| タイトル | Special Semaphore Scheme for UHF Spacecraft Communications |
| 本文（外部サイト） | http://hdl.handle.net/2060/20110013622 |
| 著者（英） | Satorius, Edgar; Butman, Stanley; Ilott, Peter |
| 著者所属（英） | California Inst. of Tech. |
| 発行日 | 2006-12-01 |
| 言語 | eng |
| 内容記述 | A semaphore scheme has been devised to satisfy a requirement to enable ultrahigh- frequency (UHF) radio communication between a spacecraft descending from orbit to a landing on Mars and a spacecraft, in orbit about Mars, that relays communications between Earth and the lander spacecraft. There are also two subsidiary requirements: (1) to use UHF transceivers, built and qualified for operation aboard the spacecraft that operate with residual-carrier binary phase-shift-keying (BPSK) modulation at a selectable data rate of 8, 32, 128, or 256 kb/s; and (2) to enable low-rate signaling even when received signals become so weak as to prevent communication at the minimum BPSK rate of 8 kHz. The scheme involves exploitation of Manchester encoding, which is used in conjunction with residual-carrier modulation to aid the carrier-tracking loop. By choosing various sequences of 1s, 0s, or 1s alternating with 0s to be fed to the residual-carrier modulator, one would cause the modulator to generate sidebands at a fundamental frequency of 4 or 8 kHz and harmonics thereof. These sidebands would constitute the desired semaphores. In reception, the semaphores would be detected by a software demodulator. |
| NASA分類 | Man/System Technology and Life Support |
| レポートNO | NPO-42910 |
| 権利 | Copyright, Distribution as joint owner in the copyright |
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