published values of asteroid thermal inertia from detailed thermophysical modeling, and provide an explanation in terms of reduced surface roughness for some discrepant results. Smooth surfaces covered in fine dust may provide an explanation for the unexpectedly low values of thermal inertia derived from thermophysical modeling for some slowly rotating main-belt asteroids (MBAs). In the case of near-Earth objects (NEOs) we show that results from the estimator are in good agreement with those from thermophysical modeling, with just a few exceptions. We discuss the special cases of the NEOs (101955) Bennu, (162173) Ryugu, and (29075) 1950 DA in the context of results from our estimator. Given the data requirements and complexity of thermophysical modeling, data-analysis tools based on relatively simple concepts can play an important role in allowing "quick-look" assessment of thermal-infrared data of asteroids, especially NEOs.Comment: 24 pages, 9 figures, Accepted Manuscript, Ap

LSST: Comprehensive NEO Detection, Characterization, and Orbits

(Abridged) The Large Synoptic Survey Telescope (LSST) is currently by far the most ambitious proposed ground-based optical survey. Solar System mapping is one of the four key scientific design drivers, with emphasis on efficient Near-Earth Object (NEO) and Potentially Hazardous Asteroid (PHA) detection, orbit determination, and characterization. In a continuous observing campaign of pairs of 15 second exposures of its 3,200 megapixel camera, LSST will cover the entire available sky every three nights in two photometric bands to a depth of V=25 per visit (two exposures), with exquisitely accurate astrometry and photometry. Over the proposed survey lifetime of 10 years, each sky location would be visited about 1000 times. The baseline design satisfies strong constraints on the cadence of observations mandated by PHAs such as closely spaced pairs of observations to link different detections and short exposures to avoid trailing losses. Equally important, due to frequent repeat visits LSST will effectively provide its own follow-up to derive orbits for detected moving objects. Detailed modeling of LSST operations, incorporating real historical weather and seeing data from LSST site at Cerro Pachon, shows that LSST using its baseline design cadence could find 90% of the PHAs with diameters larger than 250 m, and 75% of those greater than 140 m within ten years. However, by optimizing sky coverage, the ongoing simulations suggest that the LSST system, with its first light in 2013, can reach the Congressional mandate of cataloging 90% of PHAs larger than 140m by 2020.Comment: 10 pages, color figures, presented at IAU Symposium 23