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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Voyager 1 | 5/7 | https://en.wikipedia.org/wiki/Voyager_1 | reference | science, encyclopedia | 2026-05-05T13:27:04.653048+00:00 | kb-cron |
=== Interstellar medium === In March 2013, it was announced that Voyager 1 might have become the first spacecraft to enter interstellar space, having detected a marked change in the plasma environment on August 25, 2012. However, until September 12, 2013, it was still an open question as to whether the new region was interstellar space or an unknown region of the Solar System. At that time, the former alternative was officially confirmed. In 2013, Voyager 1 was exiting the Solar System at a speed of about 3.6 AU (330 million mi; 540 million km) per year, which is 61,602 km/h, 4.83 times the diameter of Earth (12,742 km) per hour; whereas Voyager 2 is going slower, leaving the Solar System at 3.3 AU (310 million mi; 490 million km) per year. Each year, Voyager 1 increases its lead over Voyager 2. Voyager 1 reached a distance of 135 AU (12.5 billion mi; 20.2 billion km) from the Sun on May 18, 2016. On September 5, 2017, that had increased to about 139.64 AU (12.980 billion mi; 20.890 billion km) from the Sun, or just over 19 light-hours; at that time, Voyager 2 was 115.32 AU (10.720 billion mi; 17.252 billion km) from the Sun. Its progress can be monitored at NASA's website.
On September 12, 2013, NASA confirmed that Voyager 1 had reached the interstellar medium in August 2012 as previously observed. The generally accepted date of arrival is August 25, 2012 (approximately 10 days before the 35th anniversary of its launch), the date durable changes in the density of energetic particles were first detected. By this point, most space scientists had abandoned the hypothesis that a change in magnetic field direction must accompany a crossing of the heliopause; a new model of the heliopause predicted that no such change would be found. A key finding that persuaded many scientists that the heliopause had been crossed was an indirect measurement of an 80-fold increase in electron density, based on the frequency of plasma oscillations observed beginning on April 9, 2013, triggered by a solar outburst that had occurred in March 2012. Electron density is expected to be two orders of magnitude higher outside the heliopause than within. Weaker sets of oscillations measured in October and November 2012 provided additional data. An indirect measurement was required because Voyager 1's plasma spectrometer had stopped working in 1980. In September 2013, NASA released recordings of audio transductions of these plasma waves, the first to be measured in interstellar space. While Voyager 1 is commonly spoken of as having left the Solar System simultaneously with having left the heliosphere, the two are not the same. The Solar System is usually defined as the vastly larger region of space populated by bodies that orbit the Sun. The craft is presently less than one-seventh the distance to the aphelion of Sedna, and it has not yet entered the postulated position of the Oort cloud, the hypothetical source region of long-period comets, regarded by astronomers as the outermost zone of the Solar System. In October 2020, astronomers reported a significant unexpected increase in density in the space beyond the Solar System as detected by the Voyager 1 and Voyager 2 space probes. According to the researchers, this implies that "the density gradient is a large-scale feature of the VLISM (very local interstellar medium) in the general direction of the heliospheric nose". In May 2021, NASA reported on the continuous measurement, for the first time, of the density of material in interstellar space and, as well, the detection of interstellar sounds for the first time.
== Future of the probe ==
=== Remaining lifespan ===
In December 2017, NASA fired all four of Voyager 1's trajectory correction maneuver (TCM) thrusters for the first time since 1980. The TCM thrusters were used in the place of a degraded set of jets to help keep the probe's antenna pointed towards Earth. Using the TCM thrusters allowed Voyager 1 to continue transmitting data to NASA for two to three more years. Due to the diminishing electrical power available, the Voyager team has had to prioritize which instruments to keep on and which to turn off. Heaters and other spacecraft systems have been turned off one by one as part of power management. The fields and particles instruments that are the most likely to send back key data about the heliosphere and interstellar space have been prioritized to keep operating. In 2023, engineers expected the spacecraft to continue operating at least one science instrument until around 2025. As of late April 2026, two instruments remain in operation.
=== Concerns with the orientation thrusters === Some thrusters needed to control the attitude of the spacecraft and point its high-gain antenna in the direction of Earth are out of use due to clogging problems in their hydrazine lines. The spacecraft no longer has a backup available for its thruster system and "everything onboard is single-string," according to Suzanne Dodd, Voyager project manager at JPL, in an interview with Ars Technica. NASA has accordingly decided to modify the spacecraft's computer software in order to reduce the rate at which the hydrazine lines clog. NASA will first deploy the modified software on Voyager 2, which is less distant from Earth, before deploying it on Voyager 1. In September 2024, NASA performed a "thruster swap", switching from a clogged set of thrusters to less clogged ones that had not been used since 2018. In May 2025, the team was able to revive the backup thrusters used for roll motion that were unusable since 2004.