oops voyager

I have nothing but admiration for the project, and the people involved in it [which may, for all I know, include Peter Greene] … But what concerns me is that Peter and I have such different interpretations of two simple words which appeared to be quite explicit.

My actual knowledge of the term ‘periodic reset’ in NASA-speak is minuscule, but I presumed to understand the meaning; based on the News Reports, and on my ‘Plain English’ interpretation of the phrase.

Peter’s interpretation differs greatly .

MichaelG.

NASA does love to entangle the language, but I must admit "periodic reset" suggests a normal, regular adjustment to correct any drift.

Whatever actually needs doing, the whole thing is a superb achievement.

Just a guess about 'periodic reset' but there are two ways the antenna could be aligned.

One is by calculating the X,Y,Z angle the antenna has to be pointed to target planet earth. This requires knowing where the satellite is and its attitude. Both can be obtained from the telemetry. The calculation is probably too much work for Voyager's tiny computer, so better done back on earth. Having done the sums, the ground station sends a command to move the antenna. All that's needed is to send the right value, and minimum power is consumed making the adjustment by the antenna motors. (Voyager's battery is tiny too.)

Given Voyager's age I bet the command was sent manually, and someone fluffed. They will never hear the end of it!

The second method is for the satellite to adjust the antenna for maximum signal. At an agreed time, normal operation stops and the satellite listens continually for a powerful 'here I am' signal sent from earth. If nothing is heard, the antenna manoeuvres until the signal is received, and then the satellite fine adjusts for a maximum.

Not hearing earth during a 'periodic reset' probably causes the satellite to keep searching until it picks something up. Having to scan the antenna probably thrashes the battery, which might go flat before normal service is resumed.

Dave

For a more-modern than Voyager description of the term … see the second paragraph on the page numbered 80 [page 90 of the PDF] in this: **LINK**

https://aerospace.org/sites/default/files/maiw/TOR-2009(8591)-14.pdf

MichaelG.

Crisis over, apparently full contact has been restored.

Probably better to follow this than rely upon ‘the media’: **LINK**

https://www.nasa.gov/feature/jpl/nasa-mission-update-voyager-2-communications-pause

MichaelG.

I don't know about Voyager in particular but spacecraft typically have multiple failsafes and backups; one example of which would be that if it doesn't receive any commands for a period of time then an automatic reset is triggered to the last known good configuration to guard against this kind of operator error.

As has been rightly pointed out this does depend on the craft having sufficient power and control to recover, but the operations teams I've encountered are highly skilled at working out what a partially defunct and beyond end of life machine is capable of - similar to some here I suspect!

See also the ISEE-3 reboot project, where a team reconstructed obsolete communications hardware and re-established contact with a mission that had ended some 15 years earlier.

The ET phone home subroutine kicked in and saved them

I'm truly amazed by this project. Launched in 1977,46 years ago, and it still works. 18.5 light hours (if there is such a unit) away from us, that's 1/2000 of the distance to the nearest star which brings home how unlikely it is that we will ever actually meet an alien civilisation.

I was wondering about the technology that is in Voyager. Launched in '77, it looks to me as if the latest microprocessor around would have been the Intel 8080 so the processing power on board can't have been anything like as high as we take for granted today. I think the 8080 had a 2MHz clock speed. The 8086 16-bit chip was launched about the same time as Voyager...

Around that time I was using 74 series TTL for my degree project and discrete transistors were still in widespread use - FETs were fairly exotic, I seem to remember. Maybe the larger semiconductor geometry makes it more reliable, in fact, in regions of space subject to cosmic rays? A pretty good effort, whatever it's using!

Intel 8080 launched in April '74 so that would have been very rapid development programming and testing to hit the '77 launch date. Even the intel 8008 launch in April 1972 would have been tight and risky?.

Good call, Neale

**LINK**

https://www.cpushack.com/space-craft-cpu.html

MichaelG.

Good article about Voyager in today's Sunday Times

I heard all this news on the late BBC news while in bed and was taken by the fact that the radio messages took over 18 hours to traverse the distance between the craft and Earth. Being an insomniac I tried to do a check of that time using 20 billion miles as the distance. I finally failed before falling asleep. In the morning I realise that the calculation was easy enough in ones head if you used scientific notation as it is 2x10^13 over 3x10^8 which is 2/3 x 10^5. Then to get to hours divide 3.6^10^3 which gives 66/3.6 = 18.3....then I could fall asleep without seeing too many zeros.

Other cures for insomnia are available