Mission Overview
================
The twin Voyager spacecraft, over the course of a dozen years, drew back the curtain on nearly half of the solar system. From launch in 1977 through the spectacular parting shots of Neptune at the outer reaches of the solar system in 1989, this pair of spacecraft explored four planets -- Jupiter, Saturn, Uranus and Neptune -- as well as dozens of moons, and the rings and magnetic environments of those planetary systems.

The Voyagers were designed to take advantage of a rare geometric arrangement of the outer planets that occurs only once every 176 years. This configuration allows a single spacecraft to swing by all four gas giants without the need for large onboard propulsion systems; the flyby of each planet both accelerates the spacecraft and bends its flight path. Without these gravity assists, the flight time to Neptune would have been 30 years.

The second of the two Voyager spacecraft, Voyager 2, was launched first, on 20 August 1977. It was followed on 5 September 1977 by Voyager 1, which was put on a faster, shorter trajectory to Jupiter. Both launches took place from the Cape Canaveral Air Force Station in Florida.

Eighteen months after launch, Voyager 1 reached Jupiter, 650 million kilometers away. The spacecraft made its closest approach on 5 March 1979, while Voyager 2 followed on 9 July of the same year. Images streamed back from the pair of spacecraft showing the complex, swirling turbulence of Jupiter's atmosphere in exquisite detail. A giant storm, three times the size of Earth, raged in Jupiter's upper atmosphere, surrounded by rippling currents that rotated about it.
Voyager 1 found nine active volcanoes erupting on Io, the innermost of Jupiter's four major moons. Four months later, Voyager 2 found that eight of the nine volcanoes were still active. A thin, dusty ring was also discovered around Jupiter, forcing revision of theories about origins and mechanics of planetary ring systems.

At Saturn, both Voyagers took high-resolution images to help determine ring composition and dynamics. The Voyager 1 encounter took place in November 1980 and the Voyager 2 encounter was in August 1981. Voyager 1 was targeted to fly close to Saturn's largest moon Titan. This resulted in a south polar passage of Saturn, which redirected the spacecraft northward of the ecliptic.

Voyager 2 continued on to Uranus where ten new moons were discovered in the Uranus system. The planet's magnetic field was found to be significantly offset from the planet's axis of rotation.

In August 1989, Voyager 2 flew past Neptune. Because Neptune receives so little sunlight, many scientists had expected to see a placid, featureless planet. Instead, Voyager showed a dynamic atmosphere with winds blowing westward, opposite the direction of rotation, at speeds faster than the winds of any other planet. Neptune revealed its Great Dark Spot, a storm system that resembled Jupiter's Great Red Spot, and a smaller, eastwardly moving cloud, called 'scooter', which went around the planet about every 16 hours. The blue planet was circled by diffuse, dusty rings; six new moons were discovered.

Voyager 2 passed over the north polar region on Neptune, using the planet's gravity to redirect the trajectory for a final encounter -- with Neptune's largest moon Triton. It then departed the solar system southward of the ecliptic.

At about the same time as Voyager 2 was encountering Neptune, Voyager 1, continuing its journey to the edge of the solar system on the north side of the ecliptic, turned its cameras back to look at the planets and take one last parting shot.
Voyager 1's 'family portrait' illustrates the vastness of the solar system and the huge expanses of emptiness within which the outer planets lie.

Both Voyagers are now headed for the outer boundary of the solar system, where the Sun becomes just one of many contributors to the interstellar environment. That edge is thought to be somewhere between 8 billion and 23 billion kilometers from the Sun. Engineers are optimistic that the Voyagers will still be transmitting data when that boundary is encountered sometime in the first quarter of the twenty-first century.

The spacecraft were assembled at and the mission was managed by the Jet Propulsion Laboratory, Pasadena, CA. Early parts of the mission have been described in more detail by [MORRISON1982].


Mission Phases
==============


VOYAGER 1 LAUNCH
----------------
The launch vehicle for Voyager 1 was a Titan/Centaur. The first stage Titan was powered by both solid and liquid fuel engines. The Centaur stage, 20 meters long and 3 meters in diameter burned a fuel combination of liquid hydrogen and liquid oxygen. The Titan boosted the Voyager Centaur combination into low Earth orbit, and the Centaur plus a small solid fuel rocket provided the energy for Voyager 1 to escape Earth orbit.

Spacecraft Id : VG1 Mission Phase Start Time : 1977-09-05 Mission Phase Stop Time : 1977-09-05 Spacecraft Operations Type : LAUNCH


VOYAGER 1 EARTH-JUPITER CRUISE
------------------------------
During the period between Launch and Jupiter Encounter, Voyager 1 probed the interplanetary medium and conducted tests and calibrations of its systems.

Spacecraft Id : VG1 Mission Phase Start Time : 1977-09-05 Mission Phase Stop Time : 1979-01-06 Spacecraft Operations Type : CRUISE


VOYAGER 1 JUPITER ENCOUNTER
---------------------------
The Voyager 1 flyby of Jupiter took place on 5 March 1979 at 12:04:36 UTC with the spacecraft closest approach only 348890 kilometers from the center of Jupiter. Among the highlights of the encounter were the discovery of a faint ring and one new satellite. Satellite encounter information is given below; 'UNK' denotes 'unknown' at time of this writing. The Voyager 1 Jupiter encounter is described in more detail by [STONE&LANE1979A].

Satellite Satellite Radial Closest Approach Name Dimensions Distance Date Distance (km) (km) (1979) (km)
--------- ----------- ---------- ------ ---------
Metis 40 128,000 UNK UNK Adrastea 24x20x14 129,000 UNK UNK Amalthea 270x166x150 181,300 5 Mar 420,200 Thebe 110x90 222,000 UNK UNK Io 3630 422,000 5 Mar 20,570 Europa 3138 661,000 5 Mar 733,760 Ganymede 5262 1,070,000 5 Mar 114,710 Callisto 4800 1,883,000 6 Mar 126,400 Leda 16 11,094,000 UNK UNK Himalia 186 11,480,000 UNK UNK Lysithia 36 11,720,000 UNK UNK Elara 76 11,737,000 UNK UNK Ananke 30 21,200,000 UNK UNK Carme 40 22,600,000 UNK UNK Pasiphae 50 23,500,000 UNK UNK Sinope 36 23,700,000 UNK UNK
Spacecraft Id : VG1 Target Name : JUPITER Mission Phase Start Time : 1979-01-06 Mission Phase Stop Time : 1979-04-13 Spacecraft Operations Type : FLYBY


VOYAGER 1 JUPITER-SATURN CRUISE
-------------------------------
During the period between Jupiter Encounter and Saturn Encounter, Voyager 1 probed the interplanetary medium, observed selected celestial targets, and conducted tests and calibrations of its systems. Mission planners used the 16 months to develop and test activity sequences which would be used during the Saturn Encounter.

Spacecraft Id : VG1 Mission Phase Start Time : 1979-04-13 Mission Phase Stop Time : 1980-08-22 Spacecraft Operations Type : CRUISE


VOYAGER 1 SATURN ENCOUNTER
--------------------------
The Voyager 1 flyby of Saturn took place on 12 November 1980 at 23:46 UTC with the spacecraft closest approach only 184300 kilometers from the center of Saturn. Among the highlights of the encounter were the separate encounter with Titan, discovery of intricate patterns within the ring system, and observation of variations among the many moons of Saturn.
Closest approaches to some of the satellites were on the dates and at the distances shown below. 'UNK' denotes 'unknown' at the time of this writing. The encounter is described in more detail by [STONE&MINER1981].

Satellite Satellite Radial Closest Approach Name Dimensions Distance Date Distance (km) (km) (1980) (km)
--------- ----------- ---------- ------ ----------
Pan 10 133,583 12 Nov UNK Atlas 40x20 137,670 UNK 219,000 Prometheus 140x100x80 139,353 UNK 300,000 Pandora 110x90x80 141,700 12 Nov 270,000 Epimetheus 140x120x100 151,472 13 Nov 121,000 Janus 220x200x160 151,422 12 Nov 297,000 Mimas 392 185,520 12 Nov 88,440 Enceladus 520 238,020 12 Nov 202,040 Tethys 1060 294,660 12 Nov 415,670 Telesto 34x28x26 294,660 12 Nov 233,000 Calypso 34x22x22 294,660 13 Nov 432,000 Dione 1120 377,400 12 Nov 161,520 Helene 36x32x30 377,400 13 Nov 237,000 Rhea 1530 527,040 12 Nov 73,980 Titan 5150 1,221,860 12 Nov 6,490 Hyperion 410x260x220 1,481,000 13 Nov 880,440 Iapetus 1460 3,560,830 14 Nov 2,470,000 Phoebe 220 12,952,000 UNK 13,500,000
Spacecraft Id : VG1 Target Name : SATURN Mission Phase Start Time : 1980-08-22 Mission Phase Stop Time : 1980-12-14 Spacecraft Operations Type : FLYBY


VOYAGER 1 INTERSTELLAR MISSION
------------------------------
After conclusion of the Saturn Encounter, Voyager 1 left the ecliptic at an angle of about 30 degrees. Its scan platform instruments were turned off, but some of the remaining instruments (primarily fields and particles) continued to monitor the environment in the outer solar system as the spacecraft traveled outward toward the heliopause.

Spacecraft Id : VG1 Mission Phase Start Time : 1980-12-14 Mission Phase Stop Time : UNK Spacecraft Operations Type : CRUISE


VOYAGER 2 LAUNCH
----------------
The launch vehicle for Voyager 2 was a Titan/Centaur. The first stage Titan was powered by both solid and liquid fuel engines. The Centaur stage, 20 meters long and 3 meters in diameter burned a fuel combination of liquid hydrogen and liquid oxygen. The Titan boosted the Voyager Centaur combination into low Earth orbit, and the Centaur plus a small solid fuel rocket provided the energy for Voyager 2 to escape Earth orbit.

Spacecraft Id : VG2 Mission Phase Start Time : 1977-08-20 Mission Phase Stop Time : 1977-08-20 Spacecraft Operations Type : LAUNCH


VOYAGER 2 EARTH-JUPITER CRUISE
------------------------------
During the period between Launch and Jupiter Encounter, Voyager 2 probed the interplanetary medium and conducted tests and calibrations of its systems.

Spacecraft Id : VG2 Mission Phase Start Time : 1977-08-20 Mission Phase Stop Time : 1979-04-25 Spacecraft Operations Type : CRUISE


VOYAGER 2 JUPITER ENCOUNTER
---------------------------
The Voyager 2 flyby of Jupiter took place on 9 July 1979 at 22:29 UTC. This was 18 weeks after the Voyager 1 Jupiter Encounter and was at a closest approach distance of 721670 kilometers from the center of Jupiter. The Voyager 2 trajectory was chosen to complement that of Voyager 1, including a much closer approach to Europa, probing southern latitudes in Jupiter's atmosphere, and an extensive investigation of Jupiter's magnetotail. Satellite encounter information is given below; 'UNK' denotes 'unknown' at time of this writing. The Voyager 2 Jupiter encounter is described in more detail by [STONE&LANE1979B].

Satellite Satellite Radial Closest Approach Name Dimensions Distance Date Distance (km) (km) (1979) (km)
--------- ----------- ---------- ------ ---------
Metis 40 128,000 UNK UNK Adrastea 24x20x14 129,000 UNK UNK Amalthea 270x166x150 181,300 9 Jul 558,370 Thebe 110x90 222,000 UNK UNK Io 3630 422,000 9 Jul 1,129,900 Europa 3138 661,000 9 Jul 205,720 Ganymede 5262 1,070,000 9 Jul 62,130 Callisto 4800 1,883,000 8 Jul 214,930 Leda 16 11,094,000 UNK UNK Himalia 186 11,480,000 UNK UNK Lysithia 36 11,720,000 UNK UNK Elara 76 11,737,000 UNK UNK Ananke 30 21,200,000 UNK UNK Carme 40 22,600,000 UNK UNK Pasiphae 50 23,500,000 UNK UNK Sinope 36 23,700,000 UNK UNK
Spacecraft Id : VG2 Target Name : JUPITER Mission Phase Start Time : 1979-04-25 Mission Phase Stop Time : 1979-08-05 Spacecraft Operations Type : FLYBY


VOYAGER 2 JUPITER-SATURN CRUISE
-------------------------------
During the period between Jupiter Encounter and Saturn Encounter, Voyager 2 probed the interplanetary medium, observed selected celestial targets, and conducted tests and calibrations of its systems. Mission planners used the 22 months to develop and test activity sequences which would be used during the Saturn Encounter.

Spacecraft Id : VG2 Mission Phase Start Time : 1979-08-05 Mission Phase Stop Time : 1981-06-05 Spacecraft Operations Type : CRUISE


VOYAGER 2 SATURN ENCOUNTER
--------------------------
The Voyager 2 closest approach to Saturn was on 26 August 1981 at 03:24 UTC and at a distance of 161000 km from the center of Saturn. The trajectory was chosen so that the spacecraft could obtain a gravitational assist from Saturn and continue on to Uranus; the timing was selected to provide better views of several satellites than had been obtained from Voyager 1. Design of science sequences was influenced by Voyager 1 results. Satellite encounters were on the dates and at the closest approach distances shown below; 'UNK' denotes 'unknown' at the time of this writing. The scan platform seized temporarily 110 minutes after Saturn closest approach, causing the central computer to disable further commands and resulting in loss of some data. When commanded again three days later (at low rate), it moved as instructed. A gyroscope calibration error between closest approach and five hours later also caused loss of data.
Scan platform activities ended on 5 September 1981. This encounter is described in more detail by [STONE&MINER1982].

Satellite Satellite Radial Closest Approach Name Dimensions Distance Date Distance (km) (km) (1981) (km)
--------- ----------- ---------- ------ ----------
Pan 10 133,583 26 Aug UNK Atlas 40x20 137,670 26 Aug 287,000 Prometheus 140x100x80 139,353 26 Aug 247,000 Pandora 110x90x80 141,700 26 Aug 107,000 Epimetheus 140x120x100 151,472 26 Aug 147,000 Janus 220x200x160 151,422 26 Aug 223,000 Mimas 392 185,520 26 Aug 309,930 Enceladus 520 238,020 26 Aug 87,010 Tethys 1060 294,660 25 Aug 93,010 Telesto 34x28x26 294,660 26 Aug 270,000 Calypso 34x22x22 294,660 26 Aug 151,590 Dione 1120 377,400 26 Aug 502,310 Helene 36x32x30 377,400 25 Aug 314,090 Rhea 1530 527,040 26 Aug 645,260 Titan 5150 1,221,860 24 Aug 666,190 Hyperion 410x260x220 1,481,000 24 Aug 431,370 Iapetus 1460 3,560,830 22 Aug 908,680 Phoebe 220 12,952,000 4 Sep 2,075,640
Spacecraft Id : VG2 Target Name : SATURN Mission Phase Start Time : 1981-06-05 Mission Phase Stop Time : 1981-09-25 Spacecraft Operations Type : FLYBY


VOYAGER 2 SATURN-URANUS CRUISE
------------------------------
During the period between Saturn Encounter and Uranus Encounter, Voyager 2 probed the interplanetary medium, observed selected celestial targets, and conducted tests and calibrations of its systems. Mission planners used the 49 months to develop and test activity sequences which would be used during the Uranus Encounter. Considerable attention was paid to the scan platform capabilities, following its seizure during the Saturn Encounter. Full scan platform operation was restored before the end of 1981.

Spacecraft Id : VG2 Mission Phase Start Time : 1981-09-25 Mission Phase Stop Time : 1985-11-04 Spacecraft Operations Type : CRUISE


VOYAGER 2 URANUS ENCOUNTER
--------------------------
The Voyager 2 closest approach to Uranus was on 24 January 1986 at 17:59 UTC at a distance of 107000 km from the center of Uranus. The trajectory was chosen so that the spacecraft could obtain a gravitational assist from Uranus and continue on to Neptune; NASA permission for the Neptune Encounter was granted during the approach to Uranus. The timing of the Uranus closest approach was selected to provide a close approach to Miranda and to allow capture of radio occultation data at the DSN tracking station in Australia (southern declination of Uranus meant that Australia was preferred for DSN tracking). Radio occultation data were also collected using the 64-m antenna at Parkes in Australia. Satellite encounters were on the dates and at the closest approach distances shown below. 'UNK' denotes 'unknown' at the time of this writing.
Satellite images were improved by implementation of image motion compensation on the spacecraft. Reed-Solomon encoding was used for the first time; real-time imaging data rates were reduced by almost 70 percent. Ground antennas were arrayed to increase receiving aperture. This encounter is described in more detail by [STONE&MINER1986].

Satellite Satellite Radial Closest Approach Name Dimensions Distance Date Distance (km) (km) (1986) (km)
--------- ----------- ---------- ------ ----------
Cordelia 26 49,800 UNK UNK Ophelia 30 53,800 UNK UNK Bianca 42 59,200 UNK UNK Juliet 62 61,800 UNK UNK Desdemona 54 62,700 UNK UNK Rosalind 84 64,400 UNK UNK Portia 108 66,100 UNK UNK Cressida 54 69,900 UNK UNK Belinda 66 75,300 UNK UNK Puck 154 86,000 UNK UNK Miranda 472 129,900 24 Jan 29,000 Ariel 1,158 190,900 24 Jan 127,000 Umbriel 1,172 265,969 24 Jan 325,000 Titania 1,580 436,300 24 Jan 365,200 Oberon 1,524 583,400 24 Jan 470,600
Spacecraft Id : VG2 Target Name : URANUS Mission Phase Start Time : 1985-11-04 Mission Phase Stop Time : 1986-02-25 Spacecraft Operations Type : FLYBY


VOYAGER 2 URANUS-NEPTUNE CRUISE
-------------------------------
During the period between Uranus Encounter and Neptune Encounter, Voyager 2 probed the interplanetary medium, observed selected celestial targets, and conducted tests and calibrations of its systems. Mission planners used the 39 months to develop and test activity sequences which would be used during the Neptune Encounter.

The DSN used this time to add a 34-m tracking antenna at the Madrid complex, to increase the diameter of their 64-m antennas to 70 meters, and to make the 70-m systems more efficient. A special microwave link was installed to permit the Parkes radio telescope to be arrayed with the Canberra DSN antenna in Australia.

Spacecraft Id : VG2 Mission Phase Start Time : 1986-02-25 Mission Phase Stop Time : 1989-06-05 Spacecraft Operations Type : CRUISE


VOYAGER 2 NEPTUNE ENCOUNTER
---------------------------
The Voyager 2 closest approach to Neptune was on 25 August 1989 at 03:56 UTC at a distance of 29240 km from the center of Neptune. The trajectory and timing were chosen so that the spacecraft could obtain a gravitational assist from Neptune and continue on for an encounter with Neptune's large satellite Triton about five hours later (closest approach at 09:10 UTC). The timing was also selected so that radio occultation data would be collected at the DSN tracking station in Australia (southern declination of Neptune meant that Australia was preferred for DSN tracking). Radio occultation data were again collected with the Parkes antenna and with a new 64-m antenna at Usuda in Japan. Satellite encounters were on the dates and at the closest approach distances shown below. 'UNK' denotes 'unknown' at the time of this writing. Data rates were increased over those at Uranus by including the Very Large Array (VLA) in New Mexico for receiving and by taking advantage of DSN upgrades made over the previous three years. This encounter is described in more detail by [STONE&MINER1989].

Satellite Satellite Radial Closest Approach Name Dimensions Distance Date Distance (km) (km) (1989) (km)
--------- ----------- ---------- ------ ----------
Naiad 54 48,000 25 Aug UNK Thalassa 80 50,000 25 Aug UNK Despina 180 52,500 25 Aug UNK Galatea 150 62,000 25 Aug UNK Larissa 190 73,600 25 Aug 60,180 Proteus 400 117,600 25 Aug 97,860 Triton 2,700 354,760 25 Aug 39,790 Nereid 340 5,509 090 25 Aug 4,652,880
Spacecraft Id : VG2 Target Name : NEPTUNE Mission Phase Start Time : 1989-06-05 Mission Phase Stop Time : 1989-10-02 Spacecraft Operations Type : FLYBY


VOYAGER 2 INTERSTELLAR MISSION
------------------------------
After conclusion of the Neptune Encounter, Voyager 2 left the ecliptic at an angle of about -30 degrees. Its scan platform instruments were turned off, but some of the remaining instruments (primarily fields and particles) continued to monitor the environment in the outer solar system as the spacecraft traveled outward toward the heliopause. During the Shoemaker-Levy 9 impact with Jupiter in July 1994, the ultraviolet spectrometer was trained on Jupiter and radio signals were recorded; but no emissions from the impact were detected.

Spacecraft Id : VG2 Mission Phase Start Time : 1989-10-02 Mission Phase Stop Time : UNK Spacecraft Operations Type : CRUISE