... the software/hardware contractor to build the FDS system and software ...
Gizmodo: What are the challenges that come with operating a mission for this long?Spilker: The spacecraft was built in the 1970s, and so that’s the technology that we had in those days. And we didn’t have very much computer memory, so we had to be very careful and think through what we could do with this tiny amount of computer memory.So the challenge with these aging components is, how long until a key piece fails? We’re well past the warranty of four years. We also have less power every year, about 4 watts less power so we have to find 4 watts per year to turn off on the spacecraft. The spacecraft had a lot of redundancy on it, so that means two of every computer and two of all the key components. We’ve been able to turn off those backup units, but we’re now at the point where, to really get a significant amount of power, all that’s left are some of the science instruments to turn off. So, that’s where we’re at.Then, of course, if you have less power, the temperature goes down inside. There’s something called a bus that has all the electronics inside, and that’s getting colder and colder. Along the outside of the bus are these tiny lines of hydrazine that go to the thrusters, so we started to worry about the thermal constraints. How cold can the lines get before they freeze? How cold can some of these other components get before they stop working? So that’s another challenge.“But we’re hopeful that we can get one, possibly two, spacecraft to the 50th anniversary in 2027.”Then there are individual tiny thrusters that align the spacecraft and keep that antenna pointed at the Earth so we can send the data back, and they’re very slowly clogging up with little bits of silica, and so their puffs are getting weaker and weaker. That’s another challenge that we’re going through to balance.But we’re hopeful that we can get one, possibly two, spacecraft to the 50th anniversary in 2027. Voyager’s golden anniversary, and perhaps even into the early 2030s with one, maybe two, science instruments.
In the latest article by Eric Berger:https://arstechnica.com/space/2025/03/white-house-may-seek-to-slash-nasas-science-budget-by-50-percent/QuoteScientists told Ars that NASA would be forced to make difficult decisions, likely including shutting off extended missions such as the Voyager
Scientists told Ars that NASA would be forced to make difficult decisions, likely including shutting off extended missions such as the Voyager
The decision [on Voyager] to go with JPL versus an industrial contractor was viewed at NASA Headquarters by John E. Naugle, Associate Administrator for Space Science, as a "many faceted problem" whose resolution was "of paramount importance to the future of NASA's Planetary Program as well as to the future of JPL." In short, JPL needed the contract to maintain employment levels in the laboratory, and NASA Headquarters needed it to maintain the vitality of its planetary program.
Things were going less well for JPL as an institution, however.NASA, JPL's sole sponsor, lacked the presidential political support that it had enjoyed before the Apollo moon landings. Since then the agency had steadily declined in national clout and technical capacity. The challenging and uplifting Apollo project had become a glorious, almost mythic, memory for NASA, rather than a gateway to the future. JPL was NASA's only center not staffed by government employees. That made it a natural target for elimination in tough times, a circumstance that added to the "creative tension" inherent in the three-sided relationship between NASA, JPL, and Caltech. Furthermore, JPL had no important role in the post-Apollo focus on the Shuttle and on related uses of astronauts in low-Earth orbit. In fact, JPL seemed to be on everybody's rumored "hit list", awaiting the next big NASA cut. Russ Drew [on Nixon's President Science Advisory Council] sometimes dropped alarming hints to me of draconian measures under discussion at OMB that would have eliminated JPL....The message was clear: NASA, a declining institution, felt it could not support JPL as it had during the halcyon days of the building of America's first satellite, first moon probes, and first planetary explorers.Unlike my predecessor Pickering, I would thus have a twofold task as director of JPL - to push U.S. planetary exploration to the hilt and, at the same time, to develop a second governmental role for JPL that would be independent of NASA. In 1976, following the oil-ptice shocks of 1973, government-supported energy research and development was the best (really the *only*) practical alternative for a high-tech, nonprofit, civilian-oriented place like JPL.So, on April 1, 1976, my first day as director of JPL, I promoted Bud Schurmeier with great fanfare and with instructions to carve out a meaningful role for JPL in energy R&D. Neither Bud nor I, as it turned out, would find deep satisfaction in these new strategic responsibilities. The ebbing of the old Apollo spirit was merging with a broader retreat of American self-expectations in the face of failures in Vietnam and at home. America would not blaze new paths in either alternative energy or planetary exploration. But in 1976 we had to try to create the kind of future that JPL, and America, deserved.
But after a month of negotiations between NASA and the White House, on 30 September 1981 NASA directed Murray to stop all work on Halley['s Comet] missions.The official end of JPL's hopes for Halley came as a jolt to Murray, who spoke bitterly of "Black September". That was not all. First, budget cuts on the Centaur project again put Galileo at risk, until JPL designers came up with yet another gravity-assist trajectory to get to Jupiter on the IUS booster. Then NASA floated a proposal to shut off the Voyager spacecraft, saving $222 million by foregoing the Uranus and Neptune encounters. It became clear that not just single projects but the entire deep-space program was at stake. In summer 1981 the OMB cut $1.1 billion from NASA's budget request. The new NASA administrator, James Beggs, insisted that such a shortfall would require dropping one of NASA's major programs, such as the shuttle, earth applications, or planetary exploration, and requested higher-level policy approval. But he did offer a suggestion. At his confirmation hearings in June, Beggs had called planetary exploration "a hallmark of the agency. It would be a disaster if we gave it up." He now pushed the planetary program on the table as a high-stakes wager in the budgetary standoff, naming it as the first item NASA would be willing to cut. He again cited the program's value, but he ranked it below astronomy in immediate potential: "the most important missions" in deep space had already been done, and the next phase of landers and sample returns could await the shuttle. He added, "Of course, elimination of the planetary exploration program will make the Jet Propulsion Laboratory in California surplus to our needs."
An alternate solution to Voyager 2's radio problem considered by NASA was to send commands through one of the science instruments, namely the planetary radio astronomy receiver. Tests conducted during September 1978 using the Stanford radio telescope indicated less received signal strength than had been anticipated, and the approach required both major changes in the onboard computer programs and the construction of a suitable ground transmitter facility. Implementation would cost an estimated $10 million ($7.5 million facility, $2.5 million project) and would require about twenty-four months to develop. Realizing that if the capability were never used, NASA would be open to criticism for having built an unnecessary facility, the Voyager Program Office decided against the planetary radio astronomy solution. (Butrica, Footnote 79)
In 1978 both Voyager spacecraft were on their way to Jupiter and a contest was held at JPL to find an amusing logo for a Voyager t-shirt and mug. Hugh von Delden, a temperature control hardware engineer at JPL, proposed the winning design. The illustration was done by artist Bill Haines, a friend of his. Von Delden had also won the design contest in 1975 for the official Mariner Jupiter/Saturn '77 logo, before the project was renamed Voyager.
The mission team wanted to fix the thrusters, deemed unusable decades ago, before the radio antenna that sends commands to the probe went offline for upgrades.Engineers at NASA’s Jet Propulsion Laboratory in Southern California have revived a set of thrusters aboard the Voyager 1 spacecraft that had been considered inoperable since 2004. Fixing the thrusters required creativity and risk, but the team wants to have them available as a backup to a set of active thrusters whose fuel tubes are experiencing a buildup of residue that could cause them to stop working as early as this fall.In addition, the mission needed to ensure the availability of the long-dormant thrusters before May 4, when the Earth-bound antenna that sends commands to Voyager 1 and its twin Voyager 2 went offline for months of upgrades.Thruster CloggingThe Voyagers launched in 1977 and are hurtling through interstellar space at around 35,000 mph (56,000 kph). Both spacecraft rely on a set of primary thrusters to gently pivot them up and down as well as to the right and left in order to keep their antennas pointed at Earth so they can send back data and receive commands. Within the primary set of thrusters are other thrusters that control the spacecraft’s roll motion. Seen from Earth, the roll motion rotates the antenna like a vinyl record to keep each Voyager pointed at a guide star it uses to orient itself. Both spacecraft have a primary and backup set for these roll movements.(Another set of thrusters, intended to change the spacecrafts’ trajectory during the flybys of the outer planets, were revived on the spacecraft in 2018 and 2019, but they can’t induce roll motion.)To manage the clogging tubes in the thrusters, engineers switch between the sets of primary, backup, and trajectory thrusters of both Voyagers. But on Voyager 1, the primary roll thrusters stopped working in 2004 after losing power in two small internal heaters. Engineers determined the broken heaters were likely unfixable and opted to rely solely on Voyager 1’s backup roll thrusters to orient the star tracker.“I think at that time, the team was OK with accepting that the primary roll thrusters didn’t work, because they had a perfectly good backup,” said Kareem Badaruddin, Voyager mission manager at JPL, which manages the mission for NASA. “And, frankly, they probably didn’t think the Voyagers were going to keep going for another 20 years.”But without the ability to control the spacecraft’s roll motion, a variety of issues would arise that might threaten the mission, so the engineering team decided to reexamine the 2004 thruster failure. They began to suspect that an unexpected change or disturbance in the circuits that control the heaters’ power supply had effectively flipped a switch to the wrong position. If they could turn the switch back to its original position, the heaters might work again, enabling them to reactivate the primary roll thrusters and use them if the backup roll thrusters that have been used since 2004 become completely clogged.Communications PauseThe solution required some puzzle-solving. The team would have to turn on the dormant roll thrusters, then try fixing and restarting the heaters. If, during that time, the spacecraft’s star tracker drifted too far from the guide star, the long-dormant roll thrusters would automatically fire (thanks to the spacecraft’s programming). And if the heaters were still off when they fired, it could trigger a small explosion, so the team needed to get the star tracker pointed as precisely as possible.It would be a race, and the team faced additional time pressure: From May 4, 2025, through February 2026, Deep Space Station 43 (DSS-43), a 230-foot-wide (70-meter-wide) antenna in Canberra, Australia, that’s part of NASA’s Deep Space Network, would be undergoing upgrades. It would be offline for most of that time, with brief periods of operation in August and December.Although the Deep Space Network has three complexes equally spaced around the globe (in Goldstone, California, and Madrid, in addition to Australia) to ensure constant contact with spacecraft as Earth rotates, DSS-43 is the only dish with enough signal power to send commands to the Voyagers.“These antenna upgrades are important for future crewed lunar landings, and they also increase communications capacity for our science missions in deep space, some of which are building on the discoveries Voyager made,” said Suzanne Dodd, Voyager project manager and director of the Interplanetary Network at JPL, which manages the Deep Space Network for NASA. “We’ve been through downtime like this before, so we’re just preparing as much as we can.”The team wanted to make sure the long-dormant thrusters would be available when the dish is back online briefly in August, by which time the thrusters currently in use on Voyager 1 might be completely clogged.The advance work paid off: On March 20, the team watched as the spacecraft executed their commands. Because of Voyager’s distance, the radio signal takes over 23 hours to travel from the spacecraft to Earth, meaning everything the team saw happening had occurred almost a day earlier. If the test had failed, Voyager might already have been in danger. But within 20 minutes, the team saw the temperature of the thruster heaters rise dramatically and knew they had succeeded.“It was such a glorious moment. Team morale was very high that day,” said Todd Barber, the mission’s propulsion lead at JPL. “These thrusters were considered dead. And that was a legitimate conclusion. It’s just that one of our engineers had this insight that maybe there was this other possible cause and it was fixable. It was yet another miracle save for Voyager.”
Sorry, I can’t find the video link. Where’re is it?
the PB-15 mode began transmitting the memory dump
ADDR CODE---- ----0000 9FCF ISZ PCTR /INCREMENT P-COUNTER FOR THIS P-PERIOD0001 801F ABS 31 /FORCE IT TO BE BETWEEN 0 AND 310002 93E0 AND PCTR,R1 /INCLUSIVE BY KEEPING ONLY 5LSB0003 9C52 SKP CMODE /IS LOWER MEMORY P-TABLE TO BE USED0004 002B JMP GOUP /NO /YES0005 8009 ABS PTAB /GENERATE ADDRESS WITHIN PTAB TABLE0006 900F ADD R1,PCTR0007 0FC0 JMI R1 /AND JUMP TO IT0008 11AF PROGID: CON $X11AF /PROGRAM ID0009 0028 PTAB: JMP PILL /ILLEGAL000A 002D JMP P1000B 0185 JMP P2...0020 0486 JMP P230021 048F JMP P240022 0028 JMP PILL /ILLEGAL...0028 91FF PILL: LXR PCTR,PCTR /RESET P-COUNTER TO 00029 9F86 ISZ PILLCT /INCREMENT ILLEGAL P-PERIOD COUNTER002A 3FFD PX: WAT 4095 /WAIT FOR NEXT CLOCK-400 INTERRUPT002B F087 GOUP: OUT 7,SETJU /SET JUMP UP002C 0000 JMP UPINT /JUMP TO UPPER MEMORY INTERRUPT...1000 F097 UPINT: OUT 7,SETAU /SET ADDRESS UP
0BE5 81C0 MODE: CON $B1000000111000000 /LOAD-STATE IS EL, NO PPS SAFING, ENG /MODE 7 (MODIFIED CRUISE TABLE AND /AACS MANEUVER (50) TABLE), AACS TEL...0FD2 FFE0 CMODE: CON $XFFE0 /CURRENT MODE (IN HEX), WHERE 0001 GS5 EQU 1 /1 = GS-5 0003 GS4B EQU 3 /3 = GS-4B PWS REPLACEMENT 0007 GS8 EQU 7 /7 = GS-8 000B PB5 EQU 11 /B = PB-5 000C PB14 EQU 12 /C = PB-14 000F PB15 EQU 15 /F = PB-15 /FFE0 = EL /FFE1 = EH /FFF2 = UV-5A (UV-5) /FFF3 = PB-16 /FFF5 = CR-5T (AKA CR-5A)
053C 1C08 SETMO: SRB LMRA /SAVE RETURN ADDRESS053D 9B20 SLC 800 /IS LINE COUNTER AT 800053E 0543 JMP SETMOA /YES /NO053F 8000 ABS 0 /RESET SKIPPR HERE BECAUSE IT IS A0540 4F83 MLD SKIPPR /CONVENIENT TIME TO DO IT0541 305D WAT 95 /EQUALIZE TIME WITH L800 PATH0542 2C08 EXC LMRA /RETURN /LINE COUNTER IS AT 8000543 5BE5 SETMOA: MRD MODE /GET MODE WORD FOR UPCOMING 48 SECONDS...
https://x.com/NASAVoyager/status/1925589712510886095NASA Voyager @NASAVoyagerAt our current distance from the Sun, solar panels are all but useless – so we use something called radioisotope thermoelectric generators (RTGs) for power. Each spacecraft is equipped with three RTGs, and current power output is about 220 watts for V1 and 223 watts for V2.
David Cummings's March 2025 Flight Software Workshop presentation, "How We Diagnosed and Fixed the 2023 Voyager 1 Anomaly from 15 Billion Miles Away", has some welcome examples of FDS assembly language. Below are 3 of the major code listings in his presentation, along with some comments. (A 4th code listing is a repeat of the listing shown in Bruce Waggoner's August 24 presentation; see an earlier post for that code listing.) A PDF of the presentation slides can be downloaded here, first entry.To refresh your memory (pun not really intended!) ...First, see Steven Pietrobon's short description of the FDS computer. Then see his longer description with the FDS instruction set.
NASA Voyager @NASAVoyagerAt our current distance from the Sun, solar panels are all but useless – so we use something called radioisotope thermoelectric generators (RTGs) for power. Each spacecraft is equipped with three RTGs, and current power output is about 220 watts for V1 and 223 watts for V2.
At the time, the longest operating planetary mission had been for nine months, and the most advanced RTGs, used to convert the heat produced from the natural radioactive decay of plutonium, lost power after ten thousand hours, slightly more than one year. Thus, even a three-year mission was a technological challenge. The power problem was eventually solved with the development of special wrappings for the thermocouples that substantially extended the life of the RTGs, and the computer systems were redesigned in order to reduce power consumption....Another crisis involved the RTGs. A material used as insulation sublimed, that is, it passed from a solid to a gaseous state and then redeposited itself on an insulating blanket, causing an electrical short in the system and lowering the power output to less than the required levels. The solution, discovered by an RCA engineer, was to put a nitride coat on the thermocouple device, which prevented the subliming and the shorts.
The RTGs' fuel spheres and housings were put through elaborate tests to demonstrate their safety in the event of a catastrophic launch abort or atmospheric re-entry. The assembled heat source was fired into cement walls, dropped from high altitude on to concrete pads, exposed to plasma arc jets to simulate atmospheric re-entry heating, and exposed to high temperature explosions simulating launch vehicle explosions.
