Galileo (spacecraft and satellite navigation)

Galileo was an unmanned NASA spacecraft which studied the planet Jupiter and its moons. Named after the Renaissance astronomer Galileo Galilei, it was launched on October 18, 1989, by the Space Shuttle Atlantis on the STS-34 mission. Galileo arrived at Jupiter on December 7, 1995, HP Pavilion dv7-4091sf Batteryvia gravitational assist flybys of Venus and Earth, becoming the first spacecraft to orbit Jupiter. Despite suffering from antenna problems, Galileo conducted the first asteroid flyby near 951 Gaspra and discovered the first asteroid moon, Dactyl, around the asteroid 243 Ida. It furthermore launched the first probe into Jupiter's atmosphereHP Pavilion dv7-4095eb Battery.[1] The mission's total cost was estimated at approximately US$1.4 billion.[2][3] The spacecraft measured the atmospheric composition of Jupiter and directly observed ammonia clouds, which seem to be created by an outflow from the lower depths of Jupiter's atmosphere. HP Pavilion dv7-4100 Battery Galileo also registered Io's volcanism and the plasma interactions between its and Jupiter's atmospheres. Other studies gave support for the popular theory of liquid oceans under the icy surface of Europa. There were also indications of similar liquid-saltwater layers under the surfaces of Ganymede and Callisto, while Ganymede was shown to possess a magnetic field. HP Pavilion dv7-4105TX BatteryNew evidence was also found for the existence of exospheres around Europa, Ganymede, and Callisto.[1] Galileo furthermore discovered that Jupiter's faint ring system consists of dust from impacts on the four small inner moons. The extent and structure of Jupiter's magnetosphere was also mapped.[1] In 1994, HP Pavilion dv7-4106TX BatteryGalileo provided the only direct observation of Comet Shoemaker-Levy 9's impact into the atmosphere of Jupiter.[1] On September 21, 2003, after 14 years in space and 8 years in the Jovian system, Galileo's mission was terminated by sending the orbiter into Jupiter's atmosphere at a speed of over 48 kilometres (30 mi) per second, HP Pavilion dv7-4130sa Battery to avoid any chance of it contaminating local moons with terrestrial bacteria. Of particular concern was the ice-crusted moon Europa, which, due to Galileo's findings, scientists now suspect harbors a potentially life-supporting subsurface saltwater ocean. Mission overviewHP Pavilion dv7-4131sa Battery Galileo's launch had been significantly delayed. Early plans saw it being launched by Space Shuttle Columbia on what was then codenamed STS-23 in January 1982, but delays in the development of the Space Shuttle allowed more time for development of the probe. HP Pavilion dv7-4140ea Battery Once it was complete, its launch was scheduled for STS-61-G on-board Atlantis in 1986. It was to use the Centaur-G liquid hydrogen-fueled booster stage for a direct trajectory to Jupiter. However, the mission was further delayed by the hiatus in launches that occurred after the Space Shuttle Challenger disaster. HP Pavilion dv7-4142eo Battery New safety protocols introduced as a result of the disaster prohibited the use of the Centaur-G stage on the Shuttle, forcing Galileo to use a lower-powered Inertial Upper Stage solid-fuel booster. The mission was re-profiled to use several gravitational slingshots, referred to as the "VEEGA" or Venus Earth Earth Gravity Assist maneuvers, HP Pavilion dv7-4150ea Battery to provide the additional velocity required to reach its destination. Venus was flown by at 05:58:48 UT on February 10, 1990 at a range of 16,106 km. Having gained 8,030 km per hour in speed, the spacecraft flew by Earth twice, the first time at a range of 960 km at 20:34:34 UT on 8 December 1990 before approaching the minor planet 951 Gaspra to a distance of 1,604 km at 22:37 UT on 29 October 1991. HP Pavilion dv7-4170eo Battery Galileo then performed a second flyby of Earth at 303.1 km at 15:09:25 UT on 8 December 1992, adding 3.7 km per second to its cumulative speed. Galileo performed close observation of a second asteroid, 243 Ida, at 16:51:59 UT on 28 August 1993 at a range of 2,410 km. The spacecraft discovered Ida has a moon Dactyl, the first discovery of a natural satellite orbiting an asteroid. HP Pavilion dv7-4180ea BatteryIn 1994, Galileo was perfectly positioned to watch the fragments of the comet Shoemaker-Levy 9 crash into Jupiter, whereas terrestrial telescopes had to wait to see the impact sites as they rotated into view. After releasing its atmospheric probe on 13 July 1995, HP Pavilion dv7-6000 Battery the Galileo orbiter became the first man-made satellite of Jupiter at 00:27 UT on 8 December 1995 when it fired its main engine to enter a 198-day parking orbit.[4] Galileo's prime mission was a two-year study of the Jovian system. The spacecraft traveled around Jupiter in elongated ellipses, HP Pavilion dv7-6000sg Battery each orbit lasting about two months. The differing distances from Jupiter afforded by these orbits allowed Galileo to sample different parts of the planet's extensive magnetosphere. The orbits were designed for close-up flybys of Jupiter's largest moons. Once Galileo's prime mission was concluded, an extended mission followed, starting on December 7, 1997; HP Pavilion dv7-6001sg Battery the spacecraft made a number of daring close flybys of Jupiter's moons Europa and Io. The closest approach was 180 km (110 mi) on October 15, 2001. The radiation environment near Io in particular was very unhealthy for Galileo's systems, and so these flybys were saved for the extended mission when loss of the spacecraft would be more acceptable. HP Pavilion dv7-6001xx Battery Galileo's cameras were deactivated on January 17, 2002, after they had sustained irreparable radiation damage. NASA engineers were able to recover the damaged tape recorder electronics, and Galileo continued to return scientific data until it was deorbited in 2003, performing one last scientific experiment —a measurement of the moon Amalthea's mass as the spacecraft swung by it. HP Pavilion dv7-6002sa Battery [edit]Spacecraft The Jet Propulsion Laboratory built the Galileo spacecraft and managed the Galileo mission for NASA. Germany supplied the propulsion module. NASA's Ames Research Center managed the probe, which was built by Hughes Aircraft Company. HP Pavilion dv7-6004ea Battery At launch, the orbiter and probe together had a mass of 2,564 kilograms (5,653 pounds) and stood seven metres tall. One section of the spacecraft rotated at 3 rpm, keeping Galileo stable and holding six instruments that gathered data from many different directions, including the fields and particles instruments. HP Pavilion dv7-6004tx Battery The other section of the spacecraft was an antenna, and data were periodically transmitted to it. Back on the ground, the mission operations team used software containing 650,000 lines of programming code in the orbit sequence design process; 1,615,000 lines in the telemetry interpretation; and 550,000 lines of code in navigation. HP Pavilion dv7-6005sg Battery [edit]Command and Data Handling (CDH) The CDH subsystem was actively redundant, with two parallel data system buses running at all times.[5] Each data system bus (aka string) was composed of the same functional elements, HP Pavilion dv7-6005tx Battery consisting of multiplexers (MUX), high-level modules (HLM), low-level modules (LLM), power converters (PC), bulk memory (BUM), data management subsystem bulk memory (DBUM), timing chains (TC), phase locked loops (PLL), Golay coders (GC), hardware command decoders (HCD) and critical controllers (CRC). HP Pavilion dv7-6006sg Battery The CDH subsystem was responsible for maintaining the following functions: decoding of uplink commands execution of commands and sequences execution of system-level fault-protection responsesHP Pavilion dv7-6007sg Battery collection, processing, and formatting of telemetry data for downlink transmission movement of data between subsystems via a data system bus The spacecraft was controlled by six RCA 1802 COSMAC microprocessor CPUs: four on the spun side and two on the despun side. Each CPU was clocked at about 1.6 MHz, HP Pavilion dv7-6008eg Battery and fabricated on sapphire (silicon on sapphire), which is a radiation-and static-hardened material ideal for spacecraft operation. This microprocessor was the first low-power CMOS processor chip, quite on a par with the 8-bit 6502 that was being built into the Apple II desktop computer at that time. Galileo's attitude control system software was written in the HAL/S programming language, also used in the Space Shuttle program. HP Pavilion dv7-6008sg Battery Memory capacity provided by each BUM was 16K of RAM, while the DBUMs each provided 8K of RAM. There were two BUMs and two DBUMs in the CDH subsystem and they all resided on the spun side of the spacecraft. The BUMs and DBUMs provided storage for sequences and contain various buffers for telemetry data and interbus communication. HP Pavilion dv7-6011sg Battery Every HLM and LLM was built up around a single 1802 microprocessor and 32K of RAM (for HLMs) or 16K of RAM (for LLMs). Two HLMs and two LLMs resided on the spun side while two LLMs were on the despun side. Thus, total memory capacity available to the CDH subsystem was 176K of RAM: 144K allocated to the spun side and 32K to the despun side. HP Pavilion dv7-6011tx Battery Each HLM was responsible for the following functions: uplink command processing maintenance of the spacecraft clockHP Pavilion dv7-6012eg Battery movement of data over the data system bus execution of stored sequences (time-event tables) telemetry control error recovery including system fault-protection monitoring and response Each LLM was responsible for the following functions: HP Pavilion dv7-6012sg Battery collect and format engineering data from the subsystems provide the capability to issue coded and discrete commands to spacecraft users recognize out-of-tolerance conditions on status inputs perform some system fault-protection functionsHP Pavilion dv7-6012tx Battery The HCD receives command data from the modulation/demodulation subsystem, decodes these data and transfers them to the HLMs and CRCs. The CRC controls the configuration of CDH subsystem elements. It also controls access to the two data system buses by other spacecraft subsystems. In addition, HP Pavilion dv7-6013eg Battery the CRC supplies signals to enable certain critical events (e.g. probe separation). The GCs provide Golay encoding of data via hardware. The TCs and PLLs establish timing within the CDH subsystem. [edit]PropulsionHP Pavilion dv7-6013tx Battery The Propulsion Subsystem consisted of a 400 N main engine and twelve 10 N thrusters, together with propellant, storage and pressurizing tanks and associated plumbing. The 10 N thrusters were mounted in groups of six on two 2-meter booms. The fuel for the system was 925 kg of monomethylhydrazine and nitrogen tetroxideHP Pavilion dv7-6014tx Battery. Two separate tanks held another 7 kg of helium pressurant. The Propulsion Subsystem was developed and built by Daimler Benz Aero Space AG (DASA) (formerly Messerschmitt–Bölkow–Blohm (MBB)) and provided by Germany, the major international partner in Project Galileo.[6] HP Pavilion dv7-6015eg Battery [edit]Electrical power Solar panels were not a practical solution for Galileo's power needs at Jupiter's distance from the Sun (it would have needed a minimum of 65 square metres (700 sq ft) of solar panels); as for batteries, HP Pavilion dv7-6015sg Batterythey would have been prohibitively massive due to the technological limitations of the time. The solution adopted consisted of two radioisotope thermoelectric generators (RTGs). The RTGs powered the spacecraft through the radioactive decay of plutonium-238. The heat emitted by this decay was converted into electricity for the spacecraft through the solid-state Seebeck effect. HP Pavilion dv7-6025eg Battery This provided a reliable and long-lasting source of electricity unaffected by the cold space environment and high radiation fields such as those encountered in Jupiter's magnetosphere. Each GPHS-RTG, mounted on a 5-meter long boom, carried 7.8 kilograms (17.2 lb) of 238Pu. HP Pavilion dv7-6055ef Battery [7] Each RTG contained 18 separate heat source modules, and each module encased four pellets of plutonium dioxide, a ceramic material resistant to fracturing. The modules were designed to survive a range of hypothetical accidents: launch vehicle explosion or fire, re-entry into the atmosphere followed by land or water impact, and post-impact situations. HP Pavilion dv7-6055sf Battery An outer covering of graphite provided protection against the structural, thermal, and eroding environments of a potential re-entry. Additional graphite components provided impact protection, while iridium cladding of the fuel cells provided post-impact containment. The RTGs produced about 570 watts at launch. HP Pavilion dv7-6065ef BatteryThe power output initially decreased at the rate of 0.6 watts per month and was 493 watts when Galileo arrived at Jupiter. A diagram of Galileo's main components. As the launch of Galileo neared, HP Pavilion dv7-6065sf Battery anti-nuclear groups, concerned over what they perceived as an unacceptable risk to the public's safety from Galileo's RTGs, sought a court injunction prohibiting Galileo's launch. RTGs had been used for years in planetary exploration without mishap: the Lincoln Experimental Satellites 8/9, launched by the U.S. Department of Defense, HP Pavilion dv7-6070sf Batteryhad 7% more plutonium on board than Galileo, and the two Voyager spacecraft each carried 80% as much plutonium as Galileo did. However, activists remembered the messy crash of the Soviet Union's nuclear-powered Cosmos 954 satellite in Canada in 1978, and the 1986 Challenger accident had raised public awareness of the possibility of explosive spacecraft failures. AlsoHP Pavilion dv7-6081eg Battery, no RTGs had ever been made to swing past the Earth at close range and high speed, as Galileo's Venus-Earth-Earth Gravity Assist trajectory required it to do. This created a novel mission failure modality that might plausibly have entailed total dispersal of Galileo's plutonium in the Earth's atmosphere. HP Pavilion dv7-6090sf BatteryScientist Carl Sagan, for example, a strong supporter of the Galileo mission, said in 1989 that "there is nothing absurd about either side of this argument." [8] After the Challenger accident, a study considered additional shielding and eventually rejected it, HP Pavilion dv7-6097ef Battery in part because such a design significantly increased the overall risk of mission failure and only shifted the other risks around (for example, if a failure on orbit had occurred, additional shielding would have significantly increased the consequences of a ground impact).[7] [edit]Instrumentation overviewHP G62-100 Battery Scientific instruments to measure fields and particles were mounted on the spinning section of the spacecraft, together with the main antenna, power supply, the propulsion module and most of Galileo's computers and control electronics. The sixteen instruments, weighing 118 kg altogether, HP G62-100EB Battery included magnetometer sensors mounted on an 11 m boom to minimize interference from the spacecraft; a plasma instrument for detecting low energy charged particles and a plasma wave detector to study waves generated by the particles; a high energy particle detector; and a detector of cosmic and Jovian dust. HP G62-100EE Battery It also carried the Heavy Ion Counter, an engineering experiment added to assess the potentially hazardous charged particle environments the spacecraft flew through, and an added Extreme Ultraviolet detector associated with the UV spectrometer on the scan platform. The despun section's instruments included the camera system; HP G62-100EJ Battery the near infrared mapping spectrometer to make multi-spectral images for atmospheric and moon surface chemical analysis; the ultraviolet spectrometer to study gases; and the photo-polarimeter radiometer to measure radiant and reflected energy. HP G62-100SL BatteryThe camera system was designed to obtain images of Jupiter's satellites at resolutions from 20 to 1,000 times better than Voyager's best, because Galileo flew closer to the planet and its inner moons, and because the more modern CCD sensor in Galileo's camera was more sensitive and had a broader color detection band than the vidicons of Voyager. HP G62-101TU Battery [edit]Instrumentation details The following information was taken directly from NASA's Galileo legacy site.[9] [edit]Despun section A detailed diagram of Galileo's instruments and subsystems. HP G62-101XX Battery The spacecraft's Solid-State Imager. [edit]Solid State Imager (SSI) The SSI was an 800-by-800-pixel solid state camera consisting of an array of silicon sensors called a "charge coupled device" (CCD). HP G62-103XX Battery Galileo was one of the first spacecraft to be equipped with a CCD camera.[citation needed] The optical portion of the camera was built as a Cassegrain telescope. Light was collected by the primary mirror and directed to a smaller secondary mirror that channeled it through a hole in the center of the primary mirror and onto the CCD. HP G62-104SA BatteryThe CCD sensor was shielded from radiation, a particular problem within the harsh Jovian magnetosphere. The shielding was accomplished by means of a 10 mm thick layer of tantalum surrounding the CCD except where the light enters the system. An eight-position filter wheel was used to obtain images at specific wavelengths. HP G62-105SA Battery The images were then combined electronically on Earth to produce color images. The spectral response of the SSI ranged from about 0.4 to 1.1 micrometres. The SSI weighed 29.7 kilograms and consumed, on average, 15 watts of power.[10][11] [edit]Near-Infrared Mapping Spectrometer (NIMS) The NIMS instrument was sensitive to 0.7-to-5.2-micrometre wavelength IR light, HP G62-106SA Batteryoverlapping the wavelength range of the SSI. The telescope associated with NIMS was all reflective (using only mirrors and no lenses) with an aperture of 229 mm. The spectrometer of NIMS used a grating to disperse the light collected by the telescope. The dispersed spectrum of light was focused on detectors of indium antimonide and silicon. HP G62-107SA Battery The NIMS weighed 18 kilograms and used 12 watts of power on average.[12][13] [edit]Ultraviolet Spectrometer / Extreme Ultraviolet Spectrometer (UVS/EUV) The Cassegrain telescope of the UVS had a 250 mm aperture and collected light from the observation target. HP G62-110ED BatteryBoth the UVS and EUV instruments used a ruled grating to disperse this light for spectral analysis. This light then passed through an exit slit into photomultiplier tubes that produced pulses or "sprays" of electrons. These electron pulses were counted, and these count numbers constituted the data that were sent to EarthHP G62-110EE Battery. The UVS was mounted on Galileo's scan platform and could be pointed to an object in inertial space. The EUV was mounted on the spun section of the spacecraft. As Galileo span, the EUV observed a narrow ribbon of space perpendicular to the spin axis. The two instruments combined weighed about 9.7 kilograms and used 5.9 watts of powerHP G62-110EO Battery.[14][15] [edit]Photopolarimeter-Radiometer (PPR) The PPR had seven radiometry bands. One of these used no filters and observed all incoming radiation, both solar and thermal. Another band allowed only solar radiation throughHP G62-110EY Battery. The difference between the solar-plus-thermal and the solar-only channels gave the total thermal radiation emitted. The PPR also measured in five broadband channels that spanned the spectral range from 17 to 110 micrometres. The radiometer provided data on the temperatures of the Jovian satellites and Jupiter's atmosphereHP G62-110SA Battery. The design of the instrument was based on that of an instrument flown on the Pioneer Venus spacecraft. A 100 mm aperture reflecting telescope collected light and directed it to a series of filters, and, from there, measurements were performed by the detectors of the PPR. The PPR weighed 5.0 kilograms and consumed about 5 watts of power. HP G62-110SO Battery [16][17] [edit]Spun section Galileo's Energetic Particles Detector. Galileo's Heavy Ion Counter. HP G62-110SS Battery [edit]Dust Detector Subsystem (DDS) The Dust Detector Subsystem (DDS) was used to measure the mass, electric charge, and velocity of incoming particles. The masses of dust particles that the DDS could detect go from 10−16 to 10−7 grams. HP G62-110SW Battery The speed of these small particles could be measured over the range of 1 to 70 kilometers per second. The instrument could measure impact rates from 1 particle per 115 days (10 megaseconds) to 100 particles per second. Such data was used to help determine dust origin and dynamics within the magnetosphere. HP G62-111EE BatteryThe DDS weighed 4.2 kilograms and used an average of 5.4 watts of power.[18][19] [edit]Energetic Particles Detector (EPD) The Energetic Particles Detector (EPD) was designed to measure the numbers and energies of ions and electrons whose energies exceeded about 20 keV (3.2 fJ). HP G62-112EE BatteryThe EPD could also measure the direction of travel of such particles and, in the case of ions, could determine their composition (whether the ion is oxygen or sulfur, for example). The EPD used silicon solid state detectors and a time-of-flight detector system to measure changes in the energetic particle population at Jupiter as a function of position and time. HP G62-112SO BatteryThese measurements helped determine how the particles got their energy and how they were transported through Jupiter's magnetosphere. The EPD weighed 10.5 kilograms and used 10.1 watts of power on average.[20][21] [edit]Heavy Ion Counter (HIC) HP G62-113SO Battery The HIC was in effect a repackaged and updated version of some parts of the flight spare of the Voyager Cosmic Ray System. The HIC detected heavy ions using stacks of single crystal silicon wafers. The HIC could measure heavy ions with energies as low as 6 MeV (1 pJ) and as high as 200 MeV (32 pJ) per nucleon. HP G62-115SE Battery This range included all atomic substances between carbon and nickel. The HIC and the EUV shared a communications link and, therefore, had to share observing time. The HIC weighed 8 kilograms and used an average of 2.8 watts of power.[22][23] [edit]Magnetometer (MAG) HP G62-115SO Battery The magnetometer (MAG) used two sets of three sensors. The three sensors allowed the three orthogonal components of the magnetic field section to be measured. One set was located at the end of the magnetometer boom and, in that position, was about 11 m from the spin axis of the spacecraft. The second set, HP G62-117SO Battery designed to detect stronger fields, was 6.7 m from the spin axis. The boom was used to remove the MAG from the immediate vicinity of Galileo to minimize magnetic effects from the spacecraft. However, not all these effects could be eliminated by distancing the instrument. The rotation of the spacecraft was used to separate natural magnetic fields from engineering-induced fields. HP G62-118EO BatteryAnother source of potential error in measurement came from the bending and twisting of the long magnetometer boom. To account for these motions, a calibration coil was mounted rigidly on the spacecraft to generate a reference magnetic field during calibrations. The magnetic field at the surface of the Earth has a strength of about 50,000 nT. HP G62-120EC Battery At Jupiter, the outboard (11 m) set of sensors could measure magnetic field strengths in the range from ±32 to ±512 nT, while the inboard (6.7 m) set was active in the range from ±512 to ±16,384 nT. The MAG experiment weighed 7 kilograms and used 3.9 watts of power.[24][25] HP G62-120EE Battery [edit]Plasma Subsystem (PLS) The PLS used seven fields of view to collect charged particles for energy and mass analysis. These fields of view covered most angles from 0 to 180 degrees, fanning out from the spin axis. HP G62-120EG Battery The rotation of the spacecraft carried each field of view through a full circle. The PLS measured particles in the energy range from 0.9 eV to 52 keV (0.1 aJ to 8.3 fJ). The PLS weighed 13.2 kilograms and used an average of 10.7 watts of power.[26][27] [edit]Plasma Wave Subsystem (PWS) HP G62-120EH Battery An electric dipole antenna was used to study the electric fields of plasmas, while two search coil magnetic antennas studied the magnetic fields. The electric dipole antenna was mounted at the tip of the magnetometer boom. The search coil magnetic antennas were mounted on the high-gain antenna feed. HP G62-120EK Battery Nearly simultaneous measurements of the electric and magnetic field spectrum allowed electrostatic waves to be distinguished from electromagnetic waves. The PWS weighed 7.1 kilograms and used an average of 9.8 watts.[28][29] [edit]Atmospheric entry probeHP G62-120EL Battery Galileo Probe The Galileo probe's descent module. Operator         NASA Mission type  Atmospheric probe Launch date   July 13, 1995HP G62-120EP Battery Launch vehicle       Space Shuttle Atlantis Inertial Upper Stage Galileo Orbiter Launch site     KSC Launch Complex 39B Kennedy Space CenterHP G62-120EQ Battery Mission duration  December 7, 1995 (57.6 minutes) COSPAR ID   1989-084E Homepage      Galileo Project Home Page Mass        339 kg (750 lb) HP G62-120ER Battery Power     580 W (LiSO2 battery) Orbital elements Eccentricity    1.03116 Inclination      8.151°HP G62-120ES Battery Periapsis         0.9928 RJ Timeline of the probe's atmospheric entry. Galileo's 339-kilogram (750 lb) atmospheric probe, built by Hughes Aircraft Company[30] at its El Segundo, California plant, HP G62-120ET Battery measured about 1.3 metres (4.3 ft) across. Inside the probe's heat shield, the scientific instruments were protected from extreme heat and pressure during its high-speed journey into the Jovian atmosphere, travelling at 47.8 kilometres (29.7 mi) per second. The probe was released from the main spacecraft in July 1995, HP G62-120EY Battery five months before reaching Jupiter, and entered Jupiter's atmosphere with no braking beforehand. The probe was slowed from its arrival speed of about 47 kilometers per second to subsonic speed in less than two minutes. This was by far the most difficult atmospheric entry ever attempted; HP G62-120SE Batterythe probe had to withstand 230 g[31] and the probe's 152 kg heat shield, making up almost half of the probe's total mass, lost 80 kg during the entry.[32][33] NASA built a special laboratory, the Giant Planet Facility, to simulate the heat load, which was similar to the convective heating experienced by an ICBM warhead reentering the atmosphere combined with the radiative heating of a thermonuclear fireball. HP G62-120SL Battery [34][35] It then deployed its 2.5-meter (8 ft) parachute, and dropped its heat shield. As the probe descended through 150 kilometers of the top layers of the Jovian atmosphere, it collected 58 minutes of data on the local weather. It only stopped transmitting when ambient pressure exceeded 23 atmospheres and temperature reached 153 °C (307 °F). HP G62-120SS Battery [36] The data was sent to the spacecraft overhead, then transmitted back to Earth. Each of 2 L-band transmitters operated at 128 bits per second and sent nearly identical streams of scientific data to the orbiter. All the probe's electronics were powered by lithium sulfur dioxide (LiSO2) batteries that provided a nominal power output of about 580 watts with an estimated capacity of about 21 ampere-hours on arrival at JupiterHP G62-120SW Battery. A diagram of the Galileo atmospheric entry probe's instruments and subsystems. The probe included six instruments for taking data on its plunge into Jupiter: an atmospheric structure instrument group measuring temperature, pressure and deceleration, HP G62-121EE Battery a neutral mass spectrometer and a helium-abundance interferometer supporting atmospheric composition studies, a nephelometer for cloud location and cloud-particle observations, a net-flux radiometer measuring the difference between upward and downward radiant flux at each altitude, HP G62-125EK Batteryand a lightning/radio-emission instrument with an energetic-particle detector that measured light and radio emissions associated with lightning and energetic particles in Jupiter's radiation belts. Total data returned from the probe was about 3.5 megabits (~458752 bytes). HP G62-125EL BatteryThe probe stopped transmitting before the line of sight link with the orbiter was cut. The likely proximal cause of the final probe failure was overheating, which sensors indicated before signal loss. The atmosphere through which the probe descended was somewhat hotter and more turbulent than expectedHP G62-125EV Battery. The probe was eventually completely destroyed as it continued to descend. The parachute would have melted first, roughly 30 minutes after entry,[37] then the aluminum components after another 40 minutes of free fall. The titanium structure would have lasted 6.5 hours more before disintegrating. Due to the high pressure, HP G62-125SL Battery the droplets of metals from the probe would finally have vaporized once their critical temperature had been reached, and mixed with Jupiter's liquid metallic hydrogen interior. [edit]Jupiter science The Pwyll crater on Europa. HP G62-130 Battery Terrain on Ganymede. After arriving on December 7, 1995 and completing 35 orbits around Jupiter throughout a nearly eight year mission, the Galileo Orbiter was destroyed during a controlled impact with Jupiter on September 21, 2003. HP G62-130EG Battery During that intervening time, Galileo forever changed the way scientists saw Jupiter and provided a wealth of information on the moons orbiting the planet which will be studied for years to come. Culled from NASA's press kit, the top orbiter science results were: Galileo made the first observation of ammonia clouds in another planet's atmosphere. HP G62-130EK BatteryThe atmosphere creates ammonia ice particles from material coming up from lower depths. The moon Io was confirmed to have extensive volcanic activity that is 100 times greater than that found on Earth. The heat and frequency of eruptions are reminiscent of early Earth. Complex plasma interactions in Io's atmosphere create immense electrical currents which couple to Jupiter's atmosphere. HP G62-130ET Battery Several lines of evidence from Galileo support the theory that liquid oceans exist under Europa's icy surface. Ganymede possesses its own, substantial magnetic field - the first satellite known to have one. HP G62-130EV Battery Galileo magnetic data provide evidence that Europa, Ganymede and Callisto have a liquid-saltwater layer under the visible surface. Evidence exists that Europa, Ganymede, and Callisto all have a thin atmospheric layer known as a 'surface-bound exosphere'. HP G62-130SD Battery Jupiter's ring system is formed by dust kicked up as interplanetary meteoroids smash into the planet's four small inner moons. The outermost ring is actually two rings, one embedded with the other. There is probably a separate ring along Amalthea's orbit, as well. HP G62-130SL Battery The Galileo spacecraft identified the global structure and dynamics of a giant planet's magnetosphere. [edit]Other science conducted by Galileo [edit]The Galileo star scannerHP G62-134CA Battery The star scanner was a small optical telescope used to provide the spacecraft with an absolute attitude reference. It was also able serendipitously to make scientific discoveries.[38] In the prime mission, it was found that the star scanner was able to detect high energy particles as a noise signal. HP G62-135EV BatteryThese data were eventually calibrated to show the particles were predominantly > 2 MeV electrons that were trapped in the Jovian magnetic belts. A second discovery occurred in 2000. The star scanner was observing a set of stars which included the second magnitude star Delta Velorum. HP G62-140EL BatteryAt one point, this star dimmed for 8 hours below the star scanner's detection threshold. Subsequent analysis of Galileo data and work by amateur and professional astronomers showed that Delta Velorum is the brightest known eclipsing binary, brighter at maximum than even Algol. HP G62-140EQ Battery [39] It has a primary period of 45 days and the dimming is just visible with the naked eye. A final discovery occurred during the last two orbits of the mission. When the spacecraft passed the orbit of Jupiter's moon Amalthea, the star scanner detected unexpected flashes of light that were reflections from moonlets. HP G62-140ES BatteryNone of the individual moonlets were sighted twice, hence no orbits were determined and the moonlets did not meet the International Astronomical Union requirements to receive designations.[40] It is believed that these moonlets most likely are debris ejected from Amalthea and form a tenuous, and perhaps temporary, HP G62-140ET Battery ring. An image of Earth taken by Galileo during the GOPEX test, clearly showing bright laser pulses coming from a transmitting telescope on the night side. Galileo's imager was panned downward during the exposure to separate the pulses, thus blurring Earth's image on the right. HP G62-140SF Battery [edit]Remote detection of life Carl Sagan, pondering the question of whether life on Earth could be easily detected from space, devised a set of experiments in the late 1980s using Galileo's remote sensing instruments to determine if life indeed could be detected during the first Earth flyby of the mission in December 1990. HP G62-140SS Battery After data acquisition and processing, Sagan et al. published a paper in Nature in 1993 detailing the results of the experiment. Galileo had found what are now referred to as the "Sagan criteria for life"; these were: strong absorption of light at the red end of the visible spectrum (especially over continents) which was caused by absorption by chlorophyll in photosynthesizing plants, HP G62-140US Battery absorption bands of molecular oxygen which is also a result of plant activity, infrared absorption bands caused by the ~1 micromole per mole (µmol/mol) of methane in Earth's atmosphere (a gas which must be replenished by either volcanic or biological activity) and modulated narrowband radio wave transmissions uncharacteristic of any known natural source. HP G62-143CL Battery Galileo's experiments were thus the first ever controls in the newborn science of astrobiological remote sensing. [41] [edit]The Galileo optical experiment In December 1992 during Galileo's second gravity assist planetary flyby of Earth, HP G62-144DX Battery another groundbreaking yet almost entirely unpublicized experiment was done using Galileo to assess the possibility of optical communication with spacecraft by detecting pulses of light from powerful lasers which were to be directly imaged by Galileo's CCD. The experiment, dubbed Galileo OPtical EXperiment or GOPEX,[42] used two separate sites to beam laser pulses to the spacecraft, HP G62-145NR Batteryone at Table Mountain Observatory in California and the other at the Starfire Optical Range in New Mexico. The Table Mountain site used a frequency doubled Neodymium-Yttrium-Aluminium Garnet (Nd:YAG) laser operating at 532 nm with a repetition rate of ~15 to 30 Hz and a pulse power (FWHM) in the tens of megawatts range, HP G62-147NR Batterywhich was coupled to a 0.6 meter Cassegrain telescope for transmission to Galileo; the Starfire range site used a similar setup with a larger transmitting telescope (1.5 m). Long exposure (~0.1 to 0.8 s) images using Galileo's 560 nm centered green filter produced images of Earth clearly showing the laser pulses even at distances of up to 6,000,000 km. HP G62-149WM Battery Adverse weather conditions, restrictions placed on laser transmissions by the U.S. Space Defense Operations Center (SPADOC) and a pointing error caused by the scan platform acceleration on the spacecraft being slower than expected (which prevented laser detection on all frames with less than 400 ms exposure times) all contributed to the reduction of the number of successful detections of the laser transmission to 48 of the total 159 frames taken. HP G62-150EE BatteryNonetheless, the experiment was considered a resounding success and the data acquired will likely be used in the future to design laser "downlinks" which will send large volumes of data very quickly, from spacecraft to Earth. The scheme is already being studied (as of 2004) for a data link to a future Mars orbiting spacecraft. HP G62-150EF Battery [43] [edit]Asteroid encounters A NASA image of 951 Gaspra. [edit]First asteroid encounter: 951 Gaspra On October 29, 1991, HP G62-150EQ Batterytwo months after entering the asteroid belt, Galileo performed the first-ever asteroid encounter by a human spacecraft, passing approximately 1,600 kilometers (990 mi) from 951 Gaspra at a relative speed of about 8 kilometers per second (18,000 mph). Several pictures of Gaspra were taken, HP G62-150ET Batteryalong with measurements using the NIMS instrument to indicate composition and physical properties. The last two images were relayed back to Earth in November 1991 and June 1992. The imagery revealed a cratered and very irregular body, measuring about 19 by 12 by 11 kilometers (12 by 7.5 by 7 miles). The remainder of data taken, including low-resolution images of more of the surface, HP G62-150EV Battery were transmitted in late November 1992.[44] [edit]Second asteroid encounter: 243 Ida and Dactyl A NASA image of 243 Ida. The bright dot to the right is its moon, Dactyl. HP G62-150SE Battery On August 28, 1993, Galileo flew within 2,400 kilometers (1,500 mi) of the asteroid 243 Ida. The probe discovered that Ida had a small moon, dubbed Dactyl, measuring only 1.4 km in diameter; this was the first asteroid moon discovered. Measurements using Galileo's solid state imager, magnetometer and NIMS instrument were taken. From subsequent analysis of this data, HP G62-150SF BatteryDactyl appears to be an SII subtype S type asteroid, and is spectrally different from 243 Ida. It is hypothesized that Dactyl may have been produced by partial melting within a Koronis parent body, while the 243 Ida region escaped such igneous processing. [edit]Spacecraft malfunctionsHP G62-150SL Battery [edit]Main antenna failure Laboratory tests verified that holding ribs 9, 10, and 11 in the stowed position most closely modeled the spacecraft's telemetry. Artist's concept of Galileo at Io; note the fully deployed high-gain antenna. HP G62-153CA BatteryCompare with below image. Artist's concept of Galileo at Jupiter with its high-gain antenna only partially deployed. For reasons which in all likelihood will never be known with certainty, Galileo's high-gain antenna failed to fully deploy after its first flyby of Earth. Investigators speculate that during the time that Galileo spent in storage after the 1986 Challenger disaster, its lubricants evaporated, HP G62-154CA Batterydamaging the system. Engineers tried thermal-cycling the antenna, rotating the spacecraft up to its maximum spin rate of 10.5 rpm, and "hammering" the antenna deployment motors—turning them on and off repeatedly—over 13,000 times; all attempts failed to open the high-gain antenna. Fortunately, HP G62-165SL Battery Galileo possessed an additional low-gain antenna that was capable of transmitting information back to Earth, although since it transmitted a signal isotropically, the low-gain antenna's bandwidth was significantly less than the high-gain antenna's would have been; the high-gain antenna was to have transmitted at 134 kilobits per second, HP G62-166SB Batterywhereas the low-gain antenna was only intended to transmit at about 8 to 16 bits per second. Galileo's low-gain antenna transmitted with a power of about 15 to 20 watts, which, by the time it reached Earth, and had been collected by one of the large aperture (70 m) DSN antennas, had a total power of about -170 dBm or 10 zeptowatts (10 × 10−21 watts) HP G62-200XX Battery.[45] Through the implementation of sophisticated technologies, the arraying of several Deep Space Network antennas and sensitivity upgrades to the receivers used to listen to Galileo's signal, data throughput was increased to a maximum of 160 bits per second.[46] By further using data compression, HP G62-201XX Battery the effective data rate could be raised to 1000 bits per second.[46][47] The data collected on Jupiter and its moons was stored in the spacecraft's onboard tape recorder, and transmitted back to Earth during the long apozene portion of the probe's orbit using the low-gain antenna. At the same time, measurements were made of Jupiter's magnetosphere and transmitted back to Earth. HP G62-219WM BatteryThe reduction in available bandwidth reduced the total amount of data transmitted throughout the mission, although 70% of Galileo's science goals could still be met.[48] [edit]Tape recorder anomalies and remote repair The failure of Galileo's high-gain antenna meant that data storage to Galileo's tape recorder for later compression and playback was absolutely crucial in order to obtain any substantial information from the flybys of Jupiter and its moons. HP G62-251XX BatteryIn October 1995, Galileo's 114-megabyte (914,489,344 bits[49]), four-track digital tape recorder, which was manufactured by Odetics Corporation, remained stuck in rewind mode for 15 hours before engineers learned what had happened and sent commands to shut it off. Though the recorder itself was still in working order, HP G62-400 Battery the malfunction possibly damaged a length of tape at the end of the reel. This section of tape was subsequently declared "off limits" to any future data recording, and was covered with 25 more turns of tape to secure the section and reduce any further stresses, which could tear it. Because it happened only weeks before Galileo entered orbit around Jupiter, HP G62-450SA Batterythe anomaly prompted engineers to sacrifice data acquisition of almost all of the Io and Europa observations during the orbit insertion phase, in order to focus solely on recording data sent from the Jupiter probe descent. In November 2002, after the completion of the mission's only encounter with Jupiter's moon Amalthea, HP G62-451SA Batteryproblems with playback of the tape recorder again plagued Galileo. About 10 minutes after the closest approach of the Amalthea flyby, Galileo stopped collecting data, shut down all of its instruments, and went into safe mode, apparently as a result of exposure to Jupiter's intense radiation environment. Though most of the Amalthea data was already written to tape, HP G62-452SA Battery it was found that the recorder refused to respond to commands telling it to play back data. After weeks of troubleshooting of an identical flight spare of the recorder on the ground, it was determined that the cause of the malfunction was a reduction of light output in three infrared Optek OP133 light emitting diodes located in the drive electronics of the recorder's motor encoder wheel. HP G62-454TU Battery The GaAs LEDs had been particularly sensitive to proton-irradiation-induced atomic lattice displacement defects, which greatly decreased their effective light output and caused the drive motor's electronics to falsely believe the motor encoder wheel was incorrectly positioned. Galileo's flight team then began a series of "annealing" sessions, where current was passed through the LEDs for hours at a time to heat them to a point where some of the crystalline lattice defects would be shifted back into place, HP G62-456TU Batterythus increasing the LED's light output. After about 100 hours of annealing and playback cycles, the recorder was able to operate for up to an hour at a time. After many subsequent playback and cooling cycles, the complete transmission back to Earth of all recorded Amalthea flyby data was successful. HP G62-460TX Battery [edit]Other radiation-related anomalies Jupiter's uniquely harsh radiation environment caused over 20 anomalies over the course of Galileo's mission, in addition to the incidents expanded upon above. Despite exceeding its radiation design limit by at least a factor of three, HP G62-467TX Batterythe spacecraft survived all these anomalies. Several of the science instruments suffered increased noise while within about 700,000 kilometres (430,000 mi) of Jupiter. The quartz crystal used as the frequency reference for the radio suffered permanent frequency shifts with each Jupiter approach. HP G62-468TX BatteryA spin detector failed, and the spacecraft gyro output was biased by the radiation environment. The SSI camera began producing totally white images when the spacecraft was hit by the exceptional 'Bastille Day' coronal mass ejection in 2000, and did so again on subsequent close approaches to Jupiter. The most severe effect was a CDS despun bus reset of the onboard computers which occurred when the spacecraft was either close to Jupiter or in the region of space magnetically downstream of the Earth. HP G62-550EE BatteryWork-arounds were found for all of these problems, and Galileo was never rendered entirely non-functional by Jupiter's radiation. [edit]Near-failure of atmospheric probe parachute History [edit]Main objectives In 1999, the different concepts (from Germany, France, Italy and the United Kingdom) for Galileo were compared and reduced to one by a joint team of engineers fThe atmospheric probe deployed its first parachute about one minute later than anticipated, HP G62-a00 Batteryresulting in a small loss of upper atmospheric readings. Through review of records, the problem was later determined to likely be faulty wiring in the parachute control system. The fact that the chute opened at all was attributed to luck.[50] It is now believed that the accelerometer controlling the parachute's pyrotechnics was installed backwards – a similar defect affected the Genesis probe's sample return capsule when it returned to Earth in September 2004, HP G62-a00EF Battery causing the capsule to crash in the Utah desert.[51] [edit]End of mission and deorbit Once its fuel supply was nearly depleted, Galileo was intentionally commanded to crash into Jupiter to eliminate any chance of a future impact with Europa that could contaminate the icy moon with terrestrial bacteria. HP G62-a01SA Battery In order to crash into Jupiter, Galileo flew by Amalthea on November 5, 2002,[52] during its 34th orbit, allowing a measurement of the moon's mass as it passed within 163.0 ± 11.7 kilometres (7.3 mi) of its surface. On April 14, 2003, Galileo reached its greatest distance from Jupiter for the entire mission, 26,000,000 kilometres (16,000,000 mi) HP G62-a02SA Battery, before plunging back towards the gas giant for its final impact.[53] At the completion of its 35th and final circuit around the Jovian system, Galileo impacted the gas giant in darkness just south of the equator on September 21, 2003, at 18:57 GMT. Its impact speed was approximately 48.26 kilometers per second (nearly 108,000 mph). HP G62-a03SA Battery [54] Galileo (satellite navigation) Galileo is a satellite navigation system currently being built by the European Union (EU) and European Space Agency (ESA). HP G62-a04EA Battery The €20 billion project is named after the Italian astronomer Galileo Galilei. One of the aims of Galileo is to provide a high-precision positioning system upon which European nations can rely, independently from the Russian GLONASS, US GPS, and Chinese Compass systems, which can be disabled in times of war or conflict. HP G62-a04SA Battery [1] When in operation it will use two ground operations centers near Munich, Germany and in Fucino, Italy. On 21 October 2011 the first two of four operational satellites were launched to validate the system. The next two will follow in 2012. Once this In-Orbit Validation (IOV) phase has been completed, HP G62-a10EV Batteryadditional satellites will be launched to reach Initial Operational Capability (IOC) around mid-decade. Full completion of the 30 satellites Galileo system (27 operational + 3 active spares) is expected by 2019.[2] Basic navigation services will be free of charge. Galileo is intended to provide horizontal and vertical positions measurements within 1 meter precision, HP G62-a10SA Batteryand better positioning services at high latitudes than other positioning systems. As a further feature, Galileo will provide a unique global Search and Rescue (SAR) function. Satellites will be equipped with a transponder which will relay distress signals from the user's transmitter to the Rescue Co-ordination Centre, HP G62-a11SA Batterywhich will then initiate the rescue operation. At the same time, the system will provide a signal to the user, informing them that their situation has been detected and that help is on the way. This latter feature is new and is considered a major upgrade compared to the existing GPS and GLONASS navigation systems, HP G62-a11SE Batterywhich do not provide feedback to the user.[3] The use of basic (low-precision) Galileo services will be free and open to everyone. The high-precision capabilities will be available for paying commercial users and for military use.[citation needed] HP G62-a12SA Battery The first satellites bear the names of eleven-year-old Thijs from Belgium and nine-year-old Natalia from Bulgaria who are the first winners of the European Commission's Galileo children's drawing competition. Competition winners from the remaining 25 Member States will name the satellites which will be launched until 2019. HP G62-a12SE Battery [4] rom all four countries. HP G62-a13EE BatteryThe first stage of the Galileo programme was agreed upon officially on 26 May 2003 by the European Union and the European Space Agency. The system is intended primarily for civilian use, unlike the United States system, which the U.S. military runs and uses on a primary basis. The U.S. reserves the right to limit the signal strength or precision of GPS, HP G62-a13SA Batteryor to shut down public GPS access completely, so that only the U.S. military and its allies would be able to use it in time of conflict. The European system will only be subject to shutdown for military purposes in extreme circumstances. It will be available at its full precision to both civil and military users. HP G62-a13SE Battery Until 2000 the precision of the GPS signal available to non-U.S.-military users was deliberately severely limited by a timing pulse distortion process known as selective availability. [edit]FundingHP G62-a14SA Battery The European Commission had some difficulty funding the project's next stage, after several allegedly "per annum" sales projection graphs for the project were exposed in November 2001 as "cumulative" projections (which for each year projected, necessarily included all previous years of sales). HP G62-a15EO BatteryThe attention that was brought to this multi-billion euro exponentially growing error in sales forecasts resulted in a general awareness in the Commission and elsewhere that it was unlikely that the program would yield the return on investment that had previously been suggested to investors and decision-makersHP G62-a15SA Battery.[5] Additionally, following the September 11, 2001 attacks, the United States Government wrote to the European Union opposing the project, arguing that it would end the ability of the United States to shut down satellite navigation in times of military operations. On 17 January 2002 a spokesman for the project stated that, HP G62-a16SA Batteryas a result of U.S. pressure and economic difficulties, "Galileo is almost dead."[6] A few months later, however, the situation changed dramatically. European Union member states decided it was important to have a satellite-based positioning and timing infrastructure that the US could not easily turn off in times of political conflictHP G62-a17EA Battery.[7] The European Union and the European Space Agency agreed in March 2002 to fund the project, pending a review in 2003 (which was finalised on 26 May 2003). The starting cost for the period ending in 2005 is estimated at €1.1 billion. The required satellites (the planned number is 30) will be launched throughout the period 2011–2014 and the system will be up and running and under civilian control from 2019. HP G62-a17SA Battery The final cost is estimated at €3 billion, including the infrastructure on Earth, which is to be constructed in the years 2006 and 2007. The plan was for private companies and investors to invest at least two-thirds of the cost of implementation, with the EU and ESA dividing the remaining cost. HP G62-a18SA BatteryAn encrypted higher-bandwidth Commercial Service with improved precision would be available at an extra cost, with the base Open Service freely available to anyone with a Galileo-compatible receiver. Costs for the project have run 50% over initial estimates.[8] [edit]Cooperation with the United StatesHP G62-a19EA Battery In June 2004, in a signed agreement with the United States, the European Union agreed to switch to a modulation known as BOC(1,1) (Binary Offset Carrier 1.1) allowing the coexistence of both GPS and Galileo, and the future combined use of both systems. The European Union also agreed to address the "mutual concerns related to the protection of allied and U.S. national security capabilities." HP G62-a19SA Battery [9] [edit]First experimental satellites: GIOVE-A and GIOVE-B The first experimental satellite, GIOVE-A, was launched in 2005 and was followed by a second test satellite, GIOVE-B, launched in 2008. HP G62-a20SA Battery The first four operational satellites for navigation were launched in 2011 and once this In-Orbit Validation (IOV) phase was has been completed, additional satellites will be launched. On 30 November 2007 the 27 EU transportation ministers involved reached an agreement that it should be operational by 2013, HP G62-a21EA Battery [10] but later press releases suggest it was delayed to 2014.[11] [edit]Funding again, governance issues Early 2007, the EU had yet to decide how to pay for the system and the project was said to be "in deep crisis" due to lack of more public funds. HP G62-a21SA Battery [12] German Transport Minister Wolfgang Tiefensee was particularly doubtful about the consortium's ability to end the infighting at a time when only one testbed satellite had been successfully launched. Although a decision was yet to be reached, HP G62-a22SA Battery on 13 July 2007[13] EU countries discussed cutting €548m ($755m, £370m) from the union's competitiveness budget for the following year and shifting some of that cash to other parts of the financing pot, a move that could meet part of the cost of the union's Galileo satellite navigation system. HP G62-a22SE BatteryEuropean Union research and development projects could be scrapped to overcome a funding shortfall. In November 2007, it was agreed to reallocate funds from the EU's agriculture and administration budgets[14] and to soften the tendering process in order to invite more EU companies. HP G62-a23SA Battery [15] In April 2008, the EU transport ministers approved the Galileo Implementation Regulation. This allowed the €3.4bn to be released from the EU's agriculture and administration budgets.[16] This will allow the issuing of contracts to start construction of the ground station and the satellites. HP G62-a24SA Battery In June 2009, the European Court of Auditors published a report, pointing out governance issues, substantial delays and budget overruns that led to project stalling in 2007, leading to further delays and failures.[17] In October 2009, HP G62-a25EA Batterythe European Commission cut the number of satellites from 28 to 22, with plans to order the remaining six at a later time. It also announced that the first OS, PRS and SoL signal will be available in 2013 and the CS and SOL sometime later. Current budget for 2006–2013 period planned for €3.4 billion was also considered as insufficientHP G62-a25SA Battery.[18] The think tank Open Europe has estimated the total cost of Galileo from start to completion, and then running it over a 20 year period, at a €22.2 billion, which will be borne entirely by taxpayers. Under the original estimates (from 2000) this cost would have been €7.7 billion, of which only €2.6 billion was to be borne by taxpayers and the rest by private investorsHP G62-a26SA Battery.[19] In November 2009, a ground station for Galileo was inaugurated near Kourou (French Guiana).[20] The launch of the first four in-orbit validation (IOV) satellites was planned for the 2nd half of 2011, while the launch of full operational capability (FOC) satellites is planned to start in late 2012. HP G62-a27SA Battery As of March 2010 it was verified that the budget for Galileo would only be available to provide the 4 IOV and 14 FOC satellites by 2014, with no funds currently committed to bring the constellation above this 60% capacity.[21] Paul Verhoef, HP G62-a28SA Battery the then current satellite navigation program manager at the European Commission indicated that this limited funding would have serious consequences commenting at one point "To give you an idea, that would mean that for three weeks in the year you will not have satellite navigation" in reference to the currently proposed 18 vehicle constellation. HP G62-a29EA Battery In July 2010 the European Commission estimated further delays and additional costs of the project to grow up to €1.5-€1.7 billion and moved the estimated date of completion to 2018. After it's completed, the system will need to be subsidized by governments at €750 million per year. HP G62-a29SA Battery [22] An additional €1.9 billion was planned to be spent bringing the system up to the full complement of 30 satellites (27 operational + 3 active spares).[8][23] In December 2010 EU ministers in Brussels have voted Prague (Czech Republic) as the headquarters of the Galileo project.[24] In January 2011, infrastructure costs up to 2020 were estimated at €5.3 billion. HP G62-a30SA Battery In that same month, Wikileaks revealed the opinion of CEO of German satellite company OHB-System, Berry Smutny. He is quoted saying that Galileo "is a stupid idea that primarily serves French interests".[25] The BBC understands €500 million (£440M) will become available to make the extra purchase, HP G62-a38EE Battery taking Europe's version of GPS from 18 operational satellites in the next few years to 24.[26] Galileo launch on a Soyuz rocket, 21 Oct 2011 The first two Galileo In-Orbit Validation satellites were launched by Soyuz ST-B flown from Guiana Space Centre on October 21, 2011. HP G62-a40SA BatteryTwo more are scheduled for launch in 2012.[27] [edit]International involvement This article is outdated. Please update this article to reflect recent events or newly available information. Please see the talk page for more information. (May 2009) In September 2003, HP G62-a43SA Battery China joined the Galileo project. China was to invest €230 million (USD 302 million, GBP 155 million, CNY 2.34 billion) in the project over the following years.[28] In July 2004, Israel signed an agreement with the EU to become a partner in the Galileo project.[29] On 3 June 2005 the EU and Ukraine signed an agreement for Ukraine to join the project, as noted in a press release. HP G62-a44EE Battery [30] As of November 2005, Morocco also joined the programme. On 12 January 2006, South Korea joined the programme. In November 2006, China opted instead to independently develop the Beidou navigation system satellite navigation systemHP G62-a44SA Battery.[31] When Galileo was viewed as a private-sector development with public-sector financial participation, European Commission program managers sought Chinese participation in pursuit of Chinese cash in the short term and privileged access to China’s market for positioning and timing applications in the longer term. HP G62-a45SA Battery However, due to security and technology-independence policy from European Commission, China was, in effect, dis-invited from Galileo and without a return of its monetary investment, a decision that was reinforced by China’s move to build its own global system, called Beidou/Compass. At the Munich Satellite Navigation Summit on March 10, HP G62-a50SG Battery a Chinese government official asked the European Commission why it no longer wanted to work with China, and when China’s cash investment in Galileo would be returned.[32] On 30 November 2007, HP G62-a53SG Batterythe 27 member states of the European Union unanimously agreed to move forward with the project, with plans for bases in Germany and Italy. Spain did not approve during the initial vote, but approved it later that day. This greatly improves the viability of the Galileo project: "The EU's executive had previously said that if agreement was not reached by January 2008, the long-troubled project would essentially be dead. HP G62-a60SA Battery"[33] On 3 April 2009, Norway too joined the programme pledging €68.9 million toward development costs and allowing its companies to bid for the construction contracts. Norway, while not a member of the EU, is a member of the ESA.[34] [edit]Political implications of Galileo projectHP G62-b00SA Battery [edit]Tension with the United States Galileo is intended to be an EU GNSS civilian system that allows all users access to it. GPS is a US GNSS military system that provides location signals that have high precision to US military users, while also providing less precise location signals to others. HP G62-b09SA Battery The GPS had the capability to block the "civilian" signals while still being able to use the "military" signal (M-band). A primary motivation for the Galileo project was European concern that the US could deny others access to GPS during political disagreements.[7] Since Galileo was designed to provide the highest possible precision (possibly even greater than GPS) to anyone, HP G62-b10SA Battery the US was concerned that an enemy could use Galileo signals in military strikes against the US and its allies (some weapons like missiles use GNSS systems for guidance). The frequency initially chosen for Galileo would have made it impossible for the US to block the Galileo signals without also interfering with their own GPS signals. HP G62-b11SA Battery The US did not want to lose their GNSS capability with GPS while denying enemies the use of GNSS. Some US officials became especially concerned when Chinese interest in Galileo was reported.[35] An anonymous European official claimed that the US officials implied they may consider shooting down Galileo satellites in the event of a major conflict in which Galileo was used in attacks against American forces. HP G62-b12SA Battery [36] The EU's stance is that Galileo is a neutral technology, available to all countries and everyone. At first, EU officials did not want to change their original plans for Galileo, but have since reached a compromise, that Galileo was to use a different frequency. This allowed the blocking/jamming of one GNSS system without affecting the otherHP G62-b13EA Battery, giving the US a greater advantage in conflicts in which it has the electronic warfare upper hand.[37] However, the frequency difference also makes it possible to jam the GPS without affecting the Galileo. [edit]GPS and GalileoHP G62-b13SA Battery One of the reasons given for developing Galileo as an independent system was that position information from GPS can be made significantly inaccurate by the deliberate application of universal Selective Availability (SA) by the US military; this was enabled until 2000, and can be re-enabled at any time. HP G62-b14SA Battery GPS is widely used worldwide for civilian applications; Galileo's proponents argued that civil infrastructure, including aeroplane navigation and landing, should not rely solely upon a system with this vulnerability. On May 2, 2000, HP G62-b15SA BatterySA was disabled by President of the United States Bill Clinton; in late 2001 the entity managing the GPS confirmed that they did not intend to enable selective availability ever again.[39] Though Selective Availability capability still exists, on 19 September 2007 the US Department of Defense announced that newer GPS satellites would not be capable of implementing Selective Availability; HP G62-b16EA Battery [40] the wave of Block IIF satellites launched in 2009, and all subsequent GPS satellites, do not support SA. As old satellites are replaced in the GPS modernization program, SA will cease to be an option. The modernization programme also contains standardized features that allow GPS III and Galileo systems to inter-operate, allowing receivers to be developed to utilise GPS and Galileo together to create an even more precise GNSS system. HP G62-b16SA Battery [edit]Final system description [edit]Galileo satellites 30 in-orbit spacecraft (including 3 spares) Orbital altitude: 23,222 km (MEO) 3 orbital planes, HP G62-b17EO Battery 56° inclination, ascending nodes separated by 120° longitude (9 operational satellites and one active spare per orbital plane) Satellite lifetime: >12 years Satellite mass: 675 kg Satellite body dimensions: 2.7 m × 1.2 m × 1.1 m Span of solar arrays: 18.7 mHP G62-b17SA Battery Power of solar arrays: 1.5 kW (end of life) [edit]Services The Galileo system will have five main services: Open access navigation This will be available without charge for use by anyone with appropriate mass-market equipment; simple timing, HP G62-b18SA Battery and positioning down to 1 metre. Commercial navigation (encrypted) High precision to the centimetre; guaranteed service for which service providers will charge fees. Safety Of life navigation Open service; for applications where guaranteed precision is essential. HP G62-b19SA Battery Integrity messages will warn of errors. Public regulated navigation (encrypted) Continuous availability even if other services are disabled in time of crisis; Government agencies will be main users. Search and rescueHP G62-b20SA Battery System will pick up distress beacon locations; feasible to send feedback, e.g. confirming help is on its way. Other secondary services will also be available. [edit]The conceptHP G62-B20so Battery Each satellite will have two rubidium atomic clocks and two passive hydrogen maser atomic clocks, critical to any satellite-navigation system, and a number of other components. The clocks will provide an accurate timing signal to allow a receiver to calculate the time that it takes the signal to reach it. HP G62-b21SA Battery This information is used to calculate the position of the receiver by trilaterating the difference in received signals from multiple satellites. For more information of the concept of global satellite navigation systems, see GNSS and GNSS positioning calculation. HP G62-b22SA Battery [edit]Satellite system [edit]Galileo satellite test beds: GIOVE GIOVE-A was successfully launched 28 December 2005. In 2004 the Galileo System Test Bed Version 1 (GSTB-V1) project validated the on-ground algorithms for Orbit Determination and Time Synchronisation (OD&TS). HP G62-b23SA BatteryThis project, led by ESA and European Satellite Navigation Industries, has provided industry with fundamental knowledge to develop the mission segment of the Galileo positioning system.[41] GIOVE-A is the first GIOVE (Galileo In-Orbit Validation Element) test satellite. It was built by Surrey Satellite Technology Ltd (SSTL), HP G62-b24SA Battery and successfully launched on 28 December 2005 by the European Space Agency and the Galileo Joint. Operation of GIOVE-A ensured that Galileo meets the frequency-filing allocation and reservation requirements for the International Telecommunication Union (ITU), a process that was required to be complete by June 2006. HP G62-b25SA Battery GIOVE-B, built by Astrium and Thales Alenia Space, has a more advanced payload than GIOVE-A. It was successfully launched on 27 April 2008 at 22:16 UTC (4.16 a.m. Baikonur time) aboard a Soyuz-FG/Fregat rocket provided by Starsem. A third satellite, GIOVE-A2, HP G62-b26SA Battery was originally planned to be built by SSTL for launch in the second half of 2008.[42] Construction of GIOVE-A2 was terminated due to the successful launch and in-orbit operation of GIOVE-B. The GIOVE Mission[43][44] segment operated by European Satellite Navigation Industries is exploiting the GIOVE-A/B satellites to provide experimental results based on real data to be used for risk mitigation for the IOV satellites that will follow on from the testbeds. HP G62-b27EA Battery ESA organised the global network of ground stations to collect the measurements of GIOVE-A/B with the use of the GETR receivers for further systematic study. GETR receivers are supplied by Septentrio as well as the first Galileo navigation receivers to be used to test the functioning of the system at further stages of its deployment. HP G62-b27SA BatterySignal analysis of GIOVE-A/B data has confirmed successful operation of all the Galileo signals with the tracking performance as expected. [edit]In-Orbit Validation (IOV) satellites These testbed satellites will be followed by four IOV Galileo satellites that will be much closer to the final Galileo satellite design. The Search & Rescue feature is not installed. HP G62 BatteryThe first two satellites were launched on 21 October 2011 from Guiana Space Centre using a Soyuz launcher.[45] Once this In-Orbit Validation (IOV) phase has been completed, the remaining satellites will be installed to reach the Full Operational Capability. Those 4 IOV Galileo satellites were constructed by Astrium GmbH and Thales Alenia Space. HP G62 Notebook PC Series Battery [edit]Full Operational Capability (FOC) satellites On 7 January 2010, it was announced that the contract to build the first 14 FOC satellites was awarded to OHB System and Surrey Satellite Technology Limited (SSTL). Fourteen satellites will be built at a cost of €566M (£510M; $811M). HP G62t-100 CTO Battery [46] Arianespace will launch the satellites for a cost of €397M (£358M; $569M). The European Commission also announced that the 85 million euro contract for system support covering industrial services required by ESA for integration and validation of the Galileo system had been awarded to Thales Alenia SpaceHP G62t Battery. Thales Alenia Space subcontract performances to Astrium GmbH and security to Thales Communications. In February 2012 eight additional satellites were ordered, bringing the total to 22 FOC satellites.[47] [edit]Science projects, HP G72-100 Battery Coins, satellites names [edit]Science projects using Galileo In July 2006 an international consortium of universities and research institutions embarked on a study of potential scientific applications of the Galileo constellation. This project, named GEO6, is a broad study oriented to the general scientific community, aiming to define and implement new applications of GalileoHP G72-101SA Battery. Among the various GNSS users identified by the Galileo Joint Undertaking, the GEO6 project addresses the Scientific User Community (UC). The GEO6 project aims at fostering possible novel applications within the scientific UC of GNSS signals, and particularly of GalileoHP G72-102SA Battery. The AGILE project is an EU-funded project devoted to the study of the technical and commercial aspects of location-based services (LBS). It includes technical analysis of the benefits brought by Galileo (and EGNOS) and studies the hybridisation of Galileo with other positioning technologies (network-based, HP G72-105SA Battery WLAN, etc.). Within these project, some pilot prototypes were implemented and demonstrated. On the basis of the potential number of users, potential revenues for Galileo Operating Company or Concessionaire (GOC), international relevance, and level of innovation, a set of Priority Applications (PA) will be selected by the consortium and developed within the time-frame of the same project. HP G72-110EL Battery These applications will help to increase and optimise the use of the EGNOS services and the opportunities offered by the Galileo Signal Test-Bed (GSTB-V2) and the Galileo (IOV) phase. [edit]CoinsHP G72-110EV Battery European Satellite Navigation commemorative coin The European Satellite Navigation project was selected as the main motif of a very high value collectors' coin: the Austrian European Satellite Navigation commemorative coin, minted on 1 March 2006. HP G72-110SA Battery The coin has a silver ring and gold-brown niobium "pill". In the reverse, the niobium portion depicts navigation satellites orbiting the Earth. The ring shows different modes of transport, an aeroplane, a car, a container ship, a train and a lorry, for which satellite navigation was developedHP G72-110SD Battery.