The Phobos program () was an uncrewed space mission consisting of two probes launched by the

Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

to study

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

and its moons Phobos and Deimos. ''Phobos 1'' was launched on 7 July 1988, and ''Phobos 2'' on 12 July 1988, each aboard a Proton-K rocket. ''

Phobos 1 ''Phobos 1'' was an uncrewed Soviet space probe of the Phobos program, Phobos Program launched from the Baikonur Cosmodrome, Baikonour launch facility on 7 July 1988. Its intended mission was to explore Mars and its moons Phobos (moon), Phobos ...

'' suffered a terminal failure en route to Mars. '' Phobos 2'' attained Mars orbit, but contact was lost before the final phase, prior to deployment of the planned Phobos landers. ''Phobos 1'' and ''2'' were of a new spacecraft design, succeeding the 4MV type used in the ''

Venera The Venera (, 'Venus') program was a series of space probes developed by the Soviet Union between 1961 and 1984 to gather information about the planet Venus. Thirteen probes successfully entered the Venusian atmosphere, including the two ...

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

ary missions of 1975–1985, and the 5VK design last used during the '' Vega 1'' and ''

Vega 2 Vega 2 (along with Vega 1) was a Soviet space probe part of the Vega program to explore Halley's comet and Venus. The spacecraft was a development of the earlier '' Venera'' craft. The name VeGa (ВеГа) combines the first two letters of the R ...

'' missions to

Comet Halley Halley's Comet is the only known short-period comet that is consistently visible to the naked eye from Earth, appearing every 72–80 years, though with the majority of recorded apparitions (25 of 30) occurring after 75–77 years. It last ...

. They each had a mass of 2600 kg (6220 kg with orbital insertion hardware attached). The program featured cooperation from 14 other nations, including Sweden, Switzerland, Austria, France, West Germany, and the United States (which contributed the use of its

NASA Deep Space Network The NASA Deep Space Network (DSN) is a worldwide Telecommunications network, network of spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that supports NASA' ...

for tracking the twin spacecraft).

Objectives

The objectives of the Phobos missions were to: * conduct studies of the interplanetary environment; * perform observations of the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

; * characterize the plasma environment in the Martian vicinity; * conduct surface and

atmospheric An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosphere ...

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

electronics Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other Electric charge, electrically charged particles. It is a subfield ...

section, surrounding a modular cylindrical experiment section. Below these were mounted four spherical tanks (the

Fregat Fregat () is an upper stage developed by NPO Lavochkin for universal compatibility with a wide range of medium- and heavy-lift launch vehicles. Fregat has been used primarily with Soyuz and Zenit rockets, and entered operational service in ...

stage) containing

hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly hazardous unless handled in solution as, for example, hydraz ...

for

attitude control Spacecraft attitude control is the process of controlling the orientation of a spacecraft (vehicle or satellite) with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, ...

and, after the main propulsion module was to be jettisoned,

orbit In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...

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 A solar panel is a device that converts sunlight into electricity by using photovoltaic (PV) cells. PV cells are made of materials that produce excited electrons when exposed to light. These electrons flow through a circuit and produce direct ...

s. Attitude was maintained through the use of a three-axis control system, with pointing maintained with Sun and

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

sensors.

Phobos 1

''Phobos 1'' operated nominally until, a few weeks into the cruise to Mars, 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. Software instructions to turn off the probe's attitude control, normally a fatal operation, 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 A promenade dance or prom is a formal dance party for graduating high school students at the end of the school year. Students participating in the prom will typically vote for a ''prom king'' and ''prom queen''. Other students may be honored ...

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'' was launched atop a

Proton-K The Proton-K, also designated Proton 8K82K after its GRAU index or SL-12 after its model number, was a Russian, previously Soviet, carrier rocket derived from the earlier Proton. It was built by Khrunichev, and launched from sites 81/23, 8 ...

with a

Blok D Blok D () is an upper stage used on Soviet and later Russian expendable launch systems, including the N1, Proton-K and Zenit. The stage (and its derivatives) has been included in more than 320 launched rockets . By 2002 its modification Bl ...

upper stage from Baikonur cosmodrome on July 12, 1988, and entered Mars orbit on January 29, 1989. ''Phobos 2'' operated nominally throughout its cruise and Mars orbital insertion phases on January 29, 1989, gathering data on the Sun, the interplanetary medium, Mars, and Phobos. Phobos 2 investigated Mars's surface and atmosphere and returned 37 images of Phobos with a resolution of up to 40 meters. Communications were lost before planned deployment of a Phobos lander.

Systems and sensors

Phobos probes carried several instruments: solar

x-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

and

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

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 A seismometer is an instrument that responds to ground displacement and shaking such as caused by quakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The out ...

to determine the internal structure of Phobos, and the " Razrez" penetrator with temperature sensors and an

accelerometer An accelerometer is a device that measures the proper acceleration of an object. Proper acceleration is the acceleration (the rate of change (mathematics), rate of change of velocity) of the object relative to an observer who is in free fall (tha ...

for testing the physical and mechanical properties of the surface. The Phobos 2

infrared spectrometer Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. It is used to study and identify chemical substances or functio ...

(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 The Paris Observatory (, ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world. Its historic building is on the Left Ban ...

) with support from

CNES CNES () is the French national space agency. Headquartered in central Paris, the agency is overseen by the ministries of the Armed Forces, Economy and Finance and Higher Education, Research and Innovation. It operates from the Toulouse Spac ...

. 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 A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, ...

**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 A Sun sensor is a navigational instrument used by spacecraft to detect the position of the Sun. Sun sensors are used for Spacecraft attitude control, attitude control, solar array pointing, gyroscope, gyro updating, and safe mode (spacecraft), fai ...

(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 * Automatic Space Plasma Experiment with Rotating Analyzer (ASPERA), an electron spectrometer and ion mass analyser from the Swedish Institute of Space Physics. * "Grunt" imaging radar - Only carried by Phobos 1

References

* * Articles in Nature 341 (1989) pages 581 - 619
Phobos Project Information (NASA NSSDC)ISM - Phobos-2 archive

External links

* ttp://www.ias.u-psud.fr/ism/ 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 The State Corporation for Space Activities "Roscosmos", commonly known simply as Roscosmos (), is a state corporation of the Russian Federation responsible for space flights, cosmonautics programs, and aerospace research. Originating from ...

Another site with processed images from the Soviet Phobos 2 mission
{{DEFAULTSORT:Phobos Program Missions to Mars 1988 in the Soviet Union 1988 in spaceflight Soviet Mars missions Derelict space probes Phobos (moon) Non Earth orbiting satellites of the Soviet Union