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In this paper we present an analysis of Kepler K2 mission Campaign 3observations of the irregular Neptune satellite, Nereid. We determined arotation period of P=11.594(+/-)0.017 h and amplitude of dm=0.0328(+/-)00018,confirming previous short rotation periods obtained in ground basedobservations. The similarities of light curve amplitudes between 2001 and 2015show that Nereid is in a low-amplitude rotation state nowadays and it couldhave been in a high-amplitude rotation state in the mid 1960's. Anotherhigh-amplitude period is expected in about 30 years. Based on the light curveamplitudes observed in the last 15 years we could constrain the shape of Nereidand obtained a maximum a:c axis ratio of 1.3:1. This excludes the previouslysuggested very elongated shape of a:c=1.9:1 and clearly shows that Nereid'sspin axis cannot be in forced precession due to tidal forces. Thermal emissiondata from the Spitzer Space Telescope and the Herschel Space Observatoryindicate that Nereid's shape is actually close to the a:c axis ratio limit of1.3:1 we obtained, and it has a very rough, highly cratered surface

Nereid from space: Rotation, size and shape analysis from Kepler/K2, Herschel and Spitzer observations