Mars 7’s Ill-Fated Voyage, Plus One

Yesterday was a strange day … so odd that I missed posting a space history anniversary. It crossed my mind, briefly, once. I’m deeply disappointed in myself, of course.

It just so happens that forty years ago yesterday — August 9, 1973 — the USSR launched Mars 7 on a Proton K rocket from the Baikonur Cosmodrome.

(Mars 7, essentially the same as Mars 6. Image from the National Space Science Data Center.)

Launched four days after its sister ship, Mars 6, and about two weeks after a companion pair of spacecraft, Mars 4 and Mars 5, Mars 7

reached Mars on 9 March 1974. Due to a problem in the operation of one of the onboard systems (attitude control or retro-rockets) the landing probe separated prematurely (4 hours before encounter) and missed the planet by 1300 km. The early separation was probably due to a computer chip error which resulted in degradation of the systems during the trip to Mars…. The lander and bus continued on into heliocentric orbits.

While we’re on the subject of ill-fated spacecraft, and to return to the usual space history routine, 45 years ago today — August 10, 1968 — Applications Technology Satellite 4 (ATS 4) launched from Cape Canaveral atop an Atlas Centaur. The rocket’s second stage failed, however, and stranded the spacecraft in a parking orbit instead of boosting it to the planned geosynchronous orbit. Put bluntly, even though some experiments were performed, “The primary objective of inserting a gravity-gradient-stabilized spacecraft into a geosynchronous orbit was not accomplished.”

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Pioneer Venus Multiprobe Mission

Thirty-five years ago today — August 8, 1978 — a US mission to Venus, featuring four separate probes, launched from Cape Canaveral on an Atlas Centaur rocket.

(Artist’s conception of one of the probes descending toward the surface of Venus. NASA image.)

The Pioneer Venus Multiprobe Bus carried the four probes on the 123-day journey to Venus. On November 16, the Bus released the Large Probe and on the 20th it released the three small probes, which were designated Day, Night, and North, according to their entry into the Venusian atmosphere.

Two Small Probes entered on the nightside, and one Small Probe and the Large Probe entered on the dayside of the planet. The spacecraft was spin-stabilized. The Large Probe took 1-1/2 h to descend through the atmosphere, while the three smaller probes reached the surface of the planet 75 min after entry…. The Probes stopped transmitting temperature data about 15 km above the surface of Venus, but two Probes survived on the surface and transmitted other data for a matter of seconds to minutes.

The Bus itself acted as a fifth probe, though it was not intended to get near the surface. It

was targeted to enter the Venusian atmosphere at a shallow entry angle and transmit data to Earth until [it] was destroyed by the heat of atmospheric friction during its descent…. [It] ceased transmitting data at an altitude of about 165 km.

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Mars 6 Launched From Baikonur

Forty years ago today — August 5, 1973 — the Soviet Union launched their third of four 1973 missions to Mars from the Baikonur Cosmodrome on a Proton K rocket.

(Mars 6. Image from the National Space Science Data Center.)

The Mars 6 “interplanetary station” featured a descent module that separated from the spacecraft bus to enter the Martian atmosphere. The bus continued on a flyby, while transmitting back telemetry.

The first pair of the USSR’s 1973 Mars spacecraft had launched in July, and reached Mars in February 1974. Mars 6 arrived at Mars on March 12, 1974.

The descent module separated from the bus at a distance of 48,000 km from Mars. The bus continued on into a heliocentric orbit after passing within 1600 km of Mars. The descent module entered the atmosphere at 09:05:53 UT at a speed of 5.6 km/s. The parachute opened at 09:08:32 UT after the module had slowed its speed to 600 m/s by aerobraking. During this time the craft was collecting data and transmitting it directly to the bus for immediate relay to Earth. Contact with the descent module was lost at 09:11:05 UT in “direct proximity to the surface”, probably either when the retrorockets fired or when it hit the surface at an estimated 61 m/s. Mars 6 landed at 23.90 S, 19.42 W in the Margaritifer Sinus region of Mars.

Mars 6 was the first spacecraft to send back data from Mars, though its lifespan was very short as indicated above. It sent back a little under 4 minutes’ worth of data (224 seconds, to be exact).

Unfortunately, much of the data were unreadable due to a flaw in a computer chip which led to degradation of the system during its journey to Mars.

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Skylab 3

Forty years ago today — July 28, 1973 — the second manned mission to the Skylab station was launched from the Kennedy Space Center on a Saturn 1B rocket.

(Skylab in its low Earth orbit. NASA image.)

The Skylab 3 crew — Alan L. Bean, Owen K. Garriott, and Jack R. Lousma — spent 59 days aboard the station. They installed a solar shield and did other station maintenance, and performed many solar and Earth observation experiments.

Skylab 3 is sometimes referred to as Skylab II, due to miscommunication about the mission numbering. The first Skylab mission, Skylab 1, was actually the mission that placed the station itself in orbit.


Ten years later, on this date in 1983, the Telstar 3A communications satellite was launched on a Delta rocket from Cape Canaveral. This was the first operational Telstar owned by AT&T; previously, AT&T had leased satellites.

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First Geosynchronous Satellite

Fifty years ago today — July 26, 1963 — a Thor Delta rocket out of Cape Canaveral placed the first geosynchronous satellite in orbit.

(Syncom 2, which looked remarkably like Syncom 1. NASA image.)

Syncom 2, a follow-on to the lost Syncom 1, was geosynchronous but not geostationary: its orbital inclination was 33 degrees from the equator, which meant that its ground track formed a figure-8, the top and bottom of which were 33 degrees north and south of the equator, respectively. The satellite enabled transmission of “voice, teletype, facsimile, and data” between ground stations and ships at sea, and proved the viability of communication relay from high orbit that science fiction author Arthur C. Clarke had envisioned many years before. The Department of Defense took over operations of the satellite in January 1965.

Also on this date in space history, 5 years before Syncom 2 launched, the Explorer 4 satellite was launched from Cape Canaveral on a Jupiter C rocket. It measured charged particles (protons and electrons) in the Earth’s radiation belts, though the satellite’s unintended tumbling made the data hard to interpret and the satellite lost power after only three months.

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First Pair of a Four-Part Soviet Mission to Mars

Forty years ago this week, the Soviet Union was in the midst of launching the first two spacecraft of a four-vehicle mission to the red planet. Each was launched from the Baikonur Cosmodrome on a Proton booster.

(Mars 4. Image from the National Space Science Data Center.)

The first of the spacecraft, Mars 4, was launched on July 21, 1973 — so 40 years ago today, it was on its way. Unfortunately, it was unable to enter orbit when it got to Mars.

It was put into Earth orbit by a Proton SL-12/D-1-e booster and launched from its orbital platform roughly an hour and a half later on a Mars trajectory. A mid-course correction burn was made on 30 July 1973. It reached Mars on 10 February 1974. Due to a flaw in the computer chip which resulted in degradation of the chip during the voyage to Mars, the retro-rockets never fired to slow the craft into Mars orbit, and Mars 4 flew by the planet at a range of 2200 km. It returned one swath of pictures and some radio occultation data which constituted the first detection of the nightside ionosphere on Mars. It continued to return interplanetary data from solar orbit after the flyby.

The first of its companion spacecraft, Mars 5, was launched on July 25, 1973 — so 40 years ago today it and its Proton booster were undergoing final preparations for launch. Mars 5 successfully achieved Martian orbit, but operated for only a short time.

After a mid-course correction burn on 3 August, the spacecraft reached Mars on 12 February 1974 at 15:45 UT and was inserted into an elliptical 1755 km x 32,555 km, 24 hr, 53 min. orbit with an inclination of 35.3 degrees. Mars 5 collected data for 22 orbits until a loss of pressurization in the transmitter housing ended the mission. About 60 images were returned over a nine day period showing swaths of the area south of Valles Marineris, from 5 N, 330 W to 20 S, 130 W. Measurements by other instruments were made near periapsis along 7 adjacent arcs in this same region.

The next two missions, Mars 6 and 7, would be launched on August 5th and 9th, respectively. The loss of Mars 5 would make their operations harder, as it had been “designed to act as a communications link to the Mars 6 and 7 landers.”

Despite their ultimate failures, the series of launches themselves were quite an achievement: preparing and launching two big boosters one right after the other, and then doing it again two weeks later. One of the most interesting experiences of my Air Force career was getting to observe the initial stages — primarily mating the spacecraft to the launch vehicle — of a Proton launch campaign at Baikonur. Having seen what goes into a single launch, that they launched four payloads in such a short time is very impressive.

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First Geosynchronous Science Satellite

Thirty-five years ago today — July 14, 1978 — “the first spacecraft dedicated completely to scientific measurements in an equatorial geostationary orbit” was launched from Cape Canaveral on a Thor Delta rocket.

(A GEOS satellite in a test chamber. Image from the “Earth Observation Portal.”)

Called GEOstationary Scientific Satellite 2, it was identical to a previous version that ended up in the wrong orbit. Built by the European Space Agency and instrumented primarily to measure Earth’s magnetic field, GEOS 2 was originally a back-up satellite. Once on orbit, according to the Earth Observation Portal, GEOS 2 “provided two years of data, was placed in hibernation for eight months, then [was] revived for eight months in 1981” to support upper atmospheric studies. After those studies, it continued to operate through 1983.

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Phobos 2 — Success, Failure, and Controversy

Twenty-five years ago today — July 12, 1988 — the Soviets launched the second of two Mars orbiters atop a Proton K rocket out of the Baikonur Cosmodrome.

(Artist’s conception of Phobos. NASA image from Wikimedia Commons.)

Phobos 2 followed close on the heels of Phobos 1, which was launched a few days earlier but eventually lost power and did not reach Mars. Phobos 2, however, reached the Red Planet and operated in Martian orbit for several weeks.

Phobos 2 operated nominally throughout its cruise and Mars orbital insertion phases, gathering data on the Sun, interplanetary medium, Mars, and Phobos. Shortly before the final phase of the mission, during which the spacecraft was to approach within 50 m of Phobos’ surface and release two landers, one a mobile `hopper’, the other a stationary platform, contact with Phobos 2 was lost. The mission ended when the spacecraft signal failed to be successfully reacquired on 27 March 1989. The cause of the failure was determined to be a malfunction of the on-board computer.

The controversy surrounding the loss of Phobos 2 is that some UFO enthusiasts have conjectured that Phobos 2 did not simply fail, but was attacked by an alien spacecraft. I won’t provide links here, but if you search online you’re sure to find sites describing the incident — including images of what is supposed to be the attacking ship or the weapon itself.

I’m not sure why the Phobos mission would warrant such interference when so many subsequent missions have succeeded without incident; maybe the aliens left the scene, or are just very selective in what space probes they choose to destroy.

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Ten years ago today — July 8, 2003 — the “Opportunity” rover launched from Cape Canaveral on a Delta II rocket.

(Opportunity rover. NASA image.)

Following about a month behind the “Spirit” rover, launched on June 10th, and known officially as Mars Explorer Rover-B, Opportunity was bound for the Meridiani Planum on Mars. The rover landed on January 25, 2004, to begin what was supposed to be a 90-sol (90 Martian days, very nearly 90 Earth days) mission.

Opportunity is still working today.

While contact with Spirit was lost in March 2010, Opportunity has continued to operate on the Martian surface: a tremendous tribute to the scientists and engineers who designed it, the technicians who built it, and the operators who direct it and keep its software updated. Long may it roll.

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Phobos 1

Twenty-five years ago today — July 7, 1988 — the Soviet Union launched a Proton-K from the Baikonur Cosmodrome carrying the Phobos 1 spacecraft.

(Phobos 1. Image from the National Space Science Data Center.)

Phobos 1, launched just a few days before its twin Phobos 2, was built to study the composition of its namesake Martian moon, and also to study the Martian atmosphere and surface by remote sensing from orbit. It also carried instruments to study the Sun and the interplanetary space environment.

The spacecraft operated well until an attitude system failure — caused by faulty software — oriented Phobos 1 away from the Sun and prevented its solar arrays from recharging its batteries. The failure occurred sometime between August 30 and September 2, 1988,* and as a result Phobos 1 never reached Mars.

*As of the posting date, the NSSDC page records this failure as happening in 1989; however, other sources (e.g., this page) give the date as 1988, when the spacecraft was on the way to Mars.

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