How Voyager 1’s telemetry broke, and what would that mean

Today I will start with memories. One of my first popular science translations in habroformat was released in early 2014 on the dev.by website (now https://devby.io/); he was called “Mars code, or how the software for the Curiosity rover was created“. The essence of this most interesting text is what an incredible level of reliability, durability, autonomy and integration of hard and software must be achieved when programming spacecraft. About a year later, I was hired by Carl Sagan’s Pale Blue Dot, published by Alpina Non-Fiction under the title “Blue dot. Space future of mankind“. I still consider this book a masterpiece of my translation work, although it looks much better in Alpina’s literary editor than in my draft. The book is named after the famous Phototaken from the Voyager 1 on February 14, 1990, when this device was in the region of Saturn.

In his book, Sagan devotes more attention to Voyagers than to any other spacecraft, devoting an entire chapter and several digressions to them, including a very lyrical. But in general, this story (Chapter 8, “The Triumph of the Voyagers”) emphasizes the same engineering insight and ingenuity that the authors of the Curiosity software are proud of. Recently, interest in Voyagers has increased again, as anomalies began to appear in the telemetry of Voyager 1, and the probes themselves, which exchanged their 45th anniversary, are close to shutting down.

A Brief History of the Voyagers

In 1969, the idea first appeared to send autonomous space probes to the giant planets in order to explore both these planets themselves (primarily Jupiter and Saturn) and their satellites. The breakthrough engineering idea that ensured the durability of these devices was the gradual transition from solar energy to nuclear energy as the devices moved away from the Sun. As a result, two devices were launched in July 1977 and headed for Jupiter and Saturn. Titan, a satellite of Saturn, was considered their ultimate goal, but in the end, the paths of the devices diverged. Voyager 2, which engineers were able to further disperse with the help of a gravitational maneuver, was able to visit the neighborhoods of all giant planets by the end of the 1980s, including Oberon (satellite of Uranus) and Triton (satellite of Neptune). Jupiter’s moons were colorfully filmed both Voyagers, but shortly thereafter Voyager 1 veered off course and off the plane of the ecliptic, heading south towards the exit of the solar system and the heliosphere.

In 1998, Voyager 1 overtookPioneer-10”, becoming the most distant man-made object from the Earth. By now, the power of plutonium engines has fallen by about 70%. In 2017, the main engines of Voyager 1 completely failed, and the mission control center again activated the thrusters, which at the beginning of the mission allowed the probe to approach the satellites of the giant planets.

Pioneer 10 and Voyagers differ from other spacecraft in that they carry messages for extraterrestrial civilizations. Pioneer 10 carries a sign that shows a hydrogen atom, a man and a woman without clothes, the approximate position of the Earth and the solar system – as well as the device itself next to people so that potential recipients of the message can judge the size of a person by the size of the device.

Voyager’s golden disc is much better known, as it contains not only pictorial, but also sound information, being, in essence, a CD. Details about its content are described in this LJ post.

Among the information transmitted by the Voyagers to Earth are photographs of active volcanoes on Io, photographs of the ice sheet of Europa, photographs of the rings of Saturn, pictures of the Oberon relief, and even the first photographs of cyclone eddies on Neptune (“large dark spots”), reminiscent of the structure of the Great The Red Spot of Jupiter, but not so durable.

Thus, over the past 30 years (after Voyager 2 passed Pluto), the probes have been working “at exhaustion” and providing information that was not planned to be obtained with their help. Voyager 1 left our system in 2012, and Voyager 2 in 2018. This was exit from the heliosphere (and beyond the heliopause) into interstellar space – that is, now both Voyagers are not affected by the solar magnetic field and solar wind. At the same time, the antennas of both devices are still directed towards the Earth, so the Voyagers can be controlled. Since Voyager 1 was about 22.3 billion km from Earth as of 2020, it takes about two days to exchange data with it. Voyager 2 is operating as usual, and in 2020 has moved away from Earth by about 18.5 billion km.

Telemetry issues

To receive Voyager telemetry data on Earth, a radio telescope is used, naturally, with newer and more powerful radar and transmitting equipment than the probe. Therefore, the upstream signal from the MCC is stronger and more accurate than the response from the probe:

The transmission of telemetry data from Voyager consists of three main stages:

  • Data Acquisition: Sensors and A/D Converters

  • Processing: computer

  • Downlink: transmitter/antenna

Telemetry from Voyager to Mission Control includes the following data:

  • Direction control: roll, pitch, yaw

  • Power supply: voltage in batteries and solar panels, the degree of discharge of batteries

  • Temperature control: temperature, heater use

  • Jet propulsion: fuel level, pressure, burn time

  • Payload: scientific measurements

The telemetry transmitted from MCC to Voyager includes the following data:

  • Direction control: equipment switching between main and standby nodes (A/B)

  • Power supply: solar panels orientation

  • Temperature control: how dampers are driven

  • Jet propulsion: combustion/jet propulsion operations

  • Payload: scientific, experimental

Susan Dodds of JPL (NASA’s Jet Propulsion Laboratory) said on NASA’s official Twitter that the data coming from Voyager 1 seems meaningless. Obviously, he is not at the point, the coordinates of which he gives. One of the three computers on Voyager 1, which is responsible for the orientation of the device (in particular, controlling the engines and controlling the antenna), made it possible to amplify the antenna signal, so data on the situation in interstellar space continues to flow to the MCC. Also, as long as this computer maintains proper antenna orientation. But the computer transmits only two values ​​as information about the orientation of the device: either a sequence of zeros, or 377.

The reasons for the failure are explained vaguely. He is associated with AACS (subsystem of spatial orientation and maneuvering control). Because the craft is good at receiving incoming commands, the Mission Control Center can manually guide Voyager 1. In this case, no emergency protection systems on the probe are triggered. Thus, it is logical to assume that the probe is intact and still has a supply of energy, but “does not know where it is.” The official and most likely explanation is the failure of the navigation system under the influence of hard radiation.

A paradoxical but logical and interesting explanation for the failure of Voyager 1 was offered by Emmanuel Markoulakis of the Hellenic Mediterranean University; while his article exists only in the form preprint. The author believes that at a distance of 156 a.u. from the Sun, where Voyager 1 is currently located, may be the region closest to the Sun with a high concentration of dark matter or matter with negative mass. Such hypothetical substances are the subject of active scientific research, as they would make it possible to obtain antigravity or inflate the Alcubierre bubble.

In doing so, he refers to article Edward Belbruno and James Green of the Royal Astronomical Society. According to their hypothesis, dark matter in gravitational terms should act directly opposite to ordinary matter – that is, a huge mass of dark matter should exert a strong repulsion on large masses of ordinary matter (planets, stars). A physical body as small as Voyager will also experience repulsion from dark matter, but the larger the volume of dark matter, the weaker this repulsion will be. Accordingly, under the influence of dark matter, Voyager 1 could have deviated from the course by a few meters (and we would not have recorded this from Earth), but the sensors could perceive this impact exactly as follows from the current NASA observations.

This post may be updated if NASA is able to fix Voyager 1 or figure out the exact cause of the failure. For now I’ll finish her famous aphorism Isaac Asimov:

The most exciting phrase you can hear in science – the phrase that announces new discoveries – is not at all “Eureka!”, but “That’s funny …”

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