David H. Rogstad

Enhancing telemetry and navigation performance with full spectrum arraying

A new arraying capability is to be introduced into the NASA Deep Space Network (DSN). It is a second-generation system employing the full spectrum combining technique first deployed to support the Galileo mission in 1996. The new arraying capability offers multimission support with real-time combining at higher data rates. In addition, for the first time in DSN history, it is also possible to array ranging signals to enhance navigation performance. With the enhanced signal-to-noise ratio (SNR) obtained from an effectively larger aperture, arraying enables support for missions whose signal level falls below the tracking threshold of a single antenna. Alternatively, it can also be used to increase the data return over that possible with a single antenna. In the extreme, the array deployment of four 34-meter antennas at Goldstone can substitute for the 70-meter antenna, the largest one in the network.

Spacecraft-to-earth communications for Juno and Mars Science Laboratory critical events

This paper describes the Entry, Descent, and Landing (EDL) Data Analysis system (EDA). The EDA software supports the real-time interpretation of Multiple Frequency-Shift Keying (MFSK) tones provided by the spacecraft. The objective of this software is to provide communication of status between the spacecraft and the mission personnel on Earth during critical events when low rate telemetry is not possible due to high dynamics and low signal-to-noise ratio (SNR). Although these communications cannot be used to affect the landing due to the length of time required at these distances, this information is important in the case of a mission failure. Mars Science Laboratory will utilize the EDA software during EDL. Juno usage will include Jupiter orbital insertion (JOI), with predicted SNR of 12-15 dB-Hz. Results are presented from the Juno tones test. Simulated signals were also generated for Juno at JOI and Mars Science Laboratory (MSL) EDL and these results are analyzed.

Design and implementation of a Deep Space Communications Complex downlink array

This paper describes the design and implementation of an array system that includes a frequency domain beamformer that will coherently combine the downlinked signals from up to eight inputs at each of NASAs three Deep Space Communications Complexes (DSCC). The array signal processor digitizes inputs with an intermediate frequency (IF) bandwidth of 100 to 600 MHz, coherently combines the inputs digitally, and transforms the combined waveform back to analog. Real-time correlation measurements are used for delay and phase calibration, allowing the system to adjust for atmospheric variations. A Downlink Array system is operational at each DSCC. Initial results from passes with the New Horizons spacecraft are presented and system performance is analyzed.