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Beyond Earth - A Chronicle of Deep Space Exploration 1958-2016

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Vega 1

Nation: USSR (102) Objective(s): Venus atmospheric entry and landing, Halley’s Comet flyby Spacecraft: 5VK (no. 901) = 5VS (Venus orbiter) + 5VP (Halley flyby + Venus lander) Spacecraft Mass: c. 4,840 kg Mission Design and Management: NPO imeni Lavochkina Launch Vehicle: Proton-K + Blok D-1 (Proton-K no. 329-01 + 11S824M no. 11L) Launch Date and Time: 15 December 1984 / 09:16:24 UT Launch Site: NIIP-5 / Site 200/39

Scientific Instruments:

Lander:

  1. meteorological complex to measure temperature and pressure
  2. VM-4 instrument to measure moisture content
  3. Sigma-3 gas chromatograph
  4. IFP aerosol x-ray fluorescence spectrometer
  5. ISAV-A optical aerosol analyzer
  6. ISAV-S ultraviolet spectrometer
  7. LSA laser aerosol meter
  8. Malakhit-M aerosol mass spectrometer (MS 1S1)
  9. BDRP-AM25 soil x-ray fluorescence spectrometer + drill
  10. GS-15STsV gamma-ray spectrometer
  11. PrOP-V penetrometer/soil ohmmeter

Balloon:

  1. temperature and pressure sensors
  2. vertical wind anemometer
  3. nephelometer
  4. light level/lighting detector

Bus:

  1. magnetometer (MISHA)
  2. PLAZMAG-1 plasma energy analyzer
  3. Tyunde-M energetic particle analyzer
  4. neutral gas mass spectrometer (ING)
  5. APV-V high-frequency plasma wave analyzer
  6. APV-N low-frequency plasma wave analyzer
  7. dust mass spectrometer (PUMA)
  8. SP-1 and SP-2 dust particle counters
  9. dust counter and mass analyzer (DUCMA)
  10. Foton dust particle recorder
  11. imaging system (TVS)
  12. infrared spectrometer (IKS)
  13. ultraviolet, visible, infrared imaging spectrometer (TKS)

Results: The twin-spacecraft Vega project, named after the combination of Venera and Gallei, the Russian words for "Venus" and "Halley," was perhaps the most ambitious deep space Soviet mission to date. The mission had three major goals: to place advanced lander modules on the surface of Venus, to deploy balloons (two each) in the Venusian atmosphere, and by using Venusian gravity, to fly the remaining buses past the Comet Halley. The entire mission was a cooperative effort between the Soviet Union (who provided the spacecraft and launch vehicle) with contributions from Austria, Bulgaria, Hungary, the German Democratic Republic (East Germany), Poland, Czechoslovakia, France (whose contribution was significant), and the Federal Republic of Germany (West Germany). In addition, one instrument, a comet dust (flux) analyzer, was provided by an American cosmic ray physicist, John A. Simpson (1916–2000), at the University of Chicago. This instrument turned out to be the only American instrument that directly studied Halley's comet during its 1986 encounter.

While the landers were similar to ones used before for exploring Venus, the balloon gondolas were completely new Soviet-made vehicles that carried U.S.-French nephelometers to measure aerosol distribution in the atmosphere. The cometary flyby probes, which contained a 120-kilogram scientific package, were protected against high-velocity impacts from dust particles. After a successful flight to Venus, Vega 1 released its 1,500-kilogram descent module on 9 June 1985, two days before atmospheric entry. As the lander descended, at 61 kilometers altitude, it released the first helium-inflated plastic balloon with a hanging gondola underneath it. Mass was around 20.8 kilograms. As the balloon drifted through the Venusian atmosphere (controlled partly by ballast), it transmitted important data on the atmosphere back to a network of tracking antennas on Earth. Balloon 1 survived for 46.5 hours, eventually succumbing due to battery failure, having traversed about 11,600 kilometers. The lander set down safely on the ground at 03:02:54 UT on 11 June 1985 at 8.1° N / 176.7° longitude on the night side of Venus in the Mermaid Plain north of Aphrodite and transmitted from the surface for 56 minutes. Temperature and pressure at the landing site were 467°C and 93.88 atmospheres, respectively. The soil sample drill failed to complete its soil analysis, having spuriously deployed about 15 minutes before reaching the surface, but the mass spectrometer returned important data.

The Vega 1 bus flew by Venus at a range of 39,000 kilometers and then headed for its encounter with Halley. After course corrections on 25 June 1985 and 10 February 1986, the spacecraft began its formal studies of the comet on 4 March when it was 14 million kilometers from its target. During the 3-hour encounter on 6 March 1986, the spacecraft approached to within 8,889 kilometers (at 07:20:06 UT) of Halley. Vega 1 took more than 500 pictures via different filters as it flew through the gas cloud around the coma. Although the spacecraft was battered by dust, none of the instruments were disabled during the encounter. Vega 1 collected a wealth of information on Halley including data on its nucleus, its dust production rate, its chemical composition, and its rotational rate. After subsequent imaging sessions on 7 and 8 March 1986, Vega 1 headed out to heliocentric orbit where it continued to transmit data from at least some of its instruments until last contact on 30 January 1987.

Vega 2

Nation: USSR (103) Objective(s): Venus atmospheric entry, Halley’s Comet flyby Spacecraft: 5VK (no. 902) = 5VS (Venus orbiter) + 5VP (Halley flyby + Venus lander) Spacecraft Mass: 4,840 kg Mission Design and Management: NPO imeni Lavochkina Launch Vehicle: Proton-K + Blok D-1 (8K82K no. 325-02 + 11S824M no. 12L) Launch Date and Time: 21 December 1984 / 09:13:52 UT Launch Site: NIIP-5 / Site 200/40

Scientific Instruments:

Lander:

  1. meteorological complex to measure temperature and pressure
  2. VM-4 instrument to measure moisture content
  3. Sigma-3 gas chromatograph
  4. IFP aerosol x-ray fluorescence spectrometer
  5. ISAV-A optical aerosol analyzer
  6. ISAV-S ultraviolet spectrometer
  7. LSA laser aerosol meter
  8. Malakhit-M aerosol mass spectrometer (MS 1S1)
  9. BDRP-AM25 soil x-ray fluorescence spectrometer + drill
  10. GS-15STsV gamma-ray spectrometer
  11. PrOP-V penetrometer/soil ohmmeter

Balloon:

  1. temperature and pressure sensors
  2. vertical wind anemometer
  3. nephelometer
  4. light level/lighting detector

Bus:

  1. magnetometer (MISHA)
  2. PLAZMAG-1 plasma energy analyzer
  3. Tyunde-M energetic particle analyzer
  4. neutral gas mass spectrometer (ING)
  5. APV-V high-frequency plasma wave analyzer
  6. APV-N low-frequency plasma wave analyzer
  7. dust mass spectrometer (PUMA)
  8. SP-1 and SP-2 dust particle counters
  9. dust counter and mass analyzer (DUCMA)
  10. Foton dust particle recorder
  11. imaging system (TVS)
  12. infrared spectrometer (IKS)
  13. ultraviolet, visible, infrared imaging spectrometer (TKS)

Results: Vega 2 was the sister spacecraft to Vega 1, and essentially performed a near-identical mission to its twin. The main lander probe set down without problems at 03:00:50 UT on 15 June 1985 in the northern region of Aphrodite, about 1,500 kilometers south-east of Vega. Landing coordinates were 7.2° S / 179.4° longitude. Temperature and pressure were recorded as 462°C and 87.11 atmospheres, respectively. The spacecraft transmitted from the surface for 57 minutes. Unlike its twin, the Vega 2 lander was able to collect and investigate a soil sample; the experiment identified an anorthosite-troctolite rock, rarely found on Earth, but present in the lunar highlands. According to the lander's data, the area was probably the oldest explored by any Venera vehicle. The mass spectrometer did not return any data. The balloon, released upon entry into the atmosphere, flew through the Venusian atmosphere, collecting data like its twin and survived for 46.5 hours of data transmission, traveling a slightly longer distance than its compatriot from Vega 1. Neither balloon on Vega 1 nor Vega 2 detected any lightning in the Venusian atmosphere.

After releasing its lander, the flyby probe continued on its flight to Comet Halley. The spacecraft initiated its encounter on 7 March 1986 by taking 100 photos of the comet from a distance of 14 million kilometers. Vega 2's closest approach (8,030 kilometers) to Halley was at 07:20 UT two days later when the spacecraft was traveling at a velocity of 76.8 kilometers/second (slightly lower than Vega 1's 79.2 kilometers/second). During the encounter, Vega 2 took 700 images of the comet of much better resolution than those from its twin, partly due to the presence of less dust outside of the coma during this transit, although many of the images were overexposed due to a failure in the primary pointing software. Ironically, Vega 2 sustained an 80% power loss during the encounter (as compared to Vega 1's 40%). Seven instruments between the two spacecraft were partially damaged, although no instrument on both were incapacitated. After further imaging sessions on 10 and 11 March 1986, Vega 2 finished its primary mission and headed out into heliocentric orbit. Like Vega 1, Vega 2 continued "a series of scientific investigations" until last contact on 24 March 1987.

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:

  1. solar wind ion detector
  2. plasma wave probe
  3. 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.

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:

  1. neutral mass spectrometer (NMS)
  2. ion mass spectrometer (IMS)
  3. Giotto radio experiment (GRE)
  4. dust impact detection system (DID)
  5. Rème plasma analyzer (RPA)
  6. Johnstone plasma analyzer (JPA)
  7. energetic particles analyzer (EPA)
  8. magnetometer (MAG)
  9. optical probe experiment (OPE)
  10. Halley multicolor camera (HMC)
  11. 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.

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