Asteroid (99942) Apophis: new predictions of Earth encounters for this potentially hazardous asteroid

Abstract

Context. The potentially hazardous asteroid (99942) Apophis, previously designated 2004 MN 4 , is emblematic of the study of asteroids that could impact the Earth in the near future. Orbit monitoring and error propagation analysis are mandatory to predict the probability of an impact and, furthermore, its possible mitigation. Several aspects for this prediction have to be investigated, in particular the orbit adjustment and prediction updates when new astrometric data are available. Aims. We analyze Apophis orbit and provide impact predictions based on new observational data, including several orbit propagations. Methods. New astrometric data of Apophis have been acquired at the Pic du Midi one-meter telescope (T1m) during March 2011. Indeed, this asteroid was again visible from ground-based stations after a period of several years of unfavorable conjunction with the Sun. We present here the original astrometric data and reduction, and the new orbit obtained from the adjustment to all data available at Minor Planet Center (until March 2011).Results. We present a new sketch of keyholes and impacts for the next century. Additionally, we discuss observational errors, astrometric reduction, orbit adjustment, and adequacy of the dynamical model used.

Statistical and numerical study of asteroid orbital uncertainty

“…More often than not, the uncertainty region is a 3σ ellipse centred on the nominal solution and its size is directly linked to the observations used. Therefore, the position of the keyhole compared with the size of the ellipse uncertainty is also important for quantifying the risk of future collision (Chesley 2006;Kochetova et al 2009;Bancelin et al 2012a). …”

The astrometricGaia-FUN-SSO observation campaign of 99942 Apophis

“…Fortunately, a collision between Apophis and the Earth can be ruled out for the foreseeable future (Bancelin et al 2012a;Farnocchia et al 2013). However, Apophis' trajectory remains difficult to predict because of a deep close encounter with the Earth in 2029.…”

“…Chesley (2006) and Giorgini et al (2008) pointed out the importance of past and future radar observations for reducing the uncertainties in Apophis' orbit and drift parameters. Bancelin et al (2012a) and Farnocchia et al (2013) also studied the impact of astrometric measurements in this respect. Their results indicate that high quality astrometric data can make a substantial contribution to improving NEA impact predictions by reducing orbit uncertainties even when radar observations are available.…”

Post mitigation impact risk analysis for asteroid deflection demonstration missions

“…One option is to study projections of the uncertainties of the nominal orbit onto close encounter target planes (bplanes), which are a 2D analog of the impact parameter commonly used in two body scattering processes (e.g. Milani et al, 2002;Bancelin et al, 2012). The uncertainty hyper-volume defined by the orbital element covariance matrix is propagated to a later close approach by solving a set of (linearized) variational equations together with the equations of motion for the nominal orbit.…”