We use statistical learning methods to construct an adaptive state estimator for nonlinear stochastic systems. Optimal state estimation, in the form of a Kalman filter, requires knowledge of the systems process and measurement uncertainty. We propose
that these uncertainties can be estimated from (conditioned on) past observed data, and without making any assumptions of the systems prior distribution. The systems prior distribution at each time step is constructed from an ensemble of least-squares estimates on sub-sampled sets of the data via jackknife sampling. As new data is acquired, the state estimates, process uncertainty, and measurement uncertainty are updated accordingly, as described in this manuscript.
We observed the near-Earth asteroid 2008 EV5 with the Arecibo and Goldstone planetary radars and the Very Long Baseline Array during December 2008. EV5 rotates retrograde and its overall shape is a 400 /pm 50 m oblate spheroid. The most prominent sur
face feature is a ridge parallel to the asteroids equator that is broken by a concavity 150 m in diameter. Otherwise the asteroids surface is notably smooth on decameter scales. EV5s radar and optical albedos are consistent with either rocky or stony-iron composition. The equatorial ridge is similar to structure seen on the rubble-pile near-Earth asteroid (66391) 1999 KW4 and is consistent with YORP spin-up reconfiguring the asteroid in the past. We interpret the concavity as an impact crater. Shaking during the impact and later regolith redistribution may have erased smaller features, explaining the general lack of decameter-scale surface structure.
Much work in SETI has focused on detecting radio broadcasts due to extraterrestrial intelligence, but there have been limited efforts to transmit messages over interstellar distances. As a check if such messages can be interpreted once received, we c
onducted a blind test. One of us coded a 75-kilobit message, which the other then attempted to decipher. The decryption was accurate, supporting the message design as a general structure for communicating with aliens capable of detecting narrow-band radio transmissions.
