def generate(self):
        """Returns (ts, rvs), where ts is a list of arrays of
        observation times (one array for each observatory), and rvs is
        a corresponding list of total radial velocity measurements."""

        ts=self.generate_tobs()
        noise=self.generate_noise(ts)
        
        rvs=[]
        for t,n in zip(ts, noise):
            rvs.append(n + np.sum(rv.rv_model(t, self.params), axis=0))

        return ts,rvs