Phobos program
Encyclopedia
The Phobos program was an unmanned space mission consisting of two probes
launched by the Soviet Union
to study Mars
and its moons
Phobos
and Deimos
. Phobos 2 became a Mars
orbiter
and returned 38 images with a resolution of up to 40 meters. Both probes suffered from critical failures.
Phobos 1 and 2 were of a new spacecraft design, succeeding the type used in the Venera
planet
ary missions of 1975-1985, last used during the Vega 1
and Vega 2
missions to comet Halley
.
Phobos 1 was launched on July 7, 1988 and Phobos 2 on July 12, 1988, each aboard a Proton-K rocket
. They each had a mass of 2600 kg
(6220 kg with orbital insertion hardware attached).
The program featured co-operation from 14 other nations including Sweden, Switzerland, Austria, France, West Germany, and the United States (who contributed the use of its Deep Space Network
for tracking the twin spacecraft).
section, surrounding a modular cylindrical experiment section. Below these were mounted four spherical tanks (the Fregat vehicle) containing hydrazine
for attitude control and, after the main propulsion module was to be jettisoned, orbit
adjustment. A total of 28 thrusters
(twenty-four 50 N thrusters and four 10 N thrusters) were mounted on the spherical tanks, with additional thrusters mounted on the spacecraft body and solar panel
s. Attitude was maintained through the use of a three-axis control system, with pointing maintained with Sun and star
sensors.
Phobos 1 operated nominally until an expected communications session on September 2, 1988 failed to occur. The failure of controllers to regain contact with the spacecraft was traced to an error in the software uploaded on August 29/August 30, which had deactivated the attitude thrusters. By losing its lock on the Sun, the spacecraft could no longer properly orient its solar arrays, thus depleting its batteries.
A natural question is "Why would a spacecraft have instructions that turn off the attitude control, normally a fatal operation?" In this case, these instructions were part of a routine used when testing the spacecraft on the ground. Normally this routine would be removed before launch. However, the software was coded in PROM
s, and so removing the test code would have required removing and replacing the entire computer. Because of time pressure from the impending launch, engineers decided to leave the command sequence in, though it should never be used. However, a single character error in constructing an upload sequence resulted in the command executing, with subsequent loss of the spacecraft.
.
The Phobos design was used again for the long delayed Mars 96
mission which ended in failure when the launch vehicle's fourth stage misfired.
expert M.Naraeva, who attributed artifacts on images to a distorted image of the shadow of Phobos on the surface of Mars.
and ultraviolet
telescopes, a neutron spectrometer and the Grunt radar experiment designed to study the surface relief of Phobos.
The lander had an x-ray/alpha spectrometer
to provide information on the chemical element composition of the surface of Phobos, a seismometer
to determine the internal structure of Phobos, and the "Razrez" penetrator with temperature sensors and an accelerometer
for testing the physical and mechanical properties of the surface.
The Phobos 2 infrared spectrometer
(ISM) obtained 45000 spectra in the near infrared (from 0.75 to 3.2 µm) in the equatorial areas of Mars, with a spatial resolution ranging from 7 to 25 km, and 400 spectra of Phobos at 700 m resolution. These observations made it possible to retrieve the first mineralogical maps of the planet and its satellite, and to study the atmosphere of Mars. ISM was developed at IAS
and DESPA (Paris Observatory
) with support from CNES
.
List of instruments:
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
launched by the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
to study Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
and its moons
Natural satellite
A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called its primary. The two terms are used synonymously for non-artificial satellites of planets, of dwarf planets, and of minor planets....
Phobos
Phobos (moon)
Phobos is the larger and closer of the two natural satellites of Mars. Both moons were discovered in 1877. With a mean radius of , Phobos is 7.24 times as massive as Deimos...
and Deimos
Deimos (moon)
Deimos is the smaller and outer of Mars's two moons . It is named after Deimos, a figure representing dread in Greek Mythology. Its systematic designation is '.-Discovery:Deimos was discovered by Asaph Hall, Sr...
. Phobos 2 became a Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
orbiter
Orbiter
An orbiter is a space probe that orbits a planet.-Asteroids:*NEAR Shoemaker...
and returned 38 images with a resolution of up to 40 meters. Both probes suffered from critical failures.
Phobos 1 and 2 were of a new spacecraft design, succeeding the type used in the Venera
Venera
The Venera series probes were developed by the Soviet Union between 1961 and 1984 to gather data from Venus, Venera being the Russian name for Venus...
planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
ary missions of 1975-1985, last used during the Vega 1
Vega 1
Vega 1 is a Soviet space probe part of the Vega program. The spacecraft was a development of the earlier Venera craft...
and Vega 2
Vega 2
Vega 2 is a Soviet space probe part of the Vega program. The spacecraft was a development of the earlier Venera craft. They were designed by Babakin Space Center and constructed as 5VK by Lavochkin at Khimki...
missions to comet Halley
Comet Halley
Halley's Comet or Comet Halley is the best-known of the short-period comets, and is visible from Earth every 75 to 76 years. Halley is the only short-period comet that is clearly visible to the naked eye from Earth, and thus the only naked-eye comet that might appear twice in a human lifetime...
.
Phobos 1 was launched on July 7, 1988 and Phobos 2 on July 12, 1988, each aboard a Proton-K rocket
Proton rocket
Proton is an expendable launch system used for both commercial and Russian government space launches. The first Proton rocket was launched in 1965 and the launch system is still in use as of 2011, which makes it one of the most successful heavy boosters in the history of spaceflight...
. They each had a mass of 2600 kg
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...
(6220 kg with orbital insertion hardware attached).
The program featured co-operation from 14 other nations including Sweden, Switzerland, Austria, France, West Germany, and the United States (who contributed the use of its Deep Space Network
Deep Space Network
The Deep Space Network, or DSN, is a world-wide network of large antennas and communication facilities that supports interplanetary spacecraft missions. It also performs radio and radar astronomy observations for the exploration of the solar system and the universe, and supports selected...
for tracking the twin spacecraft).
Objectives
The objectives of the Phobos missions were to:- conduct studies of the interplanetary environment;
- perform observations of the SunSunThe 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...
; - characterize the plasmaPlasma (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...
environment in the Martian vicinity; - conduct surface and atmospheric studies of Mars; and,
- study the surface composition of the Martian satellite Phobos.
Spacecraft design
The main section of the spacecraft consisted of a pressurized toroidal electronicsElectronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
section, surrounding a modular cylindrical experiment section. Below these were mounted four spherical tanks (the Fregat vehicle) containing 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...
for attitude control and, after the main propulsion module was to be jettisoned, orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
adjustment. A total of 28 thrusters
Rocket engine
A rocket engine, or simply "rocket", is a jet engineRocket Propulsion Elements; 7th edition- chapter 1 that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law...
(twenty-four 50 N thrusters and four 10 N thrusters) were mounted on the spherical tanks, with additional thrusters mounted on the spacecraft body and solar panel
Photovoltaic module
A solar panel is a packaged, connected assembly of solar cells, also known as photovoltaic cells...
s. Attitude was maintained through the use of a three-axis control system, with pointing maintained with Sun and star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
sensors.
Phobos 1
A natural question is "Why would a spacecraft have instructions that turn off the attitude control, normally a fatal operation?" In this case, these instructions were part of a routine used when testing the spacecraft on the ground. Normally this routine would be removed before launch. However, the software was coded in PROM
Programmable read-only memory
A programmable read-only memory or field programmable read-only memory or one-time programmable non-volatile memory is a form of digital memory where the setting of each bit is locked by a fuse or antifuse. Such PROMs are used to store programs permanently...
s, and so removing the test code would have required removing and replacing the entire computer. Because of time pressure from the impending launch, engineers decided to leave the command sequence in, though it should never be used. However, a single character error in constructing an upload sequence resulted in the command executing, with subsequent loss of the spacecraft.
Phobos 2
Phobos 2 operated nominally throughout its cruise and Mars orbital insertion phases on January 29, 1989, 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 March 27, 1989. The cause of the failure was determined to be a malfunction of the on-board computerComputer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
.
The Phobos design was used again for the long delayed Mars 96
Mars 96
Mars 96 was a failed Mars mission launched in 1996 to investigate Mars by the Russian Space Forces and not directly related to the Soviet Mars probe program of the same name. After failure of the second fourth-stage burn, the probe assembly re-entered the Earth's atmosphere, breaking up over a...
mission which ended in failure when the launch vehicle's fourth stage misfired.
Controversial "last photo"
In 1989 several photographs were published, which were made shortly before Phobos 2 failure. They led to speculations of large UFO with 20-25km size which supposedly prevented Phobos 2 from completing its mission. Shortly, these speculations were publicly dismissed by GlavcosmosGlavcosmos
Glavcosmos was established in 1985 under the Ministry of General Machine-Building as the Soviet Union's contract agency for space affairs by the government of Mikhail Gorbachev appointing Alexander Dunayev as its first director...
expert M.Naraeva, who attributed artifacts on images to a distorted image of the shadow of Phobos on the surface of Mars.
Systems and sensors
Phobos probes carried several instruments: solar x-rayX-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
and ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
telescopes, a neutron spectrometer and the Grunt radar experiment designed to study the surface relief of Phobos.
The lander had an x-ray/alpha spectrometer
APXS
An Alpha Particle X-Ray Spectrometer is a device that analyses the chemical element composition of a sample from the scattered alpha particles, emitted protons , and fluorescent X-rays after the sample is irradiated with alpha particles and X-rays from radioactive sources...
to provide information on the chemical element composition of the surface of Phobos, a seismometer
Seismometer
Seismometers are instruments that measure motions of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions, and other seismic sources...
to determine the internal structure of Phobos, and the "Razrez" penetrator with temperature sensors and an accelerometer
Accelerometer
An accelerometer is a device that measures proper acceleration, also called the four-acceleration. This is not necessarily the same as the coordinate acceleration , but is rather the type of acceleration associated with the phenomenon of weight experienced by a test mass that resides in the frame...
for testing the physical and mechanical properties of the surface.
The Phobos 2 infrared spectrometer
Thermal infrared spectroscopy
Thermal infrared spectroscopy is the subset of infrared spectroscopy that deals with radiation emitted in the infrared part of the electromagnetic spectrum. The emitted infrared radiation, though similar to blackbody radiation, is different in that the radiation is banded at characteristic...
(ISM) obtained 45000 spectra in the near infrared (from 0.75 to 3.2 µm) in the equatorial areas of Mars, with a spatial resolution ranging from 7 to 25 km, and 400 spectra of Phobos at 700 m resolution. These observations made it possible to retrieve the first mineralogical maps of the planet and its satellite, and to study the atmosphere of Mars. ISM was developed at IAS
Institut aéronautique et spatial
Institut aéronautique et spatial is the French aeronautical industry's education coordinator. IAS was created in 1980 and is located in Toulouse. It is directly under the supervision of GIFAS international committee...
and DESPA (Paris Observatory
Paris Observatory
The Paris Observatory is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world...
) with support from CNES
CNES
The is the French government space agency . Established under President Charles de Gaulle in 1961, its headquarters are located in central Paris and it is under the supervision of the French Ministries of Defence and Research...
.
List of instruments:
- "VSK" TV imaging system
- PROP-F "hopping" lander. Only carried by Phobos 2.
- ARS-FP automatic X-ray fluorescence spectrometer
- ferroprobe magnetometer
- Kappameter magnetic permeability / susceptibility sensor
- gravimeter
- temperature sensors
- BISIN conductometer / tiltmeter
- mechanical sensors (penetrometer, UIU accelerometer, sensors on hopping mechanism)
- "DAS" (long-lived autonomous station) lander
- TV camera
- ALPHA-X Alpha-Proton-X-Ray Spectrometer
- LIBRATION sun sensor (also known as STENOPEE)
- Seismometer
- RAZREZ anchor penetrometer
- Celestial mechanics experiment
- "ISM" thermal infrared spectrometer/radiometer - 1–2 km resolution
- near-infrared imaging spectrometer
- thermal imaging camera; magnetometers
- gamma-ray spectrometers
- X-ray telescope
- radiation detectors
- radar and laser altimeters
- Lima-D laser experiment - designed to vaporise material from the Phobos surface for chemical analysis by a mass spectrometer
- "Grunt" imaging radar - Only carried by Phobos 1
External links
- High quality processed images from the Phobos 2 mission
- Phobos mission images from the Space Research Institute (IKI)
- Raw image data from the Phobos 2 ISM infrared instrument
- What we are searching for on Phobos - an article on the Phobos program at the Web site of the Russian Space Agency
- Another site with processed images from the Soviet Phobos 2 mission
- The Complete Phobos 2 VSK Image Data Set