Space History for April 7

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295
Halley's Comet passed perihelion in its eighth 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.

1795
Adoption of the metre as the basic unit of length, and of the metric system in general, was first given a legal basis in France.
ref: en.wikipedia.org

1862
H. P. Tuttle discovered asteroid #73 Klytia.

1880
V. Knorre discovered asteroid #215 Oenone.

1927
The first long distance public television transmission was made, using telephone lines, from Washington, DC to New York City; the image transmitted was of Commerce Secretary Herbert Hoover.

On 7 April 1927, live TV images of Secretary of Commerce Herbert Hoover were sent over telephone lines from Washington, D.C. to "television screens" at Bell Telephone Laboratories in New York City in the first U.S. public demonstration of long-distance television transmission. The image was displayed as tiny dots of light on the 2x2.5 inch face of a neon glow lamp.

See a picture of the scene in the transmitting studio. N.B.: The photograph on this page is of far greater quality than the image transmitted over the wires at the time.
ref: www.edn.com
ref: en.wikipedia.org

1947
The largest sunspot ever observed was photographed, roughly 18 billion square km in area, an amazing 6,132 millionths (0.6%) of the visible solar disk, more than 36 times the surface area of the entire Earth.
ref: www.thesuntoday.org

1953
J. A. Brouwer discovered asteroid #1660 Wood; and K. Reinmuth discovered asteroids #2214 Carol, #2278, #2652 Yabuuti and #2806.

1959
RADAR was first bounced off the Sun, from Stanford, California.
ref: tenwatts.blogspot.com

1968
P. Wild discovered asteroids #1773 Rumpelstilz, #1830 Pogson, #1831 Nicholson and #2138 Swissair.

1968 10:09:32 GMT
USSR launched the Luna 14 orbiter to the Moon.

Luna 14 was launched 7 April 1968. The spacecraft entered a 160 x 870 km Lunar orbit with an inclination of 42 degrees at 19:25 UT on 10 April 1968. The spacecraft is believed to have been similar to Luna 12, and the instrumentation was similar to that carried by Luna 10. It provided data for studies of the interaction of the Earth and Lunar masses, the Lunar gravitational field, the propagation and stability of radio communications to the spacecraft at different orbital positions, Solar charged particles and cosmic rays, and the motion of the Moon. This flight was the final flight of the second generation of the Luna series.
ref: nssdc.gsfc.nasa.gov

1969
The Internet's symbolic birth occurred with the publication of RFC 1.
ref: www.rfc-editor.org

1970
J. A. Bruwer discovered asteroid #1794 Finsen.

1983
The first spacewalk of NASA's Shuttle program took place when astronauts Peterson and Musgrave spent about four hours, 17 minutes working outside the Challenger orbiter during the STS 6 mission.

Challenger's first launch was originally set for 20 January 1983, but was postponed due to a hydrogen leak into the number one main engine aft compartment discovered during a 20 second Flight Readiness Firing (FRF) on 18 December 1982. Cracks in the number one main engine were confirmed to be the cause of the leak during the second FRF performed 25 January 1983. All three main engines were removed while the Shuttle was on the pad and the fuel line cracks were repaired. Main engines two and three were reinstalled following extensive failure analysis and testing, while the number one main engine was replaced. An additional delay was caused by contamination to the Tracking and Data Relay Satellite-1 (TDRS-1) during a severe storm. The launch of STS 6 on 4 April 1983 then proceeded as scheduled.

The primary payload for STS 6 was the first Tracking and Data Relay Satellite (TDRS-1). A malfunction of the Inertial Upper Stage booster resulted in placement of the spacecraft into an improper but stable orbit. Additional propellant aboard the satellite was used over the next several months to gradually place TDRS-1 into its properly circularized orbit.

The first space walk of the Shuttle program was performed on 7 April 1983 by Peterson and Musgrave, lasting about four hours, 17 minutes.

Other payloads on STS 6 were: Continuous Flow Electrophoresis System (CFES), Monodisperse Latex Reactor (MLR), Radiation Monitoring Experiment (RME), Night/Day Optical Survey of Lightning (NOSL), and three Get Away Special (GAS) canisters. This mission used the first lightweight external tank and lightweight solid rocket booster casings.

STS 6 ended on 9 April 1983 when Challenger landed on revolution 81 on Runway 22, Edwards Air Force Base, California. Rollout distance: 7,244 feet. Rollout time: 49 seconds. Orbit altitude: 184 nautical miles. Orbit inclination: 28.5 degrees. Mission duration: five days, zero hours, 23 minutes, 42 seconds. Miles Traveled: 2.1 million. The orbiter was returned to Kennedy Space Center 16 April 1983.

The flight crew for STS 6 was: Paul J. Weitz, Commander; Karol J. Bobko, Pilot; Donald H. Peterson, Mission Specialist; F. Story Musgrave, Mission Specialist.
ref: www.nasa.gov

1990
Died (heart attack), Ronald Ellwin "Ron" Evans, Captain USN, NASA astronaut (Apollo 17; nearly 12d 14h in spaceflight)

Ronald E. Evans (10 November 1933 - 7 April 1990) was a NASA astronaut who occupied the Command Module pilot seat of Apollo 17, the last manned Apollo mission to the Moon. He holds the record of more time in Lunar orbit than anyone else in the world, as of 2022.

Captain Evans was one of the 19 astronauts selected by NASA in April 1966. He served as a member of the astronaut support crews for the Apollo 7 and Apollo 11 flights, and as backup Command Module pilot for Apollo 14. Evans was also backup Command Module pilot for the Apollo-Soyuz Test Project (ASTP) mission. He retired from the United States Navy on 30 April 1976, and remained active as a NASA astronaut involved in the development of NASA's Space Shuttle Program. He served as a member of the operations and training group, within the astronaut office, responsible for launch and ascent phases of the Shuttle flight program.

Evans retired from NASA in March 1977 to become a coal industry executive.
ref: en.wikipedia.org

1991
NASA's Compton Gamma Ray Observatory was deployed into Earth orbit from STS 37.

Compton Gamma Ray Observatory being deployed into Earth orbit from STS 37
Source: NSSDCA Master Catalog

The Compton Gamma Ray Observatory was the second of NASA's Great Observatories. Compton, at 17 tons, was the heaviest astrophysical payload ever flown at the time of its launch on 5 April 1991 aboard the space shuttle Atlantis, and deployed into orbit on 7 April. Compton was safely deorbited and re-entered the Earth's atmosphere on 4 June 2000.

Compton had four instruments that covered an unprecedented six decades of the electromagnetic spectrum, from 30 keV to 30 GeV. In order of increasing spectral energy coverage, these instruments were the Burst And Transient Source Experiment (BATSE), the Oriented Scintillation Spectrometer Experiment (OSSE), the Imaging Compton Telescope (COMPTEL), and the Energetic Gamma Ray Experiment Telescope (EGRET). For each of the instruments, an improvement in sensitivity of better than a factor of ten was realized over previous missions.

The Observatory was named in honor of Dr. Arthur Holly Compton, who won the Nobel prize in physics for work on scattering of high energy photons by electrons - a process central to the gamma ray detection techniques of all four instruments.

1997
Died (heart attack), Georgi S. Shonin (at Zvyozdny Gorodok, Russian Federation), Lt. General Soviet AF, Soviet cosmonaut (Soyuz 6; nearly 4d 22.75h in spaceflight)
ref: www.spacefacts.de

2001 15:02:22 GMT
NASA launched the 2001 Mars Odyssey orbiter.

2001 Mars Odyssey orbiter stowed for launch configuration
Source: NSSDCA Master Catalog

NASA's 2001 Mars Odyssey is the remaining part of the Mars Surveyor 2001 Project, which originally consisted of two separately launched missions, The Mars Surveyor 2001 Orbiter and the Mars Surveyor 2001 Lander. The lander spacecraft was cancelled as part of the reorganization of the Mars Exploration Program at NASA. The orbiter, renamed the 2001 Mars Odyssey, was nominally planned to orbit Mars for three years with the objective of conducting a detailed mineralogical analysis of the planet's surface from orbit and measuring the radiation environment. The mission had as its primary science goals to gather data to help determine whether the environment on Mars was ever conducive to life, to characterize the climate and geology of Mars, and to study potential radiation hazards to possible future astronaut missions. The orbiter also acted (and is acting, as of 2022) as a communications relay for [future] missions to Mars. It has enough propellant to function until 2025.

The 2001 Mars Odyssey was launched aboard a Delta II 7425 on 7 April 2001. In August, during the cruise to Mars, the MARIE instrument failed to respond during a routine data transfer and was put into hibernation. (Attempts to revive the instrument were successful in March 2002, and MARIE began taking scientific data from orbit on 13 March 2002.) After a seven month cruise the spacecraft reached Mars on 24 October 2001. The spacecraft used a 19.7 minute propulsive maneuver to transfer into an 18.6 hour elliptical capture orbit and used aerobraking until 11 January 2002, when the spacecraft pulled out of the aerobraking orbit into a 201 x 500 km orbit. This orbit was trimmed over the next few weeks until it became a 2-hour, approximately 400 x 400 km polar science orbit on 30 January 2002. The science mapping mission began on 19 February 2002, and on 28 May 2002, NASA reported that Odyssey's GRS had detected large amounts of hydrogen, a sign that there must be ice lying within a meter of the planet's surface. The Orbiter acts as a communications relay for the Mars Exploration Rovers (Spirit and Opportunity) which arrived in January 2004, the Mars Science Laboratory rover Curiosity, and will possibly also do so for other future missions. Data was collected from orbit until the end of the 917 day nominal mission in July 2004, and the mission was first extended for another Martian year, until September 2006.

One of the orbiter's three flywheels failed in June 2012. However, Odyssey's design included a fourth flywheel, a spare carried against exactly this eventuality. The spare was spun up and successfully brought into service. Since July 2012, Odyssey has been back in full, nominal operation mode following three weeks of 'safe' mode on remote maintenance.

On 11 February 2014, mission control accelerated Odyssey's drift toward a morning-daylight orbit to "enable observation of changing ground temperatures after sunrise and after sunset in thousands of places on Mars". The desired change occurred gradually until the intended orbit geometry was reached on 12 November 2015 when another maneuver was conducted to halt the drift. The new observations could yield insight about the composition of the ground and about temperature-driven processes, such as warm-season flows observed on some slopes, Martian morning clouds seen by the Viking Orbiter 1 in 1976, and geysers fed by spring thawing of carbon dioxide (CO2) ice near Mars' poles.

The 2001 Mars Odyssey carries star cameras, the Mars Radiation Environment Experiment (MARIE), which measures the near-space radiation environment as related to the radiation-related risk to human explorers, the Thermal Emission Imaging System (THEMIS), which maps the mineralogy of the Martian surface using a high-resolution camera and a thermal infrared imaging spectrometer, and the Gamma-Ray Spectrometer (GRS), which maps the elemental composition of the surface and determines the abundance of hydrogen in the shallow subsurface.

The main body of the 2001 Mars Odyssey is a box of 2.2 meters x 1.7 meters x 2.6 meters. The orbiter is divided into two modules, the upper equipment module and the lower propulsion module. The equipment module holds the equipment deck which supports the engineering components and the science instruments. Above the equipment module, connected by struts, is the science deck, holding the star cameras, high energy neutron detector, UHF antenna, the THEMIS instrument and a deployable 6 meter boom holding the gamma sensor head for the GRS. A set of solar array panels extends out from one side of the main bus. A parabolic high-gain dish antenna is mounted on a mast extending from one corner of the bottom of the bus. The MARIE instrument is mounted inside the spacecraft. In the propulsion module are the fuel, oxidizer and helium pressurization tanks, and the main engine. The main engine is a hydrazine and nitrogen tetroxide rocket which can produce 65.3 kg thrust, mounted in the bottom part of the propulsion module. The spacecraft had a launch mass of 725.0 kg, including 348.7 kg of fuel.

Attitude control is provided by four 0.1 kg thrusters and the spacecraft can be turned using four 2.3 kg thrusters. The spacecraft is three-axis stabilized using three primary reaction wheels and one backup. Navigation is provided by a Sun sensor, a star camera, and an inertial measurement unit. Power is provided by the gallium arsenide solar cells in the solar panel and a 16 amp-hr nickel hydrogen battery. Communications between the orbiter and Earth are in X-band via the high-gain antenna, and communications between the orbiter and any Mars landers are via the UHF antenna. Thermal control is achieved using a system of heaters, radiators, louvers, insulating blankets and thermal paint. Command and data handling is through a RAD6000 computer with 128 Mbytes RAM and 3 Mbytes of non-volatile memory.

See also the NASA/JPL 2001 Mars Odyssey Home Page
ref: nssdc.gsfc.nasa.gov

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