Ryan Mukai

Adaptive acquisition and tracking for deep space array feed antennas

The use of radial basis function (RBF) networks and least squares algorithms for acquisition and fine tracking of NASAs 70-m-deep space network antennas is described and evaluated. We demonstrate that such a network, trained using the computationally efficient orthogonal least squares algorithm and working in conjunction with an array feed compensation system, can point a 70-m-deep space antenna with root mean square (rms) errors of 0.1-0.5 millidegrees (mdeg) under a wide range of signal-to-noise ratios and antenna elevations. This pointing accuracy is significantly better than the 0.8 mdeg benchmark for communications at Ka-band frequencies (32 GHz). Continuous adaptation strategies for the RBF network were also implemented to compensate for antenna aging, thermal gradients, and other factors leading to time-varying changes in the antenna structure, resulting in dramatic improvements in system performance. The systems described here are currently in testing phases at NASAs Goldstone Deep Space Network (DSN) and were evaluated using Ka-band telemetry from the Cassini spacecraft.

Direct-to-Earth communications with Mars Science Laboratory during Entry, Descent, and Landing

Mars Science Laboratory (MSL) undergoes extreme heating and acceleration during Entry, Descent, and Landing (EDL) on Mars. Unknown dynamics lead to large Doppler shifts, making communication challenging. During EDL, a special form of Multiple Frequency Shift Keying (MFSK) communication is used for Direct-To-Earth (DTE) communication. The X-band signal is received by the Deep Space Network (DSN) at the Canberra Deep Space Communication complex, then down-converted, digitized, and recorded by open-loop Radio Science Receivers (RSR), and decoded in real-time by the EDL Data Analysis (EDA) System. The EDA uses lock states with configurable Fast Fourier Transforms to acquire and track the signal. RSR configuration and channel allocation is shown. Testing prior to EDL is discussed including software simulations, test bed runs with MSL flight hardware, and the in-flight end-to-end test. EDA configuration parameters and signal dynamics during pre-entry, entry, and parachute deployment are analyzed. RSR and EDA performance during MSL EDL is evaluated, including performance using a single 70-meter DSN antenna and an array of two 34-meter DSN antennas as a back up to the 70-meter antenna.

An array feed radial basis function tracking system for NASA's deep space network antennas

The use of radial basis function networks for fine pointing NASAs 70-meter deep space network antennas is described and evaluated. We demonstrate that such a network, working in conjunction with the array feed compensation system, and trained using the computationally efficient orthogonal least-squares algorithm, can point a 70-meter deep space antenna with RMS errors of less than 0.3 millidegree under good signal-to-noise ratio conditions, achieving significantly higher accuracies than the 0.8 millidegree benchmark for communications at Ka-band frequencies of 32 GHz.

An adaptive threshold detector and channel parameter estimator for deep space optical communications

A method for optimal adaptive setting of pulse-position-modulation pulse detection thresholds, which minimizes the total probability of error for the dynamically fading optical free space channel, is presented. The thresholds adaptive setting, in response to varying channel conditions, results in orders of magnitude improvement in probability of error, as compared to use of a fixed threshold. The adaptive threshold system itself is based on a robust channel identification system that uses average signal strengths to estimate the degree of fade and total attenuation in the channel, and a radial basis function network for estimating pulse spreads, all with excellent accuracy.

Strategic analysis for the MER Cape Verde approach

The Mars Exploration Rover Opportunity has recently completed a two year campaign studying Victoria Crater. The campaign culminated in a close approach of Cape Verde in order to acquire high resolution imagery of the exposed stratigraphy in the cliff face. The close approach to Cape Verde provided significant challenges for every subsystem of the rover as the rover needed to traverse difficult, uncharacterised terrain and approach a cliff face with the potential of blocking out solar energy and communications with Earth. In this paper we describe the strategic analyses performed by the science and engineering teams so that we could successfully achieve the science objectives while keeping the rover safe.

Reconfigurable protocol sensing for space-based applications

In this paper, we present sensing performance using an architecture for a reconfigurable protocol chip for space-based applications . We examine three common framing standards and present the sensing performance of these standards and their decorrelation statistics. We also examine the impact over lossy links. Finally, we describe a process flow for development of this sensor mechanism