i (imaginary unit number)
Iapetus
IAU
IBEX (Interstellar Boundary Explorer)
IBSS (Infrared Background Signature Survey)
IC 10
IC 10 X-1 (stellar black hole)
IC 349 (Barnard's Merope Nebula)
IC 410
IC 434 (emission nebula)
IC 59 (nebula near Gamma Cassiopeiae)
Icarus (minor planet 1566)
ICE (International Cometary Explorer)
ice
ice dwarf
ice frost
ice volcanism
ice worm
Iceland spar
ICESat (Ice, Cloud, and Land Elevation Satellite)
ice-water interface station
ICO
icosahedron
Icosian Game
Ida (minor planet 243)
IDCSP (Initial Defense Communications Satellite Program)
ideal burning
ideal gas
ideal gas law
ideal rocket
idealism
idempotent
identity
idiopathic pulmonary fibrosis
idiopathic thrombocytopenic purpura
IEH (International Extreme Ultraviolet Hitchhiker)
IEOS (International Earth Observing System)
igneous
igneous age
ignition
ignition lag
IGY (International Geophysical Year)
Ikeya-Seki, Comet (C/1965 S1)
Ikonos
ileum
ilium
illicit cargo
illuminance
ILLUSIONS AND IMPOSSIBLE FIGURES
ilmenite
image
image intensifier
image tube
IMAGE (Imager for Magnetopause-to-Aurora Global Exploration)
imaginary number
imaginary time
imaging, of extrasolar planets
IMEWS (Integrated Missile Early Warning Satellite)
immune system
immunity
immunoglobulin
immunosuppressant drug
immunotherapy
IMP (Interplanetary Monitoring Platform)
impact basin
impact crater
impact feature
impact melt
impactor
impedance
impetigo
implantable cardioverter defibrillator
impossibilities in mathematics
impossible figure
impossible trident
impulse
impulse, total
impulse-weight ratio
in situ hybridization
incandescence
incarnation and redemption
inclination
inclined plane
inclinometer
inclusion
incomputable number
incubation
incubation period
incubator
indeterminate equations
index
Index Catalogue (IC)
INDIA IN SPACE
Indian astronomy
Indian launch vehicles
Indian summer
indicator
indigo
indium
inductance
induction (electromagnetic)
induction (mathematical)
induction coil
induction hardening
induction motor
induction ring
induction sail
Indus (constellation)
INDUSTRIAL CHEMISTRY
inelastic collision
inequality
inert gas
inertia
inertia wheel
inertial force
inertial guidance
inertial platform
inertial reference frame
inertial stabilization
inertial upper stage (IUS)
infall velocity
infectious disease
inferior planet
inferior vena cava
infinite dimensions
infinite series
infinitesimal
infinity
inflammation
Inflatable Antenna Experiment (IAE)
inflationary model
inflection
inflorescence
influenza
information theory
INFOSEC
infrared
infrared astronomy
Infrared Astronomy Satellite (IRAS)
infrared astronomy satellites
infrared cirrus
infrared excess
infrared galaxy
infrared radiometer
Infrared Space Interferometer (IRSI)
Infrared Space Observatory (ISO)
infrared star
Infra-Red Telescope Facility (IRTF)
ingress
inherited
inhibitor
initiator
injection
injector
ink
Inmarsat
inner ear
Innes, Robert Thorburn Ayton (1861–1933)
Innisfree meteorite
innominate
inoculation
inorganic
INORGANIC CHEMISTRY
inorganic chemistry
INPE (Instituto Nacional de Pesquisas Espacias)
Insat
inscribed angle
inscribed circle
insect
insertion
insomnia
Inspector
instability
instability strip
instantaneous bandwidth
instrument landing system
instrumentalism
INSTRUMENTATION
insulin
INTA (Instituto Nacional de Tecnica Aeroespacial)
integer
integral
INTEGRAL (International Gamma-ray Astrophysics Laboratory)
integral equation
Integral Sign Galaxy (UGC 3697)
integrated magnitude
Integrated Truss Structure
integration
integration time
integumentary system
intelligence, artificial
intelligence, nature of
intelligent dinosaurs
Intelligent Life in the Universe
Intelsat (International Telecommunications Satellite Organization)
intensity
interacting binary
Interamnia (minor planet 704)
Interbol
intercalation compound
intercept
Intercosmos
interesting number
interference
interference pattern
interferometer
interferon
intergalactic absorption
intergalactic magnetic field
intergalactic medium (IGM)
intergalactic travel
Intergalactic Wanderer (NGC 2419)
intergranular lane
interhalogen
interior angle
intermediate filament
intermediate population star
intermediate range ballistic missile (IRBM)
internal conversion
internal energy
International Astronautical Federation (IAF)
International Astronomical Union (IAU)
International Atomic Time (TAI)
International Celestial Reference Frame (ICFR)
International Dark-Sky Association (IDA)
International Date Line
International Geophysical Year (IGY)
International Launch Services (ILS)
International Quiet Sun Years (IQSY)
International Solar Polar Mission
International Space Science Institute
International Space Station (ISS)
International Ultraviolet Explorer (IUE)
interphase
interplanetary communication
interplanetary magnetic field (IMF)
interplanetary medium
interplanetary space
interpolate
intersatellite link
intersection
interstage
interstellar absorption
INTERSTELLAR AND INTERPLANETARY MATTER
interstellar ark
Interstellar Boundary Explorer (IBEX)
interstellar cloud
interstellar colonization
interstellar communication
interstellar distances
interstellar dust
interstellar erosion
interstellar extinction
interstellar maser
interstellar medium (ISM)
interstellar molecules
interstellar polarization
Interstellar Precursor Mission
interstellar precursor missions
Interstellar Probe
interstellar probes
interstellar propulsion
interstellar radio messages
interstellar ramjet
interstellar reddening
interstellar scintillation
interstellar space
interstellar travel
interstellar wind
intervertebral disk
intestine
intracellular
intra-cluster medium
intrinsic color index
intrinsic variable
intron
intrusive
Invaders From Mars
invariant
invariant plane
invariant theory
Invasion of the Body Snatchers
inverse
inverse P Cygni profile
invertebrate
involute
inward orbital migration
Io
iodine
ion
ion exchange
ion propulsion
ionic bond
ionic crystal
ionic radius
ionization
ionization chamber
ionization equilibrium
ionization front
ionization potential
ionization temperature
ionized
ionized layers
ionizing radiation
ionosphere
Iota Horologii
Iota Orionis
IP Pegasi
iPhone
iPod
iPod nano
IRAS
IRAS-Araki-Alcock, Comet (C/1983 H1)
IRFNA (inhibited red fuming nitric acid)
iridescence
iridium (element)
Iridium (satellites)
iris (eye)
Iris (minor planet 7)
IRIS (Infrared Imaging Surveyor)
Iris (sounding rocket)
iron
iron meteorite
iron-deficiency anemia
irradiance
irradiation
irradiation illusion
irrational number
irregular galaxy
irregular moon
irregular variable
irritability
IRS (Indian Remote Sensing satellite)
IRSI
IRTS (Infrared Telescope in Space)
Irwin, James Benson (1930–1991)
ISAS (Institute of Space and Astronautical Sciences)
ischium
ISEE (International Sun-Earth Explorer)
Ishango bone
Isidis Planitia
ISIS (International Satellites for Ionospheric Studies)
island
Island One
islets of Langerhans
ISM
ISO
isobar
isochrone
isoelectronic
isogonal conjugate
isomeric transition
isomerism
isomers
isometry
isomorphism
isoperimetric inequality
isoprene
isosceles
isothermal process
isotomic conjugate
isotopes
isotopic spin
isotropic
isotropic signal
isovolume problem
Israel in space
ISS (International Space Station)
ISS (Ionospheric Sounding Satellite)
It Came From Outer Space
iterate
iteration
Itokawa (minor planet 25143)
ITOS (Improved TIROS Operating System)
IUS (inertial upper stage)
Ivuna meteorite
Izar (Epsilon Bootis)