Sakigake
Nation: Japan (1) Objective(s): Halley’s Comet flyby Spacecraft: MS-T5 Spacecraft Mass: 138.1 kg Mission Design and Management: ISAS Launch Vehicle: Mu-3S-II (no. 1) Launch Date and Time: 7 January 1985 / 19:26 UT Launch Site: Kagoshima / Launch Complex M1
Scientific Instruments:
- solar wind ion detector
- plasma wave probe
- 2 magnetometers
Results: The MS-T5 spacecraft, named Sakigake ("pathfinder") after launch, was the first deep space spacecraft launched by any other country apart from the Soviet Union or the United States (Two German Helios probes had been launched by NASA). Japan's goal had been to launch a single modest probe to fly past Comet Halley as part of a test to prove out the technologies and mission operations of the actual mission. Japan's Institute of Space and Astronautical Sciences (ISAS) launched this test spacecraft, known as MS-T5, nearly identical to the "actual" spacecraft launched later. The spin-stabilized spacecraft was launched by a new Japanese launch vehicle, the Mu-3S-II. Following two course corrections on 10 January and 14 February 1985, Sakigake was sent on a long-range encounter with Halley. The original distance to the comet was planned to be 3 million kilometers but was altered to a planned 7.6 million kilometers when the launch had to be delayed due to bad weather and problems with the launch vehicle.
<!-- image -->The spacecraft served as a reference vehicle to permit scientists to eliminate Earth atmospheric and ionospheric contributions to the variations in Giotto's transmissions from within the coma. The spacecraft's closest approach to Halley was at 04:18 UT on 11 March 1986 when it was 6.99 million kilometers from the comet. Nearly six years after the Halley encounter, Sakigake performed a gravity assist by Earth on 8 January 1992 at 88,790-kilometer range. After two more distant flybys through Earth's tail (in June 1993 and July 1994), Sakigake maintained weekly contact with the ground until telemetry was lost on 15 November 1995. Earlier, Japanese scientists had hoped to send the spacecraft on a flyby past Comet 21P/Giacobini-Zinner in 1998 but these were abandoned due to lack of sufficient propellant. Although telemetry was lost, ground control continued to receive a beacon signal until 7 January 1999, 14 years after launch.
Giotto
Nation: European Space Agency (1) Objective(s): Halley’s Comet flyby Spacecraft: Giotto Spacecraft Mass: 960 kg Mission Design and Management: ESA Launch Vehicle: Ariane 1 (V14) Launch Date and Time: 2 July 1985 / 11:23:16 UT Launch Site: CSG / ELA-1
Scientific Instruments:
- neutral mass spectrometer (NMS)
- ion mass spectrometer (IMS)
- Giotto radio experiment (GRE)
- dust impact detection system (DID)
- Rème plasma analyzer (RPA)
- Johnstone plasma analyzer (JPA)
- energetic particles analyzer (EPA)
- magnetometer (MAG)
- optical probe experiment (OPE)
- Halley multicolor camera (HMC)
- particulate impact analyzer (PIA)
Results: Giotto was the first deep space probe launched by the European Space Agency (ESA). It was named after famed Italian Renaissance painter Giotto di Bondone (c. 1267–1337) who had depicted Halley's Comet as the Star of Bethlehem in his painting Adoration of the Magi. Because the cylindrical spacecraft was designed to approach closer to Halley than any other probe, it was equipped with two dust shields separated by 23 centimeters, the first to bear the shock of impact and spread the impact energy over larger areas of the second thicker rear sheet. The design of the spacecraft was based on the spin-stabilized magnetospheric Geos satellites launched in 1977 and 1978. After launch, and further course corrections on 26 August 1985, 12 February 1986, and 12 March 1986, Giotto was put on a 500-kilometer-range flyby trajectory to the comet's core. Ballistics data on its precise voyage was based upon tracking information from the Soviet Vega 1 and 2 probes.
The Giotto spacecraft eventually passed by Halley on 14 March 1986. Closest encounter was at a distance of 596 kilometers at 00:03:02 UT, the spacecraft being the only one among the large armada of spacecraft sent to investigate Halley that actually entered the ionosphere of the comet. At a range of 137.6 million kilometers from Earth, just 2 seconds before closest approach, telemetry stopped due to impact with a heavy concentration of dust that probably knocked the spacecraft's high gain antenna out of alignment with Earth. Fortunately, data transmission was restored within 21.75 seconds (with proper orientation of the antenna restored after 32 minutes). On average, Giotto had been hit 100 times a second by particles weighing up to 0.001 grams. By the end of its encounter with Halley, the spacecraft was covered in at least 26 kilograms of dust stemming from 12,000 impacts. Giotto returned 2,000 images of Halley.
After the encounter, ESA decided to redirect the vehicle for a flyby of Earth. The spacecraft was officially put in hibernation mode on 2 April 1986. Course corrections on 10, 20, and 21 March 1986, however, set it on a 22,000-kilometer flyby of Earth on 2 July 1990 for a gravity assist (the first time that Earth had been used for such a purpose) to visit a new target: Comet 26P/Grigg-Skjellerup, which Giotto flew by at 15:30 UT on 10 July 1992 at range of approximately 200 kilometers. Eight experiments provided extensive data on a wide variety of cometary phenomena during this closest ever flyby of a comet. After formal conclusion of the encounter, Giotto was put in hibernation on 23 July 1992. Later, in September 1999, ESA scientists revealed that a second comet or cometary fragment may have been accompanying Grigg-Skjellerup during the encounter in 1992. The spacecraft repeated a flyby of Earth at 02:40 UT on 1 July 1999 at range of 219,000 kilometers but was not reactivated.
Suisei
Nation: Japan (2) Objective(s): Halley’s Comet flyby Spacecraft: Planet-A Spacecraft Mass: 139.5 kg Mission Design and Management: ISAS Launch Vehicle: Mu-3S-II (no. 2) Launch Date and Time: 18 August 1985 / 23:33 UT Launch Site: Kagoshima / Launch Complex M1
Scientific Instruments:
- ultraviolet imaging system
- electrostatic analyzer
Results: Planet-A, named Suisei ("comet") after launch, was the second of two Japanese probes launched towards Halley during the 1986 Earth encounter. The cylindrical spacecraft was launched directly on a deep space trajectory without entering intermediate Earth orbit. The main payload of the spacecraft was an ultraviolet-based imaging system that could study the huge hydrogen corona around the comet. After a course correction on 14 November 1985, Suisei flew within 152,400 kilometers of the comet's nucleus on 8 March 1986 at 13:06 UT, returning ultraviolet images of the 20 million-kilometer diameter hydrogen gas coma. Even at that relatively large distance from the comet, the spacecraft was hit by at least two dust particles, each 1 millimeter in diameter.
After the Halley encounter, in 1987, ISAS decided to send the spacecraft through an elaborate trajectory for an encounter with Comet 21P/Giacobini-Zinner on 24 November 1998, 13 years after launch. Suisei performed a series of trajectory corrections on 5–10 April 1987 to send it on a gravity assist around Earth on 20 August 1992 at a range of 60,000 kilometers. Unfortunately, hydrazine for further corrections had been depleted by 22 February 1991. The planned encounter on 28 February 1998 with Giacobini-Zinner (as well as a far distance flyby of Comet 55P/Tempel-Tuttle) had to be cancelled, formally ending the mission.
Fobos 1
Nation: USSR (104) Objective(s): Mars flyby, Phobos encounter Spacecraft: 1F (no. 101) Spacecraft Mass: 6,220 kg Mission Design and Management: NPO imeni Lavochkina Launch Vehicle: Proton-K + Blok D-2 (8K82K no. 356-02 + 11S824F no. 2L) Launch Date and Time: 7 July 1988 / 17:38:04 UT Launch Site: NIIP-5 / Site 200/39
Scientific Instruments:
Orbiter:
- Lima-D laser mass spectrometer analyzer
- Dion secondary ion mass analyzer
- radar system (RLK) (of which Plazma ionosphere study instrument only on Fobos 1)
- videospectrometric system (VSK)
- KRFM-ISM infrared spectrometer
- Termoskan infrared spectrometer
- IPNM-3 neutron detector (only on Fobos 1)
- GS-14 STsF gamma-emission spectrometer
- Ogyust optical radiation spectrometer (ISO)
- scanning energy-mass spectrometer (ASPERA)
- plasma spectrometer (MPK)
- Ester electron spectrometer
- plasma wave analyzer (APV-F / PWS)
- flux gate magnetometer (FGMM)
- magnetometer (MAGMA)
- Terek solar telescope/coronograph (only on Fobos 1)
- RF-15 x-ray photometer
- ultrasound spectrometer (SUFR)
- gamma-ray burst spectrometer (VGS)
- Lilas gamma-ray burst spectrometer
- solar photometer (IFIR)
- Taus proton and alpha-particle spectrometer
- Harp ion and electron spectrometer
- Sovikoms energy, mass, and charge spectrometer
- Sled charged-particle spectrometer
DAS:
- Al'fa x-ray and alpha-particle backscattering spectrometer
- Stenopee (Libratsiya) sun sensor to measure librations
- 2 cameras
- vibration measurement instrument (VIK) + temperature sensor
- transponder
Results: Fobos 1 and 2 were part of an ambitious mission to Mars and its 27-kilometer diameter moon Phobos that culminated a decade-long program of development. A truly multinational project that was the last hurrah for Soviet planetary exploration, the missions involved contributions from 14 other nations including Austria, Bulgaria, Czechoslovakia, Finland, France (undoubtedly the most active partner), East Germany, West Germany, Hungary, Ireland, Poland, Switzerland, Sweden, and the European Space Agency. NASA provided some tracking support through its Deep Space Network. Each spacecraft, with a newly designed standardized bus known as the UMVL, comprised a Mars orbiter for long-term studies of the planet and a 67-kilogram Long-Term Autonomous Station (DAS) which would land on Phobos, anchored by a harpoon driven into the soil, to study its geological and climactic conditions.
The core of the bus was an autonomous engine unit (using the S5.92 engine, later named Fregat) that essentially acted as the fifth stage of the Proton launch vehicle, boosting the spacecraft to Mars from a highly eccentric Earth orbit attained after a firing of the Blok D upper stage. After each spacecraft entered orbit around Mars, they were designed to make very close (c. 50 meters) flybys of Phobos (on 7 April 1989 for Fobos 1), and sample surface material using two innovative methods (using a laser and using a beam of krypton ions) that would actively disturb the soil of Phobos. Instruments would then measure and evaluate the response. After the Phobos flyby, it was planned for the spacecraft to continue science missions directed at Mars from Martian orbit. The spacecraft were loaded with an unprecedented array of experiments, making them probably the most highly instrumented deep space mission ever launched.
Fobos 1 performed a course correction en route to Mars on 16 July 1988. On 29 August 1988, instead of a routine command to switch on the GS-14STsF gamma-emission spectrometer, an erroneous command was issued as a result of a programming error, to turn off the orientation and stabilization system. As a result, the spacecraft lost proper solar orientation, i.e., the solar panels faced away from the Sun and thus began to lose power. There was no word from Fobos 1 at the next scheduled communications session on 2 September. Continuing attempts to establish contact failed, and on 3 November 1988, the Soviets officially announced that there would be no further attempts at contact. The engineer who sent the false command was apparently barred from working on the shift teams for Fobos 2. Fobos 1 meanwhile flew by Mars without entering orbit (scheduled for 23 January 1989) and eventually entered heliocentric orbit. The most significant scientific data from the mission came from the Terek solar telescope, which returned important information on some of the then-least studied layers of the solar atmosphere, the chromosphere, the corona, and the transition layer.