Voyager 1 and 2 have been significant contributions to space science, with several scientific instrument payloads that have made significant discoveries on their journeys.

The Voyager probes’ tour of our solar system gave us close up images of the outer planets, measurable insight into the composition of Saturn's rings, confirmed volcanic activity on Jupiter’s moon Io, and proved the existence of storms on Neptune.

Many of the probes’ experiments in our solar system have been successfully completed and today both are continuing their journey beyond our solar system into interstellar space. Some experiments on both Voyager 1 and Voyager 2 are still in operation and send data back to Earth, giving us further information and clues about the environment beyond our planets. This data is used to help determine where our solar system ends, and interstellar space begins.

Here is a look into both Voyager 1 and Voyager 2’s mission objectives, the experiments onboard, and the data it collected that has complimented and expanded our knowledge of our solar system.

### Mission Objectives

A brief explanation of the mission objectives of Voyager 1 and 2 are as follows (taken from NASA's website):

1. investigate the circulation, dynamics, structure, and composition of the planet's atmosphere;
2. characterize the morphology, geology, and physical state of the satellites of the planet;
3. provide improved values for the mass, size, and shape of the planet, its satellites, and any rings; and,
4. determine the magnetic field structure and characterize the composition and distribution of energetic trapped particles and plasma therein.

With these objectives in mind, context is given to the 11 experiments conducted by both probes.

### Imaging Science (ISS)

During encounters with planets and satellite objects, images were taken with resolutions between 0.5-1.0 km,(or in the case of Jupiter and Saturn, resolutions of 20km and 5km respectively). Image data was collected using a dual vidicon camera system similar to the one used on the Mariner system. Imaging data was used in tandem with other data to confirm results and observations.

##### Jupiter approach taken by Voyager 1. Image courtesy of JPL.

ISS Data Archive

The RSS is a telecommunications payload that consists of a coherent S- and X- band downlink (13 cm and 3.5 cm wavelengths), with an S-band uplink. Experiments were conducted to learn more about the properties of the ionospheres of planets and satellites, the mass and gravity fields of these objects, and the distribution of material in Saturn’s rings. Data for these experiments was obtained by studying the propagation effects on the dual radio frequency signals.

### Infrared Interferometer Spectrometer (IRIS)

The IRIS experiment consists of a single channel radiometer and a Michelson Interferometer. These instruments were used for the determination of atmosphere composition, and the thermal properties of planets or satellites.

IRIS Data Archive

### Ultraviolet Spectrometer (UVS)

The UVS measured the properties of the atmospheres and radiation of target planets and satellites. Airglow measurements look at the scattering of solar radiation in the atmosphere and occultation measurements record the reflection and refraction of sunlight while the spacecraft passes behind a planetary body. Both systems separate light into component parts with a spectrometer.

UVS Data Archive

### Triaxial Fluxgate Magnetometer (MAG)

The MAG specifically targeted Jupiter and Saturn by measuring their magnetic fields and how the solar winds interacted with them. These measurements were taken with two high-field and two low-field triaxial fluxgate magnetometers with a range of 0.1 nT - 2.0E-3 T +/- 0.1 nT.

Two high field strength, and two low field strength triaxial fluxgate magnetometers flew aboard each spacecraft.  The magnetometer experiments were used to create magnetic field models of the planets Jupiter and Saturn, and the interplanetary magnetic field created by the sun. These measurements were taken in the range of $$2\times 10^{-12}\;T$$to$$2\times 10^{-3}\;T$$

MAG Data Archive

### Plasma Spectrometer (PLS)

Two Faraday-cup plasma detectors made up the PLS, with one cup pointed towards Earth, and the other 90 degrees to it. The first cup measured macroscopic plasma ion properties including velocity, density, and pressure. The second measured charged particles with energies within the range of 10 eV - 6 keV.

PLS Data Archive

### Low-Energy Charged Particles (LECP)

The LECP takes measurements of energy particles in both interplanetary and planetary space to give insight into the energy flux differentials, distribution of electrons, distribution of ions, and the ion energy composition differential.

LECP Data Archive

### Cosmic Ray System (CRS)

The CRS focused on interstellar cosmic rays including the origins, processes, history, the nucleosynthesis of elements, the behaviour of cosmic rays in interplanetary space, as well as the environment of trapped planetary energetic-particles.

The CRS helped to determine that Voyager 1 entered Interstellar Space in 2012.

CRS data from when Voyager 1 entered interstellar space. Image courtesy of NASA.

CRS Data Archive

The PRA specifically observed Jupiter and Saturn using sweep-frequency radio waves to observe the radio emissions from these planets due to natural phenomena such as aurora and lightning.

PRA Data Archive

### Photopolarimeter System (PPS)

The PPS studied the surface texture and composition of Jupiter and Saturn as well as particles in the atmosphere. Light from the sun was reflected off of the surface of the planet or passed through the atmosphere where it reached the spacecraft. The light was passed through a variable-orientation polarizing filter and into an eight-band (2200-7300 A) filter wheel and then into a photomultiplier tube. The PPS also gathered data on the composition and density of Saturn’s rings, and density of the atmosphere of Saturn and Jupiter.

PPS Data Archive

### Plasma Wave System (PWS)

The PWS focuses on Jupiter and Saturn’s electron-density profiles and local wave-particle interactions.  Study of the plasma fields inside the solar system allows scientists to refine their models for the solar wind.  By watching the sharp changes in plasma density at the edge of the solar system, scientists were able to determine the outer reaches of the sun’s influence, and locate the transition to interstellar space.

PWS Data Archive

### Current Position Tracking

Both Voyager 1 and 2 continue to be tracked on their journey. Online websites give approximate data on their exact positions [Voyager 1 | Voyager 2], but you can also download this data over a selected period of interest too for your own modeling or general interest. This data was used to create AllAboutCircuits model of the solar system and the Voyager flight path.

The current position of the probes is provided in three coordinate systems: Solar Ecliptic (SE), Heliographic Inertial (HGI), and Heliographic Coordinate (HG). Further explanation of each system can be found here with the data downloaded here.

Feature image courtesy of JPL.