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(Click for frequent words.) 72 electric ion propulsion 65 spacecraft 65 ion thrusters 64 propulsion 63 rocket thrusters 62 Orbital Express 62 ion thruster 62 ion propulsion engines 61 scramjet engines 61 orbital insertion 61 Philae lander 61 VASIMR 61 Variable Specific 61 scramjet engine 61 xenon ion 60 orbital rendezvous 60 Nasa spacecraft 60 thruster 60 Jupiter Icy Moons 60 ramjet 60 dexterous robot 59 hypersonic speeds 59 NuSTAR 59 interplanetary missions 59 ExoMars rover 59 SSMEs 59 interplanetary spacecraft 58 IBEX spacecraft 58 PSLV rocket 58 Webb Telescope 58 GPS IIF 58 bipropellant 58 lunar explorer 58 GOCE 58 thrusters 58 spaceplane 58 Ion propulsion 57 scramjet 57 Launch Abort System 57 planetary Transits 57 Orion spacecraft 57 orbit insertion 57 J 2X 57 hypersonic flight 57 hypersonic glider 57 SpaceLoft XL 57 CHIPSat 57 orbital velocity 57 BepiColombo 57 JIMO 57 propulsion subsystem 57 Pegasus XL 57 LISA Pathfinder 57 highly elliptical orbit 57 aerobraking 57 Giove B 57 Chang'eI 56 scramjets 56 orbiting observatories 56 orbital maneuvering 56 NFIRE 56 laser altimeter 56 unpiloted 56 EPOXI mission 56 ballistic trajectory 56 Curiosity rover 56 spacecraft Chandrayaan 1 56 Churyumov Gerasimenko 56 electric propulsion 56 orbital 56 AJ# engine 56 GSLV Mk III 56 nanosatellite 56 indigenous cryogenic engine 56 Scramjet 56 orbiting telescope 56 ST5 56 xenon propellant 56 orbital maneuvers 56 orbiting telescopes 56 gravitational slingshot 56 lunar landers 56 comet chaser 56 Block 5D 56 robotic spacecraft 56 Atlas 2AS 55 inertial guidance 55 planetary missions 55 radio occultation 55 gradiometer 55 uncrewed 55 INSAT 3D 55 ramjet propulsion 55 O OREOS 55 probe Chang'e 55 D CIXS 55 Solar TErrestrial RElations Observatory 55 Satellite Launch Vehicle GSLV 55 LRO LCROSS 55 radar altimeter 55 Minotaur rocket 55 ESA Rosetta 55 SpaceShip Two 55 supersonic combustion ramjet 55 Earth orbit 55 thruster firings 55 geosynchronous 55 Huygens mission 55 geo synchronous 55 GIOVE B 55 GPS IIR M 55 Minotaur IV 55 Scramjets 55 EMALS 55 Huygens Probe 55 crewed spacecraft 55 drogue parachute 55 PSLV C# 55 Aerojet propulsion 55 X ray observatory 55 SMOS 55 OSIRIS REx 55 Foton M2 55 Atlas Centaur 55 HyFly 55 Dyna Soar 55 Reusable Launch Vehicle 55 J 2X engine 55 hydrazine thrusters 55 Infrared Pathfinder Satellite 55 asteroid Vesta 55 SBSS satellite 55 Ranging spacecraft 54 geosynchronous satellites 54 Shenzhou spacecraft 54 FASTSAT 54 indigenous cryogenic stage 54 scramjet propulsion 54 remote sensing satellite Resourcesat 54 Cassini Huygens 54 Systems NEX AIQ.H 54 Exploration Vehicle 54 radioisotope thermoelectric generators 54 Helios 2B 54 NASAs 54 maneuvering thrusters 54 SpaceX Falcon 9 54 Cloud Aerosol Lidar 54 Ares I. 54 Mars landers 54 deorbiting 54 thrust vector 54 JWST 54 PSLV C 54 autonomous rendezvous 54 orbiter lander 54 H IIA 54 Pilot George Zamka 54 Rosetta comet chaser 54 Planck spacecraft 54 Rosetta spacecraft 54 Magnetic Imager HMI 54 reusable spacecraft 54 Highly Adaptable Satellite 54 geosynchronous satellite 54 GSLV D3 rocket 54 hypersonic scramjet 54 orbiter 54 breathing scramjet engine 54 parahydrogen 54 spacecrafts 54 Foton M3 54 LORRI 54 Phobos Grunt 54 orbit 54 PSLV C6 54 BepiColombo mission 54 SIRTF 54 DMSP F# 54 Airborne Laser Testbed 54 infrared astronomy 53 robotic rovers 53 Stratospheric Observatory 53 APKWS II 53 Geo synchronous 53 EELVs 53 GSLV D3 53 Lunar Reconnaissance Orbiter LRO 53 Venus Climate Orbiter 53 cryocooler 53 suborbital trajectory 53 breathing supersonic combustion 53 Planck satellite 53 SELENE probe 53 Merlin 1C 53 NASA Stratospheric Observatory 53 EPOCh 53 MARSIS 53 Marc Rayman 53 TDRSS 53 RSRMs 53 Cygnus spacecraft 53 Ulysses spacecraft 53 Satellites GOES 53 magnetic spectrometer 53 orbit GEO 53 SMOS mission 53 APXS 53 Mars orbiter 53 Jupiter Icy Moons Orbiter 53 hypersonic propulsion 53 robotic Canadarm 53 Airborne Laser 53 supersonic combustion 53 Stardust spacecraft 53 Jules Verne ATV 53 SDACS 53 SPHERES 53 gamma ray observatory 53 Voyager spacecraft 53 ARCTUS 53 radial velocity technique 53 Sirangelo 53 Interior Laboratory GRAIL 53 STEREO spacecraft 53 Mars Reconnaissance Orbiter MRO 53 COSMO SkyMed 53 GOES O 53 Ryschkewitsch 53 Flyby spacecraft 53 NCADE 53 geo stationary orbit 53 Mars Pathfinder lander 53 cryogenic cooling 53 NextSat 53 Kliper 53 Ares IX rocket 53 unmanned probes 53 Comet Churyumov Gerasimenko 53 Voyager probes 53 liquid propellant 53 circular orbit 53 director Chuck Dovale 53 MARSIS radar 53 Laboratory MSL 53 Discovery STS 53 microshutters 53 neutron spectrometer 53 TacSat 53 ionisation 53 Characterization EPOCh 52 LADEE 52 interferometers 52 ExoMars mission 52 Rosetta orbiter 52 spaceborne 52 Earth orbiting satellites 52 solid propellants 52 retroreflector 52 DIXI 52 Foton spacecraft 52 Martian rovers 52 NASA MESSENGER spacecraft 52 orbiting gamma ray 52 SIM PlanetQuest 52 radioisotope thermoelectric generator 52 Globalstar satellites 52 Helioseismic 52 TerraSAR X 52 Heterodyne Instrument 52 suborbital spacecraft 52 microgravity environment 52 HEO payload 52 SBSS Block 52 GOCE satellite 52 lunar orbit 52 Opportunity rovers 52 geostationary earth 52 GPS IIR 52 particle beam 52 NFIRE satellite 52 Gravity Probe B 52 NASA Stardust spacecraft 52 STORRM 52 orbiting observatory 52 GSAT 5P 52 PSLV C# rocket 52 Synthetic Aperture Radar 52 Spudis 52 Gravity Probe 52 hypersonic 52 Fregat upper stage 52 Antenna LISA 52 Voltec electric 52 WISE spacecraft 52 SBIRS GEO 52 hypersonic missile 52 experimental payloads 52 MetOp 52 vectored thrust 52 MUOS satellite 52 Mars Color Imager 52 GEochemistry 52 STSS satellites 52 RS #A 52 Lunar Rover 52 Infrared Astronomy 52 Ares rocket 52 Proba 2 52 ESA Integral 52 MARSIS instrument 52 Airborne Laser ABL 52 unstowed 52 MetOp satellite 52 reboost 52 Minotaur IV rocket 52 Atlas IIAS 52 Resourcesat 2 52 Weightless Wonder 52 turbopumps 52 robotic lander 52 Skynet 5C 52 Insat 4B 52 INSAT 4CR 52 fairing separation 52 TanDEM X 52 Kepler spacecraft 52 Yarkovsky effect 52 lander 52 3rd SOPS 52 Oceansat 52 cryogenically cooled 52 X #A 52 Adaptive optics 52 adaptive optics 52 parafoil 52 retrorockets 52 lunar lander 52 NROL 52 MESSENGER spacecraft 52 SCISAT 52 highly elliptical orbits 52 railgun 51 jet propulsion 51 Mössbauer 51 STPSat 51 NASA THEMIS 51 Hubble Space Telescope HST 51 liquid propellants 51 PSLV C7 51 Gerhard Schwehm 51 detect gravitational waves 51 NEOSSat 51 Hubble gyroscopes 51 manned lunar 51 twin Voyager spacecraft 51 Krimigis 51 SpaceDev Dream Chaser 51 gamma ray spectrometer 51 instrument calibrations 51 storable propellants 51 indigenous cryogenic 51 lunar orbiter 51 CALIPSO 51 PW#A 51 Interplanetary Internet 51 AIRSS 51 Mars Pathfinder 51 Multi Purpose Crew 51 celestial observations 51 cryocoolers 51 hypersonic jet 51 Cargo Launch Vehicle 51 HB SIA 51 HIAPER 51 deorbit 51 Mars Opportunity rover 51 cryogenic engine 51 EZ Rocket 51 A#T 51 Dragon capsule 51 extrasolar planet observations 51 GOES satellites 51 RTI middleware 51 polar orbiting satellites 51 exoatmospheric kill vehicle 51 retrograde orbit 51 swingby 51 Orbiter LRO 51 tokamaks 51 X #B 51 NanoSail D 51 EO IR sensor 51 manager Gerhard Schwehm 51 orbiter robotic arm 51 Laser COIL 51 spacecraft Cassini 51 SpaceShipTwo SS2 51 SIRAL 51 Orion Ares 51 hyperspectral imager 51 outer planets 51 rechargeable lithium sulfur 51 named Rassvet 51 magnetic bearings 51 DEPTHX 51 exoplanetary 51 comet Churyumov Gerasimenko 51 Vega launcher 51 Chandrayaan II 51 KSLV 1 51 Optical Spectroscopic 51 Orion capsule 51 CX OLEV 51 Hubble Servicing 51 NASA Far Ultraviolet 51 EKV 51 robotic explorer 51 SLC 3E 51 Atlas V 51 elongated orbit 51 neutral mass spectrometer 51 Hubble 51 Caltech Jet Propulsion 51 scatterometer 51 Geosynchronous 51 Extrasolar Planet Observations 51 Pluto Charon 51 Impactor 51 Supersonic Combustion Ramjet 51 perilune 51 deorbit burn 51 gimbaled 51 nanosatellites 51 asteroid flyby 51 Yinghuo 1 51 radial velocity method 51 lunar rovers 51 GSLV rocket 51 Grammier 51 TDRS K 51 Taurus XL 51 thrust vectoring 51 Solar Sail 51 Kepler Mission 51 Martian orbit 51 Cryosat 51 Crew Launch Vehicle 51 Titan IVB 51 Solid Rocket Boosters 51 SpaceX Falcon 51 MTSAT 1R 51 heavier payloads 51 wavefront sensing 51 Orbiter MRO 51 Comet #P/Churyumov-Gerasimenko 51 Orion CEV 50 Space ENvironment GEochemistry 50 unmanned lunar orbiter 50 elliptical orbit 50 pusher propeller 50 COROT 50 Rex Geveden 50 Near Infrared Camera 50 Orion Crew 50 ARGUS IR 50 JAXA 50 twin rover Spirit 50 WGS satellite 50 SOHO spacecraft 50 LightSail 50 PSLV C9 50 SpaceshipTwo 50 orbital inclination 50 synthetic aperture 50 J 2X rocket 50 Rockot 50 hypergolic 50 Infrared Astronomy SOFIA 50 Martian rover 50 Hubble Space telescope 50 Upsilon Andromedae 50 Pluto Kuiper Belt 50 extrasolar planetary 50 manned spacecraft 50 optionally piloted 50 GSLV rockets 50 ESA Mars 50 Convection Rotation 50 RISAT 50 Galileo satellites 50 Konacki 50 MESSENGER MErcury Surface 50 UUV 50 X ray spectrometer 50 KAGUYA 50 Solid Liquid Mixtures 50 Dream Chaser 50 X ray telescopes 50 infrared observatory 50 Saturn Cassini 50 winged spacecraft 50 Orbital Pegasus 50 orbiting satellites 50 C 5M 50 exhaust plume 50 SSPTS 50 MErcury Surface Space ENvironment 50 Oceansat 2 50 hypervelocity 50 GeneSat 1 50 ray Space Telescope 50 Lunar CRater Observation 50 Shuttle Docks 50 Altair lunar lander 50 HALE UAV 50 entered lunar orbit 50 earth orbiting satellites 50 C NOFS 50 Lunar Prospector 50 ESA ERS 50 entire Milstar constellation 50 Zenit 3SL 50 cryogenic engines 50 orbiting Hubble Space Telescope 50 particle colliders 50 ASTRA 1L 50 ESA GOCE 50 Carl Marchetto 50 LOCAD PTS 50 Astro E2 50 orbits 50 NASA Gamma ray 50 VTOL aircraft 50 deformable mirror 50 Air Missile AMRAAM 50 Relations Observatory STEREO 50 ICO G1 satellite 50 ChemCam 50 Orion LAS 50 High Resolution Imaging 50 HiRISE camera 50 kinetic warhead 50 NASA 50 geo synchronous transfer 50 GPS 2R 50 geosynchronous orbit 50 Uninhabited Aerial Vehicle 50 Nuclear Spectroscopic Telescope Array 50 Jupiter flyby 50 SpaceX Dragon 50 JCSAT 9 50 RL# engine 50 Ikaros 50 Multi Object Spectrograph 50 Thermal Emission Spectrometer 50 propulsion systems 50 intercept ballistic missiles 50 flyby spacecraft 50 New Horizons spacecraft 50 GLAST spacecraft 50 Agni III 50 Lyndin 50 starboard SARJ 50 Vehicle PSLV 50 tokamak 50 navigate autonomously 50 tumbleweed rover 50 windshield wiper maneuver 50 binary asteroid 50 Zenit 3SL rocket 50 enters lunar orbit 50 RXTE 50 endurance UAV 50 DART spacecraft 50 AMPERE 50 aircraft Solar Impulse 50 Tropospheric Emission Spectrometer 50 weather satellite TIROS 50 lunar perigee 50 ESA Planck 50 CARTOSAT 2A 50 Astro Aerospace 49 polarimetric 49 spaceward 49 radar interferometry 49 Viking landers 49 Ariane rocket 49 turbopump 49 Block IIF 49 EPOXI 49 stratospheric airship 49 P#/P# truss 49 Synthetic Aperture Radar SAR 49 ultrashort pulses 49 Benthic Rover 49 synthetic aperture radar 49 Max Launch Abort 49 Jupiter Ganymede 49 YES2 49 Interplanetary Kite craft 49 Satellite Launch Vehicle 49 H IIB 49 Vehicle ATV 49 cosmological observations 49 BlueGene P 49 indigenously developed cryogenic 49 STOVL mode 49 ornithopter 49 comet flyby 49 lidar instrument 49 infrared telescope 49 Theodore von Karman 49 #P/Churyumov-Gerasimenko 49 Relative Navigation 49 imaging spectrometer 49 DISR 49 numerical simulation 49 Cassini 49 asteroid deflection 49 ESA SMART 49 Martian lander 49 Lagrangian 49 Thales Alenia 49 Kibo JPM JEM Pressurized 49 tilt rotor 49 DragonLab 49 Huygens lander 49 Keck Interferometer 49 commander Leroy Chiao 49 Ariane launcher 49 Intermediate Range Ballistic 49 STSS Demo 49 Galileo spacecraft 49 narrowband tactical 49 prograde 49 Solar Orbiter 49 orbiting 49 airborne observatory 49 Pete Siebold 49 ADM Aeolus 49 pressurized module 49 HiRISE camera aboard 49 rocket propulsion 49 polar orbiting 49 Tactical Tomahawk 49 Observatory SDO 49 Bulava submarine launched 49 Launch Vehicle 49 Manned Maneuvering Unit 49 Herschel Planck 49 GSTB V2 49 Geosynchronous Satellite Launch Vehicle 49 Ares IY 49 Mastcam 49 Mars rovers 49 unpowered glider 49 Observatory STEREO 49 thruster rockets 49 ATV Johannes Kepler 49 Express AM# 49 Mars Surveyor 49 unmanned airships 49 Alpha Particle 49 Crab Pulsar 49 IKAROS 49 Cassini Huygens spacecraft 49 NAVSTAR Global Positioning System 49 WMAP satellite 49 unpowered 49 X#B 49 GPS IIF satellites 49 satID 49 commercial spaceline 49 GOSAT 49 impactor spacecraft 49 HyShot 49 Kepler Space Telescope 49 Winglee 49 chromatographic separations 49 microgravity experiments 49 Atlantis Undocks From 49 Geosynchronous Transfer Orbit GTO 49 human spaceflight 49 MPCV 49 mission Chandrayaan 49 ultraprecise 49 Technology Demonstrator 49 VASIMR engine 49 ramjets 49 astronomical telescope 49 NASA Kepler telescope 49 orbital altitude 49 hypersonic missiles 49 monopropellant 49 electrodynamic 49 quadrupole 49 lunar orbiter Chandrayaan 49 THAAD interceptor 49 unmanned rotorcraft 49 Satellite Aided Tracking 49 orbiters 49 NPO Lavochkin 49 Based Infrared 49 Hubble Space Telescope 49 George Zamka 49 Particle accelerators 49 countdown dress rehearsal 49 NASA Cosmic Background 49 Planetary Fourier Spectrometer PFS 49 Next Generation Jammer 49 QuikSCAT 49 Dalcanton 49 Stardust capsule 49 LEOP 49 ESA Proba 49 INSAT 4B 49 manned spaceflight 49 Ares IX 49 3Dconnexion 3D mice 49 Cartosat 2B 49 Solar Optical Telescope 49 THEMIS satellites 49 lunar exploration 49 NASA STEREO 49 NASA MESSENGER 49 MP RTIP 49 A# spacecraft 49 reusable hypersonic 49 propellant 49 Daniel Tani hooked 49 Ultraviolet Optical Telescope 49 AESA 49 Lunar Surface 49 Kaveri engine 49 Crawler Transporter 49 Alexander Samokutyayev 49 Scaled Composites SpaceShipOne 49 torque multiplication 49 Eurostar E# 49 planetary transits 49 X ray telescope 49 commander Zhai Zhigang 49 propellants 49 teleoperated 49 Falcon 1e 49 superfluid helium 49 GOES N 49 situ measurements 49 spacecraft orbiting 49 supercruise 49 Vehicle CEV 49 Comet Hartley 49 Helios 2A 49 CryoSat satellite 49 ramjet engine 49 remotely piloted 49 Skyflyer Technology 49 maxon 49 photometer 49 unpressurized cargo 49 OSTM Jason 2 49 ramjet scramjet 49 inertial measurement 49 Jet Propulsion Laboratory JPL 49 spacecraft Hayabusa 49 equatorial orbit 49 Earth orbit LEO 49 SOLO TREC 48 Divine Vessel 48 electromagnetic railgun 48 subsonic speeds 48 AEHF satellite 48 infrared telescopes 48 INSAT 3A 48 ESA XMM Newton 48 MQ 8B Fire 48 lander rover 48 spectroscopic technique 48 Blackswift 48 Cosmic Origins Spectrograph COS 48 Electric Propulsion 48 Virgin Galactic SpaceShipTwo 48 JCSAT 48 VIIRS 48 NASA ICESat 48 GeneSat 48 P Churyumov Gerasimenko 48 Atlantis STS 48 hypersonic cruise missiles 48 SpaceX Dragon capsule 48 planetary rovers 48 André Borschberg 48 Adaptive Optics 48 Space Shuttle Orbiter 48 Climate Experiment GRACE 48 Deep Impact eXtended Investigation 48 gimbals 48 NASA Lunar Crater 48 robotic probes 48 Elektron oxygen generation 48 Orbital Taurus 48 SpaceLoft 48 XMM Newton 48 Sponnick 48 millisecond pulsar 48 Investigation DIXI 48 exoplanet hunter 48 Ed Weiler NASA 48 Sun synchronous orbit 48 SBIRS 48 gamma ray telescope 48 Advanced LIGO 48 Thrusters 48 THAAD radar 48 BepiColombo joint 48 RADARSAT 2 48 GE CF6 engines 48 Robert Hoot Gibson 48 Kibo module 48 visit http:/saturn.jpl.nasa.gov 48 Launch Scrubbed 48 Neptec 48 Neutral Mass Spectrometer 48 Comet Hartley 2 48 NASA Kepler spacecraft 48 Epsilon Eridani 48 Heidemarie M. 48 von Weyhe 48 interferometer 48 Crew Exploration 48 infrared ultraviolet 48 particle acceleration 48 boresight 48 Mars Odyssey spacecraft 48 multibeam 48 spacecraft SpaceShipTwo 48 extravehicular activities 48 urine recycler 48 geosynchronous Earth 48 LightSail 1 48 Mars rovers Opportunity 48 robotic landers 48 INSAT satellite 48 E 8C 48 Gamma ray Large 48 Rokot 48 orbital eccentricity 48 reentry capsule 48 planetary flybys 48 pulsed laser 48 Soyuz TMA spacecraft 48 PSLV 48 turbojets 48 Epoxi 48 GALEX 48 Alphasat 48 Hydratus 48 Planetary Transits 48 CloudSat 48 WGS satellites 48 Electromagnetic Aircraft 48 comet Boethin 48 Unmanned Combat Air 48 ULA Atlas 48 lunar module 48 innermost planet 48 GMTI 48 Simonetta Di Pipo 48 Ocean Salinity SMOS 48 SMOS Soil Moisture 48 tiltrotor 48 Proton Breeze M 48 Aerosol Polarimetry Sensor 48 lunar orbits 48 fission reactor 48 midcourse phase 48 waning gibbous 48 Launch Vehicle EELV 48 spaceship 48 VSS Enterprise 48 Ariane 5G 48 Commander Charlie Hobaugh 48 carry heavier payloads 48 rocket motors 48 lensless imaging 48 TDRS satellites 48 O. Hobaugh 48 matter antimatter annihilation 48 unmanned spacecraft 48 discover Fomalhaut 48 THAAD interceptors 48 Raman spectrometer 48 Servicing Mission 48 Sacred Vessel 48 Eutelsat KA SAT 48 Orion spaceship 48 Hyper X 48 Charles Elachi 48 Huygens 48 Chandrayaan 48 Lunar Module 48 Global Hawk 48 ExoMars 48 microrobot 48 BSAT 3a 48 BRAHMOS 48 reusable suborbital 48 payloads 48 unmanned 48 Cubesat 48 NASA Fermi Gamma 48 airglow 48 Metop 48 electromagnetic propulsion 48 BomBot 48 Mössbauer spectrometer 48 Glonass K 48 JAGM 48 thrust oscillation 48 payload 48 Viking Lander 48 Magnetic levitation 48 STP S# 48 Hubble Telescope 48 twin rover Opportunity 48 simulate weightlessness 48 supersonically 48 Nasa 48 SolarEagle 48 Meteorological Satellite 48 Binary Colloidal Alloy 48 Mossbauer spectrometer 48 Insat 3A 48 X #A scramjet 48 Flyby 48 UCAV 48 geosynchronous satellite launch 48 Situ Resource 48 cosmological parameters 48 ATV Jules Verne 48 Daniel Sacotte 48 Permanent Multipurpose Module PMM 48 GROND 48 Virgin Galactic VSS Enterprise 48 RBSP 48 orbital altitudes 48 ESA Herschel 48 planetary exploration 48 cryogenic propellants 48 Mars rover 48 Akatsuki spacecraft 48 Jeff Greason 48 INSAT 4C 48 unpressurized 48 Aegis radar 48 Greenhouse Gases Observing 48 Recovery Experiment SRE 48 Express orbiter 48 Orbital 48 Rockot launch 48 Unha 2 48 Orbiter 48 Moessbauer 48 DSCS satellites 48 Rosetta lander 48 Centaur upper 47 propellant loading 47 LCROSS spacecraft 47 Lunar Roving Vehicle 47 heaviest payloads 47 exosphere 47 lunar regolith 47 Shenzhou spaceships 47 satellite Giove 47 Lopota 47 ducted fan 47 aeroshell 47 AESA radar 47 LAGEOS 47 Mars Orbiter 47 cosmic ray particles 47 Vertical Takeoff 47 UQM ® 47 astro comb 47 Stardust NExT 47 Multi Object Spectrometer 47 EP 3E 47 Alphabus 47 lbf thrust 47 Endeavour robotic arm 47 Einstein theories 47 Lockheed Martin Skunk Works 47 Shuttle Discovery docks 47 Compton Gamma Ray 47 sun synchronous orbit 47 SLBM 47 MER rovers 47 ROSAT