Beyond_Earth-_A_Chronicle_of_Deep_Space_Exploration_1958-2016.pdf

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Results: Formally approved by NASA in August 1974, the Pioneer Venus project comprised two spacecraft to explore the atmosphere and surface of Venus. Both spacecraft used a basic cylindrical bus. Pioneer Venus 1, the orbiter, was designed to spend an extended period in orbit around Venus mapping the surface using a radar package. After a six-and-a-half-month-long journey, the spacecraft entered an elliptical orbit around Venus at 15:58 UT on 4 December 1978. It was the first American spacecraft to enter orbit around Venus, about three years after the Soviets accomplished the same feat. The initial orbital period was 23 hours, 11 minutes, which was altered within two orbits to the desired 24 hours—a maneuver that would allow the orbit's high and low points (about 160 kilometers) to occur at the same time each Earth day. Data from the radar mapper allowed scientists to produce a topographical map of most of the Venusian surface between 73° N and 63° S at a resolution of 75 kilometers. The data indicated that Venus was much more smooth and spherical than Earth. The orbiter identified the highest point on Venus as Maxwell Montes, which rises 10.8 kilometers above the mean surface. Infrared observations implied a clearing in the planet's atmosphere over the north pole. In addition, ultraviolet light photos showed dark markings that covered the clouds in the visible hemisphere. Cameras also detected almost continuous lightning activity in the atmosphere.

The spacecraft confirmed that Venus has little, if any magnetic field. Because of the nature of its orbit, Pioneer Venus 1 passed through the planet's bow shock twice per revolution, and using its magnetometer, scientists were able to observe how the planet's ionosphere interacted with the solar wind. Although the mapping radar was switched off on 19 March 1981 (having mapped 93% of the band between 74° N and 63° S), it was reactivated again in 1991, 13 years after launch, to explore the previously inaccessible southern portions of the planet. In May 1992, Pioneer Venus 1 began the final phase of its mission, maintaining its periapsis between 150 and 250 kilometers until propellant depletion. The last transmission was received at 19:22 UT on 8 October 1992, as its decaying orbit no longer permitted communications. The spacecraft burned up in the atmosphere soon after, ending a successful 14-year mission that was planned to last only eight months.

Pioneer Venus 2

Nation: USA (61) Objective(s): Venus impact Spacecraft: Pioneer Venus Multiprobe Spacecraft Mass: 904 kg Mission Design and Management: NASA / ARC Launch Vehicle: Atlas Centaur (AC-51 / Atlas no. 5031D) Launch Date and Time: 8 August 1978 / 07:33 UT Launch Site: Cape Canaveral / Launch Complex 36A

Scientific Instruments:

Spacecraft Bus:

1. neutral mass spectrometer (BNMS)
2. ion mass spectrometer (BIMS)

Large Probe:

1. neutral mass spectrometer
2. solar flux radiometer
3. gas chromatograph
4. infrared radiometer
5. cloud particle size spectrometer
6. nephelometer

Small Probes (each):

1. neutral mass spectrometer
2. gas chromatograph
3. solar flux radiometer
4. infrared radiometer
5. cloud particle size spectrometer
6. temperature, pressure, acceleration sensors
7. nephelometer

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Pioneer Project Manager Charlie Hall inspects the Pioneer Venus multiprobe at Hughes Aircraft Company in December 1976. Credit: NASA/TRW

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Results: Pioneer Venus 2, the twin to Pioneer Venus 1, comprised a main bus, a Large Probe (316.5 kilograms), and three identical Small Probes, all of which were designed to collect data during independent atmospheric entry into Venus. The probes were each shaped like cones and not designed to survive past surface impact. After a course correction on 16 August 1978, Pioneer Venus 2 released the 1.5 diameter Large Probe on 16 November 1978, while about 11.1 million kilometers from the planet. Four days later, the bus released the three Small Probes (North, Day, and Night Probes) while 9.3 million kilometers from Venus. All five components reached the Venusian atmosphere on 9 December 1978, with the Large Probe entering first. Using a combination of air drag and a parachute, the Large Probe descended through the atmosphere, entering at a velocity of 11.6 kilometers/second, slowing down, until it impacted on the Venusian surface at 19:40 UT, landing at 4.4° N / 304.0° longitude at a velocity of 32 kilometers/hour. Transmissions ceased at impact as expected.

The three 76-centimeter diameter Small Probes arrived in the atmosphere within minutes of the bigger one and descended rapidly through the atmosphere without the benefit of parachutes. They each opened their instrument doors at altitudes of about 70 kilometers and began to transmit information about the Venusian atmosphere immediately. Each took about 53–56 minutes to reach the surface. Amazingly, two of three probes survived the hard impact. The so-called Day Probe transmitted data from the surface for 67 minutes, 37 seconds, before succumbing to the high temperatures, pressures, and power depletion. Information from its nephelometer indicated that dust raised from its impact took several minutes to settle back to the ground. All three Small Probes suffered instrument failures, but not significant enough to jeopardize their main missions. Their landing coordinates were: 60° N / 4° E longitude (North Probe); 32° S / 318° E (Day Probe); and 27° S / 56° E (Night Probe). The main bus, meanwhile, burned up in the atmosphere at an altitude of 120 kilometers—about 1.5 hours after the other probes—and provided key data on higher regions. Data from the probes indicated that between 10 and 50 kilometers there is almost no convection in the atmosphere, while below a haze layer at 30 kilometers, the atmosphere is relatively clear. In addition, below an altitude of 50 kilometers, the temperatures reported from the four probes indicated very little differences even though their entry sites were separated by thousands of kilometers.

ISEE-3

Nation: USA (62) Objective(s): Sun–Earth L1 Lagrange Point, Comet Giacobini-Zinner flyby Spacecraft: ISEE-C Spacecraft Mass: 479 kilograms Mission Design and Management: NASA / GSFC Launch Vehicle: Delta 2914 (no. 144 / Thor no. 633) Launch Date and Time: 12 August 1978 / 15:12 UT Launch Site: Cape Canaveral / Launch Complex 17B

Scientific Instruments:

1. solar wind plasma detector
2. vector helium magnetometer
3. low energy cosmic ray experiment
4. medium energy cosmic ray experiment
5. high energy cosmic ray experiment
6. plasma waves spectrum analyzer
7. energetic particle anisotropy spectrometer (EPAS)
8. interplanetary and solar electrons experiment
9. radio mapping of solar disturbances experiment
10. solar wind ion composition experiment
11. cosmic ray isotope spectrometer
12. x-rays and gamma-ray bursts experiment
13. gamma-ray bursts experiment
14. cosmic-ray energy spectrum charged-particle telescope

Results: ISEE-3 was the third of three International Sun-Earth Explorers (ISEE) designed and operated by NASA in cooperation with the European Space Agency (ESA). NASA built the first and third spacecraft while ESA built the second. The three spacecraft were to simultaneously investigate a wide range of phenomena in interplanetary space. After launch, on 20 November 1978, ISEE-3 was successfully placed in a halo orbit around the L1 Sun–Earth Lagrange Point on the sunward side of Earth, about 1.5 million kilometers from Earth where the gravitational forces of Earth and the Sun are exactly counterbalanced. ISEE-3 became not only the first spacecraft to be put into orbit around a libration point, but also the first spacecraft to monitor the solar wind approaching Earth. ISEE-3 completed its primary mission in 1981, but Goddard Space Flight Center scientists proposed sending the spacecraft first, through Earth's magnetic tail, and second, into position to intercept a comet. By 10 June 1982, the spacecraft began to use its thrusters to move into the tail of Earth's magnetosphere. ISEE-3 completed the first deep survey of Earth's tail and detected a huge plasmoid of electrified gas that was ejected from Earth's magnetosphere.

After a proposal by NASA scientist Robert Farquhar, NASA agreed in August 1982 to redirect the spacecraft for a rendezvous with Comet 21P/Giacobini-Zinner. Subsequently, after a series of five complex flybys of the Moon (the last on 22 December 1983 at a range of only 120 kilometers), ISEE-3 was sent on a trajectory to encounter the comet. At this point, the spacecraft was renamed the International Cometary Explorer (ICE). On 11 September 1985 at 11:02 UT, ICE passed within 7,862 kilometers of the comet's nucleus, becoming the first spacecraft to fly past a comet. The spacecraft returned excellent data on the comet's tail, confirming theories that comets are essentially "dirty snowballs" of ice, with surface material sleeting off during motion. ICE also flew to 40.2 million kilometers of the sunward side of Comet Halley on 28 March 1986 and provided upstream solar wind data. After daily data return was ended in December 1995, NASA eventually terminated ICE operations and support on 5 May 1997 although the spacecraft's transmitter was left on in order to facilitate tracking.

In 2014, a team of independent scientists, engineers, and programmers organized an effort to "recapture" the spacecraft during its planned return to the vicinity of Earth in August 2014. The stated goal was to have ICE enter an orbit near Earth and "resume its original mission" with its 5 remaining operational instruments. With funding that came entirely from the public, the project achieved a new footing by signing an agreement with NASA in May 2014 that allowed the ISEE-3 Reboot Team to make use of a defunct NASA spacecraft. A first firing of thrusters on 2 July, the first time in 27 years, was successful but a longer firing on 8 July failed, probably due to a lack of nitrogen. In the event, the spacecraft passed by the Moon at 18:16 UT on 10 August 2014 at a range of 15,600 kilometers, just as had been expected years before. The spacecraft will continue in its existing trajectory (in heliocentric orbit) and return to the vicinity of Earth in 17 years.

Venera 11

Nation: USSR (96) Objective(s): Venus flyby and landing Spacecraft: 4V-1 (no. 360) Spacecraft Mass: 4,447.3 kg Mission Design and Management: NPO imeni Lavochkina Launch Vehicle: Proton-K + Blok D-1 (8K82K no. 296-01 + 11S824M no. 3L) Launch Date and Time: 9 September 1978 / 03:25:39 UT Launch Site: NIIP-5 / Site 81/23

Scientific Instruments:

Spacecraft Bus:

1. plasma spectrometer
2. Konus gamma-ray detector
3. Signe-2MZ1 gamma and x-ray burst detector
4. DUMS-1 ultraviolet spectrometer
5. magnetometer
6. solar wind detectors
7. cosmic ray detectors

Lander:

1. imaging system
2. Sigma gas chromatograph
3. mass spectrometer
4. gamma-ray spectrometer
5. Groza lightning detector
6. temperature and pressure sensors
7. nephelometer
8. anemometer
9. optical spectrophotometer
10. remote soil collector
11. x-ray fluorescence cloud aerosol analyzer
12. Arakhis x-ray fluorescence spectrometer + drill
13. PrOP-V penetrometer

Results: Venera 11 was one of two identical probes (the other being Venera 12) that followed up on the highly successful Soviet missions to Venus in 1975. Venera 11 and 12 differed from their predecessors principally in the fact each carried a flyby bus + lander combination instead of the previous orbiter + lander combination. Engineers reverted to the flyby combination partly because of the weight limitations of the 1978 launch window, but also because flyby probes afforded better transmission time for landers. Several of the scientific instruments were also modified and new ones added. During the outbound trip to Venus, Venera 11 was beset with technical problems. In the very first communications session with the spacecraft, it became apparent that the solar orientation system failed (coinciding with the deployment of the VHF and UHF antennae). Proper orientation was restored soon enough, with Venera 11 in a nominal constant solar-stellar orientation mode, although this was maintained only intermittently. There were also failures of the primary and backup fans of the cooling system on the descent module detected immediately after launch. On 17 October, a "curtain" on the radiative heater on the lander was closed, a month earlier than planned, to accommodate the higher than expected heating. These measures appeared to partially work to bring temperatures down on the lander.