tokens: Saturn's bow shock one of the strongest in the Solar System (e.g., Russell 1985 ), and such occasions occur under rare solar wind conditions where the near-Saturn Interplanetary (solar) Magnetic Field (IMF) strength drops to ∼0.1 nT and the shock Alfvén Mach number increases to order 100. On such occasions Cassini has witnessed electron acceleration at a quasi-parallel shock crossing (Masters et al. 2013 ), and provided evidence for shock reformation controlled by specular ion reflection (Sulaiman et al. 2015 ). The electron acceleration result indicates that there may not be an electron injection problem at high Mach number quasi-parallel collisionless shocks, in agreement with some theories (e.g., Amano Hoshino 2010 ). Here we reveal the full picture of suprathermal electrons at Saturn's bow shock revealed by Cassini . We show that the sum of all Cassini electron observations made during hundreds of shock crossings is consistent with electron acceleration theory that involves interactions with whistler waves excited by the reflected thermal electrons just upstream of the shock. The implication for the strong shocks surrounding young SNRs is that they may be able to inject thermal electrons into an acceleration process under any upstream magnetic field orientation. 2. SURVEY OF SUPRATHERMAL ELECTRON SIGNATURES AT SATURN'S BOW SHOCK The Cassini spacecraft has been in Saturn orbit since 2004 July. During the orbital tour the spacecraft has crossed Saturn's bow shock hundreds of times. The location of the shock is highly variable, and the boundary moves at speeds much greater than that of the spacecraft (Achilleos et al. 2006 ). As a result, multiple shock crossings are typically made on an inbound/outbound pass of any orbit where the spacecraft enters the region of space defined by the range of possible shock locations. Two of the sensors carried by instruments mounted on the three-axis stabilized spacecraft are particularly relevant for a survey of electron acceleration at Saturn's bow shock. The first is the Electron Spectrometer (ELS) of the Cassini Plasma Spectrometer (CAPS), which detects electrons in the (lower) energy range 0.5 eV to 26 keV (Young et al. 2004 ). The second is the Low Energy Magnetospheric Measurements System (LEMMS) of the Magnetospheric Imaging Instrument, which detects electrons in the (higher) energy range 18 keV to ∼1 MeV (Krimigis et al. 2004 ). Both ELS and LEMMS have a limited field of view (FOV). In addition, measurements of the local magnetic field vector made by the fluxgate magnetometer of the Cassini dual-technique magnetometer (MAG; Dougherty et al. 2004 ) provide an essential diagnostic of shock structure. This study is motivated by recently reported observations made by Cassini at a single (quasi-parallel) shock crossing, where suprathermal electrons were detected (Masters et al. 2013 ). The high-energy electron signature of this event is most pronounced in data taken by the more sensitive LEMMS
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