Category Archives: Space

Revolutionizing Civilian Remote Sensing: The Launch of Landsat 1

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Forty years ago today — July 23, 1972 — the Earth Resources Technology Satellite (ERTS) 1 launched from Vandenberg AFB atop a Delta rocket.

Renamed Landsat 1, the satellite was the first to demonstrate global remote sensing for “agricultural and forestry resources, geology and mineral resources, hydrology and water resources, geography, cartography, environmental pollution, oceanography and marine resources, and meteorological phenomena.”


(Landsat images of Mount St Helens. NASA image.)

According to this Landsat page, the choice of wavelengths for Landsat’s multispectral scanner (MSS) “was primarily based on forestry and geologic applications that had traditionally used Color IR photography.” At the time, multispectral imaging was “secondary and highly experimental,” according to this page, but scientists soon recognized the utility of the multispectral data.

The spacecraft operated until January 1978, five years longer than expected.

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For Want of a Hyphen, the Spacecraft Was Lost

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Fifty years ago today — July 22, 1962 — an Atlas Agena rocket launched from Cape Canaveral, carrying the Mariner 1 spacecraft.


(Artist’s conception of Mariner 1. NASA image.)

Mariner 1 was intended to fly by the planet Venus. The flight was nominal

until an unscheduled yaw-lift (northeast) maneuver was detected by the range safety officer. Faulty application of the guidance commands made steering impossible and were directing the spacecraft towards a crash, possibly in the North Atlantic shipping lanes or in an inhabited area.

Range safety destroyed the vehicle 4 minutes and 53 seconds into the launch.

The launch failure investigation found two apparent causes. First, the “Atlas airborne beacon equipment” did not operate properly. In addition,

the omission of a hyphen in coded computer instructions in the data-editing program allowed transmission of incorrect guidance signals to the spacecraft. During the periods the airborne beacon was inoperative the omission of the hyphen in the data-editing program caused the computer to incorrectly accept the sweep frequency of the ground receiver as it sought the vehicle beacon signal and combined this data with the tracking data sent to the remaining guidance computation. This caused the computer to swing automatically into a series of unnecessary course corrections with erroneous steering commands which finally threw the spacecraft off course.

Anyone who has done any computer coding knows how critical even a single character can be. In this case, it cost an entire spacecraft. The Venus flyby would have to wait.

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Lunar 'Explorer' Launched

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Forty-five years ago today — July 19, 1967 — Explorer 35 launched from Cape Canaveral on a Thor-Delta rocket.


(Explorer 35. NASA image.)

Explorer 35 was designed to study the solar wind — specifically, “the interplanetary plasma, magnetic field, energetic particles, and solar X rays” — in the vicinity of the Moon.

According to this mission page, the Explorer 35 launch was the 50th Thor-Delta mission — quite an accomplishment for the launch vehicle team.

Explorer 35 entered its elliptical lunar orbit on July 21st and began six years of observations. The spacecraft “found that the Moon has no magnetosphere, enabling the charged particles of the solar wind to hit the lunar surface,” and effectively creating a “cavity” in the solar wind. It was finally turned off on June 24, 1973.

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A New Generation of Environmental Monitoring Capabilities

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Thirty years ago today — July 16, 1982 — Landsat 4 launched atop a Delta rocket out of Vandenberg AFB.


(Landsat 4. NASA image.)

Though it was the fourth in the Landsat series of spacecraft, Landsat 4 “was a major step forward in global remote-sensing applications.” According to this NASA page,

In addition to the Multispectral Scanner System (MSS) instrument, Landsat 4 (and Landsat 5) carried a sensor with improved spectral and spatial resolution, i.e., the new satellites could see a wider (and more scientifically-tailored) portion of the electromagnetic spectrum and could see the ground in greater detail. This new instrument was known as the Thematic Mapper (TM).

The Landsat 4 TM instrument had seven spectral bands. Data was collected from the blue, green, red, near-infrared, mid-infrared (2 bands) and thermal infrared portions of the electromagnetic spectrum.

The Thematic Mapper was an important addition to the environmental monitoring instrumentation, and later Landsat spacecraft carried improved versions of it.

Landsat 4 was designed to operate for 3 years. Although some of its components failed, it continued to operate in a limited capacity until 1993. Thereafter, the spacecraft sent telemetry data until 2001, when it was decommissioned.

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An Ill-Fated Lunar Surveyor

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Forty-five years ago today — July 14, 1967 — an Atlas Centaur launched from Cape Canaveral carrying Surveyor 4.


(Sinus Medii, planned landing site for Surveyor 4, imaged in 1994 by Clementine. NASA image from Wikimedia Commons.)

Surveyor 4 was scheduled to touch down on the lunar surface on July 17th, but …

After a flawless flight to the moon, radio signals from the spacecraft ceased during the terminal-descent phase … approximately 2.5 min before touchdown. Contact with the spacecraft was never reestablished, and the mission was unsuccessful.

The original landing target was 0.4 N, 1.33 W in Sinus Medii (“Central Bay”). Surveyor 4 may have exploded before impact, as this site notes that “communications were abruptly lost 2 seconds prior to retrorocket cutoff.”

So, like its sister ship Surveyor 2, Surveyor 4 did not accomplish its mission. Good thing there were seven spacecraft in the series!

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First Private ComSat, and Closest Comet Encounter

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Fifty years ago today — July 10, 1962 — Telstar 1 launched from Cape Canaveral on a Delta rocket.


(Telstar 1. NASA image from Wikimedia Commons.)

Telstar 1 was built by AT&T Bell Telephone Laboratories, making it the first privately-built communications satellite, and broadcast the first live television signals between the U.S. and Europe. The spacecraft was short-lived — its “command channel began to behave erratically” in November and its transmitter failed in February 1963 — but it proved the concept and thereby led to the worldwide satellite communications we enjoy today.

In other space history, on this date 20 years ago, the Giotto probe made a flyby of Comet Grigg-Skjellerup, passing the comet’s nucleus at a distance of between 100-200 km (62-124 mi). It was Giotto’s second flyby, having studied Comet Halley on its primary mission, and the closest-ever flyby of a comet nucleus.

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A Martian 4th of July Sojourn

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Fifteen years ago today — July 4, 1997 — Mars Pathfinder, which launched in December 1996, landed on Mars.


(“Twin Peaks” imaged by Mars Pathfinder. NASA image.)

Mars Pathfinder consisted of a lander, named the Carl Sagan Memorial Station after touchdown, and the Sojourner rover.

From landing until the final data transmission on September 27, 1997, Mars Pathfinder returned 2.3 billion bits of information, including more than 16,500 images from the lander and 550 images from the rover, as well as more than 15 chemical analyses of rocks and soil and extensive data on winds and other weather factors. Findings from the investigations carried out by scientific instruments on both the lander and the rover suggest that Mars was at one time in its past warm and wet, with water existing in its liquid state and a thicker atmosphere.

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Cometary Mission, Presumed Lost, and a Long-Lasting Solar Explorer

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Ten years ago today — July 3, 2002 — a Delta II rocket launched from Cape Canaveral carrying the CONTOUR (Comet Nucleus Tour) spacecraft.


(Artist’s conception of CONTOUR. NASA image.)

CONTOUR operated nominally for six weeks until it started the orbital escape maneuver that would take it away from Earth.

The spacecraft was scheduled to ignite its STAR 30 solid rocket engine on 15 August 2003 at 08:49 UT (4:49 a.m. EDT). This firing was to take CONTOUR out of Earth orbit and put it on a heliocentric trajectory. However, following the scheduled firing time, no further contact was made with the craft. Telescopic surveys were made under the assumption that the firing took place on schedule, and three objects were identified near the expected position of CONTOUR, leading investigators to believe that the firing took place and that these objects were parts of the spacecraft and rocket engine. An investigation board concluded that the most likely cause of the mishap was structural failure of the spacecraft due to plume heating during the solid-rocket motor burn. Alternate possible but less likely causes determined were catastrophic failure of the solid rocket motor, collision with space debris, and loss of dynamic control of the spacecraft.

So CONTOUR was presumed lost. It was supposed to attempt fly-bys of comets Encke and Schwassmann-Wachmann-3, with a possible third flyby of comet d’Arrest.

In more successful space history, on this date in 1992 the Solar, Anomalous and Magnetospheric Particle Explorer (SAMPEX) mission launched from Vandenberg AFB on a Scout rocket. SAMPEX was designed to study cosmic rays, energetic particles emitted by the sun, and the magnetospheric particles for which it was named. The spacecraft was only expected to last about three years, but it continued to send back data until July 2004.

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Microgravity Science Lab Flies Again (Second Time's the Charm)

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Fifteen years ago today — July 1, 1997 — the Space Shuttle Columbia launched from the Kennedy Space Center carrying the Microgravity Science Laboratory (MSL).


(STS-94 launch. NASA image.)

Mission STS-94 was a “reflight” of the original MSL mission, STS-83, which launched three months earlier but ended early because of a fuel cell problem aboard Columbia. STS-94 marked the first time a shuttle mission was reflown with the same payload, same orbiter, and even the same crew. On this MSL mission — the 2nd time around — astronauts James D. Halsell, Susan L. Still, Janice E. Voss, Donald A. Thomas, Michael L. Gernhardt, Roger K. Crouch, and Gregory T. Linteris conducted a wide variety of experiments (“25 primary experiments, four glovebox investigations and four accelerometer studies”) during their 15 days in space.

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First Microgravity Laboratory Flight

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Twenty years ago today — June 25, 1992 — the Space Shuttle Columbia launched from the Kennedy Space Center carrying U.S. Microgravity Laboratory I (USML-1).


(The STS-50 crew in the Spacelab module. NASA image.)

The STS-50 crew consisted of astronauts Richard N. Richards, Kenneth D. Bowersox, Bonnie J. Dunbar, Ellen S. Baker, Carl J. Meade, Lawrence J. DeLucas, and Eugene H.Trinh. Over the course of their 13-day mission, they conducted over a dozen different experiments in the USML-1 module.

And, in bonus space history left over from my lazy birthday weekend: 30 years ago yesterday (June 24, 1982) the Soviet Union launched Soyuz T-6 from the Baikonur Cosmodrome, carrying cosmonauts Vladimir A. Dzhanibekov and Alexander S. Ivanchenko, along with French astronaut Jean-Loup Chrétien, to the Salyut 7 space station.

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