The Complete Book of Spaceflight: From Apollo 1 to Zero Gravity

208 IRBM (Intermediate Range Ballistic Missile)
successfully for 300 days, resulting in a catalogue of
about 250,000 infrared sources. Among its discoveries
were warm dust disks around certain stars, such as Vega
and Beta Pictoris, which may indicate systems of planets
in the making, “starburst” galaxies in which vast numbers
of new stars are forming, and several new comets and
asteroids.
Launch
Date: January 26, 1983
Vehicle: Delta 3914
Site: Vandenberg Air Force Base
Orbit: 884 km × 903 km × 99.0°
Mass: 1,073 kg
IRBM (Intermediate Range Ballistic Missile)
Aballistic missile with a range of 2,750 to 5,500 km.
IRFNA (inhibited red fuming nitric acid)
See nitric acid.
Iridium
A global wireless digital communication system based
on a constellation of 66 Lockheed-built communications
satellites (plus six on-orbit spares) in 780-km-high
(little LEO) orbits inclined at 86.6° to the equator.
Begun in 1997, Iridium was the first commercial satellite
system to operate from low Earth orbit. Named because
the initial design involved 77 satellites (the number of
electrons in an iridium atom), it provides voice, messaging,
and data services to mobile subscribers using
Motorola-built handheld user terminals. The satellites
are arranged in six planes, each 60° out of phase with its
neighbors, to provide global coverage. The current operator,
Iridium Satellite of Leesburg, Virginia, acquired the
system after its previous owner became bankrupt and it
appeared that the armada of satellites would be deorbited.
IRS Launches
Iris
A solid-propellant sounding rocket for exploring the
upper atmosphere.
IRIS (Infrared Imaging Surveyor)
The second infrared astronomy mission of Japan’s ISAS
(Institute of Space and Astronautical Science). IRIS will
use a 70-cm telescope, cooled to −267°C using liquid
helium, to carry out a highly sensitive survey of the
infrared sky and so help astronomers investigate further
the formation and evolution of galaxies, stars, and planets.
Also known as Astro-F, the mission has been under
development since 1997 and is due to be launched into a
sun-synchronous polar orbit by an M-5 rocket in 2004.
IRS (Indian Remote Sensing satellite)
A series of Earth resources satellites launched by the
Indian Space Research Organisation (ISRO). The first of
them, IRS-1A, followed on from the two Bhaskara experimental
resources satellites launched in 1979 and 1981.
(See table, “IRS Launches.”)
IRSI (Infrared Space Interferometer)
See Darwin.
IRTS (Infrared Telescope in Space)
A highly successful 15-cm-diameter orbiting infrared telescope
developed by Japan’s ISAS (Institute of Space and
Astronautical Science), launched aboard Japan’s SFU
(Space Flyer Unit), and retrieved by the Space Shuttle Endeavouron
mission STS-72 in December 1995. Attached to
the telescope were four instruments: a near-infrared spectrometer
(NIRS), a mid-infrared spectrometer (MIRS), a
Launch
Date: March 18, 1995
Vehicle: H-2
Site: Tanegashima
Orbit: 467 × 496 km × 29°
Spacecraft Date
Launch
Vehicle Site Orbit Mass (kg)
IRS-1A Mar. 17, 1988 Vostok M Baikonur 894 × 912 × 99° 975
IRS-1B Aug. 29, 1991 Vostok M Baikonur 890 × 917 × 99° 980
IRS-1E Sep. 20, 1993 PSLV Sriharikota Launch failure —
IRS-1C Dec. 28, 1995 Molniya-M Baikonur 805 × 817 × 99° 1,250
IRS-P3 Mar. 21, 1996 PSLV Sriharikota 818 × 821 × 99° 930
IRS-1D Sep. 29, 1997 PSLV Sriharikota 737 × 827 × 99° 1,200