Answers #2 and #4 are by the person who designed the flanges on both Viking's and Voyager's DTRs. (The flange was "designed to absorb resonances created by the clear/transparent belt wrapped around the tape, generated by the movement of the tape drive itself.")
Answer #1 and #3 have useful information and links to contemporary sources that provide more detail about high-tech the recorders were.
Incidentally, Voyager's DTR was mounted so that it's mechanical movements had minimal impact on the spacecraft's pitch and yaw, which I assume means they had the most effect on the roll axis. For the Uranus and Neptune encounters, which required long exposures and panning, finer control of Voyager 2's attitude was implemented, including counteracting even the minimal pitch and yaw effects of the DTR.
They didn't get access to the actual NASA software running in space. They wrote simple example programs to exercise the CPU emulator. The example program that is loaded when you first visit the web page simply counts down from 10.
And having the actual NASA source code would not be very useful, since the actual software interacts with complex hardware on the spacecraft, which you would have to emulate in addition to just the CPU. For example, the FDS computer interacts with all of the scientific instruments, the digital tape recorder, the telemetry output hardware, and the other two computer types on the spacecraft. (I'm not casting shade on the CPU emulator as it is an impressive achievement and the code is very high quality.)
Voyager 1 and Voyager 2 are identical, as are their computers. JPL's Voyager documentation is the property of Caltech, not NASA, and are thus not available via FOIA. People have gotten copies of selected documentation by requesting them from libraries that have copies of the original documents on file.
The 2025 YouTube video is "How We Diagnosed and Fixed the 2023 Voyager 1 Anomaly from 15 Billion Miles Away" by David Cummings of JPL.
There is a Vimeo video of the Voyager team reacting when data first began trickling in from Voyager 1 after the fix in April 2024. "Voyager 1 Team Reacts to Receiving Engineering Data From Spacecraft" (JPLraw channel): https://vimeo.com/939376171
Cummings is the one against the back wall who shoots his two arms up in the air in celebration. He and Armen Arslanian (in the blue shirt to his left, right in the image) developed the software fix.
For others, this truly excellent 2016 paper is "Voyager Interstellar Mission: Challenges of Flying a Very Old Spacecraft on a Very Long Mission" by Sun Kang Matsumoto. She was/is a Voyager Fault Protection and CCS Flight Software Systems Engineer (CCS was the onboard command computer) and she was also one of the "stars" in It's Quieter in the Twilight.
I enjoyed your video and it is well done. Unfortunately, I don't think it's true. The Voyager tape drives were similar (if not largely identical) to the earlier Viking Orbiters' DTRs. The Voyager engineers were certainly familiar pre-launch with the motions imparted to the spacecraft by the mechanical movements of the tape drive. The Voyager DTRs were specifically mounted to minimize the effects on the roll axis.
Potential problem were expected and planned for with Voyager 2's flybys of Uranus and Neptune. Because of the long exposures required for these more distant planets, like you pointed out, the engineers had to account for the attitude effects of both (i) the DTR movements and (ii) panning the cameras to keep them focused on a single point while the spacecraft was moving past at high speed. This was especially a problem at Uranus, which is tilted on its side. Voyager 2 was approaching at its north pole; with the plane of the moon's orbits perpendicular to the ecliptic - like an arrow flying into an archery target. As a result of this configuration and Voyager 2's high speed, the high-resolution observations of Uranus and its moons were compressed into a 6-hour period.
These engineering efforts are described in detail in a 1985 paper, "Voyager Flight Engineering: Preparing for Uranus", by W.I. McLaughlin and D.M. Wolff. Abstract: https://arc.aiaa.org/doi/abs/10.2514/6.1985-287 (The full paper can be found online with some effort; doi:10.2514/6.1985-287) Here's a quote from the paper (AACS is the attitude control computer and CCS is the command computer):
"The DTR is mounted on the spacecraft such that its angular momentum is introduced into the yaw and pitch axes of the spacecraft with almost none going into the roll axis. DSSCAN was first programmed to introduce cancelling momentum in the yaw axis only. The modification to the AACS and CCS software took place in an environment of a scarcity of available memory so that, from a programming point of view, it had to be carefully fit in. The "patch" was carefully tested in the Voyager Capability Demonstration Laboratory (CDL) before loading onboard Voyager 1. (The AACS and CCS programs were modified without being reassembled as is the case with all AACS and CCS changes since launch.) The CDL is a digital/analog simulation of many of the spacecraft capabilities. Modifications or tests of any degree of complexity are done first, whenever possible, on Voyager 1 before implementation on Voyager 2, a reflection of the fact that Voyager 2 still has two planetary encounters scheduled while Voyager 1 has none."
Thanks! My primary source for this was Carl Sagan's book "A Pale Blue Dot" IIRC — don't have the folder in front of me to double check, but fairly certain.
Edit: found it!
Here's the excerpt. According to Sagan they sent these instructions up. Given his details on what had to be done to boost the signal upload, it sounds like this really did happen:
"...while taking a photograph of a street scene from a moving car.
This may sound easy, but it's not: You have to neutralize the most innocent of motions. At zero gravity, the mere start and stop of the on-board tape recorder can jiggle the spacecraft enough to smear the picture.
This problem was solved by sending up commands to the spacecraft's little rocket engines (called thrusters), machines of exquisite sensitivity. With a little puff of gas at the start and stop of each data-taking sequence, the thrusters compensated for the tape-recorder jiggle by turning the entire spacecraft just a little.
To deal with the low radio power received at Earth, the engineers devised a new and more efficient way to record and transmit the data, and the radio telescopes on Earth were electronically linked together with others to increase their sensitivity. Overall, the imaging system worked, by many criteria, better at Uranus..."
Thanks for the excerpt. I read a couple of Sagan's other books many years ago and I really should read APBD sometime.
Interesting to me, Sagan's "little puff of gas" was borne out in the paper I referenced (not that Sagan needed being borne out!) and that the resulting "imaging system worked ... better at Uranus" was something I hadn't thought of. Per the paper, the Voyagers originally had minimum thruster pulse lengths of 10 ms. In the lab and then on Voyager 1, the Voyager engineers figured out that they could reduce the pulses to 5 ms, thus allowing finer control of Voyager 2's attitude at Uranus (and later Neptune) and probably better image quality than at Jupiter and Saturn. Very interesting - I really should read Sagan's book!
I really enjoyed it! Actually read it to my kids as a bedtime book, and although it was pretty advanced for them, they really stayed with it. Really too bad he's not around anymore.
Clickbait! If you read the article, there's no gloom or doom.
30 or more years ago (?), Consumer Reports did a report on toothbrushes and they did a follow-up note or article clarifying their recommendation of how often to change toothbrushes. Their recommendation was not because of bacteria as many readers apparently thought, but because the bristles get worn down and don't clean as effectively.
And the "toilet plume"? Is that more of a problem in Britain? Looking back at John Postgate's Microbes and Man (which I read back in the 1990s):
Few people realize, however, that when a used toilet is flushed, a turbulence and spray of water and excrement is generated comparable to a sneeze: in any toilet one can isolate faecal clostridia and streptococci from the ceiling, walls and door handle as well as around and beneath the seat. British water closets certainly generate such infectious aerosols; it is probable that the vortex type favoured in the USA, depending on a swirl rather than a splash to flush the closet, is less generous in the matter of dispersing faecal microbes around the room.
(That was written back in the 1990s or earlier; British folks and travelers can obviously provide more current insight than me, who has never traveled outside the U.S.!)
The Galileo hack was indeed incredible. From a post-mission paper:
"Although the primary mission was completed in December 1997, the mission was extended three times to take advantage of the spacecraft's durability with 24 more orbits. The extensions enabled additional encounters with all four of Jupiter's major moons: Io, Europa, Ganymede and Callisto. Galileo flew near a small inner moon, Amalthea, before making a planned mission ending plunge into Jupiter's atmosphere. In total, Galileo had 35 encounters of Jupiter's major moons -- 11 with Europa, 8 with Callisto, 8 with Ganymede, 7 with Io and 1 with Amalthea -- and returned more than 30 Gigabytes of data, including 14,000 images."
The paper is a very readable description of the problem, solution, and end results:
P.A. Jansma, "Open! Open! Open! Galileo High Gain Antenna Anomaly Workarounds" 2011, abstract: https://doi.org/10.1109/AERO.2011.5747657 (The full paper can be found online with some effort.)
Answers #2 and #4 are by the person who designed the flanges on both Viking's and Voyager's DTRs. (The flange was "designed to absorb resonances created by the clear/transparent belt wrapped around the tape, generated by the movement of the tape drive itself.")
Answer #1 and #3 have useful information and links to contemporary sources that provide more detail about high-tech the recorders were.
Incidentally, Voyager's DTR was mounted so that it's mechanical movements had minimal impact on the spacecraft's pitch and yaw, which I assume means they had the most effect on the roll axis. For the Uranus and Neptune encounters, which required long exposures and panning, finer control of Voyager 2's attitude was implemented, including counteracting even the minimal pitch and yaw effects of the DTR.