We investigate how a weak coronal mass ejection (CME) launched on 2016 October 8 without obvious signatures in the low corona produced a relatively intense geomagnetic storm. Remote sensing observations from SDO, STEREO and SOHO and in situ measurements from Wind are employed to track the CME from the Sun to the Earth.Using a graduated cylindrical shell (GCS) model, we estimate the propagation direction and the morphology of the CME near the Sun. CME kinematics are determined from the wide-angle imaging observations of STEREO A and are used to predict the CME arrival time and speed at the Earth. We compare ENLIL MHD simulation results with in situ measurements to illustrate the background solar wind where the CME was propagating. We also apply a Grad-Shafranov technique to reconstruct the flux rope structure from in situ measurements in order to understand the geo-effectiveness associated with the CME magnetic field structure. Key results are obtained concerning

We analyze multi-spacecraft observations associated with the 2012 July 12 Coronal Mass Ejection (CME), covering the source region on the Sun from SDO, stereoscopic imaging observations from STEREO, magnetic field characteristics at MESSENGER, and type II radio burst and in situ measurements from Wind. A triangulation method based on STEREO stereoscopic observations is employed to determine the kinematics of the CME, and the outcome is compared with the result derived from the type II radio burst with a solar wind electron density model. A Grad-Shafranov technique is applied to Wind in situ data to reconstruct the flux-rope structure and compare it with the observation of the solar source region, which helps understand the geo-effectiveness associated with the CME structure. Conclusions are as follows: (1) the CME undergoes an impulsive acceleration, a rapid deceleration before reaching MESSENGER, and then a gradual deceleration out to 1 AU, which should be noticed in CME kinematics models; (2) the type II radio burst was probably produced from a high-density interaction region between the CME-driven shock and a nearby streamer or from the shock flank with lower heights, which implies uncertainties in the determination of CME kinematics using solely type II radio bursts; (3) the flux-rope orientation and chirality deduced from in situ reconstruction at Wind agree with those obtained from solar source observations; (4) the prolonged southward magnetic field near the Earth is mainly from the axial component of the largely southward inclined flux rope, which indicates the importance of predicting both the flux-rope orientation and magnetic field components in geomagnetic activity forecasting.