3.2.2.4 Telemetry Modulation. The telemetry comes to the telemetry modulation unit (TMU) separately as a “low-rate” channel and a “high-rate” channel. Low rate is 40 bps only and its routing through the TMU is such that it can only be downlinked as uncoded bits. High rate, one of a set of rates between 10 bps and 115.2 kilobits per second (kbps), is downlinked as coded symbols. The TMU encodes the high-rate data stream with a convolutional code having constraint length of 7 and a symbol rate equal to twice the bit rate (k = 7, r = 1/2). Either modulator can biphase-modulate the telemetry symbols onto either a 22.5-kilohertz (kHz) or a 360-kHz subcarrier. A subcarrier is a symmetrical square wave signal derived from a TMU crystal oscillator that has a nominal frequency of 2.88 MHz. The 360-kHz subcarrier is required for bit rates greater than 7.2 kbps. The TMU has one modulator for the S-band downlink and another for X-band downlink. The modulated subcarrier goes to the S- or X-band exciter.
So, the same as original Canopy. From: Chuck McCown via AF Sent: Wednesday, August 31, 2022 11:13 AM To: [email protected] ; 'AnimalFarm Microwave Users Group' Cc: Chuck McCown Subject: Re: [AFMUG] OT Voyager I was taught, many years ago, that minority (might have been majority) charge carrier migration in semiconductors would render them useless in 20 years. Also solar panels are supposed to wear out in 20 years. And cosmic rays kill all semiconductors. etc etc Danged good modulation they are using whatever it is. I think it was some kind of pseudo random noise code but I may be wrong about that. A professor in an analog class told me that almost 40 years ago. From: [email protected] Sent: Wednesday, August 31, 2022 11:08 AM To: 'AnimalFarm Microwave Users Group' Cc: 'Chuck McCown' Subject: RE: [AFMUG] OT Voyager I’d bet a smaller codebase helps. No gigabytes of libraries to debug. But yeah, if something I built lasted 45 years in outer space I’d pat myself on the back a bit. From: AF <[email protected]> On Behalf Of Chuck McCown via AF Sent: Wednesday, August 31, 2022 11:50 AM To: [email protected] Cc: Chuck McCown <[email protected]> Subject: [AFMUG] OT Voyager This space vehicle launched 45 years ago started sending garbage telemetry. The folks running that show figured it was routing the data through a known defective computer. So they commanded it to switch to the good computer and they got good telemetry. Talk about latency... 16 hours. So 45 (more likely 55) year old hardware running an OS that old is still essentially rocks solid. So are the transmitters and receivers and other RF components allowing communication clear out into deep space. Damn, those engineers and coders must be proud of the job they did. -------------------------------------------------------------------------------- -- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com
-- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com
