''Interstellar Probe'' (''ISP'') is a proposed

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

space probe Uncrewed spacecraft or robotic spacecraft are spacecraft without people on board. Uncrewed spacecraft may have varying levels of autonomy from human input, such as remote control, or remote guidance. They may also be autonomous, in which th ...

designed to explore and characterize the

heliosphere The heliosphere is the magnetosphere, astrosphere, and outermost atmospheric layer of the Sun. It takes the shape of a vast, tailed bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding ...

and interstellar space. The study was originally proposed in 2018 by NASA for the

Applied Physics Laboratory The Johns Hopkins University Applied Physics Laboratory (or simply Applied Physics Laboratory, or APL) is a not-for-profit university-affiliated research center (UARC) in Howard County, Maryland. It is affiliated with Johns Hopkins University ...

. It would have a baseline launch between 2036 and 2041. The probe would launch on a direct hyperbolic trajectory to encounter

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

after six to seven months, after which the probe would travel at a speed of about per year, leaving the heliosphere after only 16 years. The probe may have the opportunity to encounter minor planets on the way out, including

Orcus Orcus was a god of the underworld, punisher of broken oaths in Etruscan and Roman mythology. As with Hades, the name of the god was also used for the underworld itself. Eventually, he was conflated with Dis Pater and Pluto. A temple to Orcus ma ...

and

Quaoar Quaoar (minor-planet designation: 50000 Quaoar) is a ringed dwarf planet in the Kuiper Belt, a ring of many icy planetesimals beyond Neptune. It has an elongated ellipsoidal shape with an average diameter of , about half the size of the dwarf ...

, though such flybys would require specific launch dates. With next-generation

radioisotope thermoelectric generators A radioisotope thermoelectric generator (RTG, RITEG), or radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electr ...

(RTGs), the mission would be designed to last for over 50 years after its launch, a similar feat reached by the ''

Voyager 1 ''Voyager 1'' is a space probe launched by NASA on September 5, 1977, as part of the Voyager program to study the outer Solar System and the interstellar medium, interstellar space beyond the Sun's heliosphere. It was launched 16 days afte ...

'' and '' 2'' probes despite their intended 5-year lifetime. The mission has been called "''Voyager'' on steroids".

Mission background

Interstellar probes such as the

Voyager program The Voyager program is an American scientific program that employs two interstellar probes, ''Voyager 1'' and ''Voyager 2''. They were launched in 1977 to take advantage of a favorable planetary alignment to explore the two gas giants Jupiter ...

were made only with the intent to visit the outer planets, with the added interstellar mission as a mere bonus. Their lifetime had never been expected to be much longer than 12 years at the most, but the probes have lasted for upwards of four decades thus far. Both ''Voyagers'' left the heliosphere in the 2010s; ''Voyager 1'' in 2012, and ''2'' in 2018. While their readings have been valuable, many of their instruments have been shut off due to a lack of power in their RTGs. In addition, neither of them are headed toward the

IBEX ribbon The IBEX ribbon is a narrow, arc-shaped structure of enhanced energetic neutral atom (ENA) emissions discovered by NASA’s Interstellar Boundary Explorer (IBEX) mission in 2009. The ribbon is a significant feature at the boundary of the heliosphe ...

, a region discovered by the

Interstellar Boundary Explorer Interstellar Boundary Explorer (IBEX or Explorer 91 or SMEX-10) is a NASA satellite in Earth orbit that uses energetic neutral atoms (ENAs) to image the interaction region between the Solar System and Outer space, interstellar space. The missi ...

where energetic neutral atoms (ENAs) seem to highly affect the heliosphere and are able to breach it at unprecedented rates. Interstellar IBEX ribbon and dwarf planets

Interstellar IBEX ribbon and dwarf planets

Primary science goals

The main goals of the ''Interstellar'' mission include characterizing the heliosphere as a habitable astrosphere by its global nature, its interactions with the Sun and the interstellar medium, and the nature of said interstellar medium. Similar goals may include viewing the Sun as a habitable exoplanetary system from beyond, with potential outbound giant or dwarf planet flybys along the way depending on chosen launch date, and understanding the universe from beyond the heliosphere.

Scientific instruments

The probe would contain two differing scientific payloads, both weighing about . One would prioritize

Lyman-alpha Lyman-alpha, typically denoted by Ly-α or Lyα, is a spectral line of hydrogen (or, more generally, of any one-electron atom) in the Lyman series. It is emitted when the atomic electron transitions from an ''n'' = 2 orbital to the gro ...

science, whereas the other would prioritize visible and infrared imaging of flyby targets. Payloads highlighted in red are exclusive to the baseline payload. Instruments in green are intended for the augmented flyby payload.

Mission operations

Launch and trajectories

The baseline launch would be in 2036 using a

Space Launch System The Space Launch System (SLS) is an American Super heavy-lift launch vehicle, super heavy-lift Expendable launch system, expendable launch vehicle used by NASA. As the primary launch vehicle of the Artemis program, Artemis Moon landing progra ...

in its Block 2 configuration, featuring an additional

Centaur A centaur ( ; ; ), occasionally hippocentaur, also called Ixionidae (), is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse that was said to live in the mountains of Thessaly. In one version o ...

and

Star 48 The Star 48 is the largest of a family of solid rocket motors used by many space propulsion and launch vehicle stages, almost exclusively as an upper stage. It was developed primarily by Thiokol Propulsion and after several mergers, is manufact ...

BV booster. This launch would put the probe on a direct trajectory to Jupiter, and after a mere seven months the probe would make a gravity assist to speed out at about 95 km/s (about 216000 mph). Alternative trajectories include bringing the Star 48 booster for a burn upon closest approach; one trajectory involving that burn at Jupiter with a slightly longer transit time, and another with about the same transit time, but passing ahead of Jupiter for a dive down near the Sun for an even faster escape trajectory. Further trajectory options have been considered, including performing flybys of

Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...

Uranus Uranus is the seventh planet from the Sun. It is a gaseous cyan-coloured ice giant. Most of the planet is made of water, ammonia, and methane in a Supercritical fluid, supercritical phase of matter, which astronomy calls "ice" or Volatile ( ...

, or

Neptune Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...

depending on launch date to help characterize planetary formation and complement missing data sets, and dwarf planets to help characterize them as ''

New Horizons ''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institut ...

'' did in 2015 with its flyby of

Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of Trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Su ...

References