In the first article dedicated to the 45th anniversary of the Voyager space program launch, we looked at how communications work on the most remote man-made spacecraft outside our solar system. Today, we’ll tell you more about what the Voyager twin spacecraft possess except for the communication system, as well as the most famous discoveries Voyager 1 made during its 44-year spacewalk.
Despite the significant reduction in funding compared to previous Apollo missions, the team of engineers and programmers who worked on the Voyagers managed to equip them with sophisticated hardware and software components. The Voyagers were based on three computer systems with double redundancy (each represented in two copies):
- CCS, which is Voyager’s computer control system – the main digital brain of Voyager, responsible for the basic processes of the spacecraft. The CCS, in particular, is responsible for receiving and reading commands to Voyager from Earth. CSS also manages the memory of two other computer systems: the FDA and the AASC. The CCS had a memory capacity of just over 70 KB, which seemed satisfactory for a trip around the solar system back in the late seventies.
- FDS is the flight data subsystem where all engineering and scientific data is collected, formatted, and stored by Voyagers. In addition, all the telemetry data collected is stored in this system. The FDS also had a magnetic tape used to record data in case it was impossible to receive a signal from the probe due to interference or failure of the Deep Space Network’s receiving antennas. The data recorded on the magnetic tape was stored and transmitted to Earth later when Voyager re-entered the best coverage area.
- AASC is the Articulation and Control Relationship System responsible for the probe’s orientation in space. It was the system that failed on Voyager 1 in May 2022, resulting in the loss of the spacecraft’s spatial orientation. At the time of its creation, AASC was a truly advanced innovation as NASA programmers used a combination of analog and digital elements, which was embodied in HYPACE (Hybrid Programmable Attitude Control Electronics) technology. HYPACE used a 4-byte serial architecture and indexed register addressing, which made it much easier to encode Voyager in three spatial axes at once. However, NASA found it senseless to invest money in developing a completely new system. Thus, HYPACE was never fully introduced in Voyager. Instead, the older CSS (Viking) technology was modified, and the NASA programmers added some HYPACE functionality.
As mentioned above, each of the three computer systems installed on the Voyagers was backed up. The CCS systems always worked in pairs, while the FDS systems worked alternately, and the AASC always had only one system working (the second one should be activated only in case of a failure of the first). The engineers responsible for creating the apparatus were guided by the idea that with the alternate operation of the probe’s computer systems, it would be possible to increase their service life significantly.
The key aspect in creating the probe’s computer systems was the ease and low-levelness of the software languages in which commands would be written for Voyager since they would have to be transmitted over billions of kilometers. NASA originally used Fortran 5 (later changed to Fortran 77) as the programming language. Today, some of the commands that Voyagers execute are written with elements of the more flexible C language.
Voyagers’ research equipment
In addition to the spatial orientation system AASC (whose failure was recorded in May 2022), there are also a number of modules to assess the parameters of the environment surrounding the spacecraft on board of the research probe. These include a magnetometer, a photopolarimeter, an infrared interferometer, a radiometer, an ultraviolet spectrometer, detectors of low-energy charged particles, cosmic rays, and plasma.
Voyager 1 is also equipped with two types of cameras: a wide-angle camera (with a focal length of 200 mm) and a narrow-angle camera (with a focal length of 1500 mm), as well as a set of special filters for better observation of planetary objects. These cameras allow Voyagers to take some of the most detailed images of planets and satellites in the solar system.
The data obtained from the equipment and tools installed on the spacecraft and photos of Voyager cameras have added more than one volume of the Encyclopedia Britannica, fully describing the planetary world of our heliosphere.
The Great Voyage
To comprehend how huge (and not just the distance covered) the Voyager-1 mission was, we have prepared a short list of the most interesting discoveries and images that Voyager 1 collected during almost 45 years of its operation.
- There was an interesting switch during the launch of the probes: Voyager 2 was launched on August 20, 1977, and Voyager 1 was launched on September 5. The second number was purposely launched 16 days earlier than the first, as it was launched on a slower trajectory. Because of this, Voyager 1 overtook its No. 2 as early as 1979 and was the first to report its observations of Jupiter. Therefore, to make it clear, NASA decided to invert the numerical order of the probes numbering.
- On March 5, 1979, the first meeting with the Jupiter system took place, resulting in the probe’s flight around the planet’s satellites known as Amalthea, Io, Ganymede, Callisto, and Europa, as well as a direct approach to the planet itself. As a result, about 18,000 photos of the Jupiter system were taken.
- On November 12? 1980, Voyager 1 reached the planetary system of Saturn. This encounter resulted in 16,000 images of the system, including detailed images of Saturn’s satellites: Titan, Tefia, Mimas, Enceladus, Rhea, and Hyperion.
- On November 14, 1980, the main mission of Voyager 1 to observe the planets of the solar system was over, and a new phase of the spacecraft’s expanded mission was launched. It was about exploring the solar system’s boundaries, followed by a trip to interstellar space.
- On February 17, 1998, Voyager 1 became the farthest artificial spacecraft from Earth when it overtook the US space probe Pioneer-10. Since then, Voyager 1 has been moving away from the Sun, on average, one astronomical unit (distance from Earth to the Sun) faster than Pioneer 10 per year.
- In 1994, Voyager 1 published a legendary picture of Earth: “A pale blue dot.”
- On August 25, 2012, Voyager 1 left the solar system and entered interstellar space. On that day, the NASA team servicing Voyager 1 recorded a sharp increase in the cosmic rays that the probe started to pick up, while solar protons virtually ceased to be defined by its detectors.
- In 2021, Voyager 1 was able to record the sounding of interstellar space – a faint and monotonous hum outside our solar system, which appears to be a faint “rain” of stellar plasma.
Along with Voyager 1’s voyage, its twin brother, Voyager 2, whose trajectory also passed near Jupiter and Saturn and later headed toward Uranus and Neptune, studied its part of the solar system. Read about the results of its mission in the next article of our Voyager series.