# # Program information file # PROGRAM_ID 2021A021 PROGRAM_TITLE Spectral Portrait of Apophis: Groundwork for the 2029 Earth Flyby PROGRAM_INV1 David Polishook PROGRAM_INV2 Michael Marsset PROGRAM_INV3 Francesca DeMeo PROGRAM_INV4 Richard Binzel PROGRAM_INV5 PROGRAM_SCICAT solar system PROGRAM_ABSTRACT_BEG The April 2029 near-Earth encounter by the asteroid Apophis is a once-in-a-lifetime event where a relatively large asteroid, will approach Earth to within a distance of ~31K km. Estimates are that a 300m asteroid approaches this close about once-per-thousand years. The scientific and physical significance of Apophis' 2029 approach is that Earth's tidal forces will modify Apophis' spin state, and possibly its shape, and creating the potential for generating seismic waves in its interior. This makes the Apophis' 2029 flyby a unique opportunity to study surface altering effects on asteroids, and if instrumented, the first direct measures of an asteroid's interior. Apophis has a 'weathered' surface [Sq-type spectrum], that may reveal its true 'fresh' character [Q-type spectrum] due to quakes imposed by Earth's tidal forces. Therefore, since surface 'refreshing' due to encounter could cause global spectral changes or local spectral changes, any current, pre-flyby variability is extremely important to establish with precision Apophis pre-encounter spectral characteristics. Early 2021 presents the only opportunity to closely scrutinize Apophis ahead of the 2029 flyby. For 2021, Apophis will be at a distance of 0.11 AU and Vmag of 15.4. Our main goal is to form a baseline reference from which any future pre- or post-flyby studies can relate to. In order to do so we aim to conduct a full spectrally rotational coverage of Apophis surface along ~30.5 h [4 h each run during 7 nights]. In order to reduce systematic errors for an accurate spectral homogeneity/heterogeneity analysis, we need to correct the measured spectral slope by the observed phase angle. In order to do so we wish to spectrally sample Apophis at multiple phase angles [~6 times, for 1.5 h each run, about once per 10 degrees of phase angle]. PROGRAM_ABSTRACT_END