Space History for April 6

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647 B.C.
Archilochus' Eclipse occurred, the earliest solar eclipse recorded by the ancient Greeks.
ref: eclipse.gsfc.nasa.gov

218
Halley's Comet passed perihelion in its seventh known passage, as determined from records by Chinese astronomers.

In 2000 years of observations since 240 BCE, Chinese records have never missed a return of Halley's Comet. From those records, Cowell and Crommelin computed the dates of perihelion passage as:

1. 15 May 240 BCE
2. 20 May 163 BCE
3. 15 August 87 BCE
4. 8 October 12 BCE
5. 26 January 66 CE
6. 25 March 141 CE
7. 6 April 218 CE
8. 7 April 295 CE
9. 13 February 374 CE
10. 3 July 451 CE
11. 15 November 530 CE
12. 26 March 607 CE
13. 26 November 684 CE
14. 10 June 760 CE
15. 25 February 837 CE
16. 17 July 912 CE
17. 2 September 989 CE
18. 25 March 1066 CE
19. 19 April 1145 CE
20. 10 September 1222 CE
21. 22.7 October 1301 CE
22. 8.8 November 1378 CE
23. 8.2 January 1456 CE
24. 25.8 August 1531 CE
25. 26.9 October 1607 CE
26. 14.8 September 1682 CE
27. 12.6 March 1758 CE
28. 15.9 November 1835 CE
29. 19.7 April 1910 CE
30. 9 February 1986 CE

Note that the precision of the dates from passage 21 onward could be computed with increased accuracy because of additional observations. However, at the time of their computation, the 1986 passage was still a future event. (The actual date was found from other sources.)

On 19 April 607, Comet 1P/607 H1 (Halley) approached within 0.0898 AU (13.5 million km, 8.4 million miles) of Earth. On 374-April-1.9, it had approached closer, having come within 0.0884 AU (13.2 million km, 8.2 million miles), and on 837-April-10.5, it became the third closest approach in history prior to 1900, passing within 0.0334 AU (5 million km, 3.1 million miles).

On 16 October 1982, astronomers David Jewitt and G. Edward Danielson using a CCD camera with the 5.1 m Hale telescope at Mt. Palomar Observatory were the first to detect Halley's Comet on its thirtieth recorded return.

1829
Died, Niels H. Abel, Norwegian mathematician (infinite series)
ref: en.wikipedia.org

1853
J. Chacornac discovered asteroid #25 Phocaea.

1855
J. Chacornac discovered asteroid #34 Circe.

1878
Prosper Henry discovered asteroid #186 Celuta.

1890
Born, Andre L. Danjon, French astronomer (Danjon Scale, color brightness of the Moon during a Lunar eclipse due to Earth's atmospheric conditions)
ref: en.wikipedia.org

1890
Born, Anthony H. G. Fokker, Dutch aircraft designer
ref: en.wikipedia.org

1891
J. Palisa discovered asteroid #309 Fraternitas.

1892
Born, Donald Wills Douglas Sr., US aircraft pioneer
ref: en.wikipedia.org

1903
Born, Harold E. "Doc" Edgerton, foremost high-speed photographer (invented stroboscopic photography)
ref: en.wikipedia.org

1905
P. Gotz discovered asteroid #563 Suleika.

1908
J. H. Metcalf discovered asteroid #755 Quintilla.

1914
The American Radio Relay League (an organization for hams - amateur radio operators) was founded.
ref: en.wikipedia.org

1916
S. Belyavskij discovered asteroid #857 Glasenappia.

1922
B. Jekhovsky discovered asteroid #977 Philippa.

1924
Four US Army Air Corps planes left Seattle on what would become the first successful around-the-world flight when two of them returned 175 days later, on September 28.
ref: en.wikipedia.org

1928
Born, James D. Watson, American molecular biologist (DNA structure, Nobel 1962 with Crick and Wilkins "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material")
ref: www.nobelprize.org

1938
Polytetrafluoroethylene resin (Teflon) was discovered by Roy J. Plunkett at EI Du Pont de Nemours & Company.
ref: en.wikipedia.org

1942
K. Reinmuth discovered asteroid #2249 Yamamoto.

1960
USSR's Sputnik 3 re-entered the atmosphere.

Sputnik 3, launched on 5 May 1958, was an automatic scientific laboratory spacecraft, conically shaped, 3.57 m long with a base diameter of 1.73 m. It was by far the largest satellite flown to that point, with a 1327 kg mass that was more than twice as much as the five previously flown satellites combined. The twelve scientific instruments provided data on pressure and composition of the upper atmosphere, concentration of charged particles, photons in cosmic rays, heavy nuclei in cosmic rays, magnetic and electrostatic fields, and meteoric particles. The Earth's outer radiation belts were detected during the flight. Due to its failed tape recorder, the spacecraft could only send data back to Earth in real time, so the only areas it could study where those in range of Soviet tracking stations, i.e. over Soviet territory. Communications were lost on 3 June 1958. The spacecraft remained in orbit until 6 April 1960.
ref: nssdc.gsfc.nasa.gov

1962 17:16:00 GMT
USSR launched Cosmos 2, the second satellite in the Soviet Earth Satellite series, which employed radio methods to study the structure of the ionosphere.
ref: nssdc.gsfc.nasa.gov

1963
Died, Otto Lyudvigovich Struve, Russian-American astronomer, one of the most distinguished and prolific astronomers of the mid-20th century (over 900 journal articles and books)
ref: en.wikipedia.org

1965 23:45:00 GMT
Intelsat 1 ("Early Bird") was launched, the first commercial geosynchronous communication satellite.
ref: nssdc.gsfc.nasa.gov

1967
T. Smirnova discovered asteroid #1804 Chebotarev.

1967 03:21:00 GMT
NASA launched ATS 2, but the satellite failed to reach its intended orbit. However, useful (although limited) data were returned from the orbit it did achieve.

ATS 2 (Applications Technology Satellite) was a medium altitude, gravity gradient stabilized spacecraft designed to (1) test new concepts in spacecraft design, propulsion, and stabilization, (2) take high quality cloudcover pictures, (3) provide in situ measurements of the aerospace environment, and (4) test improved communication systems. The cylindrically shaped spacecraft was 56 inches (142 cm) in diameter and 72 inches (183 cm) long. Its structure consisted primarily of a corrugated thrust tube with honeycombed bulkheads secured to each end. Equipment components and payload were externally mounted on the outer surface of the thrust tube as well as on a structure that slid into the interior of the thrust tube. Electric power was provided by two solar arrays mounted on either end of the spacecraft's outer shell and by two rechargeable nickel-cadmium batteries. Extending radially outward from the side of the spacecraft were four 92.5 foot (28.2 m) adjustable gravity gradient booms. The spacecraft telemetry system consisted of four 2.1 W transmitters (two at 136.47 MHz and two at 137.35 MHz), and a microwave communications experiment.

During its launch on 6 April 1967, the booster's second stage failed to ignite, resulting in an unplanned elliptical orbit. Stresses caused by this orbit eventually induced spacecraft tumbling. In spite of these conditions, useful data were obtained from some of the experiments, most notably the cosmic ray and particle experiments, and the field detection experiments. The satellite reentered the atmosphere on 2 September 1969.
ref: nssdc.gsfc.nasa.gov

1973 02:11:00 GMT
NASA launched Pioneer 11 to Jupiter and Saturn, and subsequently into interstellar space.

Pioneer 11 traveling in space, NASA artwork

Pioneer 11, launched 6 April 1973, was the second mission to investigate Jupiter and the outer Solar system, and the first to explore the planet Saturn and its main rings. Pioneer 11, like Pioneer 10, used Jupiter's gravitational field to alter its trajectory radically. It passed close to Saturn and then it followed an escape trajectory from the Solar system.

Pioneer 11 was 2.9 m long and carried a 2.74 m diameter high gain antenna. The spacecraft contained two RTG nuclear electric generators, which generated 144 W at Jupiter, but had decreased to 100 W by the time it got to Saturn. There were three reference sensors: a star (Canopus) sensor, and two Sun sensors. Attitude position could be calculated from the reference direction to the Earth and the Sun, with the known direction to Canopus as a backup. Pioneer 11's star sensor gain and threshold settings were modified, based on experience gained from the settings used on Pioneer 10. Three pairs of rocket thrusters provided spin axis control (maintained at 4.8 rpm) and change of the spacecraft velocity. The thrusters could be either fired steadily or pulsed, by command.

Communications were maintained via the omnidirectional and medium gain antennas, which operated together, connected to one receiver, while the high gain antenna was connected to the other receiver. The receivers could be interchanged by command. Two radio transmitters, coupled to two traveling wave tube (TWT) amplifiers, produced 8 W power each in the S band. Communication uplink (Earth to spacecraft) operated at 2110 MHz, and downlink (spacecraft to Earth) at 2292 MHz. At Jupiter's distance, the round trip communication time was 92 minutes. Data were received at the Deep Space Network (DSN). The spacecraft was temperature controlled to between -23 and +38 deg C (-10 to +100 deg F). An additional experiment, a low sensitivity fluxgate magnetometer, was added to the Pioneer 11 payload.

Instruments studied the interplanetary and planetary magnetic fields; Solar wind properties; cosmic rays; the transition region of the heliosphere; neutral hydrogen abundance; distribution, size, mass, flux, and velocity of dust particles; Jovian aurorae; Jovian radio waves; the atmospheres of the planets and satellites; and the surfaces of Jupiter, Saturn, and some of their satellites. Instruments carried for these experiments were a magnetometer, a plasma analyzer (for the Solar wind), a charged-particle detector, an ionizing detector, non-imaging telescopes with overlapping fields of view to detect sunlight reflected from passing meteoroids, sealed pressurized cells of argon and nitrogen gas for measuring penetration of meteoroids, a UV photometer, an IR radiometer, and an imaging photopolarimeter, which produced photographs and measured the polarization. Further scientific information was obtained from celestial mechanics and occultation phenomena.

Pioneer 11, like Pioneer 10, contains a plaque that has a drawing depicting a man, a woman, and the location of the Sun and Earth in the galaxy.

During its closest approach on 4 December 1974, Pioneer 11 passed within 34,000 km of Jupiter's cloud tops. It passed Saturn on 1 September 1979, at a distance of 21,000 km from Saturn's cloud tops, the first probe launched from Earth to do so. The spacecraft has operated on a backup transmitter since launch. Instrument power sharing began in February 1985 due to declining RTG power output. Science operations and daily telemetry ceased on 30 September 1995 when the RTG power level was insufficient to operate any experiments. As of the end of 1995 the spacecraft was located at 44.7 AU from the Sun at a nearly asymptotic latitude of 17.4 degrees above the Solar equatorial plane and was heading outward at 2.5 AU/year.

Routine tracking and project data processing operations were terminated on 31 March 1997 for budget reasons.

Obtain Pioneer 10/11 position data (heliographic coordinates)

See also the Pioneer Project page at NASA/ARC.
ref: nssdc.gsfc.nasa.gov

1984 08:58:00 EST (GMT -5:00:00)
NASA launched STS 41-C (Challenger 5, 11th Shuttle mission) to deploy the Long Duration Exposure Facility (LDEF) satellite. During the flight, the first on-orbit spacecraft repair was completed (Solar Maximum satellite).

STS 41-C was launched into the first direct ascent trajectory for the Space Shuttle on 6 April 1984 after a countdown that proceeded without delays. Using manned maneuvering units, the astronauts replaced the altitude control system and coronagraph/polarimeter electronics box in the Solar Maximum satellite while it remained in orbit on 10 April 1984. The Long Duration Exposure Facility (LDEF) was deployed, carrying 57 experiments and left on orbit with intention of retrieving it during a later mission. Other payloads carried on STS 41-C were: the IMAX camera; Radiation Monitoring Equipment (RME); Cinema 360; and the Shuttle Student Involvement Program (SSIP) experiment.

STS 41-C ended 13 April 1984 when Challenger landed on revolution 108 on Runway 17, Edwards Air Force Base, California. Rollout distance: 8,716 feet. Rollout time: 49 seconds. Launch weight: 254,254 pounds. Landing weight: 196,975 pounds. Orbit altitude: 313 nautical miles. Orbit inclination: 28.5 degrees. Mission duration: six days, 23 hours, 40 minutes, seven seconds. Miles traveled: 2.9 million. The mission was extended one day when astronauts were initially unable to grapple the Solar Maximum Mission spacecraft. The originally planned landing at KSC was scrubbed, and the mission was extended one revolution to facilitate landing at Edwards. The orbiter was returned to Kennedy Space Center 18 April 1984.

The flight crew for STS 41-C was: Robert L. Crippen, Commander; Francis R. Scobee, Pilot; George D. Nelson, Mission Specialist; James D. A. van Hoften, Mission Specialist; Terry J. Hart, Mission Specialist.
ref: www.nasa.gov

1984 09:06:30 EST (GMT -5:00:00)
This date marked the first time 11 people were simultaneously in space, 6 cosmonauts on the USSR Salyut 7 space station, 5 on NASA's Shuttle Challenger.
ref: en.wikipedia.org

1992
Died, Isaac Asimov, Russian-born American science fiction author

Isaac Asimov (2 January 1920 - 6 April 1992) was a Russian-born United States author and biochemist, a highly successful and exceptionally prolific writer best known for his works of science fiction and for his science books for the lay person. He also wrote mysteries (many of which were collected in the Black Widowers books) and fantasy, and has works in every major category of the Dewey Decimal System except Philosophy. He wrote or edited over 500 volumes, and an estimated 90,000 letters or postcards. Asimov was a long-time member of Mensa, albeit reluctantly (he described them as "intellectually combative"). The asteroid 5020 Asimov is named in his honor, as is Honda's humanoid prototype robot ASIMO.
ref: en.wikipedia.org

1997 16:04:00 GMT
USSR launched Progress M-34 carrying 2,430 kg of cargo to the Mir space station.
ref: nssdc.gsfc.nasa.gov

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