Mariner 1 was the first spacecraft of the American Mariner program

Mariner program

The Mariner program was a program conducted by the American space agency NASA that launched a series of robotic interplanetary probes designed to investigate Mars, Venus and Mercury from 1963 to 1973...

. Launched on July 22, 1962 as a Venus

Venus

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

 flyby mission, a range safety officer

Range Safety Officer

In the field of rocketry, Range Safety Officer is a generic term referring to an individual who monitors the performance of rockets in flight, and who is responsible for their remote destruction if it should be judged that they pose a hazard...

 ordered its destructive abort at 09:26:16 UT, 294.5 seconds after launch.
According to NASA's current account for the public:

The booster had performed satisfactorily 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. The destruct command was sent 6 seconds before separation, after which the launch vehicle could not have been destroyed. The radio transponder continued to transmit signals for 64 seconds after the destruct command had been sent.

What NASA's website describes as "improper operation of the Atlas airborne beacon equipment" caused the booster to lose contact with one of the guidance systems on the ground, setting the stage for an apparent software-related guidance system failure. The role of software error in the launch failure remains somewhat mysterious in nature, shrouded in the ambiguities and conflicts among (and in some accounts, even within) the various accounts, official and otherwise.

The probe's mission was later completed by Mariner 2

Mariner 2

Mariner 2 , an American space probe to Venus, was the first space probe to conduct a successful planetary encounter . The first successful spacecraft in the NASA Mariner program, it was a simplified version of the Block I spacecraft of the Ranger program and an exact copy of Mariner 1...

. However, the cryptic nature of the problems that led to the decision to abort Mariner 1, as well as the confusion in various reports on the incident, gave rise to an urban legend

Urban legend

An urban legend, urban myth, urban tale, or contemporary legend, is a form of modern folklore consisting of stories that may or may not have been believed by their tellers to be true...

 of sorts. Indirectly, this confusion also contributed to some software engineering folklore about the role of supposed Fortran

Fortran

Fortran is a general-purpose, procedural, imperative programming language that is especially suited to numeric computation and scientific computing...

 code in the guidance systems. This folklore has persisted at least as late as 2006, despite a lack of evidence that Fortran was even in use for real-time guidance computations for the Mariner missions.

"The most expensive hyphen in history"

The most consistent account was that the error was in hand-transcription of a mathematical symbol in the program specification, in particular a missing overbar. Yet the story persists of a "missing hyphen" (‐), either in the data or in the computer instructions, or even somehow in the equations. No doubt several factors contributed to the "missing hyphen" narrative and its longevity, even in official accounts from technical cognoscenti at JPL and NASA

NASA

The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

. Among the factors cited (or obvious enough):

• The overbar's resemblance to a hyphen (‾ versus ‐).
• The difficulty of explaining the real error to the American public and its elected representatives.
• External political pressures and internal schedule pressures. After all, the mission was
  • an expensive failure of a three-way collaboration (JPL, NASA, USAF),
  • legitimized within the narrative of the US-USSR space race
    Space Race
    The Space Race was a mid-to-late 20th century competition between the Soviet Union and the United States for supremacy in space exploration. Between 1957 and 1975, Cold War rivalry between the two nations focused on attaining firsts in space exploration, which were seen as necessary for national...
    
    ,
  • very high profile, as America's first planetary mission,
  • on a very tight schedule, as it was planned with a narrow launch window (45 days), leaving little time for inquiries, investigations or recriminations before the launch of Mariner 2. The official accounts (which included mentions of a missing hyphen) were the results of an inquiry conducted in less than a week.

Regardless of whatever may have given rise to initial reports of a "missing hyphen", the simplest and most consistent-sounding explanation that the public and Congress would accept would probably have been preferable to those who simply wanted to get on with the job of a Venus fly-by mission. The stories had contradictions, perhaps, but they were so technical that nobody who could have interfered with Mariner program progress was likely to care about them or even notice. (After all, even in one later NASA account, the supposed "hyphen" is reported as missing from instructions at one point in the text, and from equations at another).

Ambiguity of error location

The New York Times

The New York Times

The New York Times is an American daily newspaper founded and continuously published in New York City since 1851. The New York Times has won 106 Pulitzer Prizes, the most of any news organization...

, reporting on the results of a review board, said that the error stemmed from "the omission of a hyphen in some mathematical data"
.
However, the same report also said the hyphen was

a symbol that should have been fed into a computer, along with a mass of other coded mathematical instructions.

This sort of inconsistency or ambiguity was seen in many subsequent variations on the story, official and otherwise. "Missing hyphen" versions of the story gained from official support before the month was out. NASA official Richard B. Morrison testified before Congress that the supposed hyphen

... gives a cue for the spacecraft to ignore the data the computer feeds it until radar contact is once again restored. When that hyphen is left out, false information is fed into the spacecraft control systems. In this case, the computer fed the rocket in hard left, nose down and the vehicle obeyed and crashed.

(Note that Morrison says the spacecraft "crashed", not that it was intentionally destroyed.) In a NASA account submitted to Congress in 1963, the hyphen is described as missing in two different ways:

NASA-JPL-USAF Mariner R-1 Post-Flight Review Board determined that the omission of a hyphen in coded computer instructions transmitted incorrect guidance signals to Mariner spacecraft boosted by two-stage Atlas-Agena from Cape Canaveral on July 21. Omission of hyphen in data editing caused computer to swing automatically into a series of unnecessary course correction signals which threw spacecraft off course so that it had to be destroyed.

However, in the same 1963 report to Congress, Morrison's testimony from the previous year is recounted differently:

In testimony before House Science and Astronautics Committee, Richard B. Morrison, NASA's Launch Vehicles Director, testified that an error in computer equations for Venus probe launch of Mariner R-1 space-craft on July 21 led to its destruction when it veered off course.

JPL's Mariner Venus Final Project Report in 1965 noted that, at 4 minutes and 25 seconds into the flight there was an "[U]nscheduled yaw-lift maneuver":

...steering commands were being supplied, but faulty application of the guidance equations was taking the vehicle far off course.

Arthur C. Clarke

Arthur C. Clarke

Sir Arthur Charles Clarke, CBE, FRAS was a British science fiction author, inventor, and futurist, famous for his short stories and novels, among them 2001: A Space Odyssey, and as a host and commentator in the British television series Mysterious World. For many years, Robert A. Heinlein,...

 wrote several years later that Mariner 1 was "wrecked by the most expensive hyphen in history".

In a NASA report published in 1985, Oran Nicks offered yet another slightly differing account, but with software-related error still identified as a missing "hyphen":

The guidance antenna on the Atlas performed poorly, below specifications. When the signal received by the rocket became weak and noisy, the rocket lost its lock on the ground guidance signal that supplied steering commands. The possibility had been foreseen; in the event that radio guidance was lost the internal guidance computer was supposed to reject the spurious signals from the faulty antenna and proceed on its stored program, which would probably have resulted in a successful launch. However, at this point a second fault took effect. Somehow a hyphen had been dropped from the guidance program loaded aboard the computer, allowing the flawed signals to command the rocket to veer left and nose down. The hyphen had been missing on previous successful flights of the Atlas, but that portion of the equation had not been needed since there was no radio guidance failure. Suffice it to say, the first U.S. attempt at interplanetary flight failed for want of a hyphen.

NASA's website now says the problem was:

... apparently caused by a combination of two factors. Improper operation of the Atlas airborne beacon equipment resulted in a loss of the rate signal from the vehicle for a prolonged period. The airborne beacon used for obtaining rate data was inoperative for four periods ranging from 1.5 to 61 seconds in duration. Additionally, the Mariner 1 Post Flight Review Board determined that 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.

Other punctuation

In other versions of the legend, the bug consisted of:

• a period
  Full stop
  A full stop is the punctuation mark commonly placed at the end of sentences. In American English, the term used for this punctuation is period. In the 21st century, it is often also called a dot by young people...
  
   typed in place of a comma
  Comma (punctuation)
  The comma is a punctuation mark. It has the same shape as an apostrophe or single closing quotation mark in many typefaces, but it differs from them in being placed on the baseline of the text. Some typefaces render it as a small line, slightly curved or straight but inclined from the vertical, or...
  
  , causing a FORTRAN
  Fortran
  Fortran is a general-purpose, procedural, imperative programming language that is especially suited to numeric computation and scientific computing...
  
   statement to be misinterpreted (although there is no evidence that FORTRAN
  Fortran
  Fortran is a general-purpose, procedural, imperative programming language that is especially suited to numeric computation and scientific computing...
  
   was used in the mission). There are anecdotal reports that there was in fact such a bug in a NASA
  NASA
  The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
  
   orbit computation program at about this time, but it was a program for Project Mercury
  Project Mercury
  In January 1960 NASA awarded Western Electric Company a contract for the Mercury tracking network. The value of the contract was over $33 million. Also in January, McDonnell delivered the first production-type Mercury spacecraft, less than a year after award of the formal contract. On February 12,...
  
  , not Mariner
  Mariner program
  The Mariner program was a program conducted by the American space agency NASA that launched a series of robotic interplanetary probes designed to investigate Mars, Venus and Mercury from 1963 to 1973...
  
  , and the claim was that the bug was noticed and fixed before there could be any serious consequences.
• a missing comma
• a missing semicolon at the end of a line of code

Overbar transcription error

The error had occurred when a symbol was being transcribed by hand in the specification for the guidance program. The writer missed the superscript bar (or overline

Overline

An overline or overbar or overscore , refers to the typographical feature of a line drawn immediately above the text, for example used to indicate medieval sigla. Specifically, a line drawn over one symbol is a macron, and a line over a collection of symbols is a vinculum...

) in


by which was meant "the nth smoothed value of the time derivative of a radius R". Without the smoothing function indicated by the bar, the program treated normal minor variations of velocity as if they were serious, causing spurious corrections that sent the rocket off course. It was then destroyed by the Range Safety Officer

Range Safety Officer

In the field of rocketry, Range Safety Officer is a generic term referring to an individual who monitors the performance of rockets in flight, and who is responsible for their remote destruction if it should be judged that they pose a hazard...

.

Spacecraft and subsystems

The Mariner 1 spacecraft was identical to Mariner 2, launched 27 August 1962. Mariner 1 consisted of a hexagonal base, 1.04 meters across and 0.36 meters thick, which contained six magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

 chassis housing the electronics for the science experiments, communications, data encoding, computing, timing, and attitude control and the power control, battery, and battery charger, as well as the attitude control gas bottles and the rocket engine. On top of the base was a tall pyramid

Pyramid

A pyramid is a structure whose outer surfaces are triangular and converge at a single point. The base of a pyramid can be trilateral, quadrilateral, or any polygon shape, meaning that a pyramid has at least three triangular surfaces...

-shaped mast on which the science experiments were mounted which brought the total height of the spacecraft to 3.66 meters. Attached to either side of the base were rectangular solar panel

Photovoltaic module

A solar panel is a packaged, connected assembly of solar cells, also known as photovoltaic cells...

 wings with a total span of 5.05 meters and width of 0.76 meters. Attached by an arm to one side of the base and extending below the spacecraft was a large directional dish antenna.

The Mariner 1 power system consisted of the two solar cell wings, one 183 cm by 76 cm and the other 152 cm by 76 cm (with a 31 cm dacron extension (a solar sail) to balance the solar pressure on the panels) which powered the craft directly or recharged a 1000 Watt-hour sealed silver-zinc cell battery, which was to be used before the panels were deployed, when the panels were not illuminated by the Sun

Sun

The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

, and when loads were heavy. A power-switching and booster regulator device controlled the power flow. Communications consisted of a 3 Watt transmitter capable of continuous telemetry operation, the large high gain directional dish antenna, a cylindrical omnidirectional

Omnidirectional

Omnidirectional refers to the notion of existing in every direction. Omnidirectional devices include:* Omnidirectional antenna, an antenna that radiates equally in all directions* VHF omnidirectional range, a type of radio navigation system for aircraft...

 antenna at the top of the instrument mast, and two command antennas, one on the end of either solar panel, which received instructions for midcourse maneuvers and other functions.

Propulsion for midcourse maneuvers was supplied by a monopropellant

Monopropellant

Monopropellants are propellants composed of chemicals or mixtures of chemicals which can be stored in a single container with some degree of safety. While stable under defined storage conditions, they react very rapidly under certain other conditions to produce a large volume of energetic gases...

 (anhydrous hydrazine

Hydrazine

Hydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...

) 225 N retro-rocket. The hydrazine was ignited using nitrogen tetroxide and aluminum oxide pellets

Pelletizing

Pelletizing is the process of compressing or molding a material into the shape of a pellet. A wide range of different materials are pelletized including chemicals, iron ore, animal compound feed, and more.- Pelletizing of iron ore :...

, and thrust direction was controlled by four jet vanes situated below the thrust chamber. Attitude control with a 1 degree

Degree (angle)

A degree , usually denoted by ° , is a measurement of plane angle, representing 1⁄360 of a full rotation; one degree is equivalent to π/180 radians...

 pointing error was maintained by a system of nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 gas jets. The Sun and Earth were used as references for attitude stabilization. Overall timing and control was performed by a digital Central Computer and Sequencer. Thermal control was achieved through the use of passive reflecting and absorbing surfaces, thermal shields, and movable louvers.

The scientific experiments were mounted on the instrument mast and base. A magnetometer

Magnetometer

A magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature...

 was attached to the top of the mast below the omnidirectional antenna. Particle detectors were mounted halfway up the mast, along with the cosmic ray

Cosmic ray

Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...

 detector. A cosmic dust

Cosmic dust

Cosmic dust is a type of dust composed of particles in space which are a few molecules to 0.1 µm in size. Cosmic dust can be further distinguished by its astronomical location; for example: intergalactic dust, interstellar dust, interplanetary dust and circumplanetary dust .In our own Solar...

 detector and solar plasma

Plasma (physics)

In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...

 spectrometer

Spectrometer

A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...

 detector were attached to the top edges of the spacecraft base. A microwave radiometer

Microwave radiometer

A microwave radiometer is a radiometer that measures energy emitted at sub-millimetre-to-centimetre wavelengths known as microwaves. Their primary application has been onboard spacecraft measuring atmospheric and terrestrial radiation, and they are mostly used for meteorological or oceanographic...

 and an infrared

Infrared

Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

 radiometer

Radiometer

A radiometer is a device for measuring the radiant flux of electromagnetic radiation. Generally, the term radiometer denotes an infrared radiation detector, yet it also includes detectors operating on any electromagnetic wavelength....

 and the radiometer reference horns were rigidly mounted to a 48 cm diameter parabolic

Parabolic antenna

A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly called a dish antenna or parabolic dish...

 radiometer antenna mounted near the bottom of the mast.

In addition, a small 91 cm × 150 cm (3 feet × 5 feet) United States flag was folded and stowed on board Mariner 1 (and Mariner 2) before it was mated to the Agena

RM-81 Agena

The RM-81 Agena was an American rocket upper stage and satellite support bus which was developed by Lockheed initially for the canceled WS-117L reconnaissance satellite program...

.

External links

• NASA's article about the Mariner I
• Mariner 1 Mission Profile by NASA's Solar System Exploration
• RISKS Digest
  RISKS Digest
  The RISKS Digest or Forum On Risks to the Public in Computers and Related Systems is an online periodical published since 1985 by the Committee on Computers and Public Policy of the Association for Computing Machinery. The editor is Peter G. Neumann....
  
   detail about the Mariner I failure