Engineering topics
Townes, S. A.
Publications and source records attributed to Townes, S. A..
Operational demonstration of Ka-band telecommunications for the Mars Reconnaissance Orbiter
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Operational Demonstration of Ka-Band Telecommunications for the Mars Reconnaissance Orbiter
The objectives of the operational demonstration are to verify that the anticipated benefits of the higher carrier frequency can actually be realized under realistic operating conditions, and if possible to provide a significant enhancement to scientific data return.
Long-haul performance tradeoffs
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Performance trades for long-haul communication in deep space
A study was undertaken as part of the NASA BEACON architecture project, in order to find the most cost-effective methods for satisfying the anticipated demand. This paper serves to report preliminary conclusions from the study, which were obtained using simplified conditions sufficient to narrow down the field of competing options. Additional work will be required to obtain realistic treatments for actual selection among alternatives.
Performance trades for long-haul communication in Deep Space
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Near-toll quality digital speech transmission in the mobile satellite service
This paper discusses system considerations for near-toll quality digital speech transmission in a 5 kHz mobile satellite system channel. Tradeoffs are shown for power performance versus delay for a 4800 bps speech compression system in conjunction with a 16 state rate 2/3 trellis coded 8PSK modulation system. The suggested system has an additional 150 ms of delay beyond the propagation delay and requires an E(b)/N(0) of about 7 dB for a Ricean channel assumption with line-of-sight to diffuse component ratio of 10 assuming ideal synchronization. An additional loss of 2 to 3 dB is expected for synchronization in fading environment.
4800 B/S speech compression techniques for mobile satellite systems
This paper will discuss three 4800 bps digital speech compression techniques currently being investigated for application in the mobile satellite service. These three techniques, vector adaptive predictive coding, vector excitation coding, and the self excited vocoder, are the most promising among a number of techniques being developed to possibly provide near-toll-quality speech compression while still keeping the bit-rate low enough for a power and bandwidth limited satellite service.
Permutation codes for the Laplacian source
Permutation codes for the Laplacian source are developed. The performance of these codes is evaluated and compared with other quantizers and the rate-distortion function. It is shown that there is a bit-rate region in which the permutation codes outperform certain single-sample quantizers.
A study of the charged particle calibration requirements for the Deep Space Network
A study made of the Deep Space Network charged particle calibration requirements is discussed. The effects of charged particles on navigation and timing systems were reviewed and it was proposed that a system based upon the Global Positioning System satellites be used to measure the charged particle content of the ionosphere. The system would be required to measure the total electron content of the ionosphere to the order of 10 to the 16th power electron per square meter. Two types of systems were suggested as possible candidates for making these measurements.